Synthesis of Fused‐Pyrazines via Palladium‐Catalyzed Double Benzyl Isocyanide Insertion and Cross‐Dehydrogenative Coupling

A palladium‐catalyzed cascade reaction has been realized for the synthesis of 5H‐pyrrolo[2,3‐b]pyrazines and 5H‐pyrazino[2,3‐b]indoles from benzyl isocyanide by choosing o‐pivaloyloximes or o‐iodoanilines as a suitable substrate. The key steps involved are (i) oxidative addition of palladium through N–O or C–I cleavage; (ii) migratory double isocyanide insertion; and (iii) cross‐dehydrogenative coupling. Notable features are good functional group tolerance as well as formation of three C–C and one C–N bonds.