Synthesis of 2-(2-Nitroalkyl)indoles by Rhodium(III)-Catalyzed C-H Alkylation

The Rh(III)-catalyzed addition of the indole C2-H bond to nitroalkenes under an ambient atmosphere is disclosed, providing direct access to a wide range of 2-(2-nitroalkyl)indoles (33 examples) with excellent chemo- and regioselectivity. In addition, pyrrole derivatives also successfully participated in this Friedel-Crafts alkylation reaction. Representative nitroalkane products could be converted into structurally diverse and valuable indole derivatives. Furthermore, a series of control experiments were conducted, and a plausible mechanism was proposed.

Automated summary

The Rh(III)-catalyzed addition of indole C2-H bond to nitroalkenes at room temperature and atmospheric pressure is reported, providing a convenient method for the synthesis of a wide range of 2-(2-nitroalkyl)indoles in high yield and selectivity. Pyrrole derivatives were also successfully employed in the Friedel-Crafts alkylation reaction. The obtained nitroalkane products could be further transformed into structurally diverse and valuable indole derivatives. Control experiments were conducted and a plausible mechanism was proposed.