GB2297089A - Cytotoxic quinoxaline 1,4-dioxides - Google Patents

Abstract

Quinoxaline dioxide derivatives, some of which are novel compounds are useful as cytotoxic agents with selective activity in hypoxic cells, both in vitro and in vivo .

Description

DERIVATIVES OF QUINOXALINE 1 ,4D10XIDE PROCEDURE FOR THEIR PREPARATION AND THEIR EMPLOYMENT This invention is referred to new derivatives of 1,4-quinoxaline dioxide1 to procedures for their synthesis and their employment for the preparation of cytotoxic agents with selective activity in hypoxic cells, so much "in vitro" as "in vivo".

BACKGROUND ART In the solid tumours there is an hypoxic cellular population (Moulder, J.E & Rockwell, S., lnt.J . Radiat.Oncol. Biol. Phys. I 0:695/712,1984) that emerges because the vasculature of the tumour grows more slowly than the own tumour or because the chaotic growth of the tumoral mass can occlude partial or totally, in a permanent or transient way, the tumour vasculature. The existence of hypoxic cells in solid tumours has been demonstrated in animal tumours and in human tumour xenografts transplanted in immune deficient mice, and there are also data that support the hypothesis of their presence in human tumours (Vaupel, P. ef al., CancerRes.

49:6449-6465, 1989).

In addition to be resistant to radiotherapy (Thomlinson, R.H. & Gray, L.H. Br.J.Cancer 9:539-549, 1955), hypoxic cells can be also resistant to quimiotherapy due to their non proliferative state, and to be located beyond the diffusion distance of some compounds. However, there is a group of antitumoral agents, called bioreductive agents1 which have been designed with the idea of using the hypoxia conditions of some tumour cells to obtain a therapeutic benefit, due to the fact that the non tumoral cells are normally well oxygenated (Adams, G.E. et al., Biochem. Biophys. Res.

Comm., 72:824-829, 1976). The bioreductive agents are compounds that are converted in cytotoxic species through reduction (bioreductive activation), mechanism that it is favored at low oxygen concentrations. Among this group of compounds, derivatives of 1,2,4-benzotriazine 1,4-dioxides stand out, that, in addition to be more toxic in hypoxia, possess activity as anticancer agents (Brown, J.M. & Lemmon, M.J., CancerRes.. 50:7745-7749, 1990). An important compound of this type is SR 4233 (Tirapazamine), currently in clinic phase, which is described and recovered with other derivatives in the Patent USA 5.175.287 as well as in the Patent WO 8908647. In the requests of the Patent WO 8802366 and of the Patent WO 9104028 various derivatives of Tirapazamine are described.

Tirapazamine (3-amino-I ,2,4-benzotriazine 1,4-dioxide) is the cytotoxic agent which is activated by reduction and that, to date, has demonstrated to be more selective "in vitro" (HCR= 75 in V79 cells). However, it shows a low potency and scarce solubility in water.

Previously, derivatives of quinoxaline 1,4-dioxides had not been evaluated as cytotoxic selective agents in hypoxia. In Cihak, R. and Vontorkova, M., Mutat.Res., 144 (2): 81-84 (1985), cytogenetic effects of various quinoxaline 1,4-dioxides are described. In Davis, C.D. et al., Cancer Lett., 73 (2-3): 95-104 (1993), mutagenic effects of heterocyclic amines, more specifically of quinoxaline N-oxides, are described. In Nunoshiba, T. and Nishioka, H., Mutat. Res., 217 (3): 203-209 (1989), some quinoxaline 1,4-dioxides with genotoxic activity in Escherichia coli and Salmonella typhimurium, are described. In Usui, T., Chem.Abst., 94 (21): 167640m (1981) quinoxaline 1,4-dioxides that contain in their structure a group 5-nitro-2-furyl and have antitumoral activity, are described.In Ley and Seng, Synthesis, 415422 (July, 1975) it is described the preparation of 2-(3aimethylamino-propylamino)quinoxalin ,4- dioxide. In Seng, F. and Ley, K. Angew.Chem. 11, 1010-1011, it is described the preparation of 4-cyano-7,8-dimethyl-2-oxo-1 24-oxadiazole [2,3-a] quinoxaline 5-oxide as intermediate in lumichrome synthesis. In the German Patent request 2232468 the preparation of 4-cyano-5-oxide-2-oxo-1,2,4-oxadiazolo[2,3-a]quinoxaline from 3-amino-2 < uinoxalinecarbonitrile 1,4-dioxide and fosgene in chlorobenzene at 90 C is described.In the German Patent 2255946 the preparation of various ureas from 1,2,4-oxadiazol[2,3-3,4]benzo-1,2,4-triazine by treatment with primary and secondary amines, is described; these products were tested for bactericidal activity.

In the US Patent request 4343942 the preparation and trial as antimicrobial agents and promoters of animal growth of 6,7 replaced 3-amino-2quinoxalinecarbonitrile 1,4.

dioxide.

DESCRIPTION OF THE INVENTION The present invention is referred to derivatives of quinoxaline 1,4-dioxides that have demonstrated to be selective cytotoxic agents in hypoxia conditions. Some of the compounds are 100 times more potent, 4 times more selective, at least 10 times more soluble in water and with better therapeutic in vivo index than SR 4233.

The most of the compounds are of new synthesis.

Formula I

Wherein R2 is cyano or C(14)alkyl, -CH2-NH-NH-COO-C(14)alkyl, 0(1- 4)alkyloxycarbonyl, C(14)alkylthio, C(2-5)alkanoyl, 0(1 A)alkyl-O-CO-C( I 4)alkyl or a group of formula -C(X) =Y-Z wherein X is H or C(14)alkyl, Y is CH or N and, Z is benzoyl optionally mono- or di- substituted with halogen, C(2-5)alkanoyl or phenylamino optionally mono- or di- substituted with NO2.

Wherein R3 is H; amino optionally mono- or di- substituted with 0(1- 4)alkyloxycarbonyl; C(2-5)alkanoylamino optionally substituted on carbon with halogen; phenylthio, phenylsulfinyl or phenylsulfonyl optionally mono- di- or trisubstituted on phenyl with halogen or NO2; a group of formula -NH-C(1-6)alkyl N(A1)(A2) wherein Al and A2 are independently H or C(14)alkyl, or Al and A2 together complete a 5 or 6 membered heterocyclic ring optionally containing a N, O or S atom in lieu of a carbon atom; C(2-6)alkanoylamino; C(2-6)alkanoyl; hydroxy; mercapto; C(14)alkoxy; aryloxy; C( I -4)alkylthio; C(1-4)alkylsulfinyl; C(1- 4)alkylsulfonyl; C(14)alkyloxycarbonyl; halogen;C(1-6)alkyl; a group of formula -NH CO-Het wherein Het is a 5 or 6 membered heterocyclic ring containing one atom of O or S; C(1 -4)alkylsulfonylamino; C(1 -4)alkylsulfinylamino; C(1-6)alkylamino optionally substituted on carbon with OH, SH or halogen; arylamino; a group of formula N(A1)(A2) wherein Al and A2 are C(IA)alkyl, or Al and A2 together complete a 5 or 6 membered heterocyclic ring optionally containig a N, O or S atom in lieu of a carbon atom.

In this report the term "aryl" such and as here is indicated includes aromatic rings of 5 or 6 members, with or without heteroatoms as N, S or 0, and they can have or not 1, 2, or 3 substituents as halogen; nitro; sulfo; alkyl (16 C); alkoxy (1-6 C); carboxy; alkoxycarbonyl; cyano; carbamoyl; formyl.

R6 and R7 independently represent H; halogen; C(2-5)alkanoyl; CF3; 0(1- 4)alkyl; C(1-4)alkoxy; C(1-4)alkylthio; C(1-4)alkylsuifinyl; C(1-4)alkylsulfonyl; C(25)alkanoylamino; cyano; cyclohexyl optionally substituted with 1-2 substituents selected from NO2 and C(14)alkyl; phenyl optionally substituted with 1-2 substituents selected from NO2 and 0(14)alkyl; Ra represents H or NO2.

Formula II

X can be N. O or S. Y can be N, O, S or C.

R,, R2 and R3 are alkylic chains (14 C).

R6 and R7 independently represent H; halogen; C(2-5)alkanoyl; CF3; C(1- 4)alkyl; C(14)alkoxy; C(14)alkylthio; C(14)alkylsulfinyl; C(14)alkylsulfonyl; 0(2- 5)alkanoylamino; cyano; cyclohexyl optionally substituted with 1-2 substituents selected from NO2 and C(I4)alkyl; phenyl optionally substituted with 1-2 substituents selected from NO2 and C(14)alkyl; R6 represents H or NO2.

F6rmula Ill

R7 and R8 independently represent H; halogen; C(2-5)alkanoyl; CF3; C(1- 4)alkyl; C(14)alkoxy; C(1-4)alkylthio; C(14)alkylsulfinyl; C(14)alkylsulfonyl; 0(2- 5)alkanoylamino; cyano; cyclohexyl optionally substituted with 1-2 substituents selected from NO2 and C(14)alkyl; phenyl optionally substituted with 1-2 substituents selected from NO2 and C(14)alkyl.

Some particular quinoxalines of the invention are represented in the Figure I in which: R2 is cyano. C(14)alkylthio, C(2-5)alkanoyl or a group of formula -C(X) =Y-Z wherein X is H or C(14)alkyl, Y is CH or N and, Z is benzoyl optionally mono- or disubstituted with halogen, C(2-5)alkanoyl or phenylamino optionally mono- or disubstituted with NO2.

R3 is acylamino such as acetamido, 2-chloroacetamido or C(14)alkyl.

R6 and R7 independently represent H; halogen; C(2-5)alkanoyl; CF3; 0(1- 4)alkyl; C(1-4)alkoxy; C(1-4)alkylthio; C(1-4)alkylsulfinyl; C(1-4)alkylsulfonyl; C(25)alkanoylamino; cyano; cyclohexyl optionally substituted with 1-2 substituents selected from NO2 and C(14)alkyl; phenyl optionally substituted with 1-2 substituents selected from NO2 and C(14)alkyl; R8 represents H or NO2.

Some preferred quinoxalines of the invention are represented in the Formula I in which: R2 is cyano.

R3 is hydrogen; C(14)alkyl; chloro; prymary amino (NH2); C(14)alkylamino optionally substituted on carbon with hydroxy, mercapto or halogen; -N(A1)(A2) wherein Al and A2 are C(I-4)alkyl, or Al and A2 together complete a 5 or 6 membered heterocyclic ring optionally containing a N, O or S atom in lieu of a carbon atom.

R6 and R7 independently represent H; halogen; C(2-5)alkanoyl; CF3; C(1- 4)alkyl; C(1-4)alkoxy; C(1-4)alkylthio; C(1-4)alkylsulfinyl; C(1-4)alkylsulfonyl; C(25)alkanoylamino; cyano; cyclohexyl optionally substituted with 1-2 substituents selected from NO2 and C(1-4)alkyl; phenyl optionally substituted with 1-2 substituents selected from NO2 and C(14)alkyl; RB represents H or NO2.

Specially preferred quinoxalines of the invention are represented in the following structural formula:

Where n may be 04, preferably 2 or 3. A1 and A2 are independently hydrogen, C(14)alkyl, optionally replaced the alkyl by hydroxy, C(1-4) alkoxy, amino, C(14) alkylamino, thiol or C (14) alkylthio; Al and A2 together complete a 5 or 6 membered heterocyclic ring optionally containing a N, O or S atom in lieu of a carbon atom: the heterocyclic ring may be optionally replaced a carbon by C(1-4) alkyl.

R6 and R7 independently represent H; halogen; C(2-5)alkanoyl; CF3; 0(1- 4)alkyl; C(1-4)alkoxy; C(1-4)alkylthio; C(1-4)alkylsulfinyl; C(1-4)alkylsulfonyl; C(25)alkanoylamino; cyano; cyclohexyl optionally substituted with 1-2 substituents selected from NO2 and C(1-4)alkyl; phenyl optionally substituted with 1-2 substituents selected from NO2 and C(14)alkyl; in positions 5 and 8 may be H or NO2.

All the compounds may be in the form of some of the pharmaceutically acceptable salts, and they are prepared in a conventional method, such as by reaction of the free base in an adecuate solvent, for example diethyl ether acetone or methanol, with a solution containing an equivalent of the acid wished in a adequate solvent, for example diethyi ether, acetone or methanol. The salt precipitates in the solution or is recovered by evaporation of the solvent. Phanaceutically acceptable salts include for example, hydrochloric, hydrobromic, sulfate, oxalate, citrate, tosylate, mesylate. Also, sodium, potasium, calcium salts or from organic salts such as caffeine, ethylamine, lysine.

A quinoxaline of the invention may be administered to animal of hot blood, including to the man, in the form of a pharmacological composition that contains the quinoxaline associated with a solvent or phannacologically acceptable vehicle.

The quinoxalines of the invention are selectively toxic for hypoxic cells, so they are intended to be used in combination with other treatments more toxic for well oxygenated cells. They can be administered before and/or after radiation, in a regimen of fractionated radiotherapy. They could also be used in combination with other cytotoxic drugs such as alkylating agents, or other antitumoral drugs with different mechanism of action.

The composition may be in a form adapted for its oral administration, such as pills or capsules, or, specially, for parenteral injection, as a solution, suspension or sterile emulsion.

MODES OF CARRYING OUT THE INVENTION General method for the preparation of 3-amino-2-quinoxaline carbonitrile 1,4dioxide derivatives. The compounds are prepared starting with the benzofuroxanes of formula:

by Beirut reaction. The benzofuroxanes are prepared starting from the corresponding anilines by acylation in acetic anhydride/acetic acid and then1 nitration of the corresponding amides by using nitric acid and sulfuric acid. Hydrolysis of substituted acetamides give the substituted 2-nitroanilines which are diazotated and treated with sodium azide. Displacement by azido group and subsecuent cyclocondensation of the 2-nitroazide in boiling toluene afford the benzofuroxanes. Scheme 1. The general pathway for this synthesis has been described previously (Fitton, A.O., Smalley, R.K.

In: Practical Heterocyclic Chemistry, 57-61, Academic Press. London and New York (1968)).

Scheme 1

Beirut reaction by using malononitrile in the presence of an appropiate condensing base, such as triethylamine, give the 6 andlor 7 substituted 3-amino-2quinoxalinecarbonitrile 1,4-dioxides (Ley, K. and Seng, F. Synthesis 415-422 (1975)).

Scheme 2. (Examples 1-8). The benzofuroxane starting material is not symmetric with respect to its own 5 and 6 positions (which are the 6 and 7 positions of the resulting quinoxaline 1,4-dioxides). Therefore, a mixture of the 6- and 7-substituted materials may result. In general, Beirut reaction mainly affords the 7 isomer (Cheeseman, G.W.H. and Cookson, R.F., Condensed pyrazines, John Wiley and Sons Eds., 35: 3637 (1979)) (Mason, J.C. and Tennant, G., J. Chem. Soc. Chem. Commun., 586 (1971)). If desired, this mixture can be separated using conventional means.

Scheme 2

Nitration of 3-amino-7-methoxy-2-quinoxalinecarbonitrile 1,4 dioxide at room temperature for 10 h affords the 8-nitro derivative. Scheme 3. (Example 9).

Scheme3

Reaction of 3-amino-2-quinoxalinecarbonitrile 1,4-dioxides with anhydrides in an appropiate dry non protic solvent, yield the corresponding amides in position 3.

Scheme 4. (Examples 10 and 11).

Scheme 4

In addition reaction with sulfonyl chloride in an appropiate dry solvent such as dioxane, afford the corresponding alkylsulfonylamines and arylsulfonylamines in position 3. Scheme 5. (Example 12).

Scheme 5

Diazonium salt formation starting with 6 and/or 7 substituted 3-amino-2quinoxalinecarbonitrile 1,4-dioxides and tert-butylnitrite at 60-100 OC, and replacement by hydrogen in the presence of an hydrogen donor solvent, such as N,N-DMF, yield 2quinoxalinecarbonitrile 1,4-dioxide derivatives. Scheme 6. (Examples 13-19).

Scheme 6

Replacement of the diazonium salt by halogen in the presence of X2Cu, in an appropiate solvent, such as acetonitrile, afford the corresponding 6 andlor 7 substituted 3-chloro, 3-bromo and 3-fluoro-2-quinoxalinecarbonitrile 1,4-dioxides.

Scheme 7. (Examples 20-25).

Scheme7

Replacement of the halogen in position 3 of the quinoxaline ring by using several amines in an appropiate solvent at 5-100 "C, afford the 6 and/or 7 substituted 3-(N, N-dialkylamino)alkylamino, 3-alkylamino and 3-arylamino-2quinoxalinecarbonitrile 1,4-dioxides. Scheme 8. (Examples 26-39).

Scheme8

Reaction of the 3-chloro compounds with a diamine affords a quinoxaline dimer. Scheme 9. (Example 40).

Scheme 9

Treatment of 6 andlor 7 substituted 3-amino-2-q uinoxalinecarbonitrile 1,4dioxide with 2-chloroethylisocyanate in the presence of an appropiate dry solvent, such as dioxane or toluene. at 90-150 "C give 7 andlor 8 substituted 4-cyano-2-oxo 1 ,2,4-oxadiazolo[2,3-ajquinoxaline 5-oxide (Seng, F. and Ley, K. Angew. Ghem.

internat. Edit. Vol. 11, NO 11 (1972)). Scheme 10. (Examples 41 and 42).

Scheme 10

Reaction of 5 andlor 6 substituted benzofuroxanes with 5-alkylisoxazole in ammonia atmosphere gives 6 and/or 7 substituted 3-alkyl-2-quinoxalinecarbonitrile 1,4-dioxide. Scheme 11. (Example 43).

Scheme 11

Beirut reaction between benzofuroxanes and ketones has been described previously; thus, benzofuroxane reacts with acetone in the presence of ammonia giving 2-methytquinoxaiine 1,4-dioxide in good yield (Monge, A. et al., Ann. Quim.. 71: 248 (1975)). Scheme 12. (Example 44).

Scheme 12

With acetylacetone provides 2-acetyl-3-methylq u inoxaline 1,4-dioxide (Issidorides et ai., J. Org. Chem.. 31:4067 (1966)). Scheme 13. (Examples 45-48).

Scheme 13

With pyruvaldehyde dimethylacetal gives 2-dimethoxymethylquinoxaline 1,4dioxide (Johnston, Pfizer, Inc., Ger. Offen. 1927-337, C.A. 72, 11753 c). Scheme 14.

(Examp(es 49 and 50).

Scheme 14

Reaction with butanone gives 2,3-dimethylquinoxaline 1,4-dioxide (Landkist, J.

J. Chem. Soc.. 2822 (1953)). Scheme 15. (Example 51).

Scheme 15

Reaction with benzoylacetone yields 2-benzoyl-3-methylquinoxaline 1,4-dioxide (Haddadin et al., Tetrahedron. 32: 719 (1976)). Scheme 16. (Example 52).

Scheme 16

With ethyl acetoacetate yields 2-ethoxycarbonyl-3-methylquinoxaline 1,4dioxide (Issidorides et al., J. Org. Chem. 31 4067 (1966)). Scheme 17. (Example 53).

Scheme 17

With ethyl benzoylpyruvate affords 2-benzoylquinoxaline 1,4-dioxide. Scheme 18. (Example 54).

Scheme 18

Bromination in acetic media of 2-methylquinoxaline 1 ,4-dioxide affords the bromomethyl analogue (Elina. Khin. Geterotsike Soedin, 72: 263 (1967)), which reacts with methylcarbazate by nucleophilic displacement of the bromine. Scheme 19.

(Example 44).

Scheme 19

2-Formylquinoxaline 1,4-dioxide is obtained by hydrolysis of the acetal 2dimethoxymethylquinoxaiine 1,4-dioxide. Scheme 20. (Examples 49 and 50).

Scheme 20

Wittig reaction between the formyl group and the corresponding iluro affords 2 (3-alkyl/aryl-3-oxo-1-propenyl)quinoxaline 1,4-dioxides. Scheme 21. (Examples 49 and 50).

Scheme 21

Condensation of 2-acetyl-3-methylquinoxaline 1,4-dioxide with hydrazines and ydrazides gives the imino derivatives. Scheme 22. (Examples 45-48).

Scheme 22

Selective oxidation of 2,3-dimethylquinoxaline 1,4-dioxide with selenium dioxide provides 2-formyl-3-methylquinoxaline 1,4-dioxide. Scheme 23. (Example 51).

Scheme 23

This reacts with yluros by Wittig condensation giving ,ss-insaturated ketones.

Scheme 24. (Example 51).

Scheme 24

Reaction between benzofuroxanes and alkyl/arylthioacetones yields 2-methyl3-alkyl/arylthioquinoxaline 1,4-dioxides (Abushanab, E., J. Org. Chem. 38: 3105-3107 (1973)). Scheme 25. (Examples 55, 58 and 59).

Scheme 25

Selective oxidation of 2-methyl-3-alkyl/arytthioquinoxaline 1,4-dioxides with mchloroperbenzoic acid (MCPBA) gives the corresponding sulfinyl (1:1 quinoxalinelMCPBA) and sulfonyl (1:3 quinoxaline/MCPBA) derivatives. Scheme 26.

(Examples 56, 57, 60 and 61).

Scheme 26

Nucleophilic replacement of the sulfonyl group by chlorine in concentrated HCI gives the corresponding 2-chloroquinoxaline 1,4-dioxide. Scheme 27. (Example 62).

Scheme 27

Replacement of the sulfonyl group by amines affords the 2-amino derivative.

Scheme 28. (Example 63).

Scheme 28

Reaction between 6,7-dichloro-2-methyl-3-methylthioquinoxaline 1,4-dioxide and formamidine acetate in 2-ethoxyethanol as solvent affords 2-amino-6,7-dichloro-3methylquinoxaline 1,4-dioxide. Scheme 29. (Example 64).

Scheme 29

Treatment of quinoxaline 1,4-dioxide with potassium ferricyanide and potassium cyanide in ethanol-water produces 2,3-dicyanoquinoxaline 1,4-dioxide (Kobayashi, Y et al., J. Org. Chem., 37: 3588-3591 (1972)). Scheme 30. (Example 65).

Scheme 30

7-C hloro4cyano-2-oxo-l ,2,4-oxadiazolo[2,3-a]quinoxaline 5-oxide. reacts with ethanol giving 3ethoxycarbonylaminoj-chlorn-2-quinoxalinecarbonitrile 1,4-dioxide.

Scheme 31. (Example 66).

Scheme 31

Reaction of 4cyano-2-oxo-l ,2,4-0xadiazolo[2,3-a]quinoxaline 5-oxides with ammonia and primary amines yields the cyclocondensation to benzopteridine 5,10dioxide (Seng, F. and Ley, K., Angew. Chem. internat. Edit. 11: 1009-1011 (1972)).

Scheme 32. (Examples 66 and 67).

Scheme 32

The invention is described with reference to the drawings of which: Fig 1A and 1B are graphs of percentage surviving cells after treatment with an increasing dose of an active ingredient and Fig 2 is a graph of clonogenic cells per g tumour after treatment with an active ingredient, with or without radiation.

EXAMPLES The following examples further illustrate the compounds of the invention and methods for synthesizing and using them, and are not intended to limit the invention in any manner.

Experimental: Melting points were determined using a Mettler FP82+FP80 apparatus and are uncorrected. Eiemental analyses were obtained from vacuumaried samples (over phosphorous pentoxide at 3-4 mm Hg, 24 hours at about 60-80 C).

Infrared spectra were recorded on a Perkin-Elmer 1600 series FTIR apparatus, using potassium bromide tablets for solid products and sodium chloride plates for liquid products; the waves numbers are expressed in cm. The 'H-NMR spectra were obtained on a Brucker AC-200E (200 MHz) instrument, with tetramethylsilane as the internal reference, at a concentration of about 0.1 g1mL and with dimethylsulfoxide46, chloroform-d, trifluoracetic acid (TFA) and D2O as the solvents; the chemical shifts are reported in ppm of tetramethylsilane in 6 units. The mass spectra were recorded on a Hewlett-Packard 5988-A instrument at 70 eV.

Thin layer chromatography (TLC) was carried out on silica gel (HF, 254-266, Merck or DSF-s, Cammaga) with the indicated solvents and the plates were scanned under ultraviolet light at 254 and 366 nm. Column chromatography was carried out with silica gel 60 Merck (70-230 mesh ASTM) and indicated solvents.

Analyses indicated by the symbols of the elements or functions were within +0.4% of theoretical values. In the cases where the deviation is higher, the composition of the element deviated is indicated.

5-Chloro4-fluoro-2-nitroaniline, 4-trifluoromethoxyaniline, 4-trifluoromethyl-2nitroaniline, benzofuroxane, 5-chlorobenzofuroxane, 5-fluorobenzofuroxane, 5methoxybenzofuroxane were purchased from Maybridge.

3 ,4-Oichloroaniline, 4,5-dimethyl-2-nitroaniline, 4-methyl-2-nitroaniline, 4,5difluoro-2-nitroaniline, 3-chloro-4-methoxyaniline, 4-aminobiphenylo, tert-butyl nitrite, copper (Il) chloride, chloroacetic anhydride, acetic anhydride, 2-chloroethylisocyanate, sulfonyl chlorides. acetonitrile, 3-(N,N-dimethylamino)propylamine, 2-(N,Ndiethylamino)ethylamine, 2-(N , N-d imethyl)ethylamine, 4-(3-aminopropyl)morpholine, N-methyl-N,N-di-(3-aminopropyl)amine, 5-methylisoxazole, acetylacetone, pyruvaldehyde dimethylacetal, benzoylacetone, ethyl acetoacetate, methylcarbazate, m-chloroperbenzoic acid, formamidine acetate were purchased from the Aldrich Chemical Company. Malononitrile from Lonza. N,N-Dimethylformamide, triethylamine, K2CO3, CH2CI2, dioxane, toluene, methanol, acetone, acetic acid, nitric acid, concentrated HCI, concentrated sulfuric acid, sodium azide, butanone, selenium dioxide, chloroacetone, potassium cyanide, potassium ferricyanide, 2-ethoxyethanol, phenylhidrazine, 2,4-dinitrophenylhidrazine, thiosemicarbazide, p toluensulphonylhidrazine, p-methoxy acetophenone, acetophenone, pnitroacetophenone were purchased from Panreac.

EXAMPLE 1 Preparation of 3-amino-6(7)-chloro-2-quinoxalinecarbonitrile 1,4-dioxide

A mixture of 5-chlorobenzofuroxane (10 mmol) and malononitrile (10.6 mmol) was stirred at 0 C (ice-bath) for 10 min. A solution of triethylamine (5 drops) in N,N DMF (3mL) was added dropwise. The mixture was stirred at room temperature for 24 h. and was filtrated. The crude solid was washed with diethyl ether (72 %). The mixture of 6 and 7 chloro isomers was purified by flash chromatography. Firstly 3amino-7-chloro-2-quinoxalinecarbonitrile 1,4 dioxide was eluted with ethyl acetate (62 %), mp 263-264 C. IR (KBr) 3433-3295. 2236, 1336 cm-1. 1H NMR (dimethylsulfoxided6) 7.92 (d, 1 H, He, J= 9.0 Hz), 8.14 (s, 2 H, NH2), 8.23-8.29 (m, 2 H, H5 H8). MS (El) mie (70 eV) M+= 236. ANAL (calc. for C9H5CIN4O2) C,45,66; H,2,11; N,23,68. Found: C,45,82; H,2,11; N,23,82. The 6chloro isomer was eluted with toluene:acetic acid (TDA) (10 %), mp 260 C. 1H NMR (dimethylsulfoxide-d6) 8.00 (d, 1 H, H7, J= 8.2 Hz), 8.32 (s, 3 H, NH2 H5), 8.33 (d, 1 H, H8). MS (El) m/e (70 eV) M+= 236.

EXAMPLE2 Preparation of 3-amino-6,7-dichloro-2-quinoxalinecarbonitrile 1,4-dioxide

A) Preparation of 5,6-d ichlorobenzofuroxane 5 Steps are required for the synthesis of this benzofuroxane: 1) Preparation of 3,4-dichloroacetanilide A mixture of 3,4-dichloroaniline (8.91 g, 55 mmol), acetic anhydride (8 mL) and acetic acid (8 mL) was heated under reflux for 15 min. The mixture was poured into ice-water and the resulting precipitate was filtered and dried at 60 C in vacuo. The acetanilide was used without further purification.

2) Preparation of 4,5-dichioro-2-nitroacetanilide 8.98 g (44 mmol) of 3,4-dichloroacetanilide was added over a cooled (0 C) mixture of 60% nitric acid (20 mL) and concentrated sulfuric acid (20 mL). After stirring at 0 C for 10 min the mixture was allowed to reach the room temperature. The solution was poured into crushed ice and the precipitate filtered and dried at 60 C in vacuo.

3) Preparation of 4,5-dichloro-2-nitroaniline 4,5-Dichloro-2-nitroacetanilide (8.71 g, 35 mmol) was used without further purification. It was heated in concentrated sulfuric acid (30 mL) at 100 C for 15 min.

The reaction mixture was allowed to cool and poured into crushed ice. The resulting solid was filtrated, washed with water and dried in vacuo at 60 "C. It was used without further purification.

4) Preparation of 4,5-dichloro-2-nitrophenylazide Powdered 4,5-dichloro-2-nitroaniline (3.52 g, 17 mmol)1 concentrated HCI (20 mL) and water (60 mL) were stirred at room temperature for 5 min. The mixture was cooled at 0 C and a solution of sodium nitrite (2 g, 29 mmol) in water (10 mL) was added. The insoluble material was discarded and the clear solution was treated with an aqueous solution of sodium azide (2.5 g, 38 mmol) and sodium acetate (50 g, 0.60 mol). The resulting solid was filtrated and dried in vacuo at 20 C. CAUTION!: Azides should not be heated.

5) Preparation of 5,6-dichlorobenzofuroxane A mixture of 4,5-dichloro-2-nitrophenylazide (2.33 9, 10 mmol) and toluene (25 mL) was heated under reflux for 2 h. After removal of the solvent a brown solid was obtained and used without further purification.

B) According to the procedure described in EXAMPLE 1. (48 %), mp 265 C IR (KBr) 3281, 2230, 1367 cm-1. 1H NMR (dimethylsulfoxide-d6) 8.43 (s, 2 H, NH2), 8.49 (s, 1 H, H8), 8.53 (s, 1 H, H5). MS (EI) mle (70 eV) M+= 270. ANAL (calc. for CgH4CI2N402) C,39.85; H,1.48; N,20.66. Found: C,40.08; H,1.48; N,20.39.

EXAMPLE 3 Preparation of 3-amino-6(7)-methyl-2-quinoxalinecarbonitrile 1,4-dioxide

A) Preparation of 5-Methylbenzofuroxane 4-Methyl-2-nitrophenylazide and 5-methylbenzofuroxane were prepared starting from commercial 4-methyl-2-nitroaniline as described in EXAMPLE 2 and were used without further purification.

B) According to the procedure described in EXAMPLE 1. (52 %), mp 245-247 C. IR (KBr) 3415-3330, 2233, 1332 cm-1. 1H NMR (dimethylsulfoxide-d6) 2.49 (s, 3 H, CH3), 7.48 (d, 1 H, H7 6 isomer, J= 8.8 Hz), 7.73 (d, 1 H, H6 7 isomer, J= 8.7 Hz), 7.96 (s, 2 H, NH2 6 isomer), 8.05 (s, 2 H, H5 6(7) isomers), 8.11 (s, 2 H, NH2 7 isomer), 8.16 (d, 2 H, H8 6(7) isomers, J= 8.7 Hz). MS (El) mle (70 eV) M+= 216. ANAL (calc. for C10HBN402) C,55.56; H,3.70; N,25.92. Found: C,55.52; H,3.73; N,25.90.

EXAMPLE 4 Preparation of 3-amino-6(7)-methoxy-2-quinoxalinecarbonitrile 1,4-dioxide

According to the procedure described in EXAMPLE 1. (40 %), mp 248-249 C.

IR (KBr) 3336, 2230, 1337 cm-1. 1H NMR (dimethylsulfoxide-d6) 3.92 (s, 3 H, OCH3), 7.48 (d, 1 H, H7 6 isomer, J= 8.8 Hz), 7.73 (d, 1 H, H6 7 isomer, J= 8.7 Hz), 7.96 (s, 2 H, NH2 6 isomer), 8.05 (s, 2 H, H5 6(7) isomers), 8.11 (s, 2 H, NH2 7 isomer), 8.16 (d, 2 H, H8 6(7) isomers, J= 8.7 Hz). MS (El) m/e (70 eV) M+= 216. ANAL (calc. for C10H8N402) C,55.56; H,3.70; N,25.92. Found: C,55.52; H,3.73; N,25.90.

EXAMPLE 5 Preparation of 3-amino-6(7)-fluoro-2-quinoxalinecarbonitrile 1,4-dioxide

According to the procedure described in EXAMPLE 1. Mainly the 7 isomer was obtained (61 %), mp > 300 "C. IR (KBr) 3340, 2230, 1378 cm . 'H NMR (dimethylsulfoxide-d6) 7.81-7.89 (m, 1 H, H6), 8.00 (s, 1 H, H8), 8.05 (S, 2 H, NH2), 8.29-8.36 (m, 1 H, H5). MS (El) mte (70 eV) M = 220. ANAL (calc. for CgHsFN402) C,49.09; H,2.27; N,25.45. Found: C,48.91; H,2.34; N,25.23.

EXAMPLE 6 Preparation of 3-amino-6(7)-trifluoromethyl-2 < uinoxalinecarbonitrile 1,4-dioxide

A) Preparation 5-trifluoromethylbenzofuroxane 1) Preparation of 4-trifluoromethyl-2-nitrophenylazida Powdered 4-trifluoromethyl-2-nitroaniline (3.50 g, 17 mmol), concentrated HCI (20 mL) and water (60 mL) were stirred at room temperature for 5 min. The mixture was cooled at 0 C and a solution of sodium nitrite (2 g, 29 mmol) in water (10 mL) was added. The insoluble material was discarded and the clear solution was treated with an aqueous solution of sodium azide (2.5 g, 38 mmol) and sodium acetate (50 g, 0.60 mmol). The oil was extracted with ethyl acetate (4 x 50 mL) and the organic layer dried over Na2SO,. After removal of the solvent at room temperature a clear oil was obtained and used without further purification.

2) Preparation of 5-trifluoromethylbenzofuroxane 4-trifluoromethyl-2-nitrophenylazida (2.20 g, 9.4 mmol) was dissolved in toluene and the yellow solution was added dropwise over boiling toluene. After refluxing for 4 h and removal of the solvent a yellowish solid was obtained and used without further purification.

B) According to the procedure described in EXAMPLE 1. (55 %), mp 259-260 C. IR (KBr) 3399-3282, 2230, 1346 cm . 'H NMR (dimethylsulfoxide-d6) 7.96 (d, 1 H, H7, 6 isomer, J= 8.9 Hz), 8.24 (d, 1H, H6 7 isomer, J= 8.9 Hz), 8.47 (s, 4 H, NH2 6(7) isomers), 8.53-8.56 (m, 4 H, H5 H8 and isomers). MS (El) mle (70 eV) M+= 270. ANAL (calc. for C10H5F3N402) C,44.45; H,1.85; N,20.74. Found: C,44.29; H,1.78; N,20.65.

EXAMPLE 7 Preparation of 3-amino-6(7)-(4-nitrophenyl)-2-quinoxalinecarbonitrile 1 ,4-dioxide, hemihydrate

A) Preparation of 5-(4-Nitrophenyl)benzofuroxane 1) Preparation of 4-phenylacetanilide 4-Aminobiphenylo (10 g 59 mmol) and acetic anhydride (20 mL) were stirred and heated at 100 C for 2 h. After cooling at 20 C the mixture was poured into crushed ice and the white solid filtrated and used without further purification.

2) Preparation of 2-nitro-4-(4-nitrophenyl)acetanilide 4-Phenylacetanilide (8.30 g, 39 mmol), 60% nitric acid (20 mL) and concentrated sulfuric acid (4 mL) were heated at 100 C for 2 h. The mixture was allowed to stand at room temperature and was poured into crushed ice. The solid was filtrated and dried (60 C in vacuo).

2-nitro-4(4-nitrophenyl)aniline, 2-nitro-4-(4-nitrophenyl)phenylazide and 5-(4nitrophenyl)benzofuroxane were prepared as described in EXAMPLE 1 and were used without further purification.

B) According to the procedure described in EXAMPLE 1. (22 %), mp 225 C. IR (KBr) 3384-3257, 2231, 1343 cm-1. 1H NMR (dimethylsulfoxide-d6) 7.64-8.53 (m, 7 H, ArH).

MS (El) mle (70 eV) M = 323. ANAL (calc. for C15H9N5O4#0.5 H20) C,54.22; H,3.01; N,21.08. Found: C,54.14; H,2.95; N,20.96.

EXAMPLE 8 Preparation of 7-acetamido-3-amino-2-quinoxalinecarbonitrile 1,4-dioxide

A) 4-Acetamido-2-nitroaniiine was prepared starting from 2-nitro-1,4-phenylendiamine by controlled acetylation. The corresponding azide and benzofuroxane were prepared in the usual fashion as described in EXAMPLE 2.

B) According to the procedure described in EXAMPLE 1. IR (KBr) 3386-3257, 2235, 1341 cm-1; 1 H NMR (dimethylsulfoxidod6) 6 2.11 (s, 3 H, CH3); 7.89 (s, 2 H, NH2); 7.92 (dl 1 H, H6, J = 9.3 Hz); 8.22 (dl 1 H, H6); 8.77 (s, 1 H, H8); 10.52 (s, 1 H, NH). MS (El) m/e (70 eV) M = 259. Anal. (calc for C11H9N5O3) C, 43.32; H, 2.55; N, 25.27. Found C, 43.49; H, 2.60; N, 25.09.

EXAMPLE 9 Preparation of 3-amino-7-methoxy-8-nitro-2-quinoxalinecarbonitrile 1,4-dioxide

A mixture of 3-amino-7-methoxy-2 < ;uinoxalinecarbonitrile 1,4-dioxide (2.00 g, 8.62 mmol) and 60% HNO3 was stirred at room temperature for 10 h. The solution was neutrallized with aqueous HNaCO3 and extracted with ethyl acetate (5 x 100 mL). The organic layer was dried over Na2SO4. After removal of the solvent a red solid was obtained. Flash chromatography was carried on by eluting with a gradient of toluene/ethyl acetate.Finally, the product was recrystallized from ethyl acetate and dried in vacuo at 100 C (P205) (18%); IR (KBr) 3441-3247, 2236, 1544, 1339 cm1;1 H NMR (dimethylsulfoxide-d6) 6 4.04 (s, 3 H, CH3O); 8.02 (d, 1 H, H6, J = 9.8 Hz); 8.13 (s, 2 H, NH2); 8.44 (d, 1 H, H5). MS (El) mle (70 eV) M+= 277. Anal. (calc. for C10H7NsO5) C, 50.96; H, 3.47; N, 27.02. Found C, 50.55; H, 3.58; N, 26.64.

EXAMPLE 10 Preparation of 3-acetamido-7-chloro-2-quinoxalinecarbonitrile 1,4-dioxide

A mixture of 3-amino-7-chloro-2 < uinoxalinecarbonitrile 1,4-dioxide (1.29 g, 5.40 mmol), acetic anhydride (15 mL) and concentrated sulfuric acid (1 mL) was stirred and heated at 90 C for 25 min. The solution was poured into ice-water (100 g).

The resulting precipitate was filtered off and washed with water. Recrystallization from N,N-DMF afforded orange crystals which were washed with diethyl ether (43%), mp 229-230 C. IR (KBr) 3268, 2230, 1702; 1600, 1366, 1325, 739 cm-1.1H NMR (dimethylsulfoxide-d6) 2,30 (s, 3 H, GH3), 8.14 (m, 1 H, H6), 8.50-8.55 (m, 2 H, H5+H8), 11,30 (s, 1 H, NH). MS (El) m/e (70 eV) M+= 278. ANAL (calc. for C11H7ClN4O3) C, 47.40; H, 2.51; N, 20.11. Found: C, 47.32; H.2.49; N, 20.05.

EXAMPLE 11 Preparation of 7-chloPro-3-chloroacetamido-2ffluinoxalinecarbonitrile 1,4-dioxide

Excess chloroacetic anhydride was added over a mixture of 3-amino-7-chloro 2 < juinoxalinecarbonitrile 1,4-dioxide (0.75 g, 3.20 mmol) and dried dioxane (20 mL).

The suspension was stirred at room temperature for 30 min. The precipitated solid was collected and washed with toluene (25 mL) and light petroleum ether (25 mL) (39%), mp 155 C. iR (KBr) 3223, 2197, 1708, 1329, 675 cm-1. 1H NMR (dimethylsulfoxide-d6) 4.57 (s, 2 H, CH2CO); 8.10 (m, 1 H, H5); 8.50 (m, 2 H, H6 H); 11.6 (s, 1 H, NH). MS (El) mle (70 eV) M,-35= 278. ANAL (calc. for C11H6Cl2N4O3) C, 42.17; H, 1.92; N, 17.89. Found: C, 42.50; H, 2.07; N, 17.96.

EXAMPLE 12 Preparation of 3-methylsulfonylamino-2-quinoxalinecarbonitrile 1,4-dioxide

A complete mixture of 3-amino-2quinoxalinecarbonitrile 1,4-dioxide (1.00 g, 4.90 mmol), methanosulfonyl chloride (0.59 g, 0.15 mmol), NaHCO3 (1.009, 12,00 mmol) and dry dioxane (20 mL) was stirred at room temperature for 48 h. The solid was collected and washed with diethyl ether. Recrystallization from dioxane afforded 0.54 g (39 %), mp 255-256 C. IR (KBr) 3413-3325, 2228, 1360 cm'. 'H NMR (dimethylsulfoxide-d6) 3,49 (s, 3 H, CH3), 7.38-7.43 (m, 1 H, H6); 7.70-7.74 (m, 3 H, NH, H5, H7); 8.12 (d, 1 H, H). MS (El) mle (70 eV) M+= 280.ANAL (calc. for Ci0H8N4O4S) C, 42.85; H, 2.85; N, 20.00. Found: C, 43.25; H, 2.93; N, 20.11.

EXAMPLE 13 Preparation of 2-quinoxalinecarbonitrile 1,4-dioxide

Dry N,N-DMF (60 mL) was stirred and heated at 65 C under nitrogen atmosphere. 3-Amino-2-quinoxalinecarbonitrile 1,4-dioxide (2.30 g, 11.39 mmol) was added. Tert-butyl nitrite (4 mL) was added, and following the addition an effervescence was observed (approx. 10 min) giving a dark brown solution. Additional tert-butyl nitrite (3 mL) was injected with a needle, appearing effervescence. The mixture was stirred and heated at 70 C for 15 min, after removal of the solvent a dark waxy solid was obtained. Flash chromatography (toluenelethyl acetate 100113) gave a yellow solid which was recrystallized fron ethyl acetate to give yellow crystals (26 %), mp 195 C.

IR (KBr) 3012, 2240, 1369 cm-1.1H NMR (dimethylsulfoxide-d6) 8.03 (m, 2 H, H6, H7); 8.48 (d, 2 H, H5, H8, J=4.4); 8.91 (s, 1 H, H3). MS (E1) mle (70 eV) M+= 187. ANAL (calc. for C9H5N302) C, 57.75; H, 2.67; N, 22.46. Found: C, 58.07; H, 2.71; N, 22.16.

EXAMPLE 14 Preparation of 7-chloro-2-quinoxalinecarbonitrile 1,4-dioxide

Dry N,N-DMF (45 mL) was stirred and heated at 70 C under nitrogen atmosphere. 3-Amino-6(7)-chloro-2-quinoxalinecarbonitrile 1,4-dioxide (2.00 g, 8.46 mmol) was added. Following tert-butyl nitrite (2 mL) was injected with a needle generating an effervescence (approx. 5 min) giving a dark brown solution. Additional tert-butyl nitrite (2 mL) was necessary for completing the reaction. The mixture was stirred and heated at 70 C for 15 min, after removal of the solvent a dark waxy solid was obtained. Flash chromatography (toluenelethyl acetate 100/15) gave a yellow solid which was recrystallized fron ethyl acetate to give yellow crystals (28 %), mp 179 C.IR (KBr) 3093, 2242, 1367 cm-1.1H NMR (dimethylsulfoxide-d6) 8.05 (m, I H, H6); 8.47 (s, 1 H, H8); 8.50 (m, 1 H, H5); 8.98 (S, 1 H, H3). MS (El) mle (70 eV) M+= 221.

ANAL (calc. for CgH4CIN302) C, 48.76; H, 1.81; N, 18.96. Found: C, 48.59; H, 1.78; N, 19.19.

EXAMPLE 15 Preparation of 6,7-dichloro-2-quinoxalinecarionitrile 1,4-dioxide

Dry N,N-DMF (45 mL) was stirred and heated at 70 C under nitrogen atmosphere. 3-Amino-6,7-dichloro-2-quinoxalinecarbonitrile 1,4-dioxide (1.55 g, 5.72 mmol) was added. Tert-butyl nitrite (2 mL) was added. Following the addition an effervescence was observed (approx. 5 min) giving a dark brown solution. Additional tert-butyl nitrite (2 mL) was necessary to complete the reaction. The mixture was stirred and heated at 70 C for 15 min, after removal of the solvent a dark waxy solid was obtained.Flash chromatography (toluene/ethyl acetate 100/7) gave a yellow solid which was recrystallized fron ethyl acetate to give yellow crysta@s (8 %), mp 206 C. IR (KBr) 3082, 1362 cm-1. 1H NMR (dimethylsulfoxide-d6) 8.67 (s, 1 H, H5); 8.68 (s, 1 H, H8); 9.38 (s, 1 H, H3). MS (El) m/e (70 eV) M+= 255. ANAL (calc. for CgH3CI2N302) C, 42.19; H, 1.17; N, 16.41. Found: C,42.66; H, 1.44; N, 16.27.

EXAMPLE 16 Preparation of 7-methyl-2-quinoxalinecarbonitrile 1,4-dioxide

Dry N,N-DMF (35 mL) was stirred and heated at 70 C under nitrogen atmosphere. 3-Amino-6(7)-methyl-2-quinoxalinecarbonitrile 1,4-dioxide (0.44 g, 2.04 mmol) was added. Tert-butyl nitrite (2 mL) was added. Following the addition an effervescence was observed (approx. 5 min) giving a dark brown solution. Additional tert-butyl nitrite (2 mL) was necessary to complete the reaction. The mixture was stirred and heated at 70 C for 15 min, after removal of the solvent a dark waxy solid was obtained. By flash chromatography (toluene/ethyl acetate 100/13) a yellow solid was obtained which was recrystallized from ethyl acetate to give yellow crystals (29 %), mp 194-195 C.IR (KBr) 3070, 2226, 1360 cm-1.1H NMR (dimethylsulfoxide-d6) 7.90 (d, 1 H, H6, J=8 5 Hz); 8.25 (s, 1 H, Hô); 8.34 (d, 1 H, HS, J=8.6 Hz); 9.23 (s, 1 H, H3). MS (El) mle (70 eV) M+= 201. ANAL (calc. for C1X,H7N302) C, 59.70; H, 3.48; N, 20.89. Found: C, 60.10; H, 3.53; N, 20.58.

EXAMPLE 17 Preparation of 7-methoxy-2-quinoxalinecarbonitrile 1,4-dioxide

Dry N,N-DMF (50 mL) was stirred and heated at 70 C under nitrogen atmosphere. 3-Amino-6(7)-methoxy-2-quinoxalinecarbonitrile 1,4-dioxide (1.70 g, 7.33 mmol) was added. Tert-butyl nitrite (2 mL) was added. Following the addition an effervescence was observed (approx. 5 min) giving a dark brown solution. Additional tert-butyl nitrite (2 mL) was necessary to complete the reaction. The mixture was stirred and heated at 70 C for 15 min. After removal of the solvent a dark waxy solid was obtained. Flash chromatography (toluene/ethyl acetate 100/40) gave a yellow solid which was recrystallized fron ethyl acetate to give yellow crystals (26 %), mp 225 'C.IR (KBr) 3103, 2237, 1360 cm' tH NMR (dimethylsulfoxide-d6) 4.03 (s, 3 H, CH3O); 7.61 (dl 1 H, H6, J= 9.5 Hz); 7.74 (s, 1 H, H8); 8.40 (d, 1 H, H5, J= 9.6 Hz); 8.78 (s, 1 H, H3). MS (El) mie (70 eV) M+= 217. ANAL (calc. for C10H7N303) C. 55.30; H, 3.23; N, 19.35. Found: C, 55.52; H, 3.26; N, 19.41.

EXAMPLE 18 Preparation of 6-trifluoromethyl-2-quinoxalinecarbonitrile 1,4-dioxide and 7trifluoromethyl-2-quinoxalinecarbonitrile 1,4-dioxide

Dry N,N-DMF (50 mL) was stirred and heated at 70 C under nitrogen atmosphere. 3-Amino-6(7)-trifluoromethyl-2-quinoxalinecarbonitrile 1,4-dioxide (1.55 g, 5.74 mmol) was added. Tert-butyl nitrite (2 mL) was added. Following the addition an effervescence was observed (approx. 5 min) giving a dark brown solution. Additional tert-butyl nitrite (2 mL) was necessary to complete the reaction. The mixture was stirred and heated at 70 C for 15 min, after removal of the solvent a dark waxy solid was obtained.By flash chromatography (toluene/ethyl acetate 100/10) was obtained a yellow solid which was recrystallized fromn ethyl acetate to give yellow crystals (4 %) of the 6-trifluoromethyl isomer, mp 181-183 C. IR (KBr) 3092, 2200, 1372 cm-1. 1H NMR (dimethylsulfoxide-d6) 8.32 (d, 1 H, H8, J= 8.6 Hz); 8.70 (d, 1 H, H7, J= 9.1 Hz); 8.76 (s, 1 H, H5); 9.08 (s, 1 H, H3). MS (El) m/e (70 eV) M+= 255. ANAL (calc. for C10H4F3N3O2) C, 48.60; H, 1.82; N, 15.90. Found: C, 48.44; H, 2.02; N, 16.26. Further elution with toluene/ethyl acetate (100J12) gave the 7-trifluoromethyl isomer, which was recrystallized from ethyl acetate (11 %), mp 161 C. IR (KBr) 3107, 1370cm1. 'H NMR (dimethylsulfoxide-d,) 8.33 (d, 1 H, H5, J= 8.4 Hz); 8.71 (d, 1 H, H6, J= 9.0 Hz); 8.73 (s, 1 H, H8); 9.08 (s, 1 H, H3). MS (El) m/e (70 eV) M+= 255. ANAL (calc. for C10H4F3N3O2) C, 48.60; H, 1.82; N, 15.90. Found: C, 48.75; H, 2.05; N, 16.18.

EXAMPLE 19 Preparation of 7-(4-nitrophenyl)-2-quinoxalinecarbonitrile 1,4-dioxide

Dry N,N-DMF (50 mL) was stirred and heated at 70 C under nitrogen atmosphere. 3-Amino-6(7)-(4-nitrophenyl)-2 < uinoxaiinecarbonitriile 1,4-dioxide (1.82 g, 5.63 mmol) was added. Tert-butyl nitrite (2 mL) was added. Following the addition an effervescence was observed (approx. 5 min) giving a dark brown solution.

Additional tert-butyl nitrite (2 mL) was necessary to complete the reaction. The mixture was stirred and heated at 70 C for 15 min, after removal of the solvent a dark waxy solid was obtained. Flash chromatography (toluene/ethyl acetate 100/8) gave a yellow solid which was recrystallized fron ethyl acetate to give yellow crystals (21 %), mp 232 C. IR (KBr) 3081, 2237, 1365 cm1. 1H NMR (dimethylsulfoxide-d6) 8.21 (d, 2 H, Hz, H6., J= 8.7 Hz); 8.39 (d, 2 H, H3', H5., J= 8.7 Hz); 8.46 (d, 1 H, H6, J= 9.2 Hz); 8.60 (d, 1 H, H5, J= 8.9 Hz); 8.75 (s, 1 H, H8); 9.38 (s, 1 H, H3). MS (El) m/e (70 eV) M+= 308.

ANAL (calc. for C,5ltBN404) C, 58.44; H, 2.60; N, 18.18. Found: C, 58.40; H, 2.64; N, 18.02.

EXAMPLE 20 Preparation of 3-chloro-2-quinoxalinecarbonitrife 1,4-dioxide

A suspension of acetonitrile (40 mL) and CuCl2 (3.46 g) was stirred and heated at 70 C under N2 atmosphere. 3-Amino-2quinoxalinecarbonitrile 1,4-dioxide (2.36 g, 11.68 mmol) was added. Tert-butyl nitrite (2 x 2 mL) was injected each 20 min. The mixture was heated at 70 C for 15 min. Then was allowed to stand at Xoom temperature. Inorganic salts were filtered off and extracted with dichloromethane (300 mL), and after removal of the solvents a brown-yellowish waxy solid was obtained.

The residue was chromatographied by eluting with a gradient of toluene/ethyl acetate (100/8) giving a yellow solid. Recrystallization from ethyl acetate afforded yellow crystals (8 %), mp 197-198 C. IR (KBr) 3102, 2237, 1344 cm1. 'H NMR (dimethylsulfoxide-d6) 7.99 (t, 2 H, H6, H7, J= 8.4 Hz); 8.58 (d, 1 H, H5, J= 8.1 Hz); 8.67 (d, 1 H, Hs, J= 8.3 Hz). MS (El) mie (70 eV) M+= 221. ANAL (calc. for CgH4CIN302) C, 48.76; H, 1,81; N, 18.96. Found: C, 48.98; H, 2.02; N, 18.72.

EXAMPLE 21 Preparation of 3,7-dichloro-2-quinoxalinecarbonitrile 1,4-dioxide

A suspension of acetonitrile (100 mL), CuCI2 (6.78 g) was stirred and heated at 70 "C under N2 atmosphere. 3-Amino-6(7)-chloro-2-quinoxalinecarbonitrile 1 ,4-dioxide (5.00 g, 21.14 mmol) was added. Tert-butyl nitrite (2 x 2 mL) was injected each 20 min. The mixture was heated at 70 C for 15 min and then was allowed to stand at room temperature. Inorganic salts were filtered off and extracted with dichloromethane (300 mL), and after removal of the solvents a brown-yellowish waxy solid was obtained. The residue was chromatographied by eluting with a gradient of toluene/ethyl acetate (100/13) giving a yellow solid.Finally, recrystallization from ethyl acetate afforded yellow crystals (16 %), mp 225-226 C. IR (KBr) 3092, 2237, 1338 cm'.'H NMR (dimethylsulfoxide-d6) 8.16 (d, 1 H, H6, J= 9.2 Hz); 8.50 (s, 1 H, H8); 8.52 (d, 1 H, H5, J= 8.9 Hz). MS (El) m/e (70 eV) M = 255. ANAL (calc. for C9H3Cj2N302) C,42.19; H, 1.17; N, 16.41. Found: C, 42.20; H, 1.12; N, 16.35.

EXAMPLE 22 Preparation of 3-chloro-7-methyl-2-quinoxalinecarbonitrile 1,4-dioxide

A suspension of acetonitrile (100 mL), CuCI2 (10.00 g) was stirred and heated at 70 C under N2 atmosphere. 3-Amino-6(7)-methyl-2-quinoxalinecarbonitrile 1,4dioxide (5.50 g, 25.46 mmol) was added. Tert-butyl nitrite (2 x 2 mL every 20 min) was injected. The mixture was heated at 700C for 15 min and was allowed to stand at room temperature. Inorganic salts were filtered off and extracted with dichloromethane (300 mL), and after removal of the solvents a brown-yellowish waxy solid was obtained.

The residue was chromatographied by eluting with a gradient of toluene/ethyl acetate (100/15) giving a yellow solid. Recrystallization from ethyl acetate afforded yellow crystals (10 %), mp 210 "C. IR (KBr) 3078, 2237, 1344 cm-1. 'H NMR (dimethylsulfoxide-d6) 2.51 (s, 3 H, CH3); 7.97 (d, 1 H, H6, J= 8.7 Hz); 8.29 (s, 1 H, H8); 8.41 (d, 1 H, H5, J= 8.6 Hz). MS (El) mle (70 eV) M = 235. ANAL (calc. for C,0H6CIN302) C. 50.95; H, 2.55; N, 17.83. Found: C, 50.67; H, 2.52; N, 17.52.

EXAMPLE 23 Preparation of 3-chloro-7-methoxy-2-quinoxalinecarbonitrile 1,4-dioxide

A suspension of acetonitrile (70 mL), CuCI2 (8.23 g) was stirred and heated at 70 C under N2 atmosphere. 3-Amino6(7)-methoxy-2 < luinoxalinecarbonitrile 1,4dioxide (3.37 g, 14.53 mmol) was added. Tert-butyl nitrite (2 x 2 mL each 20 min) was injected. The mixture was heated at 70 C for 15 min and then was allowed to stand at room temperature. Inprganic salts were filtered off and extracted with dichloromethane (300 mL), and after removal of the solvents a brown waxy solid was obtained. The residue was chromatographied by eluting with a gradient of toluene/ethyl acetate (100/10) giving a yellow solid. Finally, recrystallization from ethyl acetate afforded yellow crystals (16 %), mp 218-220 C.IR (KBr) 3103, 2237, 1328 cm1. 'H NMR (dimethylsulfoxide-d,) 4.03 (s, 3 H, CH30); 7.73 (d, 1 H, H6, J= 7.5 Hz); 7.75 (s, 1 H, H8); 8.43 (d, 1 H, H5). MS (El) m/e (70 eV) M = 251. ANAL (calc. for C10H6CIN303) C, 47.71; H, 2.39; N, 16.70. Found: C,47.38; H, 2.38; N, 16.59.

EXAMPLE 24 Preparation of 3-chloro-6(7)-fluoro-2-quinoxalinecarbonitrile 1,4-dioxide

A suspension of acetonitrile (45 mL), CuCI2 (4.80 g) was stirred and heated at 70 C under N2 atmosphere. 3-Amino-6(7)-fluoro-2 < luinoxalinecarbonitrile 1,4-dioxide (3.70 g, 16.82 mmol) was added. Tert-butyl nitrite (2 x 2 mL each 20 min) was injected. The mixture was heated at 700C for 15 min and then was allowed to stand at room temperature. Inorganic salts were filtered off and extracted with dichloromethane (300 mL), and after removal of the solvents a brown waxy solid was obtained. The residue was chromatographied by eluting with a gradient of toluene/ethyl acetate (100/6) giving a yellow solid.Recrystallization from ethyl acetate afforded yellow crystals (21 %), mp 127-128 C. HPLC analyses showed a mixture of 6 and 7 isomers in a ratio of 39/61. IR (KBr) 3103, 2237, 1339 cm-1. 'H NMR (dimethylsulfoxide-d6) 7.84 (m, 2 H, H6 7 isomer, H7 6 isomer); 8.30 (s, 1 H, H5 6 isomer); 8.34 (s, 1 H, H8 7 isomer); 8.78 (d, 1 H, H5 7 isomer, J= 9.4 Hz); 8.80 (d, 1 H, H8 6 isomer, J= 9.3 Hz).

MS (El) m/e (70 eV) M = 239. ANAL (calc. for C9H3CIFN302) C, 45.09; H, 1.25; N, 17.54. Found: C, 45.31; H, 1.18; N, 17.59.

EXAMPLE 25 Preparation of 3-chloro-7-trifluoromethyi-2 < uinoxalinecarbonitrile 1,4-dioxide

A suspension of acetonitrile (50 mL), CuCI2 (6.37 g) was stirred and heated at 80 C under N2 atmosphere. 3-Amino-6(7)-trifluoromethyl-2 < uinoxalinecarbonitrile 1,4-dioxide (5.00 g, 18.52 mmol) was added. Tert-butyl nitrite (2 x 2 mL each 20 min) was injected. The mixture was heated at 700C for 15 min and then was allowed to stand at room temperature. Inorganic salts were filtered off and extracted with dichloromethane (300 mL), and after removal of the solvents a brown waxy solid was obtained. The residue was chromatographied by eluting with a gradient of toluene/ethyl acetate (100/2) giving a yellow solid. Recrystallization from ethyl acetate afforded yellow crystals (13 %), mp 230-232 C.IR (KBr) 3103, 2237, 1349 cm-1. 1H NMR (dimethylsulfoxide-d6) 8.41 (d, 1 H, H6, J= 9.1 Hz); 8.71 (d, 1 H, H5, J= 9.0 Hz); 8.80 (s, 1 H, H8). MS (El) mle (70 eV) M+= 289. ANAL (calc. for C,oH3CIF3N302) C, 41.45; H, 1.04; N, 14.51. Found: C, 41.39; H, 0.96; N, 14.39.

EXAMPLE 26 Preparation of 3-[3-(N,N-dimethylamino)propylamino]-2-quinoxalinecarbonitrile 1,4dioxide1 hydrochloride

3-Chloro-2-quinoxalinecarbonitrile 1,4-dioxide (150 mg, 0.68 mmol) was dissolved in dichloromethane (200 mL) and K2CO3 (94 mg, 0.68 mmol) was added. 3 (N,N-dimethylamino)-1-propylamino (71 mg, 0.70 mmol) was added dropwise. The mixture was stirred for 3 days at room temperature. Inorganic salts were filtered off and the solvent was removed by rotatory evaporation. Flash chromatography was carried out by using a gradient of ethyl acetate/methanol giving a red solid, which was dissolved in dry acetone. Addition of 3-5 drops of concentrated HOl gave a red precipitate which was recrystallized from acetone (53 %), mp 201 C.IR (KBr) 3220, 2942, 2761, 2226, 1360cm1.1 H NMR (dimethylsulfoxide-d6) 1.78 (q, 2 H, CH2, J= 6.5 Hz); 2.12 (s, 6 H, 2 CH3); 2.30 (t, 2 H, CH2N, J= 6.3 Hz); 3.70 (c, 2 H, NHCH2); 7.61 (t, 1 H, He, J= 7.7 Hz); 7.88 (t, 1 H, H7, J= 7.6 Hz); 8.23 (d, 2 H, H5, He, J= 8.6 Hz). MS (El) m/e (70 eV) M+= 287. ANAL (calc. for C14H17N5O2.HCl) C, 51.93; H, 5.56; N, 21.64. Found: C, 52.01; H, 5.75; N, 21.55.

EXAMPLE 27 Preparation of 7-chloro-3-[3-N,N-dimethylamino)propylamino]-2quinoxalinecarbonitrile 1,4-dioxide, hydrochloride

3,7-Dichloro-2-quinoxalinecarbonitrile 1,4-dioxide (0.51 g, 1.99 mmol) was dissolved in dichloromethane (250 mL) and K2CO3 (0.27 g, 1.99 mmol) was added. 3 (N,N-dimethylamino)-1-propylamino (0.21 g, 2.06 mmol) was added dropwise. The mixture was stirred for 3 days at room temperature. Inorganic salts were filtered off and the solvent was removed by rotatory evaporation. Flash chromatography was carried out by using a gradient of ethyl acetate/methanol giving a red solid, which was dissolved in dry acetone.Addition of 3-5 drops of concentrated HCI gave a red precipitate which was recrystallized from acetone/methanol (85 %), mp 201 "C. IR (KBr) 3241, 3070, 2953, 2226, 1595, 1339. 1178, 644 cm1 'H NMR (dimethylsulfoxide-d6) 2.21 (q, 2 H, CH2, J= 7.5 Hz); 2.73 (s, 6 H, 2 CH3); 3.09 (t, 2 H, CH2N, J= 7.5 Hz); 3.77 (c, 2 H, NHCH2, J= 6.5 Hz); 7.97 (d, 1 H, H6, J= 9.2 Hz); 8.30 (d, 1 H, H5, J= 8.9 Hz); 8.30 (s, 1 H, HB); 8.58 (t, 1 H, NH); 10.51 (bs, 1 H, HCI). MS (El) mie (70 eV) M = 321. ANAL (calc. for C14H16CIN502 HCI) C, 46,93; H, 4,75; N, 19,55. Found: C, 47,12; H, 4,93; N, 19,38.

EXAMPLE 28 Preparation of 3-[3-(N,N-dimethylamino)propylamino]-7-methyl-2quinoxalinecarbonitrile 1,4-dioxide, hydrochloride

3-Chloro-7-methyl-2-quinoxalinecarbonitrile 1,4-dioxide (0,23 9, 0.98 mmol) was dissolved in dichloromethane (150 mL) and K2CO3 (0,14 91 1.00 mmol) was added. Afterwards 3-(N,N-dimethylamino)-1-propylamino (0,107 9, 1.05 mmol) was added dropwise. The mixture was stirred for 3 days at room temperature. Inorganic salts were filtered off and the solvent was removed by rotatory evaporation. Flash chromatography was carried out by using a gradient of ethyl acetate/methanol giving a red solid, which was dissolved in dry acetone.Addition of 3-5 drops of concentrated HCI gave a red precipitate which was recrystallized from acetone/methanol and identified as the 7 isomer (39 %), mp 203 0C. lR (KBr) 3223, 2943, 2764, 2226, 1576, 1351 cm1. 1H NMR (dimethylsulfoxide-d6) 2.12 (q, 2 H, CH2, J= 7.1 Hz); 2.58 (s, 3 H, Ar-CH3); 2.76 (s, 6 H, 2 CH3); 3.12 (t, 2 H, CH2N); 3.78 (c, 2 H, NHCH2, J= 6.4 Hz); 7.81 (d, 1 H, H6, J= 8.7 Hz); 8.12 (s, 1 H, H8); 8.22 (d, 1 H, H5, J= 8.8 Hz); 8.42 (t, 1 H, NH); 10.63 (bs, 1 H, HCI). MS (El) m/e (70 eV) M = 284. ANAL (calc. for C15H19N502.HC() C, 53.33; H, 5.93; N, 20.74. Found: C, 53.14; H, 6.14; N, 20.46.

EXAMPLE 29 Preparation of 3-[3-(N,N-dimethylamino)propylamino3-7-methoxy-2- quinoxalinecarbonitrile 1,4-dioxide, bishydrochloride, 1.5 hydrate

3-Cloro-7-methoxy-2-quinoxalinecarbonitrile 1,4-dioxide (0,20 g, 0.80 mmol) was dissolved in dichloromethane (150 mL) and K2CO3 (0.11 9, 0.80 mmol) was added. 3-(N,N-dimethylamino)-1-propylamino (0,087 9, 0.85 mmol) was added dropwise. The mixture was stirred for 3 days at room temperature. Inorganic salts were filtered off and the solvent was removed by rotatory evaporation. Flash chromatography was carried out by using a gradient of ethyl acetate/methanol giving a red solid, which was dissolved in dry acetone. Addition of 3-5 drops of concentrated HCI gave a red precipitate which was recrystallized from acetone/methanol (60 %), mp 172-173 C.IR (KBr) 3370-3306, 3028, 2942, 2718, 2226, 1600, 1376, 1275, 1237 cm-1.1H NMR (dimethylsulfoxide-d6) 2.07 (q, 2 H, CH2); 2.69 (s, 6 H, 2 CH3); 3.07 (t, 2 H, CH2N); 3.74 (c, 2 H, NHCH2, J= 6.2 Hz); 3.92 (s, 3 H, OCH3); 7.56 (s, 1 H, H8); 7.58 (d, 1 H, H6, J= 8.0 Hz); 8.20 (d, 1 H, H5, J= 9.9 Hz); 8.29 (t, 1 H, NH); 11.00 (bs, 1 H, HCI). MS (El) mie (70 eV) M+= 317. ANAL (calc. for C15H19N5O3#2HCl#1.5H2O) C, 43.16; H, 5.76; N, 16.79. Found: C, 43.21; H, 5.86; N, 16.55.

EXAMPLE 30 Preparation of 3-[3-(N,N-dimethylamino)propylamino]-7-fluoro-2quinoxalinecarbonitrile 1,4-dioxide, hydrochloride, hydrate

3-cloro-6(7)-fluoro-2-quinoxalinecarbonitrile 1,4-dioxide (0,122 g, 0.51 mmol) was dissolved in dichloromethane (100 mL) and K2CO3 (0,071 9, 0.51 mmol) was added. 3-(N,N-dimethylamino)-1-propylamino (0,054 9, 0.53 mmol) was added dropwise. The mixture was stirred for 3 days at room temperature. Inorganic salts were filtered off and the solvent was removed by rotatory evaporation. Flash chromatography was carried out by using a gradient of ethyl acetate/methanol giving a red solid, which was dissolved in dry acetone.Addition of 3-5 drops of concentrated HCI gave a red precipitate which was recrystallized from acetone/methanol and identified as the 7 isomer (77 %), mp 170 C. IR (KBr) 3380, 2958, 2457, 2219, 1586, 1336 cm'.'H NMR (dimethylsulfoxide-d6) 2.01 (q, 2 H, CH2); 2.72 (s, 6 H, 2 CH3); 3.14 (t, 2 H, CH2N); 3.78 (c, 2 H, NHCH2); 8.08 (d, 1 H, H61 J= 8.2 Hz); 8.23 (m, 2 H, H5 H8); 8.45 (t, 1 H, NH); 10.83 (bs, 1 H, HCI). MS (El) m/e (70 eV) M+= 305. ANAL (calc. for C14H,6FNsO2 HCl H2O) C, 46.73; H, 5.28; N, 19,47. Found: C. 46.48; H, 5.65; N, 19.05.

EXAMPLE 31 Preparation of 3-13-(N,Ntimethylamino)propylamino]-7-trifluorometil-2- quinoxalinecarbonitrile 1,4-dioxide, hydrochloride, hemihydrate

3-cloro-(6)7-trifiuorometil-2q uinoxalinecarbonitrile 1,4-dioxide (0,46 9, 1.59 mmol) was dissolved in dichloromethane (300 mL) and K2CO3 (0,221 g, 1.60 mmol) was added. 3-(N,N-dimethylamino)-1-propylamino (0,166 g, 1.63 mmol) was added dropwise. The mixture was stirred for 3 days at room temperature. Inorganic salts were filtered off and the solvent was removed by rotatory evaporation. Flash chromatography was carried out by using a gradient of ethyl acetate/methanol giving a red solid, which was dissolved in dry acetone.Addition of 3-5 drops of concentrated HCI gave a red precipitate which was recrystallized from acetone/methanol and identified as the 7 isomer (16 %), mp 177 C. IR (KBr) 3412, 3188, 2953, 2451, 2226, 1563, 1339 cm-1.1H NMR (dimethylsulfoxide-d6) 2.10 (q, 2 H, CH2, J= 7.6 Hz); 2.75 (s, 6 H, 2 CH3); 3.10 (t, 2 H, CH2N, J= 7.6 Hz); 3.80 (c, 2 H, NHCH2, J= 6.4 Hz); 7.96 (dl H, H6, J= 8.9 Hz); 8.51 (d, 1 H, Hs, J= 10.5 Hz); 8.54 (s, 1 H, HB); 8.73 (t, 1 H, NH); 10.18 (bs, 1 H, HCI). MS (El) m/e (70 eV) M+= 355. ANAL (calc. for CisHisFaNsO2 HCI 0,5 H2O) C, 44.94; H, 4.49; N, 17.48. Found: C, 45.16; H, 4.36; N, 17.02.

EXAMPLE 32 Preparation of 3-[2-(N,N4iethylamino)ethylamino3-2-quinoxalinecarbonitrile 1 ,4- dioxide, hydrochloride. 0.25 hydrate

A mixture of 3-chloro-2 < ;uinoxalinecarbonitrile 1,4 dioxide (0,23 g, 1.04 mmol), K2CO3 (0,145 g, 1.05 mmol), 2-(N,N-diethylamino)ethylamino (0,123 g, 1.06 mmol) and CH2CI2 (100 mL) was stirred at room temperature for 3 days. Inorganic salts were filtered off and, after removal of the solvent, a red solid was obtained. Flash chromatography by eluting with a gradient of AcOEt/MeOH gave a red compound, which was redissolved in acetone. The solution was treated with 34 drops of concentrated HCI and the red solid was filtered. Recrystallization from acetone afforded red crystals (28%), mp 176 C.IR (KBr) 3177, 2953, 2654-2579, 2451, 2226, 1568, 1349 cm-1.1H NMR (dimethylsulfoxide-d6) 1.27 (t, 6 H, 2 CH3, J= 7.1 Hz); 3.19 (c, 4 H, 2 NCH2); 3.41 (t, 2 H, CH2N); 4.12 (c, 2 H, NHCH2, J= 6.2 Hz); 7.71 (t, 1 H, H6, J= 7.7 Hz); 7.97 (t, 1 H, H7, J= 7.7 Hz); 8.32 (d, 2 H, H5 H8); 8.55 (t, 1 H, NH); 10.83 (bs. 1 H, HCI). MS (El) m/e (70 eV) M = 284. ANAL (calc. for Cl5H19N502 HCI 0,25 H2O) C, 52.63; H, 5.99; N, 20.47. Found: C, 52.54; H, 6.02; N, 20.58.

EXAMPLE 33 Preparation of 7-chloro-3-[2-(N,N-diethylamino)ethylamino]-2-quinoxalinecarbonitrile 1,4-dioxide. hydrochloride, hemihydrate

A mixture of 3,7-dichloro-2-quinoxalinecarbonitrile 1,4-dioxide (0,111 9, 0.43 mmol), K2CO3 (0,060 g, 0.43 mmol), 2-(N,N-diethylamino)ethylamino (0,055 g, 0.47 mmol) and CH2CI2 (75 mL) was stirred at room temperature for 3 days. Inorganic salts were filtered off and, after removal of the solvent, a red solid was obtained. Flash chromatography by eluting with a gradient of AcOEt/MeOH gave a red compound, which was redissolved in acetone. The solution was treated with 34 drops of concentrated HCI and the red solid was filtered. Recrystallization from acetone afforded red crystals (70%), mp 165-166 C. IR (KBr) 3412, 3092, 2974, 2643, 2226, 1595, 1349 cm-1.1H NMR (dimethylsulfoxide-d6) 1.25 (t, 6 H, 2 CH3, J= 7.0 Hz); 3.19 (c, 4 H, 2 NCH2); 3.35 (t, 2 H, CH2N); 4.10 (c, 2 H, NHCH2, J= 6.0 Hz); 7.98 (d, I H, He, J= 7.7 Hz); 8.30 (t, 1 H, H5, J= 6.2 Hz); 8.31 (s, 1 H, H8); 8.64 (t, 1 H, NH, J= 6.4 Hz); 10.87 (bs, 1 H, HCI). MS (El) m/e (70 eV) M = 335. ANAL (calc. for 015H18C1N502HCI0,5 H20) C, 47.24; H, 5.25; N, 18.37. Found: C, 47.29; H, 5.58; N, 18.04.

EXAMPLE 34 Preparation of 3-[2-(N,N-diethylamino)ethylamino]-7-methyl-2-quinoxalinecarbonitrile 1,4-dioxide, hydrochloride

A mixture of 3-chloro-7-methyl-2-quinoxalinecarbonitrile 1,4-dioxide (0,21 9, 0.89 mmol), K2CO3 (0,123 g, 0.89 mmol), 2-(N,N-diethylamino)ethylamino (0,107 g, 0.92 mmol) and CH2CI2 (100 mL) was stirred at room temperature for 3 days.

Inorganic salts were filtered off and, after removal of the solvent, a red solid was obtained. Flash chromatography by eluting with a gradient of AcOEtZMeOH gave a red compound, which was redissolved in acetone. The solution was treated with 34 drops of concentrated HCI and the red solid was filtered. Recrystallization from acetone afforded red crystals (37%), mp 122-123 C. IR (KBr) 3412, 3060, 2964, 2632, 2226, 1576, 1346 cm-'. 'H NMR (dimethylsulfoxide-d6) 0.99 (t, 6 H, 2 CH3, J= 6.2 Hz); 2.47 (s, 3 H, Ar-CH3); 2.62 (c, 4 H, 2 NCH2); 2.81 (t, 2 H, CH2N); 3.75 (c, 2 H, NHCH2); 7.75 (d, 1 H, H6, J= 8.7 Hz); 8.06(s, 1 H, H8); 8.15 (t, 1 H, H5, J= 8.8 Hz); 8.17 (t, 1 H, NH).

MS (El) m/e (70 eV) M+= 298. ANAL (calc. for C,6H21NsO2 HCI) C, 54.62; H, 6.26; N, 19.91. Found: C, 54.52; H, 6.02; N, 19.53.

EXAMPLE 35 Preparation of 3-[2-(N,N-diethylamino)ethylamino]-7-methoxy-2-quinoxalinecarbonitrile 1,4-dioxide, hydrochloride, hemihydrate

A mixture of 3-chloro-7-methoxy-2-quinoxalinecarbonitrile 1,4-dioxide (0,53 9, 2.11 mmol), K2CO3 (0,29 g, 2.12 mmol), 2-(N,Naiethylamino)ethylamino (0,25 9, 2.15 mmol) and CH2CI2 (150 mL) was stirred at room temperature for 3 days. Inorganic salts were filtered off and, after removal of the solvent, a red solid was obtained. Flash chromatography by eluting with a gradient of AcOEt/MeOH gave a red compound, which was redissolved in acetone. The solution was treated with 34 drops of concentrated HCI and the red solid was filtered. Recrystallization from acetone afforded red crystals (14 %), mp 153 C.IR (KBr) 3412, 3414, 2921, 2606, 2224, 1576, 1352 cm-1.1H NMR (dimethylsulfoxide-d6) 1.30 (t, 6 H, 2 CH3, J= 7.0 Hz); 3.23 (c, 4 H, 2 NCH2); 3.42 (t, 2 H, CH2N); 3.99 (s, 3 H, OCH3); 4.11 (c, 2 H, NHCH2, J= 6.0 Hz); 7.63 (s, 1 H, H8); 7.65 (d, 1 H, H6, J= 7.8 Hz); 8.28 (d, 1 H, H5); 8.35 (t, 1 H, NH); 10.63 (bs, 1 H, HCI). MS (El) mie (70 eV) M+= 331. ANAL (calc. for C16H21N503HCl0.5H2O) C, 51.00; H, 6.11; N, 18.59. Found: C, 51.24; H, 6.24; N, 18.45.

EXAMPLE 36 Preparation of 3-[2-(N,N-diethylamino)ethylamino]-7-fluoro-2-quinoxalinecarbonitrile 1,4-dioxide, hydrochloride, 0.6 hydrate

A mixture of 3-chloro-6(7)-fluoro-2-quinoxalinecarbonitrile 1,4-dioxide (0,18 9, 0.74 mmol), K2CO3 (0,105 9, 0.76 mmol), 2-(N,N-diethylamino)ethylamino (0,09 9, 0.78 mmol) and CH2CI2 (100 mL) was stirred at room temperature for 3 days.

Inorganic salts were filtered off and, after removal of the solvent, a red solid was obtained. Flash chromatography by eluting with a gradient of AcOEtlMeOH gave a red compound, which was redissolved in acetone. The solution was treated with 34 drops of concentrated HCI and the red solid was filtered. Recrystallization from acetone afforded red crystals (53 %), mp 186 C. IR (KBr) 3412, 3423, 3092, 2964, 2643, 2226, 1579, 1349 cm1. 'H NMR (dimethylsulfoxide-d6) 1.21 (t, 6 H, 2 CH3, J= 6.8 Hz); 3.11 (c, 4 H, 2 NCH2); 3.50 (t, 2 H, CH2N); 4.03 (c, 2 H, NHCH2); 7.90 (d, 1 H, H6, J= 7.6 Hz); 8.10 (m, 2 H, H5, H8); 8.38 (bs, 1 H, NH). MS (El) mie (70 eV) M+= 319.ANAL (calc. for C15H16FN5O2#HCl#0.6H2O) C, 49.14; H, 5.51; N, 19.11. Found: C, 49.01; H, 5.67; N, 18.81.

EXAMPLE 37 Preparation of 3-[2-(N,N-diethylamino)ethylamino]-7-trifluoromethyl-2quinoxalinecarbonitrile 1,4-dioxide, hydrochloride

A mixture of 3-chloro-7-trifluoromethyl-2-quinoxalinecarbonitrile 1,4-dioxide (0,19 g, 0.66 mmol), K2CO3 (0,091 g, 0.66 mmol), 2-(N,N-diethylamino)ethylamino (0,081 9, 0.70 mmol) and CH2CI2 (75 mL) was stirred at room temperature for 3 days.

Inorganic salts were filtered off and, after removal of the solvent, a red solid was obtained. Flash chromatography by eluting with a gradient of AcOEt/MeOH gave a red compound, which was redissolved in acetone. The solution was treated with 34 drops of concentrated HCI and the red solid was filtered. Recrystallization from acetone afforded red crystals (30 %), mp 176-177 C. IR (KBr) 3209, 3092, 2974, 2397, 2237, 1574, 1360 cm-1 1H NMR (dimethylsulfoxide-d6) 1.26 (t, 6 H, 2 CH3, J= 6.9 Hz); 3.19 (c, 4 H, 2 NCH2, J= 6.5 Hz); 3.37 (t, 2 H, CH2N); 4.15 (c, 2 H, NHCH2); 7.99 (d, 1 H, H6, J= 9.0 Hz); 8.53 (d, 1 H, H5, J= 11.0 Hz); 8.55 (s, 1 H, H8); 8.79 (t, 1 H, NH); 10.81 (bs, 1 H, HCI). MS (El) mle (70 eV) M = 369.ANAL (calc. for C,6H18F3N502 HCI) C, 47.35; H, 4.69; N, 17.26. Found: C, 47.62; H, 4.84; N, 17.12.

EXAMPLE 38 Preparation of 6-chloro-3-[3-(4-morpholinyl)propylamino]-2-quinoxalinecarbonitrile 1,4dioxide, hydrochloride, and 7-chloro-3-[3-(4-morpholinyl)propylamino quinoxalinecarbonitrile 1,4-dioxide, hydrochloride

A mixture of 3,6(7)-dichloro-2-quinoxalinecarbonitrile 1,4-dioxide (0,37 g, 1.44 mmol), K2CO3 (0,20 9, 1.45 mmol), 4-(3-aminopropyl)morpholine (0,213 mg, 1.48 mmol) and CH2CI2 (250 mL) was stirred at room temperature for 4 days. The inorganic salts were discarded and the solvent removed by evaporatory rotation. The solid residue was chromatographied with a gradient of ethyl acetate/methanol. Firstly, the isomer 6 was eluted.After removal of the solvent the red solid was redissolved in acetone and precipitated as the hydrochloride salt by addition of Hcl concentrated (2 drops). Finally it was recrystallized from acetone/methanol (6%), mp 190-191 C. IR (KBr) 3423, 3198, 2932, 2547, 2226, 1574, 1349 cm-1 1H NMR (dimethylsulfoxide-d6) 2.16 (q, 2 H, CH2, J= 7.2 Hz); 3.13 (t, 2 H, CH2N); 3.32 (t, 4 H, CH2N morpholino); 3.82 (c, 2 H, NHCH2); 4.14 (t, 4 H, CH2Q morpholino); 7.70 (d, 1 H, Hz, J= 9.1 Hz); 8.29 (s, 1 H, H5); 8.31 (d, 1 H, Ha, J= 9.4 Hz); 8.64 (t, 1 H, NH); 11.14 (bs, 1 H, HCI). MS (El) m/e (rel. intensity, 70 eV) M+= 346. ANAL (calc. for C16H18CIN5O3.HCl) C, 48.00; H, 4.75; N, 17.50. Found: C, 48.04; H, 4.83; N, 17.48. The 7-chloro isomer was eluted later.After removal of the solvent the red solid was redissolved in acetone and precipitated as the hydrochloride salt, which was recrystallized from acetone/methanol (37%), mp 180-181 C. IR (KBr) 3423, 3198, 2932, 2547, 2226, 1574, 1349 cm1.1 H NMR (dimethylsulfoxide-d6) 2.14 (m, 2 H, CH2); 3.17 (t, 2 H, CH2N); 3.34 (t, 4 H, CH2N morpholino); 3.77 (c, 2 H, NHCH2); 3.93 (t, 4 H, CH20 morpholino); 7.98 (d, 1 H, H6, J= 9.3 Hz); 8.29 (s, 1 H, H8); 8.31 (d, 1 H, H5, J= 9.1 Hz); 8.59 (t, 1 H, NH); 10.75 (bs, 1 H, HCI). MS (El) m/e (70 eV) M = 346. ANAL (calc. for C16H18Cl3N5O3#HCl) C, 48.00; H, 4.75; N, 17.50. Found: C, 47.60; H, 5.04; N, 17.82.

EXAMPLE 39 Preparation of 3-(4'-butylphenyl)amino-7-chloro-2 < uìnoxalinecarbonitrile 1,4-dioxide

A mixture of 3.7-dichloro-2-quinoxalinecarbonitrile 1,4-dioxide (0.13 9, 0.51 mmol) and excess 4-butylaniline was stirred at room temperature for 24 h. The red solid was filtered and washed with a mixture of petroleum ether/ethyl acetate (911) (16 %), mp 207 C. IR (KBr) 3165, 2929, 2227, 1593, 1361 cm 1. 'H NMR (dimethylsulfoxide-d6) 0,90 (t, 3 H, CHB, J= 7,0 Hz); 1,32 (m, 2 H, CH2); 1,57 (m, 2 H, CH2); 2,60 (t, 2 H, CH2, J= 7,0 Hz); 7,24 (m, 4 H, Hz H3' H5. H6.); 8,01 (d, 1 H, H5, J= 9,1 Hz); 8,33 (s, 1 H, H8); 8,38 (d, 2 H, H6); 10,12 (bs, 1 H, NH). MS (El) m/e (70 eV) M+= 364.5.ANAL (calc. for C19H17ClN4O2) C, 61,80; H, 4,61; N, 15,19. Found: C,61,80; H, 4,86; N,14,90.

EXAMPLE. 40 Preparation of N-methyl-N, N-bis-[N'-(7-chloro-2-cyanoquinoxalinyl 1,4 dioxide)aminopropyljamine, hydrochloride

3,7-Dichloro-2-quinoxalinecarbonitrile 1,4-dioxide (0.35 g, 1.37 mmol) was dissolved in dichloromethane (150 mL3. K2CO3 (0.19 g) and N,N-[di-(3aminopropyl)]methylamine (0.10 g, 0.69 mmol) were added giving a red solid in suspension. The mixture was stirred at room temperature for 4 days. After filtering the insoluble salts and removal of the solvent by rotatory evaporation, a red solid was obtained. Flash chromatography by eluting with a gradient of ethyl acetate/methanol afforded a red solid which was recrystallized from methanol (25 %), mp 195 C.IR (KBr) 3370, 3070, 2953, 2226, 1574, 1339, 1178 cm-1 1H NMR (dimethylsulfoxide-d6) 2,12 (m, 4 H, 2 CH2); 2,77 (m, 4 H, 2 CH2N); 3,15-3,20 (bs, 3 H, NCH3); 3,79 (m, 4 H, 2 NCH2); 7,98 (d, 2 H, 2 H5, J= 9,8 Hz); 8,32 (m, 4 H, 2 H6 2 H8); 8,61 (t, 2 H, 2 NH); 10,01 (bs, 1 H, HCI). ANAL (calc. for C2H23Cl2N9O4.HCI) C, 48,35; H, 3,88; N, 20,31.

Found: C, 48,19; H, 4,01; N, 20.00.

EXAMPLE 41 Preparation of 7,8-d ichloro4-cyano-2-oxo- 1 ,2,4-oxadiazolo[2,3- a]quinoxaline 5-oxide

An homogeneous mixture of dry 3-amino-6.7-dichloro-2-quinoxalinecarbonitrile 1,4-dioxide (1.00 g, 3.70 mmol), dry dioxane (20 mL) and 2-chloroethyl isocyanate (2.40 9, 22.75 mmol) was stirred and heated at 100-110 C for 24 h. Toluene (20 mL) was added and the mixture was filtrated through active charcoal-celite. The yellow solution was allowed to stand overnight at room temperature. The yellow crystals were filtrated and washed with toluene and diethyl ether (22 %), mp 268 C. IR (KBr) 2232, 1805, 1550, 1400, 750. 1H NMR (dimethylsulfoxide-d6) 8,68 (s, 1 H, H6); 8,78(s, 1 H, H9). MS (El) m/e (70 eV) M+=296. ANAL (calc. for C10H2C12N403) C, 40,40; H, 0,68; N, 18,85; Found: C, 40,24; H, 0,68; N, 18,82.

EXAMPLE 42 Preparation of 7-chloro-4-cyano-2-oxo-1,2,4-oxadiazolo[2,3-a]quinoxaline 5-oxide

An homogeneous mixture of dry 3-amino-7-chloro-2-quinoxalinecarbonitrile 1,4dioxide (1.50 g, 6.30 mmol), 2-chloroethyl isocyanate (4.08 g, 38.73 mmol) and dry dioxane (20 mL) was stirred and heated at 100 C-100 C for 24 h. Toluene (20 mL) was added and the mixture was filtrated through active charcoalJcelite. Then it was allowed to stand overnight. The yellow crystals were filtrated and washed with toluene and ethylic ether. Finally was recrystallized from toluene (60%), mp 186 C. IR (KBr): 2234, 1814, 1544. 1395 cm-1.1H-NMR (dimethylsulfoxide-d6) 8.15 (d. 1 H. H9); 8.24 (d, 1 H, Hno); 8.54 (s, 1 H, H7). MS (El) m/e (70 eV) M+= 262.ANAL (calc. for C10H3ClN4O2) C, 45.71; H, 1.14; N, 21.33. Found: C, 46.46; H, 1.32; N, 21.41.

EXAMPLE 43 Preparation of 6.7-dichloro-3-methyl-2-quinoxalinecarbonitrile 1,4-dioxide

NH3 was bubbled for 5 min through a suspension of 5,6-dichlorobenzofuroxane (1.16 g, 5.65 mmol) in methanol (1,5 mL). A mixture of 5-methylisoxazole (0.41 g, 4.93 mmol) in methanol (0.5 mL) and a solution of KOH (0.27 g, 4.81 mmol) in methanol (2.5 mL) was added and the resulting mixture was stirred for 12 h. The yellow solid obtained was filtered off and recrystallized from chloroform/methanol (36 %), mp 204205 C. IR (KBr) 3090, 1380 cm 1. 'H NMR (dimethylsulfoxide-d6) 2,62 (s, 3 H, CH3), 8,69 (s, 2 H, H5 H8). MS (El) m/e (70 eV) M = 269. ANAL (calc. for C,OH5CI2N302) C,44,44; H,1,85; N,15,56. Found: C,44,69; H,1,95; N,16,11.

EXAMPLE 44 Preparation of 2-(methoxycarbonylhydrazino)methylquinoxaline 1,4-dioxide

A) Preparation of 2-methylquinoxaline 1,4-dioxide

A dissolution of benzofuroxane (27.20 g, 0.20 mol) in dry acetone (50 mL) was saturated with NH3. The mixture was heated under reflux for 5 h. After cooling a yellow precipitate was obtained and recrystallized fron ethanol as yellow needles (71%), mp 171-172 C.IR (KBr) 1600, 1330, 1280 cm ' 'H-NMR (dimethylsulfoxide-d6) 2,61 (s,3H,CH3); 7,60-7,91 (m, 2H, H6, H,); 8,20-8,60 (m, 2H, H5, H8). ANAL (calc. for C9H8N2O2) C, 61,36; H, 4,58; N, 15,90. Found: C, 61,49; H, 4,60; N, 15,93.

B) Preparation of 2-bromomethylquinoxaline 1,4-dioxide

A dissolution of 2-methylquinoxaline 1,4-dioxide (0.01 mol) in glacial acetic acid (50 mL) was stirred at 12 "C. A solution of bromine (15.00 mmol) in glacial acetic acid (20 mL) was added dropwise over the first dissolution. After stirring at 12-20 C for 12 h, ethanol (40 mL) and aqueous NaHCO3 solution (100 mL) were added. The yellow precipitate was filtered and recrystallized from ethanol (56%), mp 162-164 C.

This compound was used without further purification.

C) A solution of 2-bromomethylquinoxaline 1,4-dioxide (1.00 g, 4.40 mmoL) in ethanol was stirred at room temperature and mixed with another solution of methylcarbazate (1 g.; 11 mmoL) in ethanol (20 mL). The resulting mixture was heated under reflux for 8 h. After removal of the solvent a black oil was obtained and treated with cold methanol (5 mL) giving a yellow solid, which was recrystallized from methanol as yellow cristals (61%), mp 177-181 C. IR (KBr) 3370-3250, 1720, 1345, 1290 cm 'H- NMR (dimethylsulfoxide-d6) 3,65 (s, 3H, CH3); 4,05 (s, 2H, CH2); 7,38-7,56 (m, 2H, H6, H7); 8.01-8.22 (m, 2H, H5, H8); 8,53 (s, 1H, H3). ANAL (C11H12N4O4) C, H, N.

EXAMPLE 45 Preparation of 2-[1-[(2,4-dinitrophenylamino)imino]ethyl]-3-methylquinoxaline 1,4dioxide

A) Preparation of 2-acetyl-3-methylquinoxaline 1,4-dioxide

Acetylacetone (12.00 9, 0.12 mol) was dropwise added over a cooled (0 "C) solution of benzofuroxane (13.60 9, 0.10 mol) in morpholine (120 mL). The mixture was stirred at room temperature for 12 h. The yellow precipitate was collected and washed with coid isopropanol. Finally, recrystallization from isopropanol afforded yellow crystals (89%), mp 151-153 "C. IR (KBr) 1700, 1330, 1275 cm'. 1H-NMR (dimethylsulfoxide-d6) 2,48 (s, 3H, CH3); 2,70 (s, 3H, CH3); 7,78-8,02 (m, 2H, H6, H7); 8,31-8,63 (m, 2H, Hs, H8).ANAL (calc. for C11H10N2O3) C, 60,55; H, 4,62; N, 12,84.

Found: C, 60,65; H, 4,51; N, 12,91.

B) A mixture of 2,4-dinitrophenylhydrazine (2.18 g, 15 mmol), ethanol (50 mL), water (10 mL) and concentrated sulphuric acid (15 mL) was dropwise added over a solution of 2-acetyl-3-methylquinoxaline 1,4-dioxide (2.10 9, 10.00 mmol). The resulting mixture was stirred and heated under reflux for 2 h. After cooling an orange solid was obtained, filtrated and recrystallized from ethanoUN,N-DMF (40%), mp 221223 C. IR (KBr): 3298, 1616, 1326, 1277 cm '. 'H-NMR (dimethylsulfoxide-d6) 2,47 (s,3H, CH3); 2,56 (s, 3H, CH3-C=N); 7,87-8,01 (m, 3H, H6,, H6, H7); 8,41-8,55 (m, 3H, H5', H5, H8); 8,91 (s, 1H, H3'); 11,15 (s, 1H, NH).ANAL (calc. for C17H14N4O6) C, 51.25; H, 3,51; N, 21,10. Found: C, 51,46; H, 3,51; N, 21,39.

EXAMPLE 46 Preparation of 2-[1-(benzoylamino)imino]ethyl-3-methylquinoxaline 1,4-dioxide

A mixture of 2-acetyl-3-methylquinoxaline 1,4-dioxide (1.00 9, 4.58 mmol), benzylhydrazine (2.40 9, 9.16 mmol), sulfuric acid (2 drops) and ethanol (20 mL) was stirred and refluxed for 3 h. On cooling, the solid was collected and washed with cold ethanol. Recrystallization from ethanol afforded a yellow powder (52%), mp 202-204 C.IR(KBr): 3170, 1692, 1332, 1274 cm-1. 1H-NMR (dimethylsulfoxide-d6): 2,38(s, 3H, CH3); 2,51 (s,3H, CH3-C=N); 7,53-7,56 (m, 3H, H3,, H4,, H5'), 7,91-7,99 (m, 4H, H2,, H6,, H6, H7); 8,51 (m, 2H, Hg, H8); 11,17 (s, 1H, NH). ANAL (calc. for C18H16N4O3) C, 64,28; H, 4,76; N, 16,66. Found: C, 64,46; H, 4,98; N, 16,78.

EXAMPLE 47 Preparation of 2-[1 -(aminotiocarbonylamino)imino]ethyl-3-methylquinoxaline 1,4- dioxide

A mixture of 2-acetyl-3-methylquinoxaline 1,4-dioxide (1.00 g, 4,58 mmol), thiosemicarbazide, ethanol(20 mL) and concentrated HCI (2 drops) was stirred and refluxed for 20 h. After cooling a precipitate was obtained, filtered and recrystallized from ethanol/N,N-DMF (60%), mp 233-235 "C. IR (KBr): 3366, 1331, 1280 cm '* 1H-NMR (dimethylsulfoxide-d6) 2,07 (s,3H, CH3); 2,29 (s, 3H, CH3-C=N); 7,93-7,97 (m, 3H, H6', NH2); 8,38-8,51 (m, 3H, H5, H7, Ha); 10,76 (s, 1H, NH). ANAL (calc. for C,2H,3NsO2S) C, 49,48; H, 4,46; N, 24,05. Found: C, 49,76; H, 4,49; N, 23,89.

EXAMPLE 48 Preparation of 1-[(4-methylphenylsulfonylamino)imino]ethyl-3-methylquinoxaline 1,4dioxide

A mixture of p-toluensulfonylhydrazine (1.70 g, 9.17 mmol), ethanol (10 mL) and concentrated sulphuric acid (2 drops) was dropwise added over a mixture of 2acetyl-3-methylquinoxaline 1,4-dioxide (1.00 g, 4,58 mmol) and ethanol (10 mL). The complete mixture was stirred and heated for 12 h.After removal of the solvent, an oil was obtained, treated with isopropanol and recrystallized from ethanoVN,N-DMF (65%), mp 218-223 C IR (KBr): 2990, 1420, 1334, 1287 cm-1 1H-NMR (dimethylsulfoxide-d6) 2,01 (s,3H, CH3-Ar); 2,17 (s, 3H, CH3); 2,39 (s, 3H, CH3-C=N); 7,39-7,43 (d, 2H, H3,, K5,); 7,74-7,78 (d, 2H, H2,, H6,); 7,86-7,97 (m, 2H, H6, H7); 8,378,45 (m, 2H, H5, Ha), 11,21 (s, 1H,NH). ANAL (calc. for C,8H18N404S) C, 55,90; H, 4,66; N, 14,50. Found: C, 56,23; H, 4,88; N, 14,58.

EXAMPLE 49 Preparation of 2-(3-(p-chlorophenyl)-3-oxo- I -propenyl]quinoxaline 1,4-dioxide

A) Preparation of p-chorobenzoylmethylentriphenylphosphorane.

To a solution of p-chlorophenylbromomethylketone (0.10 mol) in anhidrous benzene (100 mL) was added a solution of triphenylphosphine (0.10 mol) in anhidrous benzene (100mL). The mixture was stirred at room temperature for 30 min. The white phosphonium salt was filtrated and dissolved in methanol (200 mL). Sodium methoxide (0.10 mol) in 200 mL of water was added. After stirring for 2 h., additional 400 mL of water were added. The organic compound was extracted with diethyl ether (4 x 120 mL) and dried over dry Na2SO4. After removal of the solvent, the yellow residue crystallized from a mixture of benzene/petroleum ether. The phosphorane was used without further purification.

B) Preparation of 2-dimethoxymethyiquinoxaline 1,4-dioxide

Pyruvaldehyde dimethylacetal (11.80 g, 0,10 mol) was dropwise added over a cooled (0 "C) solution of benzofuroxane (13.60 g, 0.10 moi) in diethyl ether (60 mL).

Pyrrolidine (2 drops) was added. The colour of the solution changed from yellow to purple. After stirring for 12 h. at room temperature, a yellow precipitate was isolated.

Recrystallization from ethanol afforded yellow crystals (78%), mp 145-146 "C. IR (KBr): 1610,1335,1280 cm-1 1H-NMR (dimethylsulfoxide46): 3,6 (s, 6H, CH3); 5,9 (s, 1H, CH); 7,65-7,95 (m, 2H, H6, H7); 8,37-8,70 (m, 2H, H5, H8); 8,43 (s, 1H, H2). ANAL (calc. forC11H12N2O4) C, 55,93; H, 5,12; N, 11,86. Found: C, 55,73; H, 5,01; N, 11,93.

C) Preparation of 2-formylquinoxaline 1,4-dioxide

Concentrated HCI (4 mL) was added dropwise over a dissolution of 2dimethoxymethylquinoxaline 1,4-dioxide (2.36 g, 0,01 mol) in ethanol (30 mL). The mixture was heated in a water bath for 60 min. The mixture was stirred at room temperature for 24 h. After removed of the solvent, a residue was obtained and recrystallized from chloroform (67%), mp 208-212 C IR (KBr): 1685, 1340, 1275 cm 11H-NMR (dimethylsulfoxide-d6): 7,81-8,15 (m, 2H, H6, H7); 8,24-8,60 (m, 2H, H5, H8); 8,46 (s, 1H, H2); 10,25 (s, 1H, CHO).

This compound was used without further purification.

D) 2-Formylquinoxaline 1,4-dioxide (0.10 mol) and p chlorobenzoylmethylentriphenylphosphorane (0.10 mol) were dissolved in chloroform (25 mL). The mixture was heated under reflux for 6 h. After removal of the solvent, the residue was recrystailized from ethanol (59%), mp 205-208 "C. IR (KBr): 1600, 1330, 1280 cm-1. 1H-NMR (dimethylsulfoxide-d6): 7,68 (d, 2H, H3,, H5'),8,33 (d, 1H, CH); 8,38 (d, 2H, H2,, H6,); 8,20-8,80 (m, 2H, H6, H7); 8,80-9,09 (m, 2H, H5, H8); 8,82 (d, 1H, CH); 9,88 (S, 1K, H3). ANAL (C17H11ClN203) C, H, N.

EXAMPLE 50 Preparation of 2-(3-oxo-I-butenyl)quinoxaline 1,4-dioxide

A) Preparation of acetylmethylentriphenylphosphorane.

To a solution of bromoacetone (0.10 mol) in anhidrous benzene (100 mL) was added a solution of triphenylphosphine (0.10 mol) in anhidrous benzene (100 mL). The mixture was stirred for 30 min. The white solid was filtered and dissolved in methanol (200 mL). Sodium methoxide (0.10 mol) in 200 mL of water was added. The mixture was stirred for 2 h. Water (400 mL) was added, and the organic compound extracted with diethyl ether (4 x 120 mL). The organic layer was dried over Na2SO4. After removal of the solvent, the crude solid was recrystallized from benzene/petroleum ether. The phosphorane was used without further purification.

B) 2-formylquinoxaline 1,4-dioxide (0.10 mol) and acetylmethylentriphenylphosphorane (0.10 mol) were dissolved in chloroform (25 mL).

The mixture was heated under reflux for 6 h. After removal of the solvent, the residue was recrystallized from ethanol (65%), mp 197-199 C IR (KBr): 1600, 1320, 1265 cm 1.1H-NMR (dimethylsulfoxide-d6): 2,53 (s, 3H, CH3); 7,73 (d, 1H, CH); 8,33 (d, 1H, CH); 8,36 (m, 2H, H6, H7); 8,91 (m, 2H, Hs, H8); 9,56 (s, 1H, H3). ANAL (C12H10N203) C, H, N.

EXAMPLE 51 Preparation of 2-(3-(4-methoxyphenyl)-3-oxo- 1 -propenyl]-3-methylquinoxaline 1,4dioxide

A) Preparation of 2,3-dimethylquinoxaline 1,4- dioxide

A cooled (5 "C) solution of benzofuroxane (13.60 g, 0.10 mol) and morpholine (120 mL) was stirred for 10 min. Butanone (9.60 g, 0.12 mol) was added dropwise.

The mixture was stirred at room temperature for 24 h. Reaction was carried on by TLC. After removal of the solvent, a brown gum was obtained and triturated with methanol (50 mL). The solid was recrystallized from ethanol as yellow crystals (63%), mp 192-193 C. IR(KBr): 1605, 1320, 1280 cm 1H-NMR (dimethylsulfoxide46): 2,70 (s, 6H, CH3); 7,60-7,84 (m, 2 H, H6, H,); 8,30-8,60 (m, 2H, H5, H8). ANAL (caic. for C,0H,0N202) C, 63,15; H, 5,30; N, 14,73. Found: C, 63,31; H, 5,42; N, 14,53.

B) Preparation of 2-formyl-3-methylquinoxaline 1,4-dioxide

2,3-Dimethylquinoxaline 1,4-dioxide (3.80 g, 0.02 mol) was dissolved in hot ethyl acetate (150 mL). Selenium dioxide (2.30 g, 0.02 mol) was added. The mixture was heated under reflux for 4 h. After removal of the solvent a dark-red residue was obtained and extracted with hot chloroform. The solvent was removed and a yellow solid was obtained. Recrystallization from ethanol yielded yellow crystals (73%), mp 181-184 C.

This compound was used without further purification.

C) A mixture of 2-formyl-3-methylquinoxaline I ,4-dioxide (1.90 g, 0.01 mol) and pmethoxybenzoylmethylentriphenylphosphorane (0.01 mol) and chloroform (50 mL) was heated under reflux for 12 h. After removal of the solvent a brown residue was obtained. Recrystallization from ethanol/N,N-DMF gave yellow crystals (60%), mp 197198 C. IR (KBr): 1660, 1610, 1340, 1280 cm-1.1H-NMR (dimethylsulfoxidea6): 2,97 (s, 3H, CH3); 3.95 (s, 3 H, OCH3); 7.12 (d, 2 H, K H5.); 7.85-8.10 (m, 2 H, K6 H7); 7.95 (d, 1 H, CH); 8.28 (d, 2 H, Kr H6); 8.65-8.95 (m, 2 H, H5 H8); 9.38 (d, 1 H, CH). ANAL (calc. for CtgH,6N204) C, 67.85; H, 4.79; N, 8.33. Found: C, 67.66; H, 4.90; N, 8.17.

EXAMPLE 52 Preparation of 2-benzoyl-3-methylquinoxaline I ,4-dioxide

A solution of benzoylacetone (19.40 g, 0.12 mol) in morpholine (20 mL) was dropwise added over a cooled (0 C) solution of benzofuroxane (13.60 g, 0.1 mol) in morpholine (100 mL). The mixture was stirred at room temperature for 5 h. The yellow precipitate was collected by filtration and recrystallized fron ethanol as yellow plates (87%), mp 224-225 C. IR (KBr) 1680, 1335, 1285 cm-1. 1H-NMR (dimethylsulfoxide- d6) 2,55 (s,3H, CH3); 7.47-8.17 (m, 7H, H6, H7, 5H Ar); 8,51-8,89 (m, 2H, H5, H8).

ANAL (calc. for C16H12N203) C, 68,56; H,4,31; N, 9,99.Found: C, 68,77; H, 4,40; N, 10,07.

EXAMPLE 53 Preparation of 2-ethoxycarbonyl-3-methylquinoxaline 1,4aioxide

A mixture of benzofuroxane (13.60 9, 0.10 mol) and ethyl acetylacetate (13.00 g, 0.10 mol) was stirred at 0 C. Morpholine was dropwise added (17.40 g, 0.20 mol).

After stirring at 0 C for 6 h., the mixture was cooled at -25 C and stirred for 12 h. The brown precipitate was collected and recrystallized fron ethanol as a yellow solid (82%), mp 133-134 C. IR (KBr) 1740, 1335, 1290 cm-1 1H-NMR: 1,36 (t, 3H3; 2,50 (s, 3H, CH3); 4,55 (c, 2H, CH2); 7.81-8.10 ( m. 2H, H6, H7); 8,19-8,55 (m, 2H, H5, H8).

ANAL (calc. for C12H12N204) C, 58.06; H, 4,87; N, 11,28. Found: C, 58,23; H, 4,55; N, 11,20.

EXAMPLE 54 Preparation of 2-benzoylquinoxaline 1,4-dioxide

A) Preparation of ethylbenzoylpyruvate.

Potassium (27 g, 0.67 mol) was added carefully over dry diethyl ether (200 mL) under nitrogen. Ethanol (6 x 30 mL) was added. The final solution was diluted with diethyl ether (1500 mL) and diethyl oxalate (98 g, 0,67 mol) was added. After stirring for 15 min, acetophenone (92 g, 0.70 mol) was introduced and a yellow dissolution was obtained and precipitated a yellow solid. The filtered solid washed with ethyl ether. The potassium salt was mixed with concentrated sulfuric acid (60 mL) and dry ethyl ether (750 mL) in a cooled (0 "C) system. The complete mixture was stirred for 2 h. The organic solution was washed with aqueous sodium bicarbonate and then with water. The organic layer was dried over sodium sulfate. After removal of the solvent a yellow-reddish oil was obtained which crystallized on cooling (65%).

B) A solution of ethylbenzoylpyruvate (16.40 g, 0.12 mol) in triethylamine (50 mL) and ethylacetate (30 mL) was slowly added over another solution of benzofuroxane (13.60 g, 0,10 mol) in triethylamine (200 mL). The resulting mixture was stirred at room temperature for 72 h. Reaction was carried on by TLC.The yellow solid was collected and recrystallized from ethanol-DMF as yellow cristals (63%), mp 240-243 "C. IR(KBr): 1695, 1375, 1225 cam'. 'H-NMR (chlorophorm-d): 7,45-7,75 (m, 3H, H', H4,, H5); 7,80-8,11 (m. 4H, H2', H6', H6, H7), 8,35 (s, 1H, H3); 8,50-8,82 (m, 2H, H5, H8). ANAL (Calc. for C,5H10N203) C, 67,77; H, 3,78; N, 10,52. Found: C, 67,87; H, 3,92; N, 10,18.

EXAMPLE 55 Preparation of 6,7-dichloro-3-methyl-2-methylthioquinoxaline 1,4-dioxide

A) Preparation of 1-methylthiopropanone 1-Chloropropanone (2.90 g, 31.30 mmol) was added to a solution of sodium thiomethoxide (2.20 g, 31.40 mmol) in ethanol at 0 "C. The resulting mixture was stirred and heated under reflux for 2 h. After cooling, the inorganic salts were filtered off and the solvent was removed giving a brown gum (90%). This compound was used without further purification.

B) A solution of 1-methylthiopropanone (1.10 g, 10.50 mmol) and 5,6dichlorobenzofuroxane (2.30 g, 11.20 mmol) in methanol (10 mL) was bubbled with dry ammonia for 10 min. The mixture was allowed to stand at room temperature overnight. The precipitated solid was filtered and recrystallized from methanolchloroform (30%), mp 184-185 "C. IR (KBr): 1594, 1374 cm '. 'H-NMR (d-chloroform) 2,65 (s, 3H, CH3); 2.82 (s, 3 H, SCH1); 8.62 (s, 1 H, Hs); 8.66 (s, 1 H, H8). MS (El) mie (70 eV) M = 290. ANAL (calc. for C,oH8C12N202S) C, 41.24; H, 2.75; N, 9.62. Found: C, 41.09; H, 2.77; N, 9.56.

EXAMPLE 56 Preparation of 6 .7-dichloro-2-methyl-3-methylsulfinylquinoxaline 1,4-dioxide

A solution of 6,7-dichloro-2-methyl-3-methylthioquinoxaline 1,4-dioxide (1.50 g, 5.10 mmol) in chloroform (10 mL) was stirred at 0 C for 10 min. 3-Chloroperbenzoic acid (1.00 g, 5.80 mmol) dissolved in chloroform (15 mL) was added. The mixture was stirred at room temperature for 12 h. The solution was washed with aqueous sodium bicarbonate. After drying the organic layer over sodium sulfate the solvent was removed. The resulting solid was recrystallized from methanol-chloroform (70%), mp 202-203 C.IR (KBr): 1370,1028 cm-1.1H-NMR (d-chloroform) 2,90 (s, 3H, CH3); 3.24 (s, 3 H, SOCH3); 8.46 (s, 1 H, H); 8.63 (s, 1 H, H5). MS (El) m/e (70 eV) M+= 306.

ANAL (calc. for C,0H8CI2N203S) C, 39.09; H, 2.61; N, 9.12. Found: C, 39.11; H, 2.70; N, 8.92.

EXAMPLE 57 Preparation of 6,7-dichloro-2-methyl-3-methylsulfonylquinoxaline 1,4-dioxide

A solution of 3-chloroperbenzoic acid (1.86 g, 10.80 mmol) in chloroform (18 mL) was slowly added over a cooled (0 C) solution of 6,7-dichloro-2-methyl-3methylthioquinoxaline 1,4-dioxide (0.80 g, 2,70 mmol) in chloroform (10 mL). The resulting mixture was stirred at room temperature for 12 h. After washing with aqueous sodium bicarbonate solution, the organic layer was dried over sodium sulfate. After removal of the solvent the residue was chromatographied by eluting with ethyl acetate giving a yellow solid (92%), mp 195-196 "C. IR (KBr): 1371, 1149 cm'. 'H-NMR (dchloroform) 3.03 (s, 3H, CH3); 3.67 (s, 3 H, SO2CH3); 8.63 (s, 1 H, H8); 8.70 (s, 1 H, H5). MS (El) m/e (70 eV) M+= 322. ANAL (calc. for C,0HôCI2N204S) C, 37.15; H, 2.48; N, 8.67. Found: C, 37.03; H, 2.54; N, 8.37.

EXAMPLE 58 Preparation of 6.7-dichloro-2-methyl-3-(4-nitrophenyl)thioquinoxaline I ,4-dioxide

A mixture of 1-(4-nitrophenyl)thiopropanone (1.40 9, 6.70 mmol), 5,6dichlorobenzofuroxane (1.40 g, 6.80 mmol) and methanol (10 mL) was bubbled with dry ammonia for 10 min. The complete mixture was allowed to stand at room temperature for 12 h. The precipitate was washed with methanol and recrystallized from methanol-chloroform (30%), mp 192-193 C. IR (KBr): 3095,1604,1338 cm-1.

'H-NMR (d-chloroform) 2.88 (s, 3H, CH3); 7.30 (d, 2 H, K2. H6', J= 8 Hz); 8.12 (d, 2 H, H3. H5., J= 8 Hz); 8.55 (s, 1 H, Hs); 8.72 (s, 1 H, H8). MS (El) m/e (70 eV) M+= 397.

ANAL (calc. for C,5HgCI2N304S) C, 45.23; H, 2.26; N, 10.55. Found: C, 45.34; H, 2.44; N, 10.14.

EXAMPLE 59 Preparation of 6,7-dichloro-2-methyl-3-phenylthioquinoxaline 1.4-dioxide

Dry ammonia was bubbled into a solution of 1-phenylthiopropanone (7.50 9, 45.20 mmol) and 5,6aichlorobenzofuroxane (9.30 9, 45.40 mmol) in methanol for 10 min. The mixture was allowed to stand at room temperature for 12 h. The resulting precipitate was filtered and recrystallized from methanol-chloroform (60%), mp 181182 C. IR (KBr): 3095, 1600, 1380 cm-1. 'H-NMR (d-chloroform) 2.76 (s, 3H, CH3); 7.26 (m, 5 H, Ph); 8.55 (s, 1 H, H8); 8.65 (s, 1 H, H5). MS (El) m/e (70 eV) M+= 352.

ANAL (calc. for C15H10Cl2N2O2S) C, 50.99; H, 2.83; N, 7.93. Found: C, 51.00; H, 2.87; N, 7.90.

EXAMPLE 60 Preparation of 6,7-dichloro-2-methyl-3-phenylsulfinilquinoxaline 1,4-dioxide

A mixture of 6,7-dichloro-2-methyl-3-phenylthioquinoxaline 1,4-dioxide (1.00 g, 2.80 mmol), 3-chloroperbenzoic acid (0.60 g, 3.50 mmol) and chloroform (15 mL) was stirred at room temperature for 12 h. The organic solution was washed with aqueous sodium bicarbonate solution and dried over sodium sulfate. After removal of the solvent, a yellow solid was obtained and recrystallized from methanol-chloroform (78%), mp 161-162 C. IR (KBr): 3095, 1610, 1329, 1053 cm-1.1 K-NMR (d-chloroform) 2.86 (s, 3H, CH3); 7.44 (m, 3 H, H3' K4. H, Ph); 7.95 (m, 2 H, K2. H6.Ph); 8.56 (s, 1 H, H5); 8.65 (s, 1 H, HB). MS (El) m/e (70 eV) M = 368. ANAL (calc. for Ct5H10CI2N203S) C, 48.78; H, 2.71; N, 7.59. Found: C, 48.50; H, 2.68; N, 7.70.

EXAMPLE 61 Preparation of 6,7-dichloro-2-methyl-3-phenylsulfonilquinoxaine 1,4-dioxide

A solution of 6,7-dichloro-2-methyl-3-phenylthioquinoxaline 1,4-dioxide (1.00 g, 2.80 mmol) and 3-chloroperbenzoic acid (2.30 g, 13.30 mmol) in chloroform (80 mL) was stirred at room temperature for 12 h. The organic solution was washed with aqueous sodium bicarbonate and dried over sodium sulfate. The solvent was removed and the resulting solid was recrystallized from methanol-chloroform (85%), mp 172173 "C. IR (KBr): 3090, 1356, 1128 cm'. 'H-NMR (d-chloroform) 2.54 (s, 3H, CH3); 7.50 (t, 2 H, H3. H5. Ph, J= 8 Hz); 7.69 (t, 1 H, H4. Ph, J= 8 Hz); 8.08 (d, 2 H, H2. H6.Ph, J= 8 Hz); 8.17 (s, 1 H, H5); 8.49 (s, 1 H, H8). MS (El) mle (70 eV) M+= 384. ANAL (calc. for C15H,oCI2N204S) C, 46.75; H, 2.60; N, 7.27. Found: C, 46.61; H, 2.20; N, 6.95.

EXAMPLE 62 Preparation of 2,6,7-trichloro-3-methylquinoxaline 1,4-dioxide

A solution of 6,7-dichloro-2-methyl-3-methylsulfonylquinoxaline 1,4-dioxide (0.50 9, 1.50 mmol) in concentrated HCI (4 mL) was stirred and heated at 80 "C for 30 min. The mixture was stirred at room temperature for 12 h. Addition of water (20 mL) gave a precipitate, which was filtrated and recrystallized from methanol-chloroform giving a yellow solid (24%), mp 175-176 C. IR (KBr): 1595, 1380 cm'. 'H-NMR (dchloroform) 2.82 (s, 3H, CH3); 8.73 (s, 2 H, K5 Ha). MS (El) m/e (70 eV) M+= 278.

ANAL (calc. for CgH5CI3N202) C, 38.64; H, 1.79; N, 10.02. Found: C, 38.85; H, 1.78; N, 10.07.

EXAMPLE 63 Preparation of 6,7-dichloro-3-methyl-2-[3-(N,N-dimethylamino)propylamino]quinoxaline 1,4-dioxide

[3-(N,N-Dimethylamino)propyl]amine (0.13 g, 1.30 mmol) was added dropwise over a solution of 6,7-dichloro-2-methyl-3-methylsulfonylquinoxaline 1,4-dioxide (0.50 g, 1.50 mmol) in dioxane-chloroform (10 mL-3 mL). The complete mixture was stirred and heated at 80 C for 10 h. After removal of the solvent an oil was obtained and chromatographied by eluting with dichloromethane-methanol (90/10, v/v) giving a brown-red solid (47%), mp 186-187 C.IR (KBr): 3440, 1629, 1370 cm 1. 'H-NMR (dchloroform) 1.88 (q, 2 H. CH2, J= 6 Hz); 2.25 (s, 6 H, N(CH3)2); 2.44-2.52 (m, 2 H, CH2N); 2.73 (s, 3H, CH3); 3.66 (t, 2 H, NCH2, J= 6 Hz); 7.69 (s, 1 H, NH); 8.50 (s, 1 H, H6); 8.54 (s, 1 H, H5). MS (El) m/e (70 eV) M+= 344. ANAL (calc. for C,4H1ôCI2N402) C, 48.70; H, 5.22; N, 16.23. Found: C, 48.61; H, 5.34; N, 16.03.

EXAMPLE Preparation of 2-amino-6,7-dichloro-3-methylquinoxaline 1,4-dioxide

A solution of 6,7-dichloro-2-methyl-3-methylthioquinoxaline 1,4-dioxide (0.50 g, 1.70 mmol) and formamidine acetate (0.60 g, 5.80 mmol) in 2ethoxyethanol (6 mL) was heated under reflux for 30 min. Addition of water (10 mL) and subsequent removal of the solvent afforded and oil which was chromatographied by eluting with dichlorometane/methanol (10/90) giving a yellow solid (30%), mp 235-236 "C. IR (KBr): 3413, 3327, 1344 cm . K-NMR (dimethylsulfoxide-d6) 2.54 (s, 3 H, CH3); 7.84 (s, 2 H, NH2); 8.41 (s, 1 H, H8); 8.48 (s, 1 H, H5). MS (El) m/e (70 eV) M+= 259. ANAL (calc. for CgH7CI2N302) C, 41.54; H, 2.69; N, 16.15.Found: C, 41.62; H, 2.68; N, 16.24.

EXAMPLE 65 Preparation of 2,3-dicyanoquinoxaline 1,4-dioxide

A) Preparation of quinoxaline 1,4-dioxide A mixture of benzofuroxane (4.08 g, 30.00 mmol), N,N-diethylamine (2.19 g, 30.00 mmol) and ethyl acetate (15 mL) was stirred at 0 "C for 10 min. Vinyl acetate (5.16 g, 60.00 mmol) was dissolved in ethyl acetate (5 mL) was added and the complete mixture was stirred at room temperature for 72 h. After removal of the solvent, the crude solid was recrystallized from isopropanol giving a yellow solid (79%), mp 240- 241 "C.

This compound was used without further purification.

B) A mixture of quinoxaline 1,4-dioxide (1.00 g, 6.20 mmol), potassium ferricyanide (2.44 g, 7.40 mmol), potassium cyanide (2.44 g, 30.10 mmol), ethanol (70 mL) and water (30 mL) was stirred at 0 C for 3 h. The precipitate was filtrated and purified by chromatography by eluting with ethyl acetate. Yellow solid (18%), mp 224 C. IR (KBr): 2236, 1365 cm-1.1 1H-NMR (dimethylsulfoxide-d6) 8.24-8.29 (m, 2 H, K6 H7); 8.59-8.63 (m, 2 H, H5 H8). MS (El) m/e (70 eV) M+= 212. ANAL (calc. for C,oH4N402) C, 56.60; H, 1.89; N, 26.41. Found: C, 56.36; H, 1.91; N, 26.42.

EXAMPLE 66 Preparation of 7-chloro-3-ethoxywarbonylamino-2 < uinoxalinecarbonitrile 1,4-dioxide

A solution of 7-chloro-4-cyano-2-oxo-1,2,4-oxadiazolo[2,3-a]quinoxaline S-oxide (0.50 9, 1.90 mmol) in methanol (25 mL) was heated under reflux for 2 h. The precipitate was filtrated and washed with ethyl ether and recrystallized from ethanol/dioxane (17%), mp 178 C. IR (KBr): 3414, 1724, 1531,1323 cm-1.1H-NMR (dimethylsulfoxide-d6): 1.27 (t, 3 H, CH3); 4.22 (c, 2 H, CH2); 8.09 (d, 1 H, H6); 8.46 (d, 1 H, H5); 8.49 (s, 1 H, H8). MS (El) m/e (70 eV) M+= 308. ANAL (calc. for C12H9CIN404) C, 46.68; H. 2.92; N, 18.15. Found: C, 46.55; H, 2.88; N, 17.98.

EXAMPLE 67 Preparation of 7,8-dichloro4-iminobenzopteridine 5,10-dioxide

Chloroform (20 mL) was saturated with dry ammonia and 7,8-dichtoro-2-oxo- 1,2,4-oxadiazolo[2,3-a]quinoxaline 5-oxide (0.15 g, 0.51 mmol) was added. The dark red solution was stirred for 10 h. The resulting precipitate was filtered and washed with hot acetone and diethyl ether. (56%), mp > 300 C IR (KBr): 3451, 3090, 1696, 1546, 1435 cm-1.1 H-NMR (TFA): 8.88 (s, 1 H, H6); 8.97 (s, 1 H, Hg). MS (El) m/e (70 eV) M+16= 298. ANAL (calc. for C oH5CI2N503) C, 38.22; H. 1.59; N, 22.29. Found: C, 38.28; H, 2.14; N, 22.27.

EXAMPLE 68 Preparation of 4-imino-3-l2-(N,N-dimethylamino)ethyl3benzopteridine 5,10-dioxide

A solution of 4-cyano-2-oxo-1,2,4-oxadiazolo[2,3-a]quinoxaline S-oxide (0.20 g, 0.87 mmol) in dry dichloromethane (20 mL) was stirred for 30 min. 2-(N,Ndimethylamino)ethylamine (5 drops) was added and the solution turned red. The mixture was allowed to stand at room temperature for 18 h. The purple solid was filtrated in vacuo and washed with light petroleum ether (70%), mp 222 C. IR (KBr): 3412, 1609, 1581, 1447 cm l. 'H-NMR (dimethylsulfoxide-d6): 3.02 (s, 6 H, 2 CH3); 3.41 (m, 4 H, 2 CH2); 7.30 (t, 1 H, H7); 7.51 (d, 1 H, H6); 7.69 (t, 1 H, H8); 8.13 (d, 1 H, H9); 11.42 (s, 1 H, NH). MS (El) m/e (70 eV) M± 16= 300.ANAL (calc. for C14H16N603) C, 53.16; H, 5.06; N, 26.58. Found: C, 52.85; H, 5.36; N, 26.41.

Cytotoxicity assays The cytotoxicity assays were carried out in V79 cells (Chinese hamster lung fibroblasts) obtained from the ATCC. They were grown as monolayers in EMEM 10% FBS at 370C and 5% CO2. Cells from exponentially growing cultures were trypsinized and a suspension of 2x104 cells/ ml was prepared. 30 ml of this suspension were dispensed into 50 ml glass flasks, which were hermetically sealed with rubber caps.

Cells were maintained in suspension at 370C and the flasks were gassed either with pure air or with pure Nitrogen. After thirty minutes, the compounds were added and the cells were gassed for a further two hours in the presence of the compound. At the end of the 2 hours the cells were washed and resuspended in fresh medium, they were counted and various numbers were cloned into plastic dishes. After seven days of growth at 370C and 5% CO2, the clones were fixed and stained. Clones with more than 64 ceils (equivalent to six cell divisions) were counted and the plating efficiency calculated.The surviving percentage in air and hypoxia was calculated by dividing the plating efficiency of the compound treatedwells by that of the solvent treated control cells, Compounds were tested twice in oxic and hypoxic conditions and the potency and hypoxia selectivity of the compounds were determined from dose-response graphs.

The potency is the dose which kills 99% of hypoxic cells; the lower the value, the greater the compound potency. The selectivity is determined by the Hypoxic Cytotoxicity Ratio (HCR), that is the dose in air divided by the dose in hypoxia giving the same level of cell killing. The higher the HCR, the greater the hypoxia selectivity.

In the Figure 1 the percentage at surviving cells after treatment in air or hypoxia with 2-quinoxaiinecarbonitrile 1,4-dioxide (Example 13, Fig. 1A) and 6(7)-chloro-3 [3-(N,N-dimethylamino) propylaminol-2-quinoxalinecarbonitrile 1 ,4dioxide (Example 27, Fig. 1 by, are shown. In hypoxia, 0.4 ,uM of compound 27 kills 99% of the cells (Potency = 0.4), under oxic conditions, a 250 fold greater concentration is needed to obtain the same percentage of ceil killing (HCR = 250). Under the same assay conditions the potency and HCR for Tirapazamine are 30 and 75, respectively. Thus compound 27 is 75 times more potent and 3 times more selective than Tirapazamine.

In Table I the potency and HCR of several quinoxalines are shown, all these quinoxalines are more potent than Tirapazamine and most of them are also more selective.

TABLE 1

COMPOUND Potency HCR COMPOUND Potency HCR Example 1 9 200 Example 28 1 300 Example 2 1 80 Example 29 2 200 Example 5 15 100 Example 30 0.6 170 Example 6 7 75 | Example 31 0.3 340 Exampie 9 4 8 | Example 32 0.9 | 120 Example 10 15 50 Example 33 0.5 40 Example 13 5 > 100 Example 34 3 | 100 Example 14 3 30 | Example 35 1 1 102 Example 15 0.7 10 | Example 36 0.4 | 75 Example 16 | 6 200 | Ex. 38 (6-Cl) 0.8 | > 125 Example 17 5 > 200 Ex. 38 (7-Cl) 2 300 Ex. 18 (7-Cl) 6 80 Example 40 0.7 10 Example 19 0.2 200 Example 43 0.3 30 Example 26 1 300 Example 67 5 > 12 Example 27 0.4 250 Tirapazamine 30 75 Determination of MTD The maximum tolerated dose (MTD) was determined in female Balb/C mice of 20-25g weight. The MTD was determined after a single i.p. administration and was defined as the dose which produces a 20% weight loss on the third day after dosing.

In Table II some MTD data are presented. All the compounds were prepared immediately before the injection. The 3-amino-2-quinoxalinecarbonitrile 1,4-dioxides (f, 2, 5 and 6) and Tirapazamine were suspended in Tween 80 90%/ saline 10% All of these quinoxalines are less toxic than Tirapazamine. 7-chloro-3-[3-(N,N- dimethylamino)propylamino]-2-quinoxalinecarbonitrile 1 ,4-dioxide (27) was dissolved in saline. This compound is five times more toxic than Tirapazamine.

TABLE II

COMPOUND MTD (mMols/kg) MTD (mg/kg) Example 1 0.6 142 Example 2 0.8 217 Example 5 0.6 176 Example 6 0.5 135 Example 27 0.06 25.8 Tirapazamine 0.3 # 53.4 Solubility of compound 27 In tests run in parallel on Tirapazamine and compound 27, the latter was at least 10 times more soluble than the former, although saturation was not achieved with compound 27.

COMPOUND SOLUBILITY Tirapazamine 6,7 x 10-3 M Example 27 1 > 6,7 x 10.ZM ln vivo activity of compound 27 Compound 27 was tested on EMT-6 mouse mammary tumours in an ex vivo cloning assay. It was administered in combination with radiation, so that the radiation would kill well oxygenated cells, allowing the effect of the compound on hypoxic cells to be measured. Briefly, 2 x 106 EMT-6 cells were innoculated subcutaneously in the right side of female Balb/C mice. When the tumours reached approximately 7mm in diameter the treatment began. Mice were dosed i.p. with 0.01 mblole/kg of compound 27 or 0.08 mMoleikg of Tirapazamine, given 30 minutes before each radiation session.The entire animal was irradiated with a dose of 1.5 Gy of 1 5MeV electrons from a linear accelerator (SIEMENS A.G. Modelo MEVATRON 77), twice a day (0.900h and 18.00h), on four consecutive days. Controls which received only radiation or only saline were also included. 24h after the last treatment, the tumours were removed, chopped mechanically and digested with a mixture of collagenase, pronase and DNAse. After filtering the suspension through a mesh of 35um diameter, the cells were centrifuged. Live cells, counted with Trypan blue, were cioned in RPMI 20% FBS . On day seven the clones were stained and counted.

The results are presented in Figure 2. The clonogenic capacity of the irradiated cells was 50% lower than the controls which received only saline. When Trapazamine and compound 27 were given without radiation, the cloning efficiency was markedly reduced. When compound 27 was given before each radiation dose, an enhancement of the radiation response was observed. The effect was similar to the one obtained with Tirapazamine given at an 8 fold higher dose. Since the MTD of compound 27 is 5-fold lower than that of Tirapazamine, the Therapeutic Index (effective dose:toxic dose) of compound 27 is at least 1.6 times higher than Tirapazamine.

Claims (21)

1 A compound of Formula 1

wherein: R2 is hydrogen, cyano or; R2 is C1-4alkyl. -CH2-NH-NH-COO-(C1-4alkyl), C1-4alkyloxycarthio. C1-4alkylthio.

CI alkyIsulfinyl, C1-4alkilsulfonyl. C2-Salkanoyl, or; R2 is a group of formula -CH=CH-CO-R9 wherein R9 is C1-6alkyl or phenil and phenil may be optionally replaced by 1 or 2 substituents chosen between halogen anc CI- 4alcoxi or, R2 is a group of formula -C(R10)=N-NH-R11 wherein R10 is H or C1-4alkyl and R11 is a group of formula -X-Y wherein X can be a simple link, carbonyl, thiocarbonil, thiol, sulfinyl and sulfonyl and Y can be amino and phenyl where phenyl can be optionally replaced by one or two substituents chosen between NO2, amino and methyl R3 is a group of formula -NH-C1-6alkyl-N(A1)(A2) wherein Al and A2 are independently H or C1-4alkyl optionally susbtituted the alkyl by hydroxi C14 alkoxy, amino, C1-4alkylamino, thiol or C14alkylthio or Al and A2 along with N complete a 5 or 6 membered heterocyclic ring optionally containing a N, O or S atom in lieu of a carbon atom; this ring can optionally have a carbon replaced by 01- 4alkyl or R3 represents a group of formula

wherein R2 has the meaning defined in claim 1 and R6 and R7 have the meaning defined in claim 1 or R2 and R3 together represent a group of formula -NH-CO-NR11-C(=NH)- wherein RI 1 independently represents H, 014alkyl or 01- 4alkyl-N(R12,R13) wherein R12 and R13 independently represent H or C14alkyl R6 and R7 independently represent H; halogen; CF3; C1-4alkyl; C2-5alkanoylamino; cyano; phenyl optionally substituted with 1-2 substituents selected from NO2 and C(I-4)alkyl; R8 represents H or NO2; with the exception of 1,4-dioxide 2-(3-dimethylamino-propylamino)-quinoxaline which is excluded or a pharmaceutically acceptable salt derived.

2. A compound according to claim 1 wherein R2 is cyano.

3. A compound as claims 1 or 2 wherein R6 and R7 independently represent H, CI, MeO or CF if R6 or R7 are not hydrogen

4. A compound as claims 1-3 wherein R8 is H.

5. A compound as claims 14 wherein R3 is a group of formula -NH-C1-6alkyl- N(A1 )(A2) wherein Al and A2 are independently H or C1-4alkyl optionally replaced the alkyl by hydroxy, C1-4 alkoxy, amino, C14alkylamino, thiol or C14alkylthio or Al and A2 along with N complete a 5 or

6 membered heterocyclic ring optionally containing a N, O or S atom in lieu of a carbon atom; this ring can optionally have a carbon replaced by C1-4alkyl or 6.Any of the following compounds: 6-fluorn-3-(3-dimethylamino-prnpylamino)-2uinoxalinecarbonitrile 1,4-dioxide 6-trifluoromethyl-3-(3Ximethylamino-propylamino)-2suinoxalinecarbonitrile 1,4dioxide 6-methoxy-3-(3-dimethylamino-propylamino)-2uinoxalinecarbonitrile 1,4-dioxide 6-fluoro-3-(3-dimethylaminoethylamino)-2quinoxalinecarbonitrile 1,4-dioxide 6-trifluoromethyl-3-(3-dimethylamino-ethylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 6-methoxy-3-(3-dimethylamino-ethylamino)-2uinoxalinecarbonitriIe 1,4-dioxide 6-chlorn-3-(3-dimethylaminoethylamino)-2quinoxalinecarbonitrile 1,4-dioxide 7-fluoro-3-(3-dimethylamino-propylamino)-2uinoxalinecarbonitrile 1,4-dioxide 7-trifluoromethyl-3-(3-dimethylamino-propylamino)-2-quinoxalinecarbonitrile 1,4dioxide 7-methoxy-3-(3-dimethylamino-propylamino)-2uinoxalinecarbonitrile 1,4-dioxide 7-fluoro-3-(3-dimethylaminoethylamino)-2uinoxalinecarbonitrile 1,4-dioxide 7-trifluoromethyl-3-(3-dimethylamino-ethylamino)-2-quinoxallnecarbonitrile 1,4-dioxide 7-methoxy-3-(3-dimethylamino-ethylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 7-chloro-3-(3-dimethylamino-ethylamino)-2.quinoxalinecarbonitrile 1.4-dioxide or a mixture of isomers in position 6 and 7 or a pharmaceutically acceptable salt derivated from them.

7. Any of the following compounds: 6(7)-chloro-3-(3-dimethylamino-propylamino)-3-quinoxalinecarbonitrile 1,4-dioxide 7-chloro-3-(3-dimethylamino-propylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 6-chloro-3-(3-dimethylamino-propylamino)-2-quinoxalinecarbonitrlle 1,4-dioxide or a pharmaceutically acceptable salt derivated from them.

8. A compound of: Formula 1

wherein R2 is defined in claim 1 R3 is H amino optionally mono- or di-substituted by C1-alkyloxicarbonyl; C2-Salkanoylamine optionally substituted the carbon by hydrogen, phenylthio, phenylsulphynil or phenylsulphonyl optionally mono- di- or tri-substitued the phenyl by halogen or NO2 or, R3 is a group of the formula -NH-C I -6alkyl-N(A1 )(A2) wherein Al and A2 are independently H or C14aikyl optionally replaced the alkyl by hydroxy, C14 alkoxy, amino.C14alkylamino, thiol or C14alkylthio or Al and A2 along with N complete a 5 or 6 membered heterocyclic ring optionally containing a N, O or S atom in lieu of a carbon atom; this ring can optionally have a carbon replaced by C14alkyl or R3 represents a group of formula

R2, R6 and R7 have the meaning defined in claim 1 or R2 and R3 together represent a group of formula -NH-CO-NR11-C(=NH)- wherein R11 independently represents H, C1-4alkyl or Cl- 4alkyl-N(R12.R13) wherein R12 and R13 independently represent H or C1-4alkyl or R3 represents cyano C2-6alkanoylamino C2-6alkanoyi C14alkylthio C1-4alkylsulfinyl C1-4alkylsulfonyl C1-4alkyloxycarbonyl halogen C1Xalkyl or a group of formula -NH-CO-Het wherein Het is a heterociclyc complete a 5 or 6 membered heterocyclic ring containing an O or S atom C 1 4alkylsulfonylamino C1-4alkylsulfinylamino C1-4alkylthyoamino C1 alkylamino R6 y R7 are defined in the claim 1 R8 represents H or NO2 or a compound of the formula 2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~

wherein R2, R6, R7 y R8 are defined in claim 1 or a or a pharmaceutically acceptable saltderivated fromthem for use in killing selectively hypoxic tumoral cells in a mammal.

9. A compound as claim 8 wherein R2 is cyano

10. A compound as claims 8 or 9 wherein R6 and R7 independently represent H, Cl, F, MeO or CF3 unless R6 or R7 is not hydrogen.

11. Acompound as claims 8-10 wherein R8 is H.

12. Acompound as claims 8-11 wherein R3 is a group of formula -NH-C 1 -6alkyl-N(A1 )(A2) wherein Al and A2 are independently H or C1-4alkyl optionally replaced the alkyl by hydroxy, CIA alkoxy, amino, C14alkylamino, thiol or C14alkylthio or Al and A2 along with N complete a 5 or 6 membered heterocyclic ring optionally containing a N, O or S atom in lieu of a carbon atom; this ring can optionally have a carbon replaced by C14alkyl

13. A:ompound as claim 8 where the compound ssis any of the following: 6-fluoro-3-(3-dimethylamino-propylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 6-trifluoromethyl-3-(3-dimethylamino-propylamino)-2-quinoxalinecarbonitrile 1,4 dioxide 6-methoxy-3-(3-dimethylamino-propylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 6-fluoro-3-(3-dimethylamino-ethylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 6-trifluoromethyl-3-(3-dimethylamino-ethylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 6-methoxy-3-(3-dimethylamino-ethylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 6chloro-3-(3-dimethylamino-ethylamino)-2quinoxalinecarbonitrile 1,4-dioxide 7-fluoro-3-(3-dimethylamino-propylamin)-2-quinoxalinecarbonitrile 1,4-dioxide 7-trifluoromethyl-3-(3-dimethylamino-propylamino)-2-quinoxalinecarbonitrile 1,4 dioxide 7-methoxy-3-(3-dimethylamino-propylamino)-2quinoxalinecarbonitrile 1.4-dioxide 7-fluoro-3-(3-dimethylamino-ethylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 7-trifluoromethyl-3-(3-dimethylamino-ethylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 7-methoxy-3-(3-dimethylamino-ethylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 7chloro-3-(3-dimethylamino-ethylamino)-2-quinoxalinecarbonitrile 1,4-dioxide or a mixture of isomers in position 6 and 7 or a pharmaceutically acceptable salt derivated from them.

14. A compound jas claim 8 where the compound@is@one of the following: 6(7)-chloro-3-(3-dimethylamino-propylamino)-2-quinoxalinecarbonitrile 1,4-dioxide 7-chloro-3-(3-diiethyIamino-propylamino)-2uinoxalinecarbonitdle 1,4-dioxide 6-chloro-3-(3-dimethylamino-propylamino)-2-quinoxalinecarbonitrile 1,4-dioxide or a pharmaceutically acceptable salt derivated from them.

15. Use of a compound as defined in any of claims 8-14 as medicine

16. Use of a compound as defined in any of claims 8-14 in the preparation of a medicine to selectively kill hypoxic tumoral cells in a mammal.

17 A proccess for preparation of compounds defined in claim 1 that includes the reaction of a formula 3 compound

wherein R2, R6 and R7 have a meaning defined in claim 1 with a compound with a formula NH2-C1-6alkyl-N(A1 )( 2) wherein Al and A2 have a meaning defined in claim 1 in relation with the radical R3, in presence of a polar aprotic solvent and if desired converting the compound thus obtained in a salt.

18. A compound of Formula 1

Substantially as hereinbefore described with reference to any one of the Examples.

19. A compound as defined in claim 8 for use substantially as hereinbefore described.

20. Use of a compound as defined in claim 8 substantially as hereinbefore described.

21. A process for the preparation of compounds of Formula 1

substantially as hereinbefore described with reference to any one of the Examples.