Visible-light-induced tandem radical addition-cyclization of 2-aryl phenyl isocyanides catalysed by recyclable covalent organic frameworks

A visible- light- induced tandem radical addition- cyclization sequence via 2- aryl phenyl isocyanides as the starting material and two- dimensional covalent organic frameworks ( 2D- COFs) as the photocatalyst was developed, delivering multifarious 6- substituted phenanthridines in high yields. Benefitting from the utilization of a heterogeneous photocatalyst, this protocol features easy catalyst separation and excellent recyclability. A negligible loss of the catalytic activity was observed after multiple runs. High practicability of this protocol was further demonstrated by continuous flow experiments.