Cation radical pericyclic reactions: Cyclopropanation

Abstract

Abstract Triarylaminium salts smoothly catalyze the cyclopropanation of dienes, styrenes and tetrasubstituted alkenes by ethyl diazoacetate. The reactions are regioselective and, in the case of additions to conjugated dienes, cyclopropane‐periselective. A cation radical chain mechanism involving carbene transfer from ethyl diazoacetate to a substrate cation radical is proposed.