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.