Enantio- and Regioselective Propargylation and Allenylation of β,γ-Unsaturated α-Ketoesters with Allenyl Boronate Regulated by Chiral Copper/Zinc

A method for asymmetric propargylation and allenylation of β,γ-unsaturated α-ketoesters catalyzed by Box-Cu/Box-Zn using a commercial organoboron reagent is reported. The reaction was demonstrated to be broadly tolerant of functional groups, resulting in a series of propargyl and allenyl tertiary alcohols in excellent yields with high enantio- and regioselectivities. Furthermore, the proposed mechanism was supported by density functional theory calculations. Gram-scale experiments as well as the synthesis of various chiral tertiary alcohols and glycol derivatives demonstrated the practicality of this synthetic strategy.