A simple and versatile protocol for the preparation of functionalized heterocycles utilizing 4-benzoyl-5-phenylamino-2,3-dihydrothiophene-2,3-dione

The reaction of ethyl benzoylpyruvate with phenyl isothiocyanate in alkaline medium yields 4-benzoyl-5-phenylamino-2,3-dihydrothiophene-2,3-dione (1). Reaction of the intermediate 1 with primary aromatic amines such as aniline derivatives, benzidine and secondary aliphatic amines, namely diethylamine, piperidine, morpholine and piperazine afforded the corresponding thiophene 2a–2g and amide 3a–3d derivatives. Compound 1 reacts with N,N′- and N,O-dinucleophiles such as 1,2-diaminoalkanes, 2-aminoethanol, 1-aminoguanidine, guanidine, urea, 1,2-phenylenediamine and 2-amino-4-methylphenol to form the heterocylic compounds 4–10.