Asymmetric alkylation using chiral cyclic diols to prepare a quaternary carbon

Asymmetric alkylation of cyclic and acyclic β-keto ester acetals (4, 5, 13, 14, and 18) with C2-symmetric cycloalkane-1,2-dioxy moiety proceeded in a highly diastereoselective manner to afford enol ethers (9–12, 15–17, 19a–c) with a chiral quaternary carbon.