Enantioselective Oxidative Coupling of 2-Naphthol Derivatives by Copper-(R)-1,1′-Binaphthyl-2,2′-diamine-TEMPO Catalyst

Abstract

An efficient chiral copper catalytic system [(R)-(+)-1,1′-binaphthyl-2,2′-diamine-copper(I) chloride-TEMPO] for the asymmetric oxidative coupling of 2-naphthol derivatives to synthesize enantiomerically enriched BINOL derivatives has been developed with good to excellent enantiomeric excess (up to 97% ee). The addition of a catalytic quantity of 2,2,6,6-tetramethylpiperidin-1-yl oxyl (TEMPO) to the copper-(R)-(+)-1,1′-binaphthyl-2,2′-diamine complex greatly enhanced the reactivity and enantioselectivity of the enantioselective oxidative coupling of 2-naphthol derivatives and also reduced the reaction temperature from 90 °C to room temperature in dichloromethane solvent.