Asymmetric Direct Henry Reaction of Ynals Catalyzed by Iminophosphorane

Significance

In this report, the authors present a direct asymmetric Henry reaction of ynals. The products, various propargylic alcohols, were obtained in high enantiopurity (er up to 99.5:0.5) by using the tetraaminophosphonium salt 1 as a pre-catalyst. Interestingly, the concentration of DMF is crucial for a reasonable conversion into the desired products. The authors observed a tetra­aminophosphonium cation complex with alkoxide, which should be generated during the course of the reaction and can deactivate the cation.