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 (<b>1</b>). Reaction of the intermediate <b>1</b> with primary aromatic amines such as aniline derivatives, benzidine and secondary aliphatic amines, namely diethylamine, piperidine, morpholine and piperazine afforded the corresponding thiophene <b>2a–2g</b> and amide <b>3a–3d</b> derivatives. Compound <b>1</b> reacts with <i>N,N</i>′- and <i>N,O</i>-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 <b>4–10</b>.