Spiroannulations of β-Ketothioamides with Bromoenals via Selective -Michael Addition and -Michael Addition-Triggered Cascade Reactions.

A spiroannulation reaction of β-ketothioamides with aromatic β-bromoenals and aromatic α-bromoenals via selective -Michael addition and -Michael addition-triggered cascade reactions has been developed. This protocol provides a novel and rapid approach for the synthesis of substituted spirothiopyran and spirothiophene derivatives under mild conditions with moderate to good yields and a broad substrate scope.