Process for preparing pure anastrozole
a technology of anastrozole and process, applied in the field of process for preparing pure anastrozole, can solve the problems of major disadvantage of the synthetic route mentioned in the said patents
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example-1
2,2′-[5-(1H-1,2,4-Triazol-1-ylmethyl)-1,3-phenylene]di(2-methylpropiononitrile) (1), Anastrozole
[0013]4-Amino-1-[3,5-bis-(1-cyano-1-methylethyl)benzyl]-1H-[1,2,4]triazolium bromide (5) (70 g) was dissolved in conc. HCl (280 mL) in a 5 L R.B. flask and cooled to −5 ° C. A solution of sodium nitrite (15 g) in water (70 mL) was slowly added to the reaction mixture at 0-5° C. in 4 hrs and the reaction mixture was stirred for one hour at 0-5° C. and further at 10-20° C. for next 3 hours. The reaction mixture was quenched by the addition of a solution of urea (4.5 g) in water (15 mL). Toluene (700 mL) was added to the reaction mixture and the heterogeneous solution was further cooled down to 0-5° C. The solution was basified by the addition of liquor ammonia (365 mL) slowly in 4 hours at 5-25° C. Organic layer was separated and further washed with water (200 mL). Aqueous layer was removed and a solution of cone. HCl (140 mL) in water (140 mL) was added to the organic layer slowly in 30 mi...
example-2
Removal of Related Substances (6) and (7) from Anastrozole
[0014]Anastrozole (33 g) from example-2 was dissolved in isopropanol (100 mL) at 45-50° C. The solution was cooled down to 25-35° C. and cyclohexane (100 mL) was added drop wise in 30 minutes. The solution was stirred at 25-35° C. for 2 hours; the precipitated solid product was filtered and washed with fresh cyclohexane (30 mL×2) and dried at 50° C. to get 23 g of pure Anastrozole contaminated with related substance (6) as 0.09% and with related substance (7) below detection limit.
example-3
Purification of Anastrozole
[0015]Pure Anastrozole (11 g) from Example-2 was further purified by dissolving in isopropanol (33 mL) at 45-50° C. The solution was cooled down to 25-35° C. and cyclohexane (33 mL) was added drop wise in 30 minutes. The solution was stirred at 25-35° C. for 2 hours; the precipitated solid product was filtered and washed with fresh cyclohexane (30 mL×2) and dried at 50° C. to get 8.9 g of pure Anastrozole containing with 0.03% of (6) as related substance and another related substance (7) below detection limit. Related substance (6) can be further removed below detection limit by repeating the same process.
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