Indian Patents. 213303:REGIOSPECIFIC PROCESS FOR THE PREPARATION OF 4-[1-(4-CYANOPHENYL)-1-(1,2,4 TRIAZOL-1-YL)METHYL]BENZONITRILE

Title of Invention	REGIOSPECIFIC PROCESS FOR THE PREPARATION OF 4-[1-(4-CYANOPHENYL)-1-(1,2,4 TRIAZOL-1-YL)METHYL]BENZONITRILE
Abstract	A regiospecific process for the preparation of 4-[1-(4-cyanophenyl)-1-(1,2,4-triazol-1-yl) methyl]benzonitrile comprising reacting 4-halomethylbenzonitrile with 4-amino-1,2,4-triazole followed by deamination and reaction with 4-fluorobenzonitrile.

Full Text	FORM 2 THE PATENTS ACT, 1970 (39 OF 1970) COMPLETE SPECIFICATION (See section 10) REGIOSPECIFIC PROCESS FOR THE PREPARE CYANOPHENYL)-l-(l,2,4-TRIAZOL-l-YL)METHYL. SUN PHARMACEUTICAL INDUSTRIES LTD. A company incorporated under the laws of India having their office at ACME PLAZA, ANDHERI-KURLA ROAD, ANDHERI (E), MUMBAI-400059. MAHARASHTRA, INDIA The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed. REGIOSPECIFIC PROCESS FOR THE PREPARATION OF 4-[l- (4-CYANOPHENYL)-l-(l,2,4-TRIAZOL-l-YL)METHYL]BENZONITRILE The present invention relates to a regiospecific process for the preparation of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, free of isomeric and triaryl impurities. 4-[l-(4-cyanophenyl)-l-(1,2,4-triazol-l-yl)methyl]benzonitrile or"Letrozole (INN name) is an antineoplastic agent. Formula 1 PRIOR ART: United States Patent No. 4978672 (referred to herein as "672, Indian Reference not available) provides 4-[alpha- (4-cyanophenyl)-l-(l,2,4-triazolyl)-methyl]benzonitrile and the process of its preparation. The patent discloses reacting 4-bromomethylbenzonitrile with 1,2,4-triazole to yield 4-[l-(l,2,4-triazol-l-y!)merhyl]benzonitrile. 4-[l-(l,2,4-triazol-l-yl)methyl]benzonitrile is then reacted with 4-fluorobenzonitrile to give 4-[l-(4-cyanophenyI)-l-(l,2,4-triazol-l-yl)methyl]benzonitriie. This patent does not disclose the purity of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, compound of formula 1. When we followed the patented process we also get the unwanted isomer 4-[l-(l,2,4-triazo!-4-yl)methyl]benzonitrile, a compound of formula 4 (20 to 40%) in step 1. When the reaction mixture of step 1 is treated with 4-fluorobenzonitrile it yields 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)-methyl]-benzonitrile, a compound of formula 1, and its isomer, a compound of formula 5. Thus the impurity of formula 4 has to be separated before treating it with 4-fluorobenzonitrile, which involves an additional step of column purification, which is reported in "672 and makes the process tedious and commercially unviable. Formula 4 Formula 5 Further, if the intermediate contains an impurity like 4-toluonitrile or other related impurities, that are present in the raw material viz. 4-(bromomethyl)benzonitrile, in step 2, the impurities would participate in the reaction with 4- fluorobenzonitrile leading to the formation of 4-[l,l-Bis(4-cyanophenyl)methyl]benzonitrile (referred to herein as "tris impurity") compound of formula 6 and other side products. CN NC, OBJECTS OF THE INVENTION: The object of the present invention is to provide a regiospecific process for the preparation of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, free of impurities viz. 4-[l-(4-cyanophenyl)-l-(l,2,4-triazo!-4-yl)methyl]benzonitrile, compound of formula 5, and 4-[l,l-Bis(4-cyanophenyl)methyl]benzonitrile compound of formula 6. 3 Formula 3 Formula 4 Another object of the present invention is to provide a regiospecific process for the preparation of 4-[l-(lH-l,2,4-triazoI-l-yI)methylene]benzonitrile, a compound of formula 3, substantially free of compound of formula 4 by eliminating the formation of an unwanted isomer. Yet another object of the present invention is to purify the intermediate compound of formula 2, which is a precursor to the regioselective isomer using simple purification technique, in-order to eliminate all the impurities, which would be present in its raw material and yield compound of formula 1 free of also the "tris impurity" compound of formula 6. The regiospecific process for preparation of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, said process comprising NC. formula 1 4 (a) reacting 4-halomethylbenzonitrile with 4-amino-l,2,4-triazoIe to give 4-[(4-amino-4H-l,2,4-triazolium-l-yl)methyl]benzonitrile halide, a compound of formula 2; Formula 2 Formula 3 (b) (c) deaminating the compound of formula 2 to 4-[l-(lH-l,2,4-triazol-l-yl)methylene]benzonitrile, a compound of formula 3; and reacting the compound of formula 3 with 4-fluorobenzonitrile. The present invention also provides a regiospecific process for the preparation of compounds of formulae 2 and 3 and simple purification of compound of formula 2. DETAILED DESCRIPTION OF THE INVENTION: The present invention provides a regiospecific process for the preparation of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, substantially free of impurities starting with 4-amino-l,2,4-triazole in which the possibility of 4-akylation is blocked by an amino group. This eliminates the formation of the unwanted impurity 4-[l-(l,2,4-triazol-4-yl)methyl]benzonitrile, a compound of formula 4, which leads to the impurity, a compound of formula 5, in the final stage preparation of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, compound of formula 1. . Formula 4 5 The process of the present invention provides 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol- l-yl)methyI]benzonitrile, a compound of formula 1, substantially free of impurities. The impurities may be 4-[l-(4-cyanophenyl)-I-(l,2,4-triazol-4- yI)methyl]benzonitrile, compound of formula. 5, and/or 4-[l,l-Bis(4-cyanophenyl)methyI]benzonitrile, compound of formula 6. Formula 6 4-[l-(4-cyanophenyI)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, compound of formula 1, provided by the process of this invention has purity greater than 99.5%, preferably greater than 99.8%. The regiospecific process of the present invention is carried out in 3 steps by reacting 4-halomethylbenzonitrile with 4-amino-l,2,4-triazole to obtain 4-[(4-amino-1,2,4-triazolium-l-yl)methyl]benzonitrile halide, a compound of formula 2, deaminating to obtain 4-[l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 3, and reacting the compound of formula 3 with 4-fluorobenzonitrile to yield 4-[l-(4-cyanophenyI)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, substantially free of impurities. . According to one embodiment of the process of the present invention step (a) of the process is carried out by reacting 4-halomethylbenzonitrile with 4-amino-1,2,4-triazole by heating in a solvent selected from water, alcohols selected from alkyl, aryl or alkylaryl alcohols like ethanol, methanol, n-propanol, isopropanol, n-butanol, isobutanol, benzyl alcohol and the like; ketones selected from alkyl, aryl or alkylaryl ketones such as acetone, methylisobutyl ketone, methylethyl ketone, acetophenone; nitriles such as benzonitriie, acetonitrile; and dimethylsulphoxide, diphenylether, dirnethylformarnide, dichlorobenzene and the like. 6 4-halomethyibenzonitrile may be selected from 4-chloromethylbenzonitrile, 4-iodomethylbenzonitrile and 4-bromomethylbenzonitrile; the preferred being 4-brornomethylbenzonitrile. According to the preferred process of the present invention step (a) of the process may be carried out in an alcoholic solvent like isopropanol. The process of the present invention step (a) is carried out at temperatures ranging from about 20 to 150°C, preferably about 15 to 100°C, the most preferred being about 80 to 85°C. The process of the present invention step (a) is carried out for about 3 to 8 hours, preferably about 4 to 6 hours, the most preferred being about 5 hours. The reaction mixture on completion of the reaction is cooled and filtered. The compound of formula 2 obtained may be purified by standard techniques known to those skilled in this art for instance, simple leaching with solvents like ketones, nitrites, esters, ethers, preferably alcohols and alkanes, most preferred being isopropanol and hexane to give pure compound of formula 2. According to another embodiment of the process of the present invention step (b) is carried out by deaminating compound of formula 2 using any deaminating agent like (i) nitrites which may be selected from inorganic nitrites of sodium or potassium, and organic nitrites such as alkyl nitrites, preferably sodium nitrite is used; or (ii) nitrous acid. The preferred deaminating agent being nitrous acid. Nitrous acid may be prepared insitu by reacting inorganic nitrite with mineral acid. In the preferred process of the present invention step (b) is carried out by deaminating compound of formula 2 with sodium nitrite in the presence of mineral acid like hydrochloric acid under cold conditions about 0 to 5°C over a period of about 6 to 8 hours. 7 The reaction mixture may be worked up by standard techniques known to those skilled in this art. For instance, the unreacted nitrous acid is decomposed with urea at the end of the reaction and impurities removed by extraction with a solvent selected from halo substituted or unsubstituted alkyl and aryl hydrocarbons such as hexane, toluene, xylenes, methylene chloride, chlorobenzene and the like, alkyl or aryl ketones like methylisobutyl ketone, and the like, preferably dichloromethane. The aqueous solution is adjusted to pH > 8 with a base. Preferable base being an aqueous ammonical solution. After adjusting the pH compound of formula 3 is extracted with a solvent selected from halo substituted or unsubstituted alkyl and aryl hydrocarbons such as hexane, toluene, xylenes, methylene chloride, chlorobenzene and the like, alkyl or aryl ketones like acetone, methylisobutyl ketone, and the like, preferably dichloromethane. The organic layer containing the compound of formula 3 is washed with water and then concentrated by heating and/or applying vacuum to give a syrupy liquid. The syrupy liquid is then converted to a solid by adding a solvent mixture of two or more solvents selected from halo substituted or unsubstituted alkyl and aryl hydrocarbons such as hexane, toluene, xylenes, methylene chloride, chlorobenzene and the like, alkyl or aryl ketones like acetone, methylisobutyl ketone, methylethyl ketone and the like, alky or aryl alcohols like ethanol, methanol, isopropanol, benzyl alcohol and the like, alky or aryl nitriles like benzonitrile, acetonitrile and the like, preferably isopropanol and hexane mixture. The volume ratio of isopropanol to hexane may vary from 10:90 to 90:10, preferably 50:50, the most preferred being 20:80. The solution containing the solids is cooled to below 25°C, preferably 8-10°C, stirred, filtered and washed with an aprotic solvent selected from aliphatic hydrocarbons, aromatic hydrocarbons .and the like, most preferably hexane to yield a compound of formula 3. 8 The compound of formula 3 obtained by the process of the present invention is free of its isomer, compound of formula 4. According to yet another embodiment of the process of the present invention step (c) is carried out by treating the compound of formula 3 with 4-fluorobenzonitrile to yield 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, substantially free Of impurities in an organic solvent such as dimethylformamide in the presence of a base such as potassium tertiary butoxide at lower temperatures such as -5 to -10°C. The reaction mixture is worked up by standard techniques known to those skilled in this art. For instance, at the end of the reaction the reaction mixture is worked up by extracting with an organic solvent, concentrating, and optionally purifying to yield 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, substantially free of impurities. The purifying methods may be selected from washing, extracting, suspending, precipitating, leaching, recrystallizing and the like. Preferably, recystallization of compound of formula 1 with a solvent selected from polar and non-polar solvents such as alcohols, ketones and esters, preferably esters, the preferred being ethyl acetate. Methods of preparing 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile are disclosed in United States Patent No. 4978672 (Indian Reference not available). The invention is illustrated but not restricted by the description in the following example. 9 EXAMPLES EXAMPLE 1 (a) Preparation of 4-[(4-amino-l,2,4- triazolium-l-yI)methy1] benzonitrile bromide, compound of formula 2: 4-bromomethylbenzonitrile (300.0 gm, 1.530 moles) was heated with 4-amino-1,2,4-triazole (141.5 gm, 1.683 moles) in isopropanol (3.0 L) as a solvent for 5.0 hours at 80°-85°C temperature. Reaction mixture was cooled gradually to room temperature and further to 0°-5°C temperature and stirred for 2.0 hrs and filtered. (b) Purification of 4-[(4-amino-l,2,4- triazoHum-l-yI)methyl] benzonitrile bromide, compound of formula 2: The filtered solid was washed with isopropanol (300.0 ml) followed by hexane (300.0 ml), gave 4-[(4-amino-1,2,4- triazolium-l-yl)methyl] benzonitrile bromide, compound of formula 2. (310.0 gm, 72.2% yield). (c) Preparation of 4-[l-(l,2,4- triazoI-l-yl)methyl] benzonitrile, compound of formula 3: 4-[(4-amino-1,2,4- triazoliurn-l-yl)methyl] benzonitrile bromide (275.0 gm, 0.982 moles) was dissolved in water (1.1L) and cooled to 0°-5°C temperature. To this solution, was added hydrochloric acid (196.5 ml, 1.963 moles) at 0°-5uC temperature followed by solution of sodium nitrite (74.5 gm, 1.080 moles) in water (275.0 ml) at 0°-5 C temperature within 6.0 hrs, followed by stirring at 30°-35°C temperature for 2.0-3.0 hrs. After reaction was over, unreacted nitrous-acid was decomposed with urea, extracted with dichloromethane to remove impurities. Finally, aqueous layer was basified to pH 8.0-8.5 by adding 25% ammonia solution and product was extracted with dichloromethane An organic layer containing product was washed with water and concentrated to give syrupy liquid, to which was added isopropanol:hexane (20:80), slurry so obtained was cooled to 8-10°C temperature, 10 stirred for 2.0 hrs, filtered and washed with hexane (75.0ml) to give 4-[l-(l,2,4-triazolyl)methyl] benzonitrile, compound of formula 3 free of compound of formula 4. (150.0 gm, 82.9% yield) (d) Preparation of 4-[l-(4-cyanophenyI)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, compound of formula 1: The solution of 4-[l-(l,2,4-triazolyl)methyl]benzonitrile (100 gm, 0.543 moles) in N,N-dimethylformamide (500 ml) was added at 10° to -5° C temperature to the solution of potassium tertiary butoxide (122 gm, 1.085 moles) in N,N-dimethylformamide (750 ml ) and stirred for 1.0 hour. To this solution, was added a solution of 4-fluorobenzonitrile (77 gm, 0.592 moles) in N,N-dimethylformamide (500 ml) at -10° to -5° C temperature and stirred for 3.0 hours. Reaction mixture was then neutralized to pH 7.5-8.0 by adding 1.0 N hydrochloric acid (700 ml) and concentrated to remove N, N-dimethylformamide under vacuum. To the residue was added water and product was extracted with ethyl acetate. An organic layer was washed with water and concentrated under vacuum. To the residue was added, isopropyl alcohol, stirred for 1.0 hour and filtered the crude product (125.0 gm). Crude product was recrystallized from hot ethyl acetate (1.37 L) to give 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl3benzonitrile, compound of formula 1. (90 g, 58 % yield, 99.90 % HPLC purity). 11 We claim". 1. A regiospecific process for preparation of 4-[l-(4-cyanophenyl)-l-(1,2,4- triazol-l-yl)methyl]benzonitri!e, a compound of formula 1, said process comprising NC Formula 1 (a) reacting 4-halomethyIbenzonitrile with 4-amino-l,2;4-triazole to give 4-[(4-amino-4H-l,2,4-triazolium-l- yl)methyl]benzonitrile halide, a compound of Formula 2; (b) Formula 2 deaminating the compound of formula 2 to 4-[l-(lH-l,2,4-triazol-I-yl)methylene]benzonitrile, a compound of formula 3; and (c) Formula 3 reacting the compound of formula 3 with 4-fluorobenzonitrile. 12 A process as claimed in claim 1 wherein in step (a) the 4-halomethyl - benzonitrile is 4-bromomethylbenzonitrile. A process as claimed in claim 1 wherein step (a) is carried out in the presence of a solvent selected from an alcohol. A process as claimed in claim 3 wherein the alcohol is isopropanol. A process as claimed in claim 1 wherein step (a) is carried out at a temperature from about 20 to 150°C for about 3 to 8 hours. A process as claimed in claim 1 wherein compound of formula 2 is further purified by leaching the product of step (a) with an organic solvent(s) selected from ketones, nitriles, esters, ethers, alcohols and alkanes or mixtures thereof. A process as claimed in claim I wherein step (b) is carried out by dearninating the compound of formula 2 to 4-[l-(lH-l,2,4-triazoM- yl)methyIene]benzonitrile, a compound of formula 3 with nitrous acid generated insitu with an inorganic nitrite and a mineral acid like hydrochloric acid. A process as claimed in claim 7 wherein the compound of formula 3 is free of its isomer, compound of formula 4. formula 4 A process as claimed in claim 1 further comprising purification of the compound of formula 1 wherein the said purification maybe selected from washing, extracting, suspending, precipitating, leaching and recrystallizing. A process as claimed in claim 9 wherein the compound of formula 1 is purified by recrystallizing from ethyl acetate. A process as claimed in claim 9 wherein 4-[l-(4-cyanophenyl)-l-(1,2,4-triazol-l-yl)methyl]benzonitrile has purity greater than 99.5%. 13 12. A process as claimed in claim 9 wherein 4-{i-(4-cyanophenyI)-l-( 1,2,4-triazol-l-yl)methyI]benzonitriIe is free from the impurities compounds of formulae 5 and 6. 13. A process as claimed in claims 1 to 12 substantially as herein describedand illustrated by example 1. Dated this 5th day of February, 2003. DILIP SHANGHVI CHAIRMAN AND MANAGING DIRECTOR SUN PHARMACEUTICAL INDUSTRIES LIMITED 14

Full Text

FORM 2
THE PATENTS ACT, 1970 (39 OF 1970)
COMPLETE SPECIFICATION (See section 10)
REGIOSPECIFIC PROCESS FOR THE PREPARE CYANOPHENYL)-l-(l,2,4-TRIAZOL-l-YL)METHYL.
SUN PHARMACEUTICAL INDUSTRIES LTD.
A company incorporated under the laws of India having their office at ACME PLAZA, ANDHERI-KURLA ROAD, ANDHERI (E), MUMBAI-400059.
MAHARASHTRA, INDIA
The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.

REGIOSPECIFIC PROCESS FOR THE PREPARATION OF 4-[l- (4-CYANOPHENYL)-l-(l,2,4-TRIAZOL-l-YL)METHYL]BENZONITRILE
The present invention relates to a regiospecific process for the preparation of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, free of isomeric and triaryl impurities. 4-[l-(4-cyanophenyl)-l-(1,2,4-triazol-l-yl)methyl]benzonitrile or"Letrozole (INN name) is an antineoplastic agent.

Formula 1 PRIOR ART:
United States Patent No. 4978672 (referred to herein as "672, Indian Reference not available) provides 4-[alpha- (4-cyanophenyl)-l-(l,2,4-triazolyl)-methyl]benzonitrile and the process of its preparation. The patent discloses reacting 4-bromomethylbenzonitrile with 1,2,4-triazole to yield 4-[l-(l,2,4-triazol-l-y!)merhyl]benzonitrile. 4-[l-(l,2,4-triazol-l-yl)methyl]benzonitrile is then reacted with 4-fluorobenzonitrile to give 4-[l-(4-cyanophenyI)-l-(l,2,4-triazol-l-yl)methyl]benzonitriie. This patent does not disclose the purity of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, compound of formula 1. When we followed the patented process we also get the unwanted isomer 4-[l-(l,2,4-triazo!-4-yl)methyl]benzonitrile, a compound of formula 4 (20 to 40%) in step 1. When the reaction mixture of step 1 is treated with 4-fluorobenzonitrile it yields 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)-methyl]-benzonitrile, a compound of formula 1, and its isomer, a compound of formula 5. Thus the impurity of formula 4 has to be separated before treating it with 4-fluorobenzonitrile, which involves an additional

step of column purification, which is reported in "672 and makes the process tedious and commercially unviable.

Formula 4 Formula 5
Further, if the intermediate contains an impurity like 4-toluonitrile or other related impurities, that are present in the raw material viz. 4-(bromomethyl)benzonitrile, in step 2, the impurities would participate in the reaction with 4- fluorobenzonitrile leading to the formation of 4-[l,l-Bis(4-cyanophenyl)methyl]benzonitrile (referred to herein as "tris impurity") compound of formula 6 and other side products.
CN
NC,
OBJECTS OF THE INVENTION:
The object of the present invention is to provide a regiospecific process for the preparation of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, free of impurities viz. 4-[l-(4-cyanophenyl)-l-(l,2,4-triazo!-4-yl)methyl]benzonitrile, compound of formula 5, and 4-[l,l-Bis(4-cyanophenyl)methyl]benzonitrile compound of formula 6.
3

Formula 3

Formula 4

Another object of the present invention is to provide a regiospecific process for the preparation of 4-[l-(lH-l,2,4-triazoI-l-yI)methylene]benzonitrile, a compound of formula 3, substantially free of compound of formula 4 by eliminating the formation of an unwanted isomer.

Yet another object of the present invention is to purify the intermediate compound of formula 2, which is a precursor to the regioselective isomer using simple purification technique, in-order to eliminate all the impurities, which would be present in its raw material and yield compound of formula 1 free of also the "tris impurity" compound of formula 6.

The regiospecific process for preparation of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, said process comprising
NC.

formula 1
4

(a)

reacting 4-halomethylbenzonitrile with 4-amino-l,2,4-triazoIe to give 4-[(4-amino-4H-l,2,4-triazolium-l-yl)methyl]benzonitrile halide, a compound of formula 2;

Formula 2

Formula 3

(b)
(c)

deaminating the compound of formula 2 to 4-[l-(lH-l,2,4-triazol-l-yl)methylene]benzonitrile, a compound of formula 3; and reacting the compound of formula 3 with 4-fluorobenzonitrile.

The present invention also provides a regiospecific process for the preparation of compounds of formulae 2 and 3 and simple purification of compound of formula 2.
DETAILED DESCRIPTION OF THE INVENTION:
The present invention provides a regiospecific process for the preparation of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, substantially free of impurities starting with 4-amino-l,2,4-triazole in which the possibility of 4-akylation is blocked by an amino group. This eliminates the formation of the unwanted impurity 4-[l-(l,2,4-triazol-4-yl)methyl]benzonitrile, a compound of formula 4, which leads to the impurity, a compound of formula 5, in the final stage preparation of 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, compound of formula 1. .

Formula 4

5

The process of the present invention provides 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-
l-yl)methyI]benzonitrile, a compound of formula 1, substantially free of impurities.
The impurities may be 4-[l-(4-cyanophenyl)-I-(l,2,4-triazol-4-
yI)methyl]benzonitrile, compound of formula. 5, and/or 4-[l,l-Bis(4-cyanophenyl)methyI]benzonitrile, compound of formula 6.

Formula 6 4-[l-(4-cyanophenyI)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, compound of formula 1, provided by the process of this invention has purity greater than 99.5%, preferably greater than 99.8%.
The regiospecific process of the present invention is carried out in 3 steps by reacting 4-halomethylbenzonitrile with 4-amino-l,2,4-triazole to obtain 4-[(4-amino-1,2,4-triazolium-l-yl)methyl]benzonitrile halide, a compound of formula 2, deaminating to obtain 4-[l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 3, and reacting the compound of formula 3 with 4-fluorobenzonitrile to yield 4-[l-(4-cyanophenyI)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, substantially free of impurities. .
According to one embodiment of the process of the present invention step (a) of the process is carried out by reacting 4-halomethylbenzonitrile with 4-amino-1,2,4-triazole by heating in a solvent selected from water, alcohols selected from alkyl, aryl or alkylaryl alcohols like ethanol, methanol, n-propanol, isopropanol, n-butanol, isobutanol, benzyl alcohol and the like; ketones selected from alkyl, aryl or alkylaryl ketones such as acetone, methylisobutyl ketone, methylethyl ketone, acetophenone; nitriles such as benzonitriie, acetonitrile; and dimethylsulphoxide, diphenylether, dirnethylformarnide, dichlorobenzene and the like.
6

4-halomethyibenzonitrile may be selected from 4-chloromethylbenzonitrile, 4-iodomethylbenzonitrile and 4-bromomethylbenzonitrile; the preferred being 4-brornomethylbenzonitrile.
According to the preferred process of the present invention step (a) of the process may be carried out in an alcoholic solvent like isopropanol.
The process of the present invention step (a) is carried out at temperatures ranging from about 20 to 150°C, preferably about 15 to 100°C, the most preferred being about
80 to 85°C.
The process of the present invention step (a) is carried out for about 3 to 8 hours, preferably about 4 to 6 hours, the most preferred being about 5 hours.
The reaction mixture on completion of the reaction is cooled and filtered. The compound of formula 2 obtained may be purified by standard techniques known to those skilled in this art for instance, simple leaching with solvents like ketones, nitrites, esters, ethers, preferably alcohols and alkanes, most preferred being isopropanol and hexane to give pure compound of formula 2.
According to another embodiment of the process of the present invention step (b) is carried out by deaminating compound of formula 2 using any deaminating agent like (i) nitrites which may be selected from inorganic nitrites of sodium or potassium, and organic nitrites such as alkyl nitrites, preferably sodium nitrite is used; or (ii) nitrous acid. The preferred deaminating agent being nitrous acid. Nitrous acid may be prepared insitu by reacting inorganic nitrite with mineral acid.
In the preferred process of the present invention step (b) is carried out by deaminating compound of formula 2 with sodium nitrite in the presence of mineral acid like hydrochloric acid under cold conditions about 0 to 5°C over a period of about 6 to 8
hours.
7

The reaction mixture may be worked up by standard techniques known to those skilled in this art. For instance, the unreacted nitrous acid is decomposed with urea at the end of the reaction and impurities removed by extraction with a solvent selected from halo substituted or unsubstituted alkyl and aryl hydrocarbons such as hexane, toluene, xylenes, methylene chloride, chlorobenzene and the like, alkyl or aryl ketones like methylisobutyl ketone, and the like, preferably dichloromethane.
The aqueous solution is adjusted to pH > 8 with a base. Preferable base being an aqueous ammonical solution.
After adjusting the pH compound of formula 3 is extracted with a solvent selected from halo substituted or unsubstituted alkyl and aryl hydrocarbons such as hexane, toluene, xylenes, methylene chloride, chlorobenzene and the like, alkyl or aryl ketones like acetone, methylisobutyl ketone, and the like, preferably dichloromethane. The organic layer containing the compound of formula 3 is washed with water and then concentrated by heating and/or applying vacuum to give a syrupy liquid. The syrupy liquid is then converted to a solid by adding a solvent mixture of two or more solvents selected from halo substituted or unsubstituted alkyl and aryl hydrocarbons such as hexane, toluene, xylenes, methylene chloride, chlorobenzene and the like, alkyl or aryl ketones like acetone, methylisobutyl ketone, methylethyl ketone and the like, alky or aryl alcohols like ethanol, methanol, isopropanol, benzyl alcohol and the like, alky or aryl nitriles like benzonitrile, acetonitrile and the like, preferably isopropanol and hexane mixture. The volume ratio of isopropanol to hexane may vary from 10:90 to 90:10, preferably 50:50, the most preferred being 20:80.
The solution containing the solids is cooled to below 25°C, preferably 8-10°C, stirred, filtered and washed with an aprotic solvent selected from aliphatic hydrocarbons, aromatic hydrocarbons .and the like, most preferably hexane to yield a compound of formula 3.
8

The compound of formula 3 obtained by the process of the present invention is free of its isomer, compound of formula 4.
According to yet another embodiment of the process of the present invention step (c) is carried out by treating the compound of formula 3 with 4-fluorobenzonitrile to yield 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, substantially free Of impurities in an organic solvent such as dimethylformamide in the presence of a base such as potassium tertiary butoxide at lower temperatures such as -5 to -10°C.
The reaction mixture is worked up by standard techniques known to those skilled in this art. For instance, at the end of the reaction the reaction mixture is worked up by extracting with an organic solvent, concentrating, and optionally purifying to yield 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, a compound of formula 1, substantially free of impurities. The purifying methods may be selected from washing, extracting, suspending, precipitating, leaching, recrystallizing and the like. Preferably, recystallization of compound of formula 1 with a solvent selected from polar and non-polar solvents such as alcohols, ketones and esters, preferably esters, the preferred being ethyl acetate.
Methods of preparing 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile are disclosed in United States Patent No. 4978672 (Indian Reference not available).
The invention is illustrated but not restricted by the description in the following example.
9

EXAMPLES EXAMPLE 1
(a) Preparation of 4-[(4-amino-l,2,4- triazolium-l-yI)methy1] benzonitrile
bromide, compound of formula 2:
4-bromomethylbenzonitrile (300.0 gm, 1.530 moles) was heated with 4-amino-1,2,4-triazole (141.5 gm, 1.683 moles) in isopropanol (3.0 L) as a solvent for 5.0 hours at 80°-85°C temperature. Reaction mixture was cooled gradually to room temperature and further to 0°-5°C temperature and stirred for 2.0 hrs and filtered.
(b) Purification of 4-[(4-amino-l,2,4- triazoHum-l-yI)methyl] benzonitrile
bromide, compound of formula 2:
The filtered solid was washed with isopropanol (300.0 ml) followed by hexane (300.0 ml), gave 4-[(4-amino-1,2,4- triazolium-l-yl)methyl] benzonitrile bromide, compound of formula 2. (310.0 gm, 72.2% yield).
(c) Preparation of 4-[l-(l,2,4- triazoI-l-yl)methyl] benzonitrile, compound of
formula 3:
4-[(4-amino-1,2,4- triazoliurn-l-yl)methyl] benzonitrile bromide (275.0 gm, 0.982 moles) was dissolved in water (1.1L) and cooled to 0°-5°C temperature. To this solution, was added hydrochloric acid (196.5 ml, 1.963 moles) at 0°-5uC temperature followed by solution of sodium nitrite (74.5 gm, 1.080 moles) in water (275.0 ml) at 0°-5 C temperature within 6.0 hrs, followed by stirring at 30°-35°C temperature for 2.0-3.0 hrs. After reaction was over, unreacted nitrous-acid was decomposed with urea, extracted with dichloromethane to remove impurities. Finally, aqueous layer was basified to pH 8.0-8.5 by adding 25% ammonia solution and product was extracted with dichloromethane An organic layer containing product was washed with water and concentrated to give syrupy liquid, to which was added isopropanol:hexane (20:80), slurry so obtained was cooled to 8-10°C temperature,
10

stirred for 2.0 hrs, filtered and washed with hexane (75.0ml) to give 4-[l-(l,2,4-triazolyl)methyl] benzonitrile, compound of formula 3 free of compound of formula
4. (150.0 gm, 82.9% yield)
(d) Preparation of 4-[l-(4-cyanophenyI)-l-(l,2,4-triazol-l-yl)methyl]benzonitrile, compound of formula 1:
The solution of 4-[l-(l,2,4-triazolyl)methyl]benzonitrile (100 gm, 0.543 moles) in N,N-dimethylformamide (500 ml) was added at 10° to -5° C temperature to the solution of potassium tertiary butoxide (122 gm, 1.085 moles) in N,N-dimethylformamide (750 ml ) and stirred for 1.0 hour. To this solution, was added a solution of 4-fluorobenzonitrile (77 gm, 0.592 moles) in N,N-dimethylformamide (500 ml) at -10° to -5° C temperature and stirred for 3.0 hours. Reaction mixture was then neutralized to pH 7.5-8.0 by adding 1.0 N hydrochloric acid (700 ml) and concentrated to remove N, N-dimethylformamide under vacuum. To the residue was added water and product was extracted with ethyl acetate. An organic layer was washed with water and concentrated under vacuum. To the residue was added, isopropyl alcohol, stirred for 1.0 hour and filtered the crude product (125.0 gm). Crude product was recrystallized from hot ethyl acetate (1.37 L) to give 4-[l-(4-cyanophenyl)-l-(l,2,4-triazol-l-yl)methyl3benzonitrile, compound of formula 1. (90 g, 58 % yield, 99.90 % HPLC purity).
11

We claim".

1. A regiospecific process for preparation of 4-[l-(4-cyanophenyl)-l-(1,2,4-
triazol-l-yl)methyl]benzonitri!e, a compound of formula 1, said process
comprising
NC

Formula 1

(a)

reacting 4-halomethyIbenzonitrile with 4-amino-l,2;4-triazole
to give 4-[(4-amino-4H-l,2,4-triazolium-l-
yl)methyl]benzonitrile halide, a compound of Formula 2;

(b)

Formula 2
deaminating the compound of formula 2 to 4-[l-(lH-l,2,4-triazol-I-yl)methylene]benzonitrile, a compound of formula 3;
and

(c)

Formula 3
reacting the compound of formula 3 with 4-fluorobenzonitrile.

12

A process as claimed in claim 1 wherein in step (a) the 4-halomethyl -
benzonitrile is 4-bromomethylbenzonitrile.
A process as claimed in claim 1 wherein step (a) is carried out in the presence
of a solvent selected from an alcohol.
A process as claimed in claim 3 wherein the alcohol is isopropanol.
A process as claimed in claim 1 wherein step (a) is carried out at a
temperature from about 20 to 150°C for about 3 to 8 hours.
A process as claimed in claim 1 wherein compound of formula 2 is further
purified by leaching the product of step (a) with an organic solvent(s) selected
from ketones, nitriles, esters, ethers, alcohols and alkanes or mixtures thereof.
A process as claimed in claim I wherein step (b) is carried out by dearninating
the compound of formula 2 to 4-[l-(lH-l,2,4-triazoM-
yl)methyIene]benzonitrile, a compound of formula 3 with nitrous acid
generated insitu with an inorganic nitrite and a mineral acid like hydrochloric
acid.
A process as claimed in claim 7 wherein the compound of formula 3 is free of
its isomer, compound of formula 4.

formula 4
A process as claimed in claim 1 further comprising purification of the compound of formula 1 wherein the said purification maybe selected from washing, extracting, suspending, precipitating, leaching and recrystallizing. A process as claimed in claim 9 wherein the compound of formula 1 is purified by recrystallizing from ethyl acetate.
A process as claimed in claim 9 wherein 4-[l-(4-cyanophenyl)-l-(1,2,4-triazol-l-yl)methyl]benzonitrile has purity greater than 99.5%.
13

12. A process as claimed in claim 9 wherein 4-{i-(4-cyanophenyI)-l-( 1,2,4-triazol-l-yl)methyI]benzonitriIe is free from the impurities compounds of formulae 5 and 6.

13. A process as claimed in claims 1 to 12 substantially as herein describedand illustrated by example 1.
Dated this 5th day of February, 2003.
DILIP SHANGHVI CHAIRMAN AND MANAGING DIRECTOR SUN PHARMACEUTICAL INDUSTRIES LIMITED
14

Documents:

167-mum-2003-claims(granted)-(06-02-2003).doc

167-mum-2003-claims(granted)-(06-02-2003).pdf

167-mum-2003-correspondence(17-6-2007).pdf

167-mum-2003-correspondence(ipo)-(20-12-2006).pdf

167-mum-2003-form 1(06-02-2003).pdf

167-mum-2003-form 1(12-03-2003).pdf

167-mum-2003-form 18(13-03-2006).pdf

167-mum-2003-form 2(granted)-(06-02-2003).doc

167-mum-2003-form 2(granted)-(06-02-2003).pdf

167-mum-2003-form 3(06-02-2003).pdf

167-mum-2003-form 3(31-03-2003).pdf

167-mum-2003-form-pct-ipea-409(19-11-2007).pdf

167-mum-2003-form-pct-isa-210(19-11-2007).pdf

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Patent Number

213303

Indian Patent Application Number

167/MUM/2003

PG Journal Number

04/2008

Publication Date

25-Jan-2008

Grant Date

26-Dec-2007

Date of Filing

06-Feb-2003

Name of Patentee

SUN PHARMACEUTICAL INDUSTRIES LTD

Applicant Address

ACME PLAZA, ANDHERI-KURLA ROAD, ANDHERI (E), MUMBAI-400 059,

Inventors:

#	Inventor's Name	Inventor's Address
1	MR. PATEL HETALKUMAR VIRENDRABHAI	SUN PHARMA ADVANCED RESEARCH CENTRE, AKOTA ROAD, AKOTA, BARODA 390020
2	Jani Raja Jyotir	SUN PHARMA ADVANCED RESEARCH CENTRE, AKOTA ROAD, AKOTA, BARODA 390020
3	Thennati Rajamannar	SUN PHARMA ADVANCED RESEARCH CENTRE, AKOTA ROAD, AKOTA, BARODA 390020

PCT International Classification Number

C07D209/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA