Artificial Chiral Trinuclear Zn Catalysts: Design, Self-Assembly and Unprecedented Efficiency in Asymmetric Hydroboration of Ketones
Jingxi He, Shuxin Jiang, Yu Qiu, Yingchao Liu, Kuiling Ding, Xiaoming Wang
Abstract
The development of artificial catalysts with efficiency that can rival those of Nature's enzymes represents one of the foremost yet challenging goals in homogeneous metal catalysis. Inspired by the exceptional performance of metalloenzymes, the design and development of highly efficient bi/multinuclear catalysts via judicious ligand design, by taking advantage of the cooperative action of the proximal catalytic sites, has attracted great attention. Herein, we report the self-assembly of a chiral hexadentate BINOL-dipyox ligand with zinc acetate into a well-defined trinuclear zinc complex, which demonstrated ultrahigh catalytic productivity in the enantioselective hydroboration of ketones with an unprecedented turnover number (TON) of 19,400 at an extremely low catalyst loading (0.005 mol %). Mechanistic investigations reveal that a cooperative Lewis acid activation mode is operating in the catalytic process, hence, underscoring the unique advantages of the trinuclear architecture.