Patent ID: 8178680
Filing Date: 2012-05-15
Classification: C07D

Abstract:
1. A method for the preparation of a compound of formula (I) comprising: (a) reacting a compound of formula (II) (b) quenching the reaction mixture with water and sodium hydroxide; (c) extracting the reaction mixture obtained in step (b) with a water-immiscible solvent, thereby removing impurities from the reaction mixture; (d) adding acetic acid to the reaction mixture obtained in step (c), thereby lowering pH of the reaction mixture; (e) extracting the product obtained in step (d) with a solvent selected from an ester solvent and a chloro solvent; (f) concentrating the reaction mixture obtained in step (e); (g) diluting the reaction mixture obtained in step (f) with a solvent selected from a keto solvent or an ester solvent; (h) treating the product obtained from step (g) with an amine of formula (R) (i) optionally, purifying the compound of formula (IVa) obtained in step (h) using a hydrocarbon solvent, a keto solvent or a mixture thereof; and (j) reacting the product of step (h) or step (i) with sodium methoxide in methanol at a temperature of 20-40° C. for 1-2 hours, thereby converting the compound of formula (IVa) into the compound of formula (I) without converting the compound of formula (IVa) to montelukast free acid.