We present a general protocol for the formal Michael addition of acetone to α,β‐unsaturated esters and amides, a transformation difficult to perform using current methods. The protocol comprises of an amidine catalyzed relay ring‐opening and fragmentation of 3,4‐dihydropyranones. The reaction proceeds under mild conditions, has a broad substrate scope and the products can be isolated in good to excellent yields. The method can be applied to homochiral substrates with total preservation of chiral information, generating products in high optical purity. Kinetic experiments supported by quantum chemical modeling indicate a mechanism in which the catalyst takes a bifunctional role, acting both as a Brønsted base and as a hydrogen‐bond donor.