Synthesis of Heteroaryl Triazenes via Rh(III)-catalyzed Annulation Reactions with Alkynyl Triazenes

A synthetic route towards polycyclic heteroaryl triazenes has been developed. Alkynyl triazenes were coupled to phenyl-substituted indoles, imidazoles and sydnones via rhodium-catalyzed double C-H or C-H/N-H activation reactions. The oxidative annulations gave triazenes connected to imidazo[1,2-a] quinoline, indolo[2,1-a] isoquinoline and sydnone-quinoline scaffolds in moderate to excellent yields. The triazene-bearing fused sydnone-quinolines were used for subsequent orthogonal transformations. The sydnone moiety allowed for post-functionalization via 1,3-dipolar cycloadditions in excellent yields, and the triazene group can be substituted by a range of functional groups.