WO 2016024224, New Patent, Trelagliptin, SUN PHARMA

SUN PHARMACEUTICAL INDUSTRIES LIMITED [IN/IN]; Sun House, Plot No. 201 B/1 Western Express Highway Goregaon (E) Mumbai, Maharashtra 400 063 (IN)

BARMAN, Dhiren, Chandra; (IN).
NATH, Asok; (IN).
PRASAD, Mohan; (IN)

The present invention provides a process for the preparation of 4-fluoro-2- methylbenzonitrile of Formula (II), and its use for the preparation of trelagliptin or its salts. The present invention provides an efficient, simple, and commercially friendly process for the preparation of 4-fluoro-2-methylbenzonitrile, which is used as an intermediate for the preparation of trelagliptin or its salts. The present invention avoids the use of toxic and hazardous reagents, high boiling solvents, and bromo intermediates such as 2-bromo-5-fluorotoluene, which is lachrymatory in nature and thus difficult to handle at a commercial scale.

Trelagliptin is a dipeptidyl peptidase IV (DPP-IV) inhibitor, chemically designated as 2- [[6-[(3i?)-3 -aminopiperidin- 1 -yl] -3 -methyl -2,4-dioxopyrimidin- 1 -yljmethyl] -4-fluorobenzonitrile, represented by Formula I.

Formula I

Trelagliptin is administered as a succinate salt of Formula la, chemically designated as 2-[[6-[(3i?)-3-aminopiperidin-l-yl]-3-methyl-2,4-dioxopyrimidin-l-yl]methyl]-4-fluorobenzonitrile butanedioic acid (1 : 1).

Formula la

U.S. Patent Nos. 7,795,428, 8,288,539, and 8,222,411 provide a process for the preparation of 4-fluoro-2-methylbenzonitrile by reacting 2-bromo-5-fluorotoluene with copper (I) cyanide in N,N-dimethylformamide.

Chinese Patent No. CN 102964196 provides a process for the preparation of 4-fluoro-2-methylbenzonitrile by reacting 4-fluoro-2-methylbenzyl alcohol with cuprous iodide in the presence of 2,2′-bipyridine and 2,2,6,6-tetramethylpiperidine oxide (TEMPO) in an anhydrous ethanol.

Copper (I) cyanide is toxic to humans, and therefore its use in the manufacture of a drug substance is not advisable. In addition, 2-bromo-5-fluorotoluene is converted to 4-fluoro-2-methylbenzonitrile by refluxing in N,N-dimethylformamide at 152°C to 155°C for 24 hours. This leads to some charring, resulting in a tedious work-up process and low yield. Furthermore, the use of reagents like cuprous iodide, 2,2′-bipyridine, and 2,2,6,6-tetramethylpiperidine oxide (TEMPO) is hazardous and/or environmentally-unfriendly, and therefore their use in the manufacture of a drug substance is not desirable.

The present invention provides an efficient, simple, and commercially friendly process for the preparation of 4-fluoro-2-methylbenzonitrile, which is used as an intermediate for the preparation of trelagliptin or its salts. The present invention avoids the use of toxic and hazardous reagents, high boiling solvents, and bromo intermediates such as 2-bromo-5-fluorotoluene, which is lachrymatory in nature and thus difficult to handle at a commercial scale.

EXAMPLES

Example 1 : Preparation of 4-fluoro-2-methylbenzaldoxime

4-Fluoro-2-methylbenzaldehyde (1.38 g) was added to ethanol (10 mL) to obtain a solution. To this solution, hydroxylamine hydrochloride (2.76 g) and pyridine (1 mL) were added, and then the mixture was stirred at 20°C to 25 °C for 3 hours. The solvent was recovered up to maximum extent from the reaction mixture under reduced pressure to afford the title compound. Yield: 3.1 g

Example 2: Preparation of 4-fluoro-2-methylbenzaldoxime

4-Fluoro-2-methylbenzaldehyde (5 g) was added to ethanol (37 mL) to obtain a solution. To this solution, hydroxylamine hydrochloride (10 g) and N,N-diisopropylethylamine (3.6 mL) were added, and then the mixture was stirred at 20°C to 25 °C for 2 hours. The solvent was recovered up to maximum extent from the reaction mixture under reduced pressure to afford the title compound. Yield: 3.1 g

Example 3 : Preparation of 4-fluoro-2-methylbenzaldoxime

4-Fluoro-2-methylbenzaldehyde (10 g) was added to ethanol (40 mL) to obtain a solution. To this solution, hydroxylamine hydrochloride (20 g) and N,N-diisopropylethylamine (7.5 mL) were added, and then the mixture was stirred at 20°C to 25 °C for 4 hours. The solvent was recovered from the reaction mixture under reduced pressure to afford the title compound. Yield: 11.0 g

Example 4: Preparation of 4-fluoro-2-methylbenzaldoxime

4-Fluoro-2-methylbenzaldehyde (50 g) was added to ethanol (500 mL) to obtain a solution. To this solution, hydroxylamine hydrochloride (70 g) and N,N-diisopropylethylamine (36 mL) were added, and then the mixture was stirred at 20°C to 25 °C for 6 hours. The solvent was recovered from the reaction mixture under reduced pressure to afford the title compound. Yield: 51.0 g

Example 5 : Preparation of 4-fluoro-2-methylbenzaldoxime

4-Fluoro-2-methylbenzaldehyde (20 g) was added to ethanol (200 mL) to obtain a solution. To this solution, hydroxylamine hydrochloride (20 g) and N,N-diisopropylethylamine (18 mL) were added, and then the mixture was stirred at 20°C to 25 °C for 4 hours. The solvent was recovered from the reaction mixture under reduced pressure to obtain a residue. Deionized water (60 mL) was charged into the residue, and then the slurry was stirred at 0°C to 5°C for 1 hour. The solid obtained was filtered, then washed with deionized water (2 x 20 mL). The wet solid was dried in an air oven at 40°C to 45 °C for 4 hours to 5 hours. The crude product obtained was recrystallized in ethanol (50 mL) to afford the pure title compound. Yield: 21.0 g

Example 6: Preparation of 4-fluoro-2-methylbenzaldoxime

4-Fluoro-2-methyl benzaldehyde (50 g) was added to ethanol (500 mL) to obtain a solution. To this solution, hydroxylamine hydrochloride (50 g) and N,N-diisopropylethylamine (46.4 mL) were added, and then the mixture was stirred at 20°C to 25 °C for 4 hours. The solvent was recovered from the reaction mixture under reduced pressure to obtain a residue. Deionized water (150 mL) was charged to the residue, and then the slurry was stirred at 0°C to 5°C for 1 hour. The solid obtained was filtered, then washed with deionized water (2 x 50 mL). The wet solid was dried in an air oven at 40°C to 45 °C for 4 hours to 5 hours. The crude product obtained was recrystallized in ethanol (200 mL) to afford the pure title compound. Yield: 53.5 g

Example 7: Preparation of 4-fluoro-2-methylbenzonitrile

4-Fluoro-2-methylbenzaldoxime (3.1 g) and phosphorous pentoxide (1 g) were added to toluene (30 mL) to obtain a reaction mixture. The reaction mixture was refluxed at 110°C to 115°C for 24 hours. After completion of the reaction (monitored by TLC), the reaction mixture was cooled to 25°C to 30°C. Deionized water (30 mL) was added to the mixture and then the layers were separated. The organic layer was concentrated under reduced pressure to afford the title compound. Yield: 1.1 g

Example 8: Preparation of 4-fluoro-2-methylbenzonitrile

4-Fluoro-2-methylbenzaldoxime (3 g) and phosphorous pentoxide (2 g) were added to toluene (30 mL) to obtain a reaction mixture. The reaction mixture was refluxed at 110°C to 115°C for 24 hours. After completion of the reaction (monitored by TLC), the reaction mixture was cooled to 25°C to 30°C. Deionized water (30 mL) was added to the mixture and then the layers were separated. The organic layer was concentrated under reduced pressure to afford the title compound. Yield: 1.0 g

Example 9: Preparation of 4-fluoro-2-methylbenzonitrile

4-Fluoro-2-methylbenzaldoxime (5 g) and concentrated sulphuric acid (2 mL) were added to toluene (100 mL) to obtain a reaction mixture. The reaction mixture was refluxed at 110°C to 115°C for 5 hours. After completion of the reaction (monitored by TLC), the reaction mixture was cooled to 25°C to 30°C. Deionized water (50 mL) was added to the mixture and then the layers were separated. The organic layer was concentrated under reduced pressure to afford the title compound. Yield: 3.24 g

Example 10: Preparation of 4-fluoro-2-methylbenzonitrile

4-Fluoro-2-methylbenzaldoxime (25 g) and concentrated sulphuric acid (35 g) were added to toluene (500 mL) to obtain a reaction mixture. The reaction mixture was refluxed at 110°C to 115°C for 6 hours. After completion of the reaction (monitored by TLC), the reaction mixture was cooled to 25°C to 30°C. Deionized water (250 mL) was added to the mixture and then the layers were separated. The organic layer was concentrated under reduced pressure to afford the title compound. Yield: 20.5 g

Example 11 : Preparation of 4-fluoro-2-methylbenzonitrile

4-Fluoro-2-methyl benzaldoxime (5 g) and sodium bisulphate monohydrate (3.1 g) were added to toluene (50 mL) to obtain a reaction mixture. The reaction mixture was refluxed at 110°C to 115°C for 12 hours. After completion of the reaction (monitored by TLC), the reaction mixture was cooled to 25°C to 30°C, then filtered, and then washed with toluene (10 mL). The filtrate was concentrated under reduced pressure to afford the title compound. Yield: 3.0 g

Example 12: Preparation of 4-fluoro-2-methylbenzonitrile

4-Fluoro-2-methyl benzaldoxime (50 g) and sodium bisulphate monohydrate (31.6 g) were added to toluene (500 mL) to obtain a reaction mixture. The reaction mixture was refluxed at 110°C to 115°C using a Dean-Stark apparatus for 12 hours. After completion of the reaction (monitored by TLC), the reaction mixture was cooled to 25 °C to 30°C, then filtered, and then washed with toluene (100 mL). The filtrate was concentrated under reduced pressure to afford a crude product. The crude product obtained was recrystallized in a mixture of toluene (200 mL) and hexane (500 mL) to afford the title compound.

Yield: 38.0 g

Sun Pharma managing director Dilip Shanghvi.

/////////////WO 2016024224, New Patent, Trelagliptin, SUN PHARMA