Highly Enantioselective Reactions of Cyclohexanone and<i>β</i>,<i>γ</i>-Unsaturated<i>α</i>-Keto Ester: The Tuning of Chemo-selectivities by Secondary and Primary Amine Catalysts
作者:Jianwei Wei、Wengang Guo、Xin Zhou、Xin Du、Yan Liu、Can Li
DOI:10.1002/cjoc.201400431
日期:2014.10
amphiphilic imidazole based secondary and primary amine catalysts were synthesized and shown to be very effective with an acid cocatalyst for the asymmetric reaction of cyclohexanone to β,γ‐unsaturated α‐keto ester. Interestingly, primary and secondary amine catalysts show different regio‐selectivities in this reaction. Under the catalysis of secondary amine 1, excellent enantioselectivities were observed for
合成了一系列基于两亲咪唑的仲胺和伯胺催化剂,它们显示出与酸助催化剂非常有效地使环己酮不对称反应成β,γ-不饱和α-酮酯。有趣的是,伯胺和仲胺催化剂在该反应中显示出不同的区域选择性。在仲胺1的催化下,以水为溶剂,环己酮与β,γ-不饱和α-酮酯直接3 + 3反应生成的产物具有极好的对映选择性。而且,相同的反应物被伯胺2催化导致醛醇缩合反应,从而提供具有高非对映选择性和高达97%ee的相应产物。使用气相模型对过渡态进行的理论研究表明,空间效应对仲胺1和伯胺2的不同化学选择性诱导起着重要作用。