Diene-dienophile dual reactivity of conjugated vinyl sulfines

The discovery of a new and facile synthesis of α,β-unsaturated thioaldehyde S-oxides has enabled the exploration of the diene-dienophile reactivity of these novel heterocumulenes. Unlike some previous reports, the addition of (Z)-β,β-dimethylvinyl and (Z)-β-styryl sulfines to either cyclic or acyclic dienes proceeds in a non-stereospecific manner, yielding three stereoisomers. In contrast, the latter sulfine reacts as a diene with norbornene and other dienophiles to give a single product.