Thio Diels–Alder reactions of α,β-unsaturated 1,3-oxathiolanes with aliphatic olefins and 1,3-dienes

A series of α,β-unsaturated 1,3-oxathiolanes reacted with aliphatic olefins such as norbornene and with various 1,3-dienes in the presence of TiCl4 leading to dihydrothiapyrans, via a cycloaddition-type reaction. The unsaturated oxathiolanes acted as masked heterodienes in this thio Diels–Alder reaction.