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

• Published in: Angewandte Chemie International Edition Vol. 59; no. 27; pp. 11130 - 11135
• Main Authors: Yang, Long, Steinbock, Ralf, Scheremetjew, Alexej, Kuniyil, Rositha, Finger, Lars H., Messinis, Antonis M., Ackermann, Lutz
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 26.06.2020; John Wiley and Sons Inc
• Subjects: Chemistry; Chemistry, Multidisciplinary; C−H activation; dehydrogenation; electrochemistry; nitrogen heterocycles; Physical Sciences; ruthenium; Science & Technology; electrochemistry; DIRECT ARYLATIONS; CLEAVAGE; H BOND ACTIVATION; FUNCTIONALIZATION; ruthenium; C-H activation; BENZAMIDES; ACETOXYLATION; RUTHENIUM(II); nitrogen heterocycles; dehydrogenation; CATALYZED OXIDATIVE COUPLING/CYCLIZATION; C-H; C−H activation
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202000762

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. New mechanism: A ruthenium‐catalyzed electrochemical dehydrogenative annulation reaction of imidazoles with alkynes delivers bridgehead N‐fused [5,6]‐bicyclic heteroarenes through regioselective C−H/N−H annulation without metal oxidants. Novel azaruthenabicyclo[3.2.0]heptadienes were identified as key intermediates. Mechanistic studies suggest an oxidatively induced reductive elimination pathway within a ruthenium(II/III) regime.