Patent ID: 8754261
Filing Date: 2014-06-17
Classification: C07B,C07C

Abstract:
1. A process for the preparation of O-desmethyl Venlafaxine, or pharmaceutically acceptable salts, which comprises: (a) provision of compound of (5RS)-5-(4-methoxyphenyl)-3-methyl-1-oxa-3-azaspiro[5,5]undecane, namely the spiro-venlafaxine; (b) conversion of spiro-venlafaxine into spiro-venlafaxine hydrochloride salt and isolation of said salt in pure form; (c) obtaining O-desmethyl Venlafaxine free base in a one-pot process using spiro-venlafaxine hydrochloride salt as starting material, wherein said one-pot process of step is performed by first O-demethylating of the spiro-venlafaxine hydrochloride obtained from step (b) and subsequently treating the reaction mass with paraformaldehyde, formic acid and water at elevated temperature, preferably from about 105° C. to about 1-10° C., to obtain O-desmethyl Venlafaxine free base.