Ketene N,S-acetals in heterocyclic synthesis:Part 1:Synthesis of N-phenyl-2-ylidene and 2,5-diylidene-4-thiazoIidinone derivatives

摘要

Ketene N,S-acetal potassium salts (2a-g),prepared via reaction of active methylenes (la-g) with phenyl isothiocyanate in the presence of potassium hydroxide,were allowed to react with ethyl chloroacetate or chloroacetamide to afford the corresponding 2-ylidene-4-thiazoIidinones (3a-g) in good yields.Compounds (3a-g) reacted with a variety of aromatic aldehydes to afford the corresponding 5-arylidene-2-ylidene-4-thiazolidinone derivatives (10a-e).Reaction of compound (3a) with triethylorthoformate afforded 5-ethoxymethylene-2-ylidene-4-thiazolidinone derivative (7),which was allowed to react with ammonia or phenyl hydrazine to give the corresponding enamino or hydrazino derivatives (8a) or (8b),respectively.