An efficient method for the synthesis of 6-trichloromethylphenanthridines by benzoyl peroxide promoted cyclization reaction of 2-isocyanobiphenyls with carbon tetrachloride is developed. A radical pathway is proposed and evidenced for the reaction mechanism. This reaction tolerates a wide range of functional groups and the resulting 6-trichloromethylphenanthridines can be utilized as a useful synthetic precursor for corresponding 6-substituted phenanthridines.

An efficient method for the synthesis of 6-(arylthio)phenanthridines by tert-butyl peroxybenzoate (TBPB)-promoted cyclization reaction of 2-isocyanobiphenyls with thiols is developed. A radical pathway is proposed and evidenced for the reaction mechanism. It tolerates a wide range of substrates and represents a practical approach to 6-arylthiophenanthridines.

Further transformation of the products to 6‐functionalized phenanthridines is demonstrated.