CA1121817A - Cyanocarboxamidines and quinazoline process - Google Patents

Abstract

111. Abstract Novel cyanocarboxamidines and a method for their preparation are disclosed. The use of these new cyanocarboxamidines as inter-mediates in the one step synthesis of antihypertensive 4-amino-2-(4-substituted-piperazine-1-yl)-quinazolines is also disclosed.

Description

CYANOCARBOXAMIDINES AND QU:[NAZOLINE PROCESS

I. Description:

TECHNICAL FIELD

This invention relates to new and useful N-cyano-N'-phenylcarboxamidines and to their chemical method of preparation. More particularly, the instant invention is concerned with use of the novel carboxamidine compounds as starting material for a one-step synthesis of antihypertensive agents such as the various 4-amino-2-(4-substituted piperazine-l-yl)quinazolines described in U.S. Patents 3,511,836; 3,669,968; 4,001,237; 4,001,238; and 4,101,548; and the 2-(4-substituted homopiperazino)-4-amino-6,7-dimethoxy-quinazolines of U.S. Patent 3,920,636.

BACKGROUND OF PRIOR ART

F. H. S. Curd, et al., J. Chem. Soc. 1759 (1948) describes a procedure for the preparation of 2,4-dichloroquina-zolines. As illustrated below, the Curd, et al. process involves cyclization of an ortho-ureido derivative (1) of various aromatic acids, amides, nitriles and esters with aqueous base or acid to form a 2,4-(lH,3H) quinazolinedione

(2) which is chlorinated to the 2,4-dichloroquinazoline (3).

3 ~ " ~ CH3 ~ N ~

(1) Cl ~ (2) C 3 ~N /J\ C~

(3) The foregoing procedure of Curd, et al. had been employed in the preparation of various quinazolines disclosed in Hess, U.S. Patents 3,511,836 and 3,669,568; Cronin, U.S. Patent 3,517,005; Partyka, et al., U.S. Patents 4,001,237; 4,001,238;
and 4,060,615.
Hess U.S. Patent 3,935,213 describes a process for preparing quinazolines illustrated by formula (6) which involves the use of compounds of formulas (4) and (5) as set forth below.

CH3O ~ / Q A-N
3 ~ NH2 R (5) ,J` '-- /~ V

(6) 8 1 7' German Patent 2,261,739 (1974) (See Chem. Abs. 81, 84394q (1974)) discloses the following synthesis of quinazolin-2,4-dlones:

R~ ~ NHR2 + ClCNC0 ~~~~ ~ ~

Z. Budesinsky, et al., Coll. Czech. Chem. Commun., 37, 2779 (1972) report that treatment of 1-aryl-3-acylureas (7) with polyphosphoric acid yields 4-aroyl (or alkyl)-2-(lH)-quin-azolinones (8). R2 RL~`~CNHCR~ > ~
(7) (8) W. Ried, et al., Chem. Ber., 109, 2706 (1976) (Chem. Abs.
(1976)) describes the reaction of chloroformamidines of formula (9) with cyanamide derivatives of formula (10) to yield 4-amidino-quinazolines of formula (11).

N-C-NH.

R - ¢ . ~ . _~ R

(~) (10) (11) 17' The process of the instant invention for preparing quinazolines characterized by formula (I) below and the Ried, et al. procedure set forth above differ sisnificantly in a number of respects. In the Ried, et al. procedure, the cyano nitrogen in the cyanamide derivative (10) becomes part of the quinazoline ring (i.e., the number 3 position) whereas in the instant invention, the cyano nitrogen of cyanamide becomes the 4-amino group attached to the quinazoline ring.

BRIEF SUMMARY OF INVENTION

Broadly described, this invention is concerned with a new process for the preparation of antihypertensive quinazolines generally typified by formula I

A NH~
~. ,f J ~ I - R~ (I) The instant process involves a one-step conversion of novel piperazinyl substituted N-cyano-N'-phenylcarboxamidines to formula I quinazoline products.

DETAILED DESCRIPTION OF INVENTION

As indicated hereinabove, one aspect of the instant invention is concerned with a process for preparing quinazoline compound of formula I

A NH, ~\~--R, (CH2) n wherein n is equat to 2 or 3;
A is hydrogen or lower alkoxy of 1 to 4 carbon atoms inclusive;

8 and C are independently selected from the group consisting of lower alkoxy of 1 to 4 carbon atoms inclusive;

Rl is selected from the group consisting of lower alkyl of from 1 to 6 carbon atoms inclusive; R2CO in which R2 is cycloalkenyl, cycloalkyl, methylcycloalkyl in which cycloalkyl and cycloalkenyl are from 3 to 8 carbon atoms inclusive; hydroxyalkoxy from 2 to 6 carbon atoms inclusive or phenyl; and ZC=O in which I is a hetero-cyclic radical selected from the group consisting of Ra t ~d ' ~} Re and ~ Re in which X is either oxygen or sulfur, Ra is lower alkyl of 1 to 6 carbon atoms inclusive, Rb is selected from the group consisting of hydrogen, 11~1817 amino, lower alkyl of 1 to 4 carbon atoms inclusive and NHC02Rc in which Rc i~i lower alkyl of 1 to 4 carbon atoms inclusive, R~ and Re are independently selected from the group consisting of hydrogen, lower alkyl of 1 to 6 carbon atoms inclusive, lower '! alkoxy of 1 to 6 carbon atoms inclusive, and lower alkylthio of 1 to 6 carbon atoms inclusive which comprises cyclizing a cyanocarboxamidine of formula II

B 1~ (Cl~ n wherein the symbols "A, B, C, n and Rl are as recited above.

Preferred embodiments of the foregoing process for the preparation of compounds characterized by formula I are those wherein;

(a) The compound of formula II employed in 4-methyl-piperazine-l-~N-cyano-N'-(3,4-dimethoxyphenyl)]-carboxamidine;
(b) The compound of formula II employed is 4-(2-furoyl)-p;peraz;ne-l-~N-cyano-N'-(3,4-dimethoxyphenyl)~-carboxamidine;
(c) The compound of formula II employed is 4-(5-methylthio-1,3,4-oxadiazole-2-carbonyl)piperazine-1-[N-cyano-N'-~3,4-dimethoxyphenyl)]carboxamidine;

(d) The cyclization process is carried out by treating the compound of formula II with phosphorus trichloride or phosphorus pentachloride in a solvent amount of phosphorus oxychloride;
(e) The cyclization process is carried out by treating the co~pound of formula II with phosphorus tribromide or phosphorus pentabromide in a solvent amount of phosphorus oxybromide;
(f) The cyclization process is carried out by treating the compound of formula II with aqueous hydrochloric acid;
(g) The cyclization process is carried out by treating the compound of formula II with hydrogen chloride in phosphorus oxychloride;
(h) The cyclization process is carried out by treating the compound of formula II with a Lewis acid catalyst;
(i) The cyclization process is carried out at a temperature of 25-125;
(j) The cyclization process is carried out at a temperature of 70-100;
(k) The cyclization process is carried out for a period of 1 to 3 hours at a temperature ;n the range of 70-100.

A preferred embodiment of the present invention is a process for the preparation of a quinazoline of formula Ia N~2 CH30 ~A ~ ~Ia) C~130 N ~/N-C

11'~1~1 7 which comprises cyclizing a cyanocarboxamidine having formula IIa CX30 ~ NC-NH ~ 0 ~ (Ila) CH30 ~ N=C- N-C - 0 Another preferred embodiment of the present invention is the process for the preparation of a quinazoline of formula Ib N~
CH30 ~ ~ ~ -C ~ 0 ~ -CH3 which comprises cyclizing a cyanocarboxamidine having formula S IIb CH30 ~ NC-NH o r ~ (IIb) CH,0 ~ N-C - ~ -C o ~ S-CH3 Another preferred embodiment of the present invention is a process for the preparation of a quinazoline of for~ula Ic NH~
CH30 ~ ~0~ r 1 (Ic) CH30 ~ ~ ~ -C ~

~ L8~7 which comprises cyclizing a cyanocarboxamidine having formula IIC

CH30~ NC-NH ~\ O
CH30--~!LN=C~ C~ (IIc) Another preferred embodiment of the present invention is the process for the preparation of a quinazoline of formula Id ~1 Cd 3 ~N O OH
CH30~ J{~-COCHZC(CH3), (Id) which comprises cyclizing a cyanocarboxamidine having formula IId CH,O~ NC-NH O OH
CH,O~LN-C-N/~I-COCH~ C(CH,) z (lId) Preferred groups of compounds contemplated within the class of cyanocarboxamidines of formula II are those wherein:

(a) the A, B and C substituted phenyl radical is 3,4-dimethoxyphenyl, n is 2, or 3 and Rl is selected from the group consisting of methyl, cyclopentyl, 2-furoyl, 5-methylthio-l,3,4-oxadiazole-2-carbonyl, 2-methyl-2-hydroxypropoxycarbonyl;
(b) The A, B and C substituted phenyl radical is 2,3,4-trimethoxyphenyl, n is 2 or 3 and Rl is selected from the group consisting of methyl, cyclopentyl, 1~1817 --1 o--2-furoyl, 5-methylthio-1,3,4-oxadiazole-2-carbonyl, 2-methyl-2-hydroxypropoxycarbonyl.

Particularly prepared cyanocarboxamidines of formula II are:

4-methylpiperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]-carboxamidine;
4-(2-furoyl)piperazine-1-[N-cyano-N'-(3,4-dimethoxy-phenyl)]carboxamidine;
4-(5-methylthio-1,3,4-oxadiazole-2-carbonyl)piperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine;
4-(2-methyl-2-hydroxypropoxycarbonyl)piperazine-1-[N-cyano-N'-(2,3,4-trimethoxyphenyl)]carboxamidinei 4-(cyclopentylcarbonyl)piperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine;
4-(2-furoyl)homopiperazine-1-[N-cyano-N'-(3,4-dimethoxy-phenyl]carboxamidine It is to be understood that the term "cycloalkyl" as used herein includes cycloalkyl radicals containing 3 to 8 ring carbon atoms inclusive and encompasses such groups as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl. The term "methylcycloalkyl" refers to the aforementioned cycloalkyl radicals containing from 3 to 8 ring carbons inclusive having a methyl substituent and encompasses such groups as l-methyl-cyclopropyl, l-methylcyclopentyl, 2-methylcyclopentyl, 3-methylcyclopentyl, l-methylcyclohexyl, 2-methylcycloheptyl, 4-methylcyclohexyl, and the like. By the term "cycloalkenyl", it is intended to refer to those having from 4 to 8 ring carbon atoms inclusive containing a single ring carbon-carbon double bond encompassing such groups as l-cyclobutenyl, l-cyclopentenyl, 2-cyclopentenyl, 3-cyclopentenyl, l-cyclohexenyl, 2-cyclohexenyl, and the like.

It is also to be understood that by the terms "lower alkyl" and "lower alkoxy", as used herein, it ;s meant that the carbon chain which comprises these groups include both straight and branched carbon radicals of the designated number of carbon atoms inclusive. Exemplary of carbon chain radicals have 1 to 4 carbon atoms inclusive are methyl, ethyl, propyl, isopropyl, l-methylpropyl, 2-methylpropyl, and tert.-butyl.

By the term "independently selected", as used herein, it is meant that the recited substituents such as A, B, C, Rd and ! Re may or may not be identical.

Conversion of formula II carboxamidines to quinazolines of formula I is carried out by treating the formula II carboxamidines with cyclizing reagents such as phosphorus trichloride or phosphorus pentachloride in a solvent amount of phosphorus oxychloride. Other phosphorus halides and phosphorus oxyhalides such as phosphorus tribromide and phosphorus pentabromide in a solvent amount phosphorus oxybromide may be employed. Ring closure of the carboxamidines of formula II to the quinazoline compounds of formula I is acid catalyzed with reagents such as aqueous hydrochloric acid, hydrogen chloride in phosphorus oxychlor;de, trichloroacetic acid or Lewis acid catalyst such as ZnC12, FeC13, AlC13, AlBr3, and the like.

With respect to carrying out the reaction with phosphorus halides, approximately equimolar portions of the formula II
carboxamidines and phosphorus halides are employed with a convenient solvent amount of phosphorus oxyhalide relative to the amount of carboxamidine starting material. The ter~
"solvent amount" used herein, refers to a quantity of phosphorus oxychloride or phosphorus oxybromide sufficient to provide good mixing and handling characteristics with respect to the reaction mixtures. For this purpose, a ratio of from about 2 to 15 ml. of the phosphorus halide for each gram of the carboxamidine reactant of formula II is generally preferred.

Commonly used temperatures for carrying out the cyclization reaction range from about 25-125 with a particularly preferred temperature range of from about 70-100. As will be appreciated by those skilled in the art, reaction tlme and conditions required for cyclization of the compounds of formula II and formation of the compounds of formula I vary according to several factors such as temperatures and reaction times. For instance, at lower temperatures, long reaction periods are needed, while at higher temperatures, the cyclization reaction is completed in a shorter time. Reaction periods from about 0.5 to 24 hrs. can be used with a period of 1.0 to 3.0 hrs. preferred at a temperature in the range of about 70-100 .

During the cyclization reaction of the formula II carbox-amidines, the cyano carbon acts as a carbonium ion forming a carbon-carbon bond with the benzene nucleus thereby establishing the quinazoline ring while the cyano nitrogen becomes the quinazoline 4-amino group.

The carboxamidines of formula II used as starting materials in the instant process for preparation of quinazoline compounds of formula I are themselves new compounds which are prepared by (a) treating the corresponding urea or thiourea of formula III

NH-C~ i-R, (III) C CH2);, wherein the symbols "A, B, C, n, and Rl'' are as recited above and Y is sulfur or oxygen with an R-X alkylating reagent in which R is lower alkyl ll'~i817 of 1 to 4 carbon atoms inclusive or an aryl derivative containing electron withdrawing groups (e.g., 2,4-dinitrophenyl), X is halogen (e.g., Cl, Br, and I), lower alkyl S04 of 1 to 4 carbon atoms inclusive, phenyl S03, F3CS03, and the `! like to provide a hydrohalide intermediate of formula IV
A~

C NR~C - N/ ~ -~ (Iv) wherein the symbols "A, B, C, n, R, Rl, X and Y"
are as recited above, and then (b) reacting the halide intermediate IV with cyanamide to provide carboxamidines of formula II.

Alkylation of urea and thiourea starting materials of formula III and subsequent reaction with cyanamide is normally carried out in a reaction inert organic solvent. Suitable solvents include dioxane, tetrahydrofuran, dimethyl sulfoxide, diethyl sulfoxide, and alkanol solvents such as methanol, ethanol, or isoamyl alcohol. The reaction can be conducted at temperatures vary;ng within the range of from about 25 to 100C. for a period of about 0.5 to 24 hrs.

In addition to the above process, alternate methods for preparing carboxamidines of formula II can be employed as depicted in the reaction schemes below.

,~

Method A
A

~, 3--t --NH2 + (CH3S) 2C-~C~ 7 , C
(V) A ~ N-Rl B ~L " For~ula Il (VI) Method B

r~ ' }~N-Rl I (CH3S) 2C=NCN

(VII) A>~::~
B ~LH2 .lC-N ~
Fo~mula I I
, \_J
(VIII) 3~ 7 Thus, reaction of (CH3S)2C=NCN or chemical equivalents thereof with formula V anilides or formula VII piperazines wherein the symbols "A, B, C, n and Rl" are as previously defined provide cyano intermediates VI and VIII, respectively. Treating the cyano intermediate VI with a piperazine of Formula VII or the cyano intermediate VIII with an aniline of Formula V
affords the formula II carboxamidines.

The formula III urea and thioureas are obtained by reacting appropriately substituted phenylisocyanates and phenyl-isothiocyanates with N-substituted piperazines and homopiperazines in an inert reaction solvent such as ethanol. Required piperazine and homopiperazine starting material is obtained by conventional procedures; e.g. acylation of piperazine or homopiperazine with o ZCCl wherein Z is as previously defined.

In addition to being useful intermediates in the preparation of the compounds of formula I, the carboxamidines of formula II
are also valuable for their anti-ulcer properties, for instance, 4-~2-furoyl)piperazine-l-[N-cyano-N'-(3,4-dimethoxyphenyl)]-carboxamidine and 4-(5-methylthio-1,3,4-oxadiazole-2-carbonyl)-piperazine-l-~N-cyano-N'-3,4-diméthoxyphenyl]carboxamidine at a subcutaneous dose of lO mg/kg and 3 mg/kg body weight, respectively, inhibit acid secretion in the pylorus ligated rat model of Shray, Gastroenterology, 5, 43 (1946).

The following examples further illustrate the present invention and will enable others skilled in the art to understand it more completely. It is to be understood that the invention is not limited solely to the particular examples given below.
All temperatures expressed herein are in degrees centrigrade.

~ L8 1 7 Example I

4-Methylpiperazine-l-[N-cyano-N'-(3,4-dimethoxyphenyl)]-carboxamidine CH 30 ~_ NC-~"d CH30-- ~=C `;~I-C-~3 (a) A solution of 3,4-dimethoxyphenyl isothiocyanate (6.8 g., 34.8 mmoles) obtained according to the procedure of G. M. Dyson, et al., J. Chem. Soc., 436 (1927) in 34 ml. of absolute ethanol is added to a stirred solution of N-methyl-piperaz;ne (3.49 9., 30.8 mmoles) in 100 ml. of absolute ethanol. After heating the solution of reflux for a 2 hr.
period, the solvent is removed under reduced pressure. The semi-solid residue thus obtained is first crystallized from toluene to provide 8.95 9. (87% yield), m.p. 156-159.5 of the carbothioamide intermediate. Crystallization of this material from nitromethane affords analytically pure 4-methylpiperazine-1-(N-3,4-dimethoxyphenyl) carbothioamide, m.p. 158-161.

Anal. Calcd. for C14H21N302S: C, 56.92; H, 7-16; N, 14-23;
S, 10.85. Found: C, 56.74; H, 7.38; N, 14.40; S, 10.90.

(b) Methyl iodide (1.2 9., 0.0303 mole) is added to a suspension of 4-methylpiperazine-1-(N-3,4-dimethoxyphenyl)-carbothioamide (8.95 9., 0.0303 mole) in 125 ml. of methanol.
The reaction mixture is then stirred at reflux temperature for a period of 2 hr. and cooled to 25. Cyanamide (8.7 g., 0.27 mole) is added to the cooled solution and reflux continued for an additional 16 hr. period. After the solvent is removed under reduced pressure, residual oil is made strongly basic with acqueous 4.0 N sodium hydroxide and then extracted with chloroform. The chloroform extracts are washed with water, saturated brine solution and dried. Concentration of the ~! dried solution affords a residual gum which when rubbed under cold toluene provides 4.46 g., (49~ yield) of crystalline material, m.p. 155-158. Recrystallization from toluene affords analytically pure 4-methylpiperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]-carboxamidine, m.p. l60-l63.

Anal- Calcd- for C15H2lN32 C~ 59-3 ;
Found: C, 58.95; H, 6.83; N, 22.35.

(c) Following the procedure of Example l(a), but employing an equimolar amount of 3,4-dimethoxyphenylisocyanate in place of lS 3,4-dimethoxyphenylisothiocyanate, there is produced N-(3,4-dimethoxyphenyl)-4-methyl-l-piperazinecarboxamide. The carboxamide treated with methyl iodide and then with cyanamide according to the procedure of Example l(b) provides 4-methyl-piperazine-l-[N-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine.

Example 2 4-(2-Furoyl)piperazine-l-[N-cyano-N'-(3,4-dimethoxyphenyl)~-carboxamidine CH30--~ NC-NH- 0 CEI30~L N=C~

(a) A solution of 3,4-dimethoxyphenyl isothiocyanate (3,21 9., 16.4 mmoles) in 10 ml. of absolute ethanol is added to a stirred solution of 1-(2-furoyl)piperazine (2.96 9., 16.4 mmoles) prepared according to the procedure of M. Desai, et al., Org. Prep. Proced.
Int., 8, 85 (1976) in 35 ml. of absolute ethanol and the reaction solution refluxed for a period of 2.5 hr. Concentration of the reaction mixture under reduced pressure provides a dark yellow gum which rubbed under cold ethanol affords 5.39 9., (87% yield) of yellow solid material, m.p. 183-187. Crystallization of this material from acetonitrile affords analytically pure 4-(2-furoyl)-piperazine-l-(N-3,4-dimethoxyphenyl)-carbothioamide, m.p. 185-188.

Anal. Calcd. for C18H21N3045: C, 57.59; H, 5.64; N, 11-19;
S, 8.54. Found: C, 57.23; H, 5.48; N, 11.53; S, 8.54.

(b) To a suspension of 4-(2-furoyl)piperazine-1-(N-3,4-dimethoxy-phenyl)carbothioamide (22.0 9., 0.0586 mole) in 400 ml. of methanol is added methyl iodide (8.32 9., 0.0586 mole). The mixture is stirred and rèfluxed for a per;od of 2.5 hr. and then cooled to 20.
Cyanamide (18.7 9., 0.445 mole) is added to the cooled solution, and the mixture refluxed for an additional period of 16 hr. and the solvent evaporated under reduced pressure to provide an oily residuewhich is made strongly basic with aqueous 4.0 N sodium hydroxide.
The basic mixture is extracted with chloroform and the chloroform extracts washed first with water and then with saturated brine solution. After drying, the chloroform extract is concentrated under reduced pressure providing a residual gum which is crystallized by rubbing under cold ethanol to afford 11.1 9. (49% yield) of white solid, m.p. 181-183.5. Crystallization of this material from ethanol provides analytically pure 4-(2-furoyl)piperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine, m.p. 186.5-188.5.
Anal- Calcd- for C19H21N54 C~ 59-52; H~ 5-52; N~ 18-27-Found: C, 59.13; H, 5.40; N, 18.07.

(c) Following the procedure of Example 2(a), but employing equimolar amount of 3,4-dimethoxyphenylisocyanate in place of 3,4-l7 _19_ dimethoxyphenylisothiocyanate, there is obtained N-(3,4-dimethoxy-phenyl)-4-(2-furoyl)-1-piperazinecarboxamide. Reaction of the carboxamide with methyl iodide and then with cyanamide according to the procedure of Example 2(b) provides 4-(2-furoyl)piperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine.
!

Example 3 4-(5-Methylthio-1,3,4-oxadiazole-2-carbonyl)piperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine CH,O ~ NC-NH O
CH30 ~ ~ =C~ C ~ ~ S-C~I3 (a) 1-(5-Methylthio-1,3,4-oxadiazole-2-carbonyl)p;perazine hydrochloride (5.29 9., 0.02 mole) is first added to a stirred solution of triethylamine (2.02 9., 0.02 mole) in 50 ml. of absolute ethanol followed in 5 min. by a solution of 3,4-dimethoxyphenyl isothiocyanate (3.90 9., 0.02 mole) in 15 ml. of absolute ethanol to provide a pale yellow gummy precipitate. The reaction mixture is heated to reflux (during which time the gum crystallizes), diluted with 28 ml. of absolute ethanol, refluxed for an addit;onal 3 hr.
period and filtered. The collected material is washed with absolute ethanol and crystallized from methanol to provide 4.41 9. (52Yo yield) of 4-(5-methylthio-1,3,4-oxadiazole-2-carbonyl)piperazine-1-(N-3,4-dimethoxyphenyl)carbothioamide, m.p. 143.5-147.

Anal- Calcd- for C17H21N54S2 C, 48.21; H~ 5-00, N~ 16-54i S, 15.14. Found: C, 48.28; H, 4.90; N, 16.46; S, 15.19.

(b) Methyl iodide (1.06 g., 7.44 mmoles) is added to a suspension of 4-(5-methylth;o-1,3,4-oxadiazole-2-carbonyl)-piperazine-1-(N-3,4-dimethoxyphenyl)carbothioamide (3.15 9., 7.44 mmoles) in 100 ml. of methanol. The mixture is st;rred at reflux temperature for a period of 2.5 hr. and the resulting solution concentrated under reduced pressure to a wlume of about 60 ml. where a precipitate begins. The mixture is chilled at 0 and filtered to yield 2.93 9. (70%) yield) of 1-~methylthio-EN-(3,4-dimethoxyphenyl)[iminocarbonyl]-4-(5-methylthio-1,3,4-oxadiazole-2-carbonyl)-piperazine hydroiodide, m.p. 180.5-185 (dec.). Crystal-lization from ethanol provided analytically pure hydroiodide inter-mediate, m.p. 184-187 (dec.).

Anal Calcd. for C18H23N50452 HI: C, 38.24i H, 4-28; N~ 12-39-Found: 38.49; H, 4.44; N, 12.01.

(c) Cyanamide (0.66 g., 15.7 mmoles) is added to l-Emethylthio-[N-(3,4-dimethoxyphenyl)]iminocarbonyl]-4-(5-methylthio-1,3,4-oxa-diazole-2-carbonyl)piperazine (2.44 9., 5.58 mmoles) free base in 35 ml. of absolute ethanol. The mixture is stirred at reflux tem-perature for a period of 20 hr., cooled in an ice bath and filtered to provide 1.12 g. (49% yield) of off-white solid, m.p. 175-181.
Crystallization of this material from methanol affords analyt;cally pure 4-(5-methylthio-1,3,4-oxadiazole-2-carbonyl)piperazine-1-EN-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine, m.p. 174-178.

Anal. Calcd. for C18H21N704S: C, 50.12i H, 4-90; N~ 22-73-Found: C, 50.08; H, 4.73; N, 22.57.

(d) Following the procedure of Example 3(a), but employing an equimolar amount of 3,4-dimethoxyphenylisocyanate in place of 3,4-dimethoxyphenylisothiocyanate, there is obtained N-(3,4-dimethoxyphenyl)-4-(5-methylthio-1,3,4-oxadiazole-2-carbonyl)-1-piperazine carboxamide. Reaction of the carboxamide with methyliodide and then with cyanamide according to the procedures of Examptes 3(b) and 3(c), respectively, provides 4-(5-methylthio-1,3,4-oxadiazole-2-carbonyl)piperazine-1-[N-cyano-N'-3,4-dimethoxyphenyl)]-carboxamidine.

Example 4 4-(2-Methyl-2-hydroxvpropoxycarbonyl)p;perazine-1-[N-cyano-N'-2,3,4-trimethoxyphenyl]carboxamidine CH30 ~ NC-NH ~ OH
CH30 ~ C--101- OCH~C(CH3) 2 OCH3 . ~

Reaction of 2,3,4-trimethoxyphenylisothiocyanate with 1-(2-methyl-2-hydroxypropoxycarbonyl)piperazine according to the procedure of Example l(b) provides 4-(2-methyl-2-hydroxypropoxycarbonyl)-piperazine-l-(N-2,3,4-trimethoxyphenyl)carbothioamide. Subsequent reaction of the carbothioamide with methyl iodide and then with cyanamide according to the procedure of Example l(b) accords 4-(2-methyl-2-hydroxypropoxycarbonyl)piperazine-1-~N-cyano-N'-2,3,4-trimethoxyphenyl]carboxamidine.

Example 5 4-(Cyclopentylcarbonyl)piperazine-1-~N-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine CH30 ~C~LNC- IH o~--C{l Following the procedure of Example l(a) but employing an equimolar amount of N-(cyclopentylcarbonyl)piperazine in place of N-methylpiperazine, there is produced 4-(cyclopentylcarbonyl)-piperazine-l-(N-3,4-dimethoxyphenyl)carbothioamide. Reaction of the carbothioamide with methyl iodide and then with cyanamide according to the procedure of Example l(b) affords 4-(cyclopentyl-3~ 7 carbonyl)piperazine-l-[N-cyano-N'-(3,4-dimethoxyphenyl]carboxamidine.

Example 6 4-(2-Furoyl)homopiperazine-l-[N-cyano-N'-(3,4-dimethoxyphenyl]-, carboxamidine C~30 ~ N c---N ~ - c ~

Followin~ the procedure of Example l(a-b) but substituting 1-(2-furoyl)homopiperazine for 1-(2-furoyl)piperazine, the title compound is obtained.

Example 7 4-Amino-6,7-dimethoxy-2-(4-methylpiperazine-1-yl)quinazoline dihydrochloride Phosphorus pentachloride (0.31 9., 1.48 mmoles) is added with stirring to 10 ml. of phosphorus oxychloride followed in 5 min.
by 4-methylpiperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]-carboxamidine of Example 1 (0.45 9., 1.48 mmoles). The reaction mixture is heated at 95-98 for a period of 2.5 hr. during which time a yellow gum forms and changes to a suspended sol;d by the end of the heating period. The reaction mixture is then cooled to 30 and excess phosphorus oxychloride removed under reduced pressure to provide a residual material which is treated cautiously with ice/
water. The aqueous phase is filtered and the filtrate concentrated under reduced pressure to provide a brown oil which is crystallized by rubbing under cold acetone. Insoluble material is collected and crystallized from methanol to afford 0.175 9., 31% yield of 4-amino-6,7-dimethoxy-2-(4-methylpiperazine-1-yl)-quinazoline dihydrochloride, m.p. 280-282 (dec) identical with the sample prepared according to the procedure clescribed in U.S. Patent 3,511,836.

Example 8 4-Amino-6,7-dimethoxy-2-[4-(2-furoyl)piperazine-1-yl]quinazoline ! 5 hydrochloride Hydrogen chloride gas is bubbled for a period of 8 min. into a cold, stirred mixture of 4-(2-furoyl)piperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine of Example 2 (3.0 9., 7.82 mmoles) in 45 ml. of phosphorus oxychloride. After addition of the hydrogen chloride gas, the reaction mixture is stirred at 25-30 for 10 min.
and then heated at 70-75 for a period of 75 min. during which time a gummy solid separates. The reaction mixture is cooled to 30, the excess phosphorus oxychloride removed under reduced pressure and residual material rubbed under ice/water to provide a solid. The sol;d is collected to afford 2.76 9. (84% yield) of 4-amino-6,7-dimethoxy-2-[4-(2-furoyl)piperazine-1-yl~quinazoline hydrochloride identical with a sample prepared according to the procedure of U.S.
3,511,836.

Example 9 4-Amino-6,7-dimethoxy-2-14-(5-methylthio-1,3,4-oxadiazole-carbonyl]piperazine-l-yl]quinazoline hydrochloride Hydrogen chloride gas is bubbled for a period of 4 min. into a cold, stirred mixture of 4-(5-methylthio-1,3,4-oxadia7O1e-2-carbonyl)piperazine-l-[N-cyano-N'-(3,4-dimethoxyphenyl)~carboxamidine of Example 3 (0.16 9., 0.37 mmoles) in 6 ml. of phosphorus oxychloride and the mixture then stirred at 25-30 for an additional 8 min.
period and finally heated to 72-75 for a period of 75 min. during which time a pale yellow solid precipitates. After the heating period, the mixture is cooled to 30, excess phosphorus oxychloride removed under reduced pressure and residual solid rubbed under ice/water and collected to provide 4-amino-6,7-dimethoxy-2-[4-(5-methylthio-l,3,4-oxadiazole-2-carbonyl]piperazine-l-yl]quinazoline hydrochloride in 95% yield identical to a sample prepared according to the pro-cedure of U.S. Patent 4,00l,238.

Example lO

The cyclization procedure illustrated in Examples l-3 is repeated with the following cyanocarboxamides:

4-(2-methyl-2-hydroxypropoxycarbonyl)piperazine-l-[N-cyano-N'-(2,3,4-trimethoxyphenyl)]carboxamidine, 4-(cyclopentylcarbonyl)piperazine-l-[N-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine, 4-~2-furoyl)homopiperazine-l-[N-cyano-N'-(3,4-dimethoxy-phenyl)]carboxamidine, to produce respectively, (a) 4-amino-6,7,8-trimethoxy-2-[4-(2-methyl-2-hydroxy-propoxycarbonyl)piperazine-l-yl]quinazoline, (b) 4-amino-6,7-dimethoxy-2-[4-cyclopentylcarbonyl)-piperazine-l-yl]quinazoline, (c) 4-amino-6,7-dimethoxy-2-[4-(2-furoylhomopiperazine-l-yl)]quinazoline.

STATEMENT OF INDUSTRIAL APPLICATION

The novel N-cyano-N'-phenylcarboxamidine compounds of this invention are particularly valuable as intermediates in the pre-paration of antihypertensive 4-amino-2-(4-substituted-piperazine-l-yl)-quinazolines. The invention includes the method of preparation .817 of the novel N-cyano-N'-phenylcarboxamidines as well as the one step synthesis of the aforesaid antihypertensive compounds utilizing the novel N-cyano-N'-phenylcarboxamidines of the invention.

The novel N-cyano-N'-phenylcarboxamidine compounds are also ! 5 valuable in the treatment of ulcers.

Claims (15)

1. A process for preparing a quinazoline compound of formula I

wherein n is the integer 2 or 3;
A is hydrogen or lower alkoxy of 1 to 4 carbon atoms inclusive;
B and C are independently selected from the group consisting of lower alkoxy of 1 to 4 carbon atoms inclusive;
R1 is selected from the group consisting of lower alkyl or from 1 to 6 carbon atoms inclusive;
R2CO in which R2 is cycloalkenyl, cycloalkyl, methylcycloalkyl in which cycloalkyl and cyclo-alkenyl are from 3 to 8 carbon atoms inclusive;
hydroxyalkoxy from 2 to 6 carbon atoms inclusive or phenyl; and ZC=O in which Z is a heterocyclic radical selected from the group consisting of , , , , and in which X is either oxygen or sulfur, Ra is lower alkyl of 1 to 6 carbon atoms inclusive, Rb is selected from the group consisting of hydrogen, amino, lower alkyl of 1 to 4 carbon atoms inclusive and NHCO2Rc in which Rc is lower alkyl of 1 to 4 carbon atoms inclusive, Rd and Re are independently selected from the group consisting of hydrogen, lower alkyl of 1 to 6 carbon atoms inclusive, lower alkoxy of 1 to 6 carbon atoms inclusive, and lower alkylthio of 1 to 6 carbon atoms inclusive which comprises cyclizing a cyanocarboxamidine of formula II

(II) wherein the symbols "A, B, C, n and R1" are as recited above.

2. The process of Claim 1 wherein the compound of formula II employed is 4-methylpiperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]carboxamidine.

3. The process of Claim 1 wherein the compound of formula II employed is 4-(2-furoyl)piperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)carboxamidine, having the formula

4. The process of Claim 1 wherein the compound of formula II employed is 4-(5-methylthio-1,3,4-oxadiazole-2-carbonyl)piperazine-1-[N-cyano-N'-(3,4-dimethoxyphenyl)]-carboxamidine, having the formula

5. The process of any of Claims 1 to 3 wherein the cyclization process is carried out by treating the compound of formula II with phosphorus trichloride or phosphorus pentachloride in a solvent amount of phosphorus oxychloride.

6. The process of any of Claims 1 to 3 wherein the cyclization process is carried out by treating the compound of formula II with phosphorus tribromide or phosphorus pentabromide in a solvent amount of phosphorus oxybromide.

7. The process of any of Claims 1 to 3 wherein the cyclization process is carried out by treating the compound of formula II with aqueous hydrochloric acid.

8. The process of any of Claims 1 to 3 wherein the cyclization process is carried out by treating the compound of formula II with hydrogen chloride in phosphorus oxychloride.

9. The process of any of Claims 1 to 3 wherein the cyclization process is carried out by treating the compound of formula II with a Lewis acid catalyst.

10. The process of any of Claims 1 to 3 wherein the cyclization process is carried out at a temperature of 25-125°.

11. The process of any of Claims 1 to 3 wherein the cyclization process is carried out at a temperature of 70-100°.

12. The process of any of Claims 1 to 3 wherein the cyclization process is carried out for a period of 1 to 3 hours at a temperature in the range of 70-100°.

13. A process as in Claim 1 for the preparation of a quinazoline of formula Ic (Ic) which comprises cyclizing a cyanocarboxamidine having formula IIc (IIc)

14. A process as in Claim 1 for the preparation of a quinazoline of formula Id (Id) which comprises cyclizing a cyanocarboxamidine having formula IId (IId)

15. A process for the preparation of quinazolines of the formula:

wherein R is hydrogen or methoxy and R' is cyclopentyl, furyl, thienyl, 2-hydroxyalkoxy or by cyclizing compounds of the formula:

wherein R and R' are as above.