Synthesis of dihydrothiophenes by an amino-directed thioisomunchnone - Alkene cycloaddition reaction

Dihydrothiophenes can easily be obtained by a general protocol involving th e reaction of 2-aminothioisomunchnones with electron-deficient alkenes. The overall process can be interpreted as a sequential [3+2] cycloaddition/rin g-opening cyclization reaction. The structures of the products could be une quivocally assigned by X-ray diffraction analysis. A theoretical study at a semiempirical level (PM3) with a further single-point refinement of energi es at the B3LYP/6-31G(*) level also offers mechanistic insights into the st ereochemical outcome.