Highly Enantioselective Michael Addition of α-Substituted Cyano Ketones to β,γ-Unsaturated α-Keto Esters using Bifunctional Thiourea-Tertiary Amine Catalysts: An Easy Access to Chiral Dihydropyrans
作者:Sheng-Li Zhao、Chang-Wu Zheng、Hai-Feng Wang、Gang Zhao
DOI:10.1002/adsc.200900516
日期:2009.11
An asymmetric Michael addition of α-substituted cyano ketones to β,γ-unsaturated α-keto esters to form chiral dihydropyrans catalyzed by a series of α-amino acid-derived thiourea-tertiary amines is presented. A novel tyrosine-derived thiourea catalyst was identified as the optimal catalyst providing the desired product in 91–95% yields and with 90–96% ee at a low catalyst loading of 2.0 mol%. The utility
提出了α-取代的氰基酮向β,γ-不饱和的α-酮酯的不对称迈克尔加成反应,形成了一系列α-氨基酸衍生的硫脲-叔胺催化的手性二氢吡喃。一种新型的酪氨酸衍生的硫脲催化剂被确定为最佳催化剂,可在91%至95%的收率下以90%至96%的ee提供所需的产物,而催化剂的负载量仅为2.0 mol%。通过将二氢吡喃产物容易地转化成药学上有用的二氢吡啶来举例说明该反应的效用。