CA1276750C - Process for preparing thiophene compounds - Google Patents

Abstract

"Process for preparing thiophene compounds"
ABSTRACT
A process for preparing a thiophene compound of formula:
where R1, R2, R3 and R4 have the meanings given in the description, or a pharmaceutically acceptable addition salt thereof.
Said compounds are useful in treating tumors.

Description

~ '~7~i7';() "Process for preparing thiophene compounds"
* * * * * * * * * * *
This invention relates to a process for preparing a thiophene compound of formula:

R ~ R
R4 ~ ``S ~ -- R1 (I) 1~
wherein R1 is hydrogen, p-nitrophenoxy, halogen, carboxy, CON(R5,Rb), CONH(CHR9) -COOH, CH2NHR8, NH(CHR9)nAR10, CH=NOH, N02, CHO, OR7 and where in turn R5 and R6, the same or different, are hydrogen, a straight or branched alkyl having 1-8C atoms, a heterocyclic ring selected from the group compris-ing thiophene and imidazole, ascorbyl, peptidyl having up to 5 amino acids or a sugar radical; or R5 and R6 together with the nitrogen atom to which they are linked form the groups necessary for completing a 5-membered heterocyclic ring which may contain other heteroatoms selected from the group consisting of O and N;
R7 has the meanings indicated above for R5 and R6; R8 is an acyl of an aliphatic carboxylic acid having 1-4C atoms; R9 is hydrogen or methyl; Rlo is methyl or phenyl; n is 1,2,3 or 4;
and A is CO or S02;
R2 is hydrogen, N02, halogen, CH(COOH)2, OH, (CH2) COOH where in turn n is 0,1,2,3 or 4;
R3 is hydrogen, N02, OH;
4 Y 9 ' 2' 9 ' 2 3' ' 5' 6 R5 and R6 have the meanings indicated above, provided however that at least two of the substituents Rl, R2, 3 ~ ) 7.j() R3 and R4 are not hydrogen; and R1 is not H when R2 and R4 are N02, and R3 is H; is not iodine when R2 is N02, R3 is H, and R4 is N02 or CH3S02; is not p-nitrophenoxy when R2 is N02 and both R3 and R4 S are H; and is nst CONH2 or COOH when R4 is N02 and both R2 and R3 are H
or a pharmaceutically acceptable addition salt thereof with pharmaceutically acceptable bases or acids.
In the preferred compounds R1 is H, bromine, iodine, carboxy, p-nitrophenoxy, CON(R5,R6), CONH(CHR9) -COOH, NH(CHR9) AR1o, CH=NOH where in turn R5 and R6, the same or different, are hydrogen, a straight or branched alkyl having 1-3C atoms, or together with the nitrogen atom to which they are linked, are the groups neces5ary to complete a morpholine or a pipera~ine ring; R9 is hydrogen or methyl; R1o is methyl or phenyl; n is 1, 2 or 3; and A is tO or S02;
R2 is hydrogen, nitro, carboxy or CH~COOH)2;
R3 is hydrogen or nitro; and R4 is hydrogen, bromine, iodine, nitro or 502-CH3.

~.~'7~i7'il) - 3a -It is a further object of the present invention and the present invention further provides a pharmaceutical composition for treating tumors, containing an effective amount of a compound of the general formula (I) R4 ~ S ~ Rl (I) wherein Rl is hydrogen, p-nitrophenoxy, halogen, carboxy, CON(R5R6), CONH(CHRg)n-COOH~ CH2NHR8, NH(CHRg)nARlo~ CH=NOH, N02, CHO, OR7 and wherein R5 and R6 are the same or different and each represent hydrogen, a straight or branched alkyl having 1-8 carbon atoms, a heterocyclic ring selected from the group comprising thiophene and imidazole, ascorbyl, PeptidylhaVing up to 5 amino acids or a sugar radical; or R5 and R6, together with the nitrogen atom to which they are linked, represent a group necessary for forming a 5-membered heterocyclic ring which may contain other heteroatoms selected from the group consisting of 0 and N; R7 has the meanings indicated hereinbefore for R5 and R6; R8 is an acyl of an aliphatic carboxylic acid having 1-4 carbon atoms; Rg is hydrogen or methyl; Rlo is methyl or phenyl; n is 1, 2, 3 or 4 and A is C0 or S02;
R2 is hydrogen, N02, halogen, CH(COOH)2, OH, (CH2)nCOOH where in turn n is 0,1,2,~ or 4;

~{i7~j(.) - 3b -R3 is hydrogen, N02, OH;
R4 is hydrogen, N02, halogen, S02CH3, OH, N(R5,R6) wherein R5 and R6 have the meanings indicated above, provided however that at least two of the substituents Rl, R2, R3 and R4 are not hydrogen or an addition salt thereo~
with pharmaceutically acceptable acids or bases, together with a pharmaceutically acceptable diluent.
It is a still further object of the present invention and the invention provides for a pharmaceutical composition for treating tumors which contain an effective amount of a compound of formula ~I) wherein A pharmaceutical composition according to claim 1, containing a compound of formula I wherein Rl is H, bromine, iodine, carboxy, p-nitrophenoxy, CON(R5,R6), CONH(CHRg)n-COOH~ NH(CHRg)nARlo~ CH=NOH and wherein R5 and R6 are the same or different and each represent hydrogen, a straight or branched alkyl having 1-3 carbon atoms, or together with the nitrogen atom to which they are linked, represent a group necessary to complete a morpholine or a piperazine ring; Rg is hydrogen or methyl;
Rlo is methyl orphenyl; n is 1, 2 or 3; and A is C0 or SO2;
R2 is hydrogen, nitro, carboxy or CH(COOH)2;
R3 is hydrogen or nitro; and R4 is hydrogen, bromine, iodine, nitro or S02CH3;

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- 3c -or an acid addition salt thereof with pharmaceutically acceptable acids or bases, together with a pharmaceutically acceptable diluent.
The pharmacological action of the compounds of formula I is performed through inhibition of neoplastic growth of cells, blocking of reactions of ox~gen radicals, and radiosensitization. These compounds are thus particularly useful in tumor therapy.
The compounds of this invention may be prepared according to conventional techniques.
Examples of conventional technigues for preparing new compounds of formula I are nitration and halogenation of the thiophene ring, preparation of reactive derivatives of the carboxylic function, such as acid chloride, and use thereof to ~ ~7~j751~

prepare the amides.
Nitration is preferably performed by suspending the proper thiophene derivative in acetic anhydride and adding fuming nitric acid. The reaction mixture is then poured into cold water or water and ice and the desired product is separated by conventional techniques such as filtration or extraction with suitable solvents, e.g. ethyl ether.
Examples of conventional techniques for preparing halo-thio-phene derivatives are the treatment of the proper thiophene derivative (a) with a solution of a halogen, e.g. chlorine or brominer in acetic acid, or (b) with sulfuryl chloride in carbon tetrachloride in the presence of a suitable catalyst such as stannous chloride.
The preparation of reactive derivatives of the carboxylic function such as the acyl chlorides may be also performed by conventional techniques such as treatment with thionyl chloride or phosphorus pentachloride.
The acyl halides may be then reacted in a conventional manner with ammonia, primary or secondary amines, alcohols, phenols, 2û sugars, hydrazines and the like to afford amides, esters or hydrazides.
According to their very nature the compounds of formula I can form addition salts with pharmaceutically acceptable inorganic or organic bases or acids, and these salts are another object of this invention.
The biological and pharmacological activity of the compounds under examination was tested on cell cultures and under gamma radiations. Concentrations of lû , 5 x 10 , lO and 10 M of each compound were used. These aqueous solutions were added to cell cultures containing from 5Q to 60 L 929 cells per mm ;

nutrient solution RPM-1-1640 containing 3% calf serum. Contact between the cells and the compound under examination was conti-nued for six hours under nitrogen and under air. Parts of the solutions during the contact with the drug were irradiated in gamma cell with 1000, 2000 and 3000 rad always using a control sample without the drug.
The results obtained are given in Table 2 (cytotoxicity) and in Table 1 (radiosensitization of the cells in hypoxic condition, in comparison with Misonidazole, a drug known as a radiosensitizer).
For testing the reactivity with oxygen radicals, solutions of the compounds under examination in very pure water were submit-ted to irradiation by an electron flow in accordance with the following procedure:
(a) Reactivity with OH radicals.
The irradiated solution for measurement of reactivity with OH
radicals contained KCNS 10 M and increasing concentrations of the compounds under examination. The concentrations were 10 and 6 X 10 for the first five compounds of Table 1, 10 and 10 , 10 M for the other eight compounds.
The water used for the tests was neutral and made absolutely pure by deionization and four distillations also in the presence of oxidizing agents (KMnO4).
The irradiation conditions were: pulse 50nsec, dose 13 Gy.
Absorption was performed at ~ = 500nm. The results are given in Table 3.
(b) Reactivity with 2 radicals.
The 2 species was generated by irradiation of a 5 x 10 M
solution of potassium formiate satured with 2 with 12Me~ pulsed electron beams.

The concentration of the 2 radical produced is depending from the irradiation dose (which is proportional to the length of the pulse) and was in any case in excess with respect to the concentration of the reacting substance.
The results are qiven in Table 3.

Radiosensitization Index (R.S.I) Compound Concentration R.S.l.
7 ~ 1.38 8 " 1.30 9 " 1.56 ~ 1.58 11 " 1.65 12 " 1.88 13 " 1.65 Misonidazole 1 X 10 M 1.65 Cytotoxicity Index Culture time Ohr 6hr 12hr 24hr Concentration of the compound: 10 M
Control (number of cells) 40 62 80 166 Compound 12 S 50 60 74 t36 TAaLE 3 ~7~j7r~(l Reactivity with OH and 2 radicals measured as a speed constant Compound K (M-l ~l) K (M-~
9 3.1 X 10 22.3 X 10 l X 101 3.3 X 104 12 7~2 X 109 1.0 X 104 13 8.0 X 10 2.3 X 10 The acute toxicity test was carried out by oral and intravenous route on male mice, weighing 19-21 g, which were deprived of meal for 16 hrs before treatment. Oral administra-tion was performed by a gastric probe at doses of 500, 750, 1000 and 2000 mg/kg respectively, of the compounds under examination in aqueous solution of Tween (R). The intravenous administra-tions was performed in the caudal vein at doses of 100 and 200 mg/kg in 0.9% sodium chloride solution. The administered volumes were lml/20g by oral route and 0.5 ml/20g by intravenous route.
After administration the mice were kept under control for 14 days.
The results are given in Table 4.
When occured, the death of the mice receiving the compounds by oral route happened from 4 to 24 hrs after administration and was preceded by trembles, fits and dyspnea. The animals which survived did not show any pathological symptom.
No death occured after intravenous administration.
For therapeutical purposes the compounds of formula I or their salts with pharmaceutically acceptable bases or acid will be administered in vivo in dosages sufficient to reach the desired pharmacological effect. Said quantities will depend on the type of disease to be treated, the patient's condition and weight, the administration route, and other parameters known to 7~i7'i~) .``,' I
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the artisan.
Generally the dose shall be comprised from 1 to 500 mg/kg/day, preferably from 1 to 100 mg/kg/day.
The compounds of formula I or their salts with pharmaceuti-cally acceptable bases or acids will be preferably administered in finished pharmaceutical forms by parental or injectable route.
Examples of suitable pharmaceutical forms for oral admini-stration are tablets, capsules, pills, syrups and solutions.
lG For parenteral administration sterile and lyophilized solu-tions are preferred.
Together with the active ingredient, i.e. a compound of formula l or a salts thereof with pharmaceutically acceptable bases or acids, the pharmaceutical forms may also contain suitable inert and nontoxic solid and liquid diluents as well as preservatives, stabilizing, moistening and emulsifying agents, salts to regulare osmotic pressure, buffers, dyes, flavouring agents, and the like.
They may be prepared by known techniques and may also contain other active ingredients.
The following examples are intended to illustrate the inven-tion without however limiting it.

(a) 5-nitro-Z-thiophenecarboxylic acid.

2-thiophenecarboxylic acid (12.8 9; 0.1 mol) is suspended in 30 ml of acetic anhydride; to the mixture thus obtained cooled to 10C and stirred vigourously are added slowly 9 ml of fuming nitric acid ~d=1.49g/ml). At the end the mixture appears homogeneous. lt is poured into water and ice, extracted with ethyl ether and dried; the solvent is removed by evaporation.

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Yield, 70% after separation of the 4-nitro-2-thiophenecarboxylic acid analog owing to the different solubility in water of their barium salts; m.p. 157-158C.
5-nitro-3-thiophenecarboxylic acid, m.p. 146C, is prepared in a similar manner.
(b) 4-nitro-2-cyanothiophene.
To a solution of 2-cyanothiophene (10.9 9; 0.1 mol) in 25 ml of acetic anhydride (t = 10C) are added 9 ml of fuming nitric acid (d = 1.49 g/ml).
lG The temperature is kept under control. When the reaction is complete the reaction mixture is poured into ice, the precipita-te is filtered, dried, dissolved in 40 ml of ethyl alcohol, and crystallized up to constant melting point (102C); Yield, 30%.
(c) 4-nitro-2-thiophenecarboxylic acid.
A mixture of 4-nitro-2-cyanothiophene (1.5 g; 0.1 mol) in 20 ml of concentrate hydrochloric acid is heated for two hours. As hydrolysis proceeds the reactant goes into solution. The desired product precipitates from the reaction mixture by cooling; m.p.
152-154C (water).
(d) 5-bromo-3-thiophenecarboxylic acid.
A solution containing 16 9 of Br2 (0.1 mol) in glacial acetic acid (200 ml) is added slowly to a solution of 3-thiophenecarbo-xylic acid (12.8 9; 0.1 mol) in 100 ml of glacial acetic acid.
The mixture is stirred for 20' and then poured into water and ice.
The white precipitate is filtered, washed and crystallized from water. Yield, 70%.
(e) 5-nitro-2-thiophenecarboxylic acid chloride.
The crystallized acid (1.7 9; 0.01 mol) is refluxed with an excess of thionyl chloride (0.2 mol) for 60'. The excess of ~ .7~ j 7r~( ) 1, thionyl chloride is removed under vacuum; after distillation in vacuum the desired product solidifies slowly.
5-bromo-3-thiophenecarboxylic acid chloride and its analogs are prepared in a similar manner.

5-nitro-2-thiophenecarboxylic acid amides.
5-nitro-2-thiophenecarboxylic acid chloride is dissolved in toluene and treated with a 4% aqueous solution of sodium hydro-xide containing an equimolecular quantity of the desired amino acid or amine.
The two phases are separated and the product is obtained by acidification of the aqueous phase. Alternatively when the desired product is poorly soluble in water, it is recovered from the organic phase.
The nitrothienylamides may also be obtained by nitration of the amides.
In this manner were prepared N-(5-nitro-2-carboxythienyl)-beta-alanine, m.p. 159-160C (Com-pound 7);
N-(5-nitro-2-carboxythienyl)-gamma-amino-butyric acid, m.p.
110C (dec.) (Compound 8);
5-nitro-2-carboxythiophene-morpholinamide, m.p. 141-143C (Com-pound 9);
5-nitro-2-carboxythiophene-N-methyl-piperazinamide, m.p. 136-138C (Compound 10).

5-nitro-2-(N-acetyl)-thienylamine (Compound 11).
2-thienylamine (11.3 9; 0.1 mol) is added to 30 ml of acetic anhydride cooled to 5C.
The reaction mixture is stirred for 60 minutes and 9 ml of ~ ~7~;75~) fuming nitric acid (d = 1.49 g/ml) are then added slowly.
The mixture is allowed to stand for 20', poured into water and extracted with ethyl ether. The organic layer is dried over sodium sulfate and the solvent is evaporated.

Ethyl-2-(N-(5-nitro-2-thienylamine))-methyl-ketone (Compound 14).
5-nitro-2-thienylamine (3.2 9; 0.02 mol) is dissolved ,n 20 ml of ethyl elcohol.
10To this solution are added 20 ml of a solution of methyl-vinyl-ketone (1.5 9; 0.02 mol) in methyl alcohol.
The solution is allowed to stand overnight.
The solvent is evaporated and the residue is taken up with alcoholic hydrochloric acid.
The product i5 then crystallized from ethyl alcohol as hydrochloride, m.p. 141-144C.

Ethyl-2-(N-(5-nitro-2-thienylamine))-phenyl-sulfone.
5-nitro-2-thienylamine (3.2 9; 0.02 mol) is dissolved in 20 ml of methanol. To this solution is added phenyl-vinyl-sulfone (3.4 9; 0.02 mol) in 20 ml of methanol.
The solution is allowed to stand overnight and acidified with alcoholic hydrochloric acid.
The product is then crystallized from ethyl as hydrochloride, m.p. 133-135C.

5-bromo-2-thiophenaldoxime (Compound 13).
5-bromo-2-thiophenaldehyde (3.8 9; 0.02 mol) is dissolved in hot methyl alcohol.
A solution of hydroxylamine hydrochloride (1.93 9; 0.11 mol) '1 '~7~i7';t) in methyl alcohol is added. The solution is allowed to stand overnight and diluted with water; the precipitate is collected by filtration; m.p. 147C.

5-nitro-3-thiophenemalonic acid (Compound 12).
A mixture of thiophene-3-malonic acid (3.7 9; 0.02 mol) in 15 ml of acetic anhydride is cooled to 5C on a water/ice bath.
1.7 ml of fuming nitric acid (d = 1.49 g/ml) is added drop-wise slowly. The reaction mixture is allowed to stand for 20'.
The reaction mixture is poured into water and extracted with ethyl ether. The organic layer is dried over sodium sulfate and the solvent is evaporated. The residue is crystallized from a little ethyl acetate, m.p. 127-130C.

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Claims (2)

1. A pharmaceutical composition for systemic administration to human beings for blocking the reactions of oxygen radicals in cells and for sensitization of cells, said composition containing an effective amount of the general formula (I) (I) wherein R1 is hydrogen, p-nitrophenoxy, halogen, carboxy, CON(R5R6), CONH(CHR9)n-COOH, CH2NHR8, NH(CHR9)nAR10, CH=NOH, NO2, CHO, OR7 and wherein R5 and R6 are the same or different and each represent hydrogen, a straight or branched alkyl having 1-8 carbon atoms, a heterocyclic ring selected from the group comprising thiophene and imidazole, ascorbyl, peptidyl having up to 5 amino acids or a sugar radical or R5 and R6, together with the nitrogen atom to which they are linked, represent a group necessary for forming a 5-membered heterocyclic ring which may Claim 1 continued contain other heteroatoms selected from the group consisting of 0 and N; R7 has the meanings indicated hereinbefore for R5 and R6; R8 is an acyl of an aliphatic carboxylic acid having 1-4 carbon atoms, R9 is hydrogen or methyl; R10 is methyl or phenyl; n is 1,

2, 3 or 4; and A is CO or SO2;
R2 is hydrogen, NO2, halogen, CH(COOH)2, OH, (CH2)nCOOH where in turn n is 0,1,2,3 or 4;
R3 is hydrogen, NO2, OH;
R4 is hydrogen, NO2, halogen, SO2CH3, OH, N(R5,R6) wherein R5 and R6 have the meanings indicated above, provided however that at least two of the substituents R1, R2, R3 and R4 are not hydrogen or an addition salt thereof with pharmaceutically acceptable acids or bases, together with a pharmaceutically acceptable diluent.

2. A pharmaceutical composition as claimed in claim 1 containing a compound of formula I as defined in claim 1 wherein R1 is H, bromine, iodine, carboxy, p-nitrophenoxy, CON(R5,R6), CONH(CHR9)n-COOH, NH(CHR9)nAR10, CH=NOH and wherein R5 and R6 are the same or different and each represent hydrogen, a straight or branched alkyl having 1-3 carbon atoms, or together with the nitrogen atom to which they are linked, represent a group necessary to complete a morpholine or a piperazine ring; R9 is hydrogen or methyl; R10 is methyl orphenyl n is 1, 2 or 3; and A
is CO or SO2;
R2 is hydrogen, nitro, carboxy or CH(COOH)2;
R3 is hydrogen or nitro; and R4 is hydrogen, bromine, iodine, nitro or SO2CH3.