Synthesis of 6-Phenanthridinephosphonates via a Radical Phosphonation and Cyclization Process Mediated by Manganese(III) Acetate

6-Phenanthridinephosphonates have interesting biological activities and potential pharmaceutical applications. However, methods for preparing these compounds are very limited. In this report, dialkyl 6-phenanthridinephosphonates were synthesized through Mn(OAc)(3)-mediated radical phosphonation of 2-isocyanobiaryls in good to excellent yields under relatively mild reaction conditions. As one of its notable features, the radical process allows the direct formation of a P-C bond and the construction of a phenanthridine ring in one reaction.