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.