Patent ID: 9233924
Filing Date: 2016-01-12
CPC Classification: A61K,B01J,C07D

Claim Text:
1. A method for preparing substantially pure d-threo-methylphenidate hydrochloride, the method comprising: (i) obtaining a first solution comprising an aqueous solution of an inorganic base and a water miscible solvent; (ii) obtaining a second solution comprising an N-methyl-N-nitroso amine of formula (IV): (iii) adding the second solution to the first solution, thereby generating diazomethane; and (iv) reacting substantially pure d-threo-ritalinic acid hydrochloride with the diazomethane generated in step (iii) for at least about five hours to obtain the substantially pure d-threo-methylphenidate hydrochloride, wherein the reaction is performed at a temperature of about −20° C. to about 10° C., wherein R 2 represents a member selected from the group consisting of R and R wherein a molar ratio of diazomethane to the substantially pure d-threo ritalinic acid hydrochloride is about 4 to 9.