Goodman C Guy, Johnson Jeffrey S
Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-3290, United States.
J Am Chem Soc. 2014 Oct 22;136(42):14698-701. doi: 10.1021/ja508521a. Epub 2014 Oct 9.
The dynamic kinetic resolution of β-halo α-keto esters via an asymmetric cross-benzoin reaction is described. A chiral N-heterocyclic carbene catalyzes the umpolung addition of aldehydes to racemic α-keto esters. The resulting fully substituted β-halo glycolic ester products are obtained with high levels of enantio- and diastereocontrol. The high chemoselectivity observed is a result of greater electrophilicity of the α-keto ester toward the Breslow intermediate. The reaction products are shown to undergo highly diastereoselective substrate-controlled reduction to give highly functionalized stereotriads.
描述了通过不对称交叉安息香反应对β-卤代α-酮酯进行动态动力学拆分。手性N-杂环卡宾催化醛对外消旋α-酮酯的极性翻转加成反应。由此得到的全取代β-卤代乙醇酸酯产物具有高对映体和非对映体选择性。观察到的高化学选择性是α-酮酯对布雷斯洛中间体具有更高亲电性的结果。反应产物经高度非对映选择性的底物控制还原反应，得到高官能化的立体三元组。
