Process for preparation of duloxetine hydrochloride

An improved process for synthesis of duloxetine hydrochloride (1) having chiral purity greater than 99.9% that is characterized by the following: (i) preparation of racemic condensed compound (RS)-N,N-di methyl-3-(1-naphthyloxy)-3-(2-thienyl)propanamine (4) by reaction of racemic hydroxy compound (2) with 1-fluoronaphthalene (3) in presence of a base such as sodamide, potassium amide or potassium bis(trimethylsilyl)amide (KHDMS) in polar aprotic solvent, (ii) optical resolution of racemic condensed compound (5a+5b) with di-benzoyl-L-tartaric acid (7, DBTA, R=H) or di-para-anisoyl-L-tartaric acid (7, DATA, R=OCH3) to obtain crude (S)-N.N-dimethyl-3-(1-naphthyloxy)-3-(2-thienyl)propanamine dibenzoyl tartarate salt (8a) or (S)-N.N-dimethyl-3-(1-naphthyloxy)-3-(2-thienyl)propanamine di-p-anisoyl tartarate salt (9a) respectively, (iii) optionally purification of crude tartarate salts (8a or 9a) by crystallization, (iv) optionally purification of duloxetine hydrochloride (1) by crystallization and (v) racemization of undesired (R)-N,N-di methyl-3-(1-naphthyloxy)-3-(2-thienyl)propanamine (5b) by treatment with base potassium bis(trimethylsilyl)amide (KHDMS) to obtain racemic mixture of condensed compounds (5a and 5b).