Morgan‐Walls Cyclization

Abstract

The synthesis of phenanthridine derivatives by means of the treatment of N ‐acyl ortho ‐aminobiphenyls with ZnCl 2 at high temperature or with POCl 3 is generally referred to as the Pictet–Hubert phenanthridine synthesis. The study finds that modification is unsuccessful for the transformation of ortho ‐formamidobiphenyl itself to the parent phenanthridine scaffold and nitrobenzene and HBF 4 have been used to catalyze such a cyclization. This modification is known as Morgan–Walls cyclization. This reaction has been applied for the synthesis of phenanthridine derivatives, especially for 6‐substituted phenanthridines.