Li W, Liu X, Tan F, Hao X, Zheng J, Lin L, Feng X * Sichuan University, Chengdu, P. R. of China
Catalytic Asymmetric Homologation of α-Ketoesters with α-Diazoesters: Synthesis of Succinate Derivatives with Chiral Quaternary Centers.
Angew. Chem. Int. Ed. 2013;
52: 10883-10886
Key words
diazo esters - α-keto esters - yttrium
Significance
The Lewis acid catalyzed homologation of carbonyl compounds with diazo compounds can realize synthetically useful carbon chain extension. The authors achieve the asymmetric homologation of acyclic α-keto esters with α-diazo esters by using chiral N,N′-dioxide-yttrium(III) complexes. Both aryl- and alkyl-substituted α-keto esters are applicable, providing the corresponding succinate derivatives in good yields and enantioselectivities.
Comment
The use of bulky adamantyl α-diazo esters can suppress the formation of undesired by-products. Steric hindrance on the 2,6-positions of the phenyl ring in the ligand is also essential to improve both enantioselectivity and reactivity. The attack of α-diazo ester occurs from re-face of the coordinating α-keto ester preferably due to the obstruction of si-face by the aryl group in the N,N′-dioxide ligand.
