Synthesis of Phenanthridines by Radical Caryl-Caryl Coupling

Abstract

Treatment of N-(o-bromobenzyl)anilines with 1-3 equivalent amounts of n-tributyltinhydride, in the presence of 0.5 to 0.6b mol equiv. of AIBN, results in the formation of phenanthridines in good yields. The mechanism of the oxidation step is probed with a deuterated aniline derivative and azobiscyclohexylcarbanonitrile (ABCN) as the initiator. It is shown that the carbon centred radical derived from the latter does not act as the hydrogen abstracting species.