Organocatalyzed Conjugate Umpolung of α,β‐Unsaturated Aldehydes for the Synthesis of γ‐Butyrolactones

Advantage organocatalysis: N-heterocyclic carbenes can generate homoenolate equivalents under mild conditions by conjugate umpolung of α,β-unsaturated aldehydes. This organocatalytic reaction allows an efficient one-step synthesis of substituted γ-butyrolactones 1 (see scheme, Mes=mesityl).