Ir(III)-Catalyzed Asymmetric C–H Activation/Annulation of Sulfoximines Assisted by the Hydrogen-Bonding Interaction

Transition-metal-catalyzed asymmetric C–H activation
reactions
generally rely on the design of ligands with sterically bulky groups
to create a chiral environment for enantioinduction through steric
repulsion. Here we describe an Ir­(III)-catalyzed asymmetric C–H
activation enabled by noncovalent interactions. A broad range of sulfur-stereogenic
sulfoximines was prepared in high yields with excellent enantioselectivities via the asymmetric C–H activation/annulation of sulfoximines
with diazo compounds. Desymmetrization, kinetic resolution, and parallel
kinetic resolution are compatible with this protocol. Detailed DFT
calculations suggested that the N–H···O hydrogen
bonding interaction between sulfoximine and the chiral carboxylic
acid ligand was crucial for the high enantiocontrol. Moreover, chiral
iridacycle intermediates were isolated, characterized, and subjected
to stoichiometric reactions. Computational and experimental studies
suggested that the C–H cleavage step was the rate- and enantio-determining
step.