Conformational equilibria of six-membered ring sulphoxides: the effect of β-electron-withdrawing groups

Abstract

¹ H N.m.r. parameters are reported for various six-membered ring sulphoxides. Chemical shift and coupling constant data reveal that the oxides of thian-3-one and 3-dicyanomethylenethian adopt preferentially the axial SO conformer. Introduction of a sulphur atom into these ring systems at the remaining position β to the sulphinyl group increases the amount of equatorial SO conformer. Orbital–orbital interactions in these and related systems are considered.