Diastereoselective Cyclopropanation through Michael Addition‐Initiated Ring Closure between α,α‐Dibromoketones and α,β‐Unsaturated Fischer Carbene Complexes

Abstract

The diastereoselective synthesis of tetrasubstituted cyclopropanes is described. The two‐step procedure is based on the 3‐exo‐tet Michael addition‐initiated ring closure. In the first step, the enolates derived from α,α‐dibromoketones react with the α,β‐unsaturated Fischer alkoxycarbene complexes to obtain tetrasubstituted cyclopropanes, which are then treated with ceric‐ammonium nitrate to yield the final products. The methodology tolerates diverse functional groups, and high diastereoselectivity (dr ≥ 98:2) is observed in all cases.