Synthesis of 6-Phosphorylated Phenanthridines by Mn(II)-Promoted Tandem Reactions of 2-Biaryl Isothiocyanates with Phosphine Oxides.

A novel Mn(II)-promoted tandem phosphorylation/cyclization reaction of 2-biaryl isothiocyanates with phosphine oxides is described. This is the first general method to synthesize 6-phosporylated phenanthridines from 2-biaryl isothiocyanates. The approach is featured by oxidant-free, low loading of P-reagent, easy operation, and high functional group tolerance.