PROCESS FOR THE SYNTHESIS OF BENZYLIDENE ROSIGLITAZONE BASE

Process for the synthesis of 5-{4-[N-methyl-N-(2-pyridyl)-amino-ethoxy]-benzylidene}-thiazolidine-2,4-dione (INN name: benzylidene-rosiglitazone) of formula (I), which consist of the following steps: Step a) reaction of 2-chloro-pyridine and 2-(N-methylamino)-ethanol Step b) reaction of the obtained compound of formula (III) with 4-fluorobenzaldehyde Step c) reaction of the obtained compound of formula (IV) with thiazolidine-2,4-dione characterized by dissolving 4-{2-[N-methyl-N-(2-pyridyl)amino]-ethanol of formula (III) obtained in Step a) in toluene and using it in Step b) without isolation; reacting the solution of compound of formula (III) in toluene in Step b) with 4-fluorobenzaldehyde in the presence of aqueous alkali hydroxide solution and phase transfer catalyst at 25-50° C.; reacting the solution of the benzaldehyde derivative of formula (IV) obtained in Step b) in toluene in Step c) and isolating the desired product.