A chiral bis-phosphine monoxide–gold(i) complex enables asymmetric dearomative cyclization of β-naphthol derivatives

Abstract

Chiral phosphine ligands play a pivotal role in gold(I)-catalyzed asymmetric reactions, yet their efficacy is often constrained by limited strategies for chiral induction. While traditional ligands rely primarily on steric effects, the linear geometry of Au(I) centers demands innovative ligand designs capable of synergistic interactions beyond spatial hindrance. This challenge motivates the development of ligands incorporating supplementary weakly coordinating groups to enhance enantiocontrol. We herein report four novel chiral gold(I) complexes based on bis-phosphine monoxide ligands (BPMOs), namely (R)-BINAP(O)-AuCl 3a, (R)-MeO-BiPhep(O)-AuCl 3b, (S)-SegPhos(O)-AuCl 3c and (R,R)-DuPhos(O)-AuCl 3d, derived from commercially available biphosphine ligands via mono-oxidation and Au(I)-complexation. The catalytic utility of these complexes was evaluated in the intramolecular catalytic asymmetric dearomatization (CADA) reaction of β-naphthol derivatives, among which, complex 3a [(R)-BINAP(O)-AuCl] exhibited superior performance, delivering a series of spiro-naphthalenone products in good yields with moderate to high enantiomeric excess. Experimental and computational studies reveal that the PO moiety in 3a facilitates a critical hydrogen-bonding interaction with the substrate, synergizing with Au(I)-alkyne coordination to rigidify the transition state and amplify stereocontrol. This work establishes chiral BPMO–Au(I) complexes as versatile catalysts for asymmetric dearomatization, with demonstrated scalability and applicability toward diverse β-naphthol substrates.