6-Aroylated Phenanthridines via Base Promoted Homolytic Aromatic Substitution (BHAS)

Readily accessible 2-isocyanobiphenyls react with aromatic aldehydes via base promoted homolytic aromatic substitution (BHAS) to give 6-aroylated phenanthridines. Reactions occur via addition of acyl radicals to the isonitrile functionality and subsequent intramolecular BHAS of the intermediate imidoyl radicals. Initiation of the radical chain reaction is best achieved with small amounts of FeCl3 (0.4 mol %), and the commercially available and cheap fBuOOH is used as the oxidant.