Spiroannulations of β-Ketothioamides with Bromoenals via Selective <i>C</i>-Michael Addition and <i>S</i>-Michael Addition-Triggered Cascade Reactions

A spiroannulation reaction of β-ketothioamides with aromatic β-bromoenals and aromatic α-bromoenals via selective <i>C</i>-Michael addition and <i>S</i>-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.