A DFT Study on Rh-Catalyzed Asymmetric Dearomatization of 2-Naphthols Initiated with C-H Activation: A Refined Reaction Mechanism and Origins of Multiple Selectivity

Comprehensive DFT calculations have been performed to pursue deeper understandings on the mechanism of Rh-catalyzed asymmetric dearomatization of 2-naphthols initiated with C-H activation, which was developed by our group recently. A refined reaction mechanism is described here to account for the experimentally observed high enantio- and regioselectivity. Although the C-H activation was suggested to be involved in the turnover-limiting step, the enantioselectivity of the reaction was found to be determined during the migratory insertion of the alkyne. Different from the originally proposed mechanism, the final dearomatized product is afforded via a [1,3']-reductive elimination directly from the eight-membered rhodacyclic intermediate generated from the migratory insertion step. In addition, the pi-pi interaction between the phenyl substituent on the alkyne and 2-naphthol might partially contribute to the high regioselectivity when unsymmetrical alkynes were employed as the substrates.