Chemo- and Regioselective Synthesis of Functionalized 1H-imidazo[1,5-a]indol-3(2H)-ones via a Redox-Neutral Rhodium(III)-Catalyzed [4+1] Annulation between Indoles and Alkynes

Alkynes generally serve as C-2 synthons in transition-metal-catalyzed C-H annulations, herein, exploiting electron-deficient alkynes as unconventional C-1 synthons, the chemo- and regiospecific synthesis of functionalized 1H-imidazo[1,5-a]indol-3(2H)-ones via a redox-neutral rhodium(III)-catalyzed [4+1] annulation of N-carbamoyl indoles has been achieved. This process is characterized by high chemo- and regioselectivity, broad substrate scope, good tolerance of functional groups, moderate to high yields and mild redox-neutral conditions, thus affording a robust approach to access valuable 1H-imidazo[1,5-a]indol-3(2H)-ones.

Automated summary

This study achieved the synthesis of functionalized 1H-imidazo[1,5-a]indol-3(2H)-ones by utilizing electron-deficient alkynes as unconventional C-1 synthons in a redox-neutral rhodium(III)-catalyzed [4+1] annulation. The process exhibited high chemo- and regioselectivity, broad substrate scope, good tolerance of functional groups, moderate to high yields, and mild redox-neutral conditions, providing a robust method to access valuable 1H-imidazo[1,5-a]indol-3(2H)-ones.