Intramolecular Cyclopropanation of Active Methylene Derivatives Based on FeCl2 or FeCl3‐Promoted Radical‐Polar Crossover Reactions

Abstract

AbstractRadical‐polar crossover reactions were studied for the intramolecular cyclopropanation of active methylene derivatives. In the presence of FeCl3 as a stoichiometric oxidant and K2HPO4 as a base, the dehydrogenative cyclopropanation of active methylenes proceeded through the FeCl3‐promoted oxidative radical cyclization followed by the ionic cyclization to give the bicyclic cyclopropanes. The use of α‐chloro‐active methylenes leads the subcatalytic cyclopropanation involving two redox pathways. In the presence of K2HPO4, the redox cyclopropanation proceeded by using FeCl2 (20 mol%) in combination with ligand (20 mol%).