Enantioselective Copper(I)/Chiral Phosphoric Acid Catalyzed Intramolecular Amination of Allylic and Benzylic C-H Bonds

Abstract

Radical-involved enantioselective oxidative C-H bond functionalization by a hydrogen-atom transfer (HAT) process has emerged as a promising method for accessing functionally diverse enantioenriched products, while asymmetric C(sp³ )-H bond amination remains a formidable challenge. To address this problem, described herein is a dual Cu^I /chiral phosphoric acid (CPA) catalytic system for radical-involved enantioselective intramolecular C(sp³ )-H amination of not only allylic positions but also benzylic positions with broad substrate scope. The use of 4-methoxy-NHPI (NHPI=N-hydroxyphthalimide) as a stable and chemoselective HAT mediator precursor is crucial for the fulfillment of this transformation. Preliminary mechanistic studies indicate that a crucial allylic or benzylic radical intermediate resulting from a HAT process is involved.

Keywords: C−H activation; amination; asymmetric catalysis; copper; radicals.