Successive cycloadditions between 4-fluoro-5-trifluoromethyl-1,2-dithiole-3-thione and dimethyl acetylenedicarboxylate: New fluorinated thiaheterocycles through new reaction mechanisms

The cycloaddition reaction between dimethyl 2-(1-fluoro-2-trifluoromethyl-2-thioxoethylidene)-1,3-dithiole-4,5-dicarboxylate and dimethyl acetylenedicarboxylate proceeds efficiently under irradiation conditions in air. A study of the reaction conditions resulted in the proposal of a chain mechanism initiated by a photochemically induced single-electron transfer to oxygen. On the other hand, the cycloadduct can be transformed into a rearranged hydroxylated product by filtration through silica gel. Either the cycloadduct or its rearranged product can be obtained selectively in a one-pot process from the parent 1,2-dithiole-3-thione. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).