A transition-metal-free
method for the synthesis of C6 phenanthridine
derivatives by arylative cyclization of 2-isocyanobiphenyls with arylamines
in one pot was developed. Mechanistic studies suggest that electrophilic
aromatic substitution (S<sub>E</sub>Ar) of a nitrilium intermediate
and homolytic aromatic substitution (HAS) of an imidoyl radical intermediate
are two competitive reaction pathways involved in the annulation step