Ascorbic acid promoted [4 + 2] benzannulation: a mild, operationally simple approach to the synthesis of phenanthrenes

Abstract

A mild, simple and metal-free radical [4 + 2] benzannulation for the generation of phenanthrenes has been developed. A substoichiometric reductant, ascorbic acid (vitamin C), is harnessed as the radical initiator. This method has a broad substrate scope, and various substituted phenanthrenes were obtained in moderate to good yields at room temperature without irradiation.