Anion-Assisted Copper/Chiral Diamine-Catalyzed Aerobic Oxidation for the Kinetic Dearomative Spirocyclization of...

The utilization of arenols was realized via the catalytic asymmetric dearomatization (CADA) to deliver a broad range of valuable chiral compounds. In this field, CADA of arenols, especially 2-naphthols with diversified external electrophiles has been well established, however the oxidative CADA of 2-naphthols with an external nucleophile, proceeding via an initial SET-oxidation to reverse its polarity, is rare. Herein, we report our recent development on the copper/chiral diamine-catalyzed kinetic spirocyclization of 2-naphthols under ambient conditions, in which the axial and spiro-central elements of chirality could be simultaneously achieved in a one-step kinetic resolution process. The robust nature of the oxidative CADA strategy is reflected by a broad scope of 2-naphthol substrates with good control of the enantioselectivity. DFT calculations suggested that the anion of chloride played a crucial role in the control of enantioselectivity by forming hydrogen bonds with the hydroxyl group in the substrate and the diamine ligand. The matched coordination of naphthol substrates with chiral copper(II) catalyst leads to the subsequent oxidation to access the latter stereospecific spirocyclization.