Enantiocontrolled Synthesis of Tertiary α‐Hydroxy‐α‐ynyl Esters by Dimethylzinc‐Mediated Addition of Alkynes to α‐Keto Esters

A perhydro‐1,3‐benzoxazine behaves as an excellent chiral ligand in the nucleophilic addition of alkynylzinc derivatives, prepared from terminal alkynes and dimethylzinc, to α‐keto esters without using other Lewis acids. The enantioselectivity is excellent and homogeneous for a wide variety of aromatic and heteroaromatic α‐keto esters. Aliphatic enolizable α‐keto esters were alkynylated with moderate enantioselection.