Cobalt-catalyzed preparation of quinoxalines

Quinoxaline is an important heterocycle present in a plethora of compounds with a wide range of biological activities. [1] An efficient cobalt-catalyzed annulation of terminal alkynes and o‑phenylenediamines to prepare various substituted quinoxalines was recently published by Guo et Coll. [2] This methodology is illustrated in the Scheme below.

o-Phenylenediamine derivatives bearing both electron-donating and electron-withdrawing groups, as well as on the aryl ring of terminal alkynes, are suitable for this transformation. It should be pointed out that non-aromatic terminal alkynes can be also used. A full mechanistic investigation of this transformation is reported.

[1] S. K. Suthar et al., Eur. J. Med. Chem. Reports 2022, 5, 10040.
[2] H.-R. Yang, Z.-Y. Hu, X.-C. Li, L. Wu, X.-X. Guo, Org. Lett. 2022, 24, 8392-8396.