Reaction of Dicarbomethoxycarbene with Thiophene Derivatives

Photolysis of derivatives of dimethylmalonate thiophene-S,C-ylide provides dicarbomethoxycarbene, which can react with thiophene to form dimethyl (2-thienyl)malonate. By generation of dicarbomethoxycarbene from the dibenzothiophene-based ylide in neat thiophene, it is shown that the thienylmalonate is not a product of rearrangement of the thiophene ylide, in contrast to thermolysis results. Formation of the thienylmalonate is suppressed by substitution of any sort in the 2- and 5-positions on the thiophene and by substitution with an electron-withdrawing substituent.