Process for preparation of zolmitriptan

An improved process for the preparation of Zolmitriptan (I), comprising

• a) reacting an aqueous solution of diazotized (S)-4-(4-aminobenzyl)-1,3-oxazolidin-2-one with stannous chloride in hydrochloric acid at −15 to 10° C.,
• b) adjusting pH of the reaction mass to between 2 to 6 after completion of reaction,
• c) filtering the reaction mass,
• d) readjusting the pH of the filtrate between 6 to 10 to obtain (S)-4-(4-hydrazinobenzyl)-1,3-oxazolidin-2-one of formula (III),
• e) converting (S)-4-(4-hydrazinobenzyl)-1,3-oxazolidin-2-one of formula (III) to (S)-4-(4-hydrazinobenzyl)-1,3-oxazolidin-2-one hydrochloride of formula (IIIa) by treatment with hydrochloric acid in an organic solvent,
• f) treating (S)-4-(4-hydrazinobenzyl)-1,3-oxazolidin-2-one hydrochloride of formula (IIIa) with N,N dimethylaminobutyraldehyde diethyl acetal (IV) in aqueous medium at ambient to reflux temperature,
• g) adjusting the pH of the second reaction mixture mass to between 7 to 8, and
• h) isolating Zolmitriptan (I) of desired purity.