Triphenylphosphine-Mediated Synthesis of the E/Z Isomers of Methyl 6-(1,2-Di(methoxycarbonyl))-8-(ethyl Carbamoylformyl)-2-oxo-2H-chromene-4-carboxylate

Triphenylphosphine-mediated reaction of dimethyl acetylenedicarboxylate with ethyl (2-hydroxyphenylcarbamoyl)formate in boiling toluene produces a mixture of methyl 8-(ethyl carbamylformyl)-2-oxo-2H-chromene-4-carboxylate and the E/Z isomers of methyl 6-(1,2-di(methoxycarbonyl)-8-(ethyl carbamoylformyl)-2-oxo-2H-chromene-4-carboxylate in moderate yields.