Aza‐Ruthena(II)‐Bicyclo‐[3.2.0]‐Heptadiene: Key Intermediate for Ruthenaelectro(II/III/I)‐Catalyzed Alkyne Annulations

A ruthenium-catalyzed electrochemical dehydrogenative annulation reaction of imidazoles with alkynes has been established, enabling the preparation of various bridgehead N-fused [5,6]-bicyclic heteroarenes through regioselective electrochemical C-H/N-H annulation without chemical metal oxidants. Novel aza-ruthena-bicyclo-[3.2.0]-heptadienes were fully characterized and identified as key intermediates. Mechanistic studies are suggestive of an oxidatively-induced reductive elimination pathway within a ruthenium(II/III) regime.