Copper–amine-complex-catalyzed highly selective oxidative cross-coupling of 2-naphthols: Synthesis of C1-Symmetric BINOLs

Abstract

An efficient catalytic system based on a copper–amine complex was developed for the oxidative cross-coupling of 3-hydroxy-2-naphthoic acid derivatives and 2-naphthols under mild conditions. The method tolerated a broad substrate scope, and a series of C₁-symmetrical BINOL derivatives were obtained in excellent yields (up to 93 %). In addition, the model reaction was easily amplified to the gram scale with a relatively consistent yield. The control experiments showed that in this catalytic system, the homocoupling reactions of 2-naphthol derivatives do not take place, and the degree of homocoupling for the 3-hydroxy-2-naphthoic acid derivatives did not exceed 10 %, thereby indicating a high chemical selectivity. At last, a possible mechanism was proposed based on high-resolution mass spectrometry and previous studies.