Substituent and Lewis Acid Promoted Dual Behavior of Epoxides towards [3+2]-Annulation Reactions with DonorAcceptor Cyclopropanes: Synthesis of Substituted Cyclopentane and Tetrahydrofuran

Substituent and Lewis acid promoted generation of functionalized enolates from epoxides is developed. Divergent attack of the enolate on donor-acceptor cyclopropanes, i.e. Cattack or O-attack depending upon substituents present in both reacting partners, produced different products. C-attack gave functionalized cyclopentane derivatives, whereas O-attack fur-nished tetrahydrofuran derivatives through [3+2]-annulation reactions. Moreover, to increase the utility of our method, synthesized diastereomeric cyclopentane derivatives were converted into synthetically useful cyclopentene and cyclopentanone analogs.