Competition for regiochemical control between substituents of some 2,3-disubstituted buta-1,3-dienes in the Diels–Alder reactions
Abstract
Several 3,4-disubstituted 3-sulfolenes 1a–j, the precursors for the corresponding 2,3-disubstituted 1,3-dienes 2a–j, are conveniently prepared and undergo Diels–Alder reactions smoothly with methyl acrylate under thermal conditions where the order of para-directing ability of different substituents is OTBS≃CN > SPh > OMe≃CO2Me > OTs > OAc.