Azaruthena(II)‐bicyclo[3.2.0]heptadiene: Key Intermediate for Ruthenaelectro(II/III/I)‐catalyzed Alkyne Annulations

Abstract

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 azaruthenabicyclo[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.

Ruthenaelectro‐Catalyzed Domino Three‐Component Alkyne Annulation for Expedient Isoquinoline Assembly

“…[11] Compared with rhodium [12] and iridium [13] electrocatalysis, economically attractive ruthenaelectrocatalysis continues to be underdeveloped. [14] Within our program on electrochemical C À H activation, [15] we have now devised a sustainable ruthenaelectro-catalyzed three-component reaction to assemble versatile isoquinolines in a domino manner. [16] Salient features of our findings include 1) multi-component assembly in a one-pot fashion with a cost-effective ruthenium catalyst, [8f] 2) isolation and full characterization of ruthenacycle intermediates, and 3) mechanistic insights into oxidation-induced reductive elimination [17] at ruthenium(II) by experiments and calculation ( Figure 1)…”

Electrochemically Enabled Intramolecular and Intermolecular Annulations of Alkynes

“…In 2020, Ackermann and co-workers [39] reported a set of ruthenium-catalyzed electrochemical dehydrogenative annulations of imidazoles 98 with alkynes 99. The scope and versatility of this set of reactions were explored with various imidazole and alkyne substrates.…”

Divergent Rhodium-Catalyzed Electrochemical Vinylic C–H Annulation of Acrylamides with Alkynes

“…Ackermann and co-workers demonstrated Ru-catalyzed electrochemical vinylic C-H annulation of acrylamides with symmetric internal alkynes at elevated temperature (140 °C). 18 Herein, we report the first example of a transition metal-catalyzed electrochemical vinylic C-H annulation of acrylamides with alkynes in an undivided cell under mild reaction conditions, specifically by the action of a Rh catalyst. Importantly, divergent syntheses of a-pyridones and cyclic imidates are achieved by varying the N-substituent of the acrylamides.…”