Synthesis of Dihydrothiophenes by an Amino-Directed Thioisomünchnone−Alkene Cycloaddition Reaction

Abstract

Dihydrothiophenes can easily be obtained by a general protocol involving the reaction of 2-aminothioisomünchnones with electron-deficient alkenes. The overall process can be interpreted as a sequential [3+2] cycloaddition/ring-opening cyclization reaction. The structures of the products could be unequivocally assigned by X-ray diffraction analysis. A theoretical study at a semiempirical level (PM3) with a further single-point refinement of energies at the B3LYP/6−31G* level also offers mechanistic insights into the stereochemical outcome.