Iron-Catalyzed Directed C2-Alkylation and Alkenylation of Indole with Vinylarenes and Alkynes

http://pubs.acs.org/doi/abs/10.1021/ol503395g

Iron-Catalyzed Directed C2-Alkylation and Alkenylation of Indole with Vinylarenes and Alkynes

Mun Yee Wong, Takeshi Yamakawa, and Naohiko Yoshikai*

Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological Universåity, Singapore 637371, Singapore

Org. Lett., 2015, 17 (3), pp 442–445
DOI: 10.1021/ol503395g
Publication Date (Web): January 9, 2015

Abstract

An iron–N-heterocyclic carbene catalyst generated from an iron(III) salt, an imidazolinium salt, and a Grignard reagent promotes alkylation and alkenylation reactions at the indole C2-position with vinylarenes and internal alkynes, respectively, via imine-directed C–H activation. The former reaction affords 1,1-diarylalkane derivatives with exclusive regioselectivity. Deuterium-labeling experiments suggest that these reactions involve oxidative addition of the C–H bond to the iron center, insertion of the unsaturated bond into the Fe–H bond, and C–C reductive elimination.