Iridium‐Catalyzed Enantioselective Intermolecular Indole C2‐Allylation
James A. Rossi‐Ashton, Aimee K. Clarke, James R. Donald, Chao Zheng, Richard J. K. Taylor, William P. Unsworth, Shu‐Li You
Abstract
Abstract The enantioselective intermolecular C2‐allylation of 3‐substituted indoles is reported for the first time. This directing group‐free approach relies on a chiral Ir‐(P, olefin) complex and Mg(ClO 4 ) 2 Lewis acid catalyst system to promote allylic substitution, providing the C2‐allylated products in typically high yields (40–99 %) and enantioselectivities (83–99 % ee ) with excellent regiocontrol. Experimental studies and DFT calculations suggest that the reaction proceeds via direct C2‐allylation, rather than C3‐allylation followed by in situ migration. Steric congestion at the indole‐C3 position and improved π–π stacking interactions have been identified as major contributors to the C2‐selectivity.