Oxidative C-H/C-H Annulation of Imidazopyridines and Indazoles through Rhodium-Catalyzed Vinylene Transfer

Org Lett. 2020 May 1;22(9):3547-3550. doi: 10.1021/acs.orglett.0c00975. Epub 2020 Apr 13.

Abstract

Transition-metal-catalyzed C-H activation followed by oxidative annulation with alkynes has been an efficient synthetic tool for the assembly of various polyaromatic scaffolds. Despite the substantial progress in this field, it is still a significant challenge to achieve the synthesis of nonsubstituted vinylene-fused compounds. In this contribution, we report a Rh-catalyzed C-H/C-H vinylene cyclization adopting vinylene carbonate as a "vinylene transfer" agent. This protocol achieves the direct annulative π-extension of imidazole- and pyrazole-fused aromatics.