Cascade double isocyanide insertion and C–N coupling of 2-iodo-2′-isocyano-1,1′-biphenyls

A palladium-catalyzed double isocyanide insertion using 2-iodo-2-isocyano-1,1-biphenyls followed by copper-catalyzed intramolecular C-N coupling, delivering a unique heterocyclic structure containing both phenanthridine and carbazole scaffolds, has been developed. In this cascade process, four chemical bonds, including two C-C, one C-O, and one C-N bonds are formed consecutively without isolating an intermediate. The strategy of using a functionalized isocyanide in double insertion provides a quick approach for constructing heterocyclic systems with high bond-forming efficiency.