Sequential pericyclic reaction of unsaturated xanthates. Intramolecular cycloaddition selectivity of the 2,4-alkadienyl 2-alkenyl sulfides

Article abstract of DOI:10.1016/0040-4020(96)00853-8

Heating of S-(1-vinyl-2-alkenyl) S-(2-alkenyl or alkynyl) dithiocarbonates (dithiolcarbonates) derived from [3,3]-sigmatropic rearrangement of O-(2,4-alkadienyl) S-(2-alkenyl or alkynyl) dithiocarbonates (xanthates) gave the 2,4-alkadienyl 2'-(alkenyl or alkynyl) sulfides, which then underwent intramolecular Diels-Alder cycloaddition to give hydrobenzo[c]thiophene derivatives. The thermal cyclization of O-(2,4-pentadienyl) derivatives of xanthate afforded mixtures of the cycloadducts, in which the cis-FUSED products slightly predominated over the trans-isomers. The selectivity of IMDA reactions is discussed based on the ab initio calculation data.