Pd-Catalyzed Asymmetric Allenylation of Secondary Phosphine Oxides with Enyne-Type Propargylic Carbamates for the Construction of Chiral Allenyl Phosphine Oxides

Chiral allenyl phosphine oxides represent a significant
kind of
synthetic target with promising potential for various applications.
However, explorations toward their asymmetric synthesis remain scarce,
primarily due to the competitive coordination of phosphine oxides
with metal catalysts. Herein, we report a Pd-catalyzed enantioselective
allenylation of secondary phosphine oxide for the efficient construction
of a variety of chiral allenyl phosphine oxides. The success of this
reaction arises from the enhanced (bidentate form) coordination of
a newly designed, fungicide-inspired enyne-type propargylic carbamate
with a chiral Pd complex. This protocol features high yields and enantioselectivities,
scalability, and versatile derivatization. Mechanistic studies confirmed
the exclusion of a kinetic resolution pathway.