Radical Cyclization Cascades of Unsaturated Meldrum’s Acid Derivatives

Unsaturated, differentially substituted Meldrum’s acid derivatives undergo cascade cyclizations upon ester reduction with SmI₂–H₂O. The cascade cyclizations proceed in good yield and with high diastereocontrol and convert simple, achiral starting materials to complex molecular architectures, bearing up to four stereocenters, in a single operation. The cascades are triggered by the generation and trapping of unusual radical-anions formed by electron transfer to the ester carbonyl.