One-pot two-component [3 + 2] cycloaddition/annulation protocol for the synthesis of highly functionalized thiophene derivatives.

An efficient and experimentally rapid protocol for the synthesis of hitherto unreported 2,3-dicarboalkoxy-4-aroyl/heteroaroyl/alkanoyl thiophenes has been developed via 1-2 (C-S) and 3-4 (C-C) bond connections promoted by 4-dimethylaminopyridine (DMAP). Optimally, the reaction takes only 3-5 min when β-oxodithioester and dialkyl acetylenedicarboxylate are stirred in DCM at room temperature in the presence of DMAP. This method allows a clean and general synthesis of previously inaccessible and synthetically demanding thiophenes containing the ferrocenyl group. The speed, experimental ease, and high yields of this process are improvements over existing methods to access this important substructure.