Defying Ring Strain: New Approaches to Cyclopropanes

Beating ring strain: Two novel cyclopropanation reactions (see scheme; LA=Lewis acid, Nu=nucleophile) achieved a great level of selectivity using surprisingly mild conditions. The first used epoxides as a source of methylene in the synthesis of enantioenriched cyclopropanes. The second pushed the limit of the well-established allylic alkylation chemistry to the synthesis of three-membered rings with excellent ee values.