Strained azetidinium ylides: New reagents for cyclopropanation

Azetidinium ylides showed a remarkable ability to perform the cyclopropanation of Michael acceptors. Ephedrine-derived azetidinium ylides allowed the formation of substituted cyclopropanes in good yields and at a high level of stereoselectivity. The determination of the relative stereochemistries in the produced cyclopropanes gave some insight into the reaction mechanism.