Cobalt-Catalyzed Enantioselective C-H Arylation of Indoles.

Abstract

Atropoisomeric (hetero)biaryls are scaffolds with increasing importance in the pharmaceutical and agrochemical industries. Although it is the most obvious disconnection to construct such compounds, the direct enantioselective C-H arylation through the concomitant induction of the chiral information remains extremely challenging and uncommon. Herein, the unprecedented earth-abundant 3d-metal-catalyzed atroposelective direct arylation is reported, furnishing rare atropoisomeric C2-arylated indoles. Kinetic studies and DFT computation revealed an uncommon mechanism for this asymmetric transformation, with the oxidative addition being the rate- and enantio-determining step. Excellent stereoselectivities were reached (up to 96% ee), while using an unusual N-heterocyclic carbene ligand bearing an essential remote substituent. Attractive dispersion interactions along with positive C-H---π interactions exerted by the ligand were identified as key factors to guarantee the excellent enantioselection.