A metal-free cyclization reaction of 2-isocyanobiphenyls with amide derivatives by using tert-butyl peroxybenzoate (TBPB) as oxidant was developed, which provided an access to pharmacologically interesting 6-amidophenanthridine compounds. The reactions proceeded through a sequence of functionalization of the C(sp(3))-H bond adjacent to the nitrogen atom and intramolecular radical aromatic cyclization with good chemistry yields.