Simple one-step syntheses of heterocyclic systems from (4Z)-2-phenyl-4-(thien-2-ylmethylene)-1,3(4H)-oxazol-5-one

Abstract

The title compound (Ia) was synthesized and its (Z)-configuration was assigned. The present investigation was intended to study the behaviour of Ia towards nitrogen, carbon, and oxygen nucleophiles. Thus, reaction of Ia with p-toluidine in ethanol or in acetic acid afforded the thienylaminomethylidene-(4H)-oxazol-5-one and alkenamide without oxazolone ring together with the imidazolinone, respectively. Hydrazinolysis and azidolysis of Ia resulted in the vinylthiophene and tetrazole derivatives. The triazine and oxadiazinone were obtained upon the effect of phenylhydrazine and hydroxylamine on Ia, respectively. When compound Ia was allowed to react with carbon nucleophiles, namely phenylmagnesium bromide or dry benzene under Friedel - Crafts conditions, it gave the acylated product benzoylaminovinylthiophene whereas the ester thienylpropenoate was obtained from the reaction of Ia with sodium ethoxide. In the absence of aromatic hydrocarbon and in tetrachloroethane as inert solvent containing anhydrous AlCl3, Ia underwent intramolecular alkylation and/or acylation to afford the respective thieno[3,2-c]pyridine and cyclopentadieno[b]thiophene respectively.