Amine-Mediated Ring-Opening And Ring-Closure Reaction Of EWG-Activated 2-Methylene-1,3-dithioles

Thiophenes are widespread in nature and a variety of multisubstituted thiophenes form an internal part of numerous products and pharmaceuticals. Thiophene derivatives also find applications, as a kind of functional materials, in dyes, liquid crystals, molecular wires, organic light-emitting diodes, field-effect transistors etc. Moreover, multisubstituted thiophenes represent extremely versatile organic intermediates. In view of their vast application in the areas of biology, material and chemistry, it is of great importance to develop efficient synthetic methods towards multisubstituted thiophenes, especially polyfunctionalized thiophenes. There are two general methods that have been reported in the literature. One is the direct functionalization of the thiophene ring (usuallyα?metalation orβ?halogenation). The other is via the annulation reactions of suitably substituted open chain precursors. The latter may allow regioselective preparation of the thiophene derivatives and thus represents an attractive, but less developed methodology.Over the past decades, the utility ofα?oxo ketene-(S,S)-acetals as versatile intermediates in organic synthesis has been recognized. In recent years, our research group has devoted to the synthetic applications ofα?oxo ketene-(S,S)-acetals. In this thesis, I would like to represent an amine-mediated ring-opening and ring-closing reaction of electron-withdrawing group-activated 2-methylene-1,3-dithioles. As a result, multifunctionalized and bicyclic thieno[3,2-b]thiopyran-4-ones were successfully prepared in one-pot and high yields. My research includes the following three aspects:1,Explore the possibility of amine-mediated ring-opening and ring-closure reaction of EWG-activated 2-methylene-1,3-dithioles.2,The application of amine-mediated ring-opening and ring-closure reaction of EWG-activated 2-methylene-1,3-dithioles to synthesize polyfunctionalized thiophenes. The optimization of the reaction conditions, the scope of the reactions and possible mechanism were investigated in detail.3,The ring-opening and subsequent ring-closure reaction of alkenoyl-containing 2-methylene-1,3-dithioles and its application in the synthesis of substituted thieno[2,3-b]thiopyrans.We have synthesized eighteen compounds which have been characterlized by IR, 1H NMR, 13C NMR spectra and Single-crystal X-ray analysis.