Syntheses of Novel Tetrasubstituted Thiophenes from Benzene-1,2-Diamines, Ethyl Bromopyruvate, Malononitrile, and Aryl Isothiocyanates

Abstract

Synthesis of highly functionalized tetrasubstituted thiophenes has been reported involving 3-(bromomethyl)quinoxalin-2(1H)-ones as activated halomethylene compounds precursors. Thus sequential base mediated condensation of readily available malononitrile with aryl isothiocyanates followed by S–alkylation of the resulting enethiolate salts with 3-(bromomethyl)quinoxalin-2(1H)-one compounds and concurrent intramolecular enamine type condensation of S–alkylated compounds affords substituted thiophenes in excellent yields.