Achiral Cp^xIr(III)/Chiral Carboxylic Acid Catalyzed Enantioselective C–H Amidation of Ferrocenes under Mild Conditions

Abstract

Ir(III)-catalyzed enantioselective C–H activation generally relies on the combination of chiral Ir(III) cyclopentadienyl complexes with chiral carboxylic acids to ensure high enantiocontrol. We report herein the achiral CpxIr(III)-catalyzed enantioselective C–H amidation of ferrocenes. Crucial to the high enantioselectivity is the use of a chiral carboxylic acid ligand derived from tert-leucine via Pd(II)-catalyzed γ-C(sp3)–H arylation and a sterically more hindered CpxIr(III) catalyst. This reaction proceeds smoothly under very mild conditions (0 °C) and tolerates a wide range of ferrocene carboxamides and dioxazolones, providing the amidation products in good yields with high enantioselectivity (up to 97.5:2.5 er). This protocol might open the way for achiral CpxIr(III)-catalyzed asymmetric C–H activation.