Silver-Catalyzed Tandem C=C Bond Hydroazidation/Radical Addition/Cyclization of Biphenyl Acetylene: One-Pot Synthesis of 6-Methyl Sulfonylated Phenanthridines

A silver-catalyzed tandem carbon!carbon triple bond hydroazidation, radical addition, and cyclization of biphenyl acetylene is described under mild conditions, leading to the formation of 6-methyl sulfonylated phenanthridines in good yields. In this novel cascade reaction, most of the atoms are incorporated into the product without cleavage of the CC bond. Mechanistic studies suggest the reaction should proceed through an iminyl radical reactive intermediate.