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

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