Michael addition of the dienolate derived from 2-butenoic acid to 1,3-diphenylpro-penone occurs through a 1,2-addition followed by a 3,3-sigmatropic rearrangement. α,γ -re-gioselectivity found for Michael addition to other styryl ketones depends on the steric parameter of the substituents at the carbonyl group, in agreement with the same tandem addition rearrangement mechanism.