Organocatalytic Enantio- and Diastereoselective Construction of <i>syn</i>-1,3-Diol Motifs via Dynamic Kinetic Resolution of In Situ Generated Chiral Cyanohydrins
syn-1,3-dioxanes as protected 1,3-diols via dynamickineticresolution of in situ generated chiral cyanohydrins has been developed. This method involves a reversible cyanohydrin formation/hemiacetalization/intramolecular oxy-Michael addition reactioncascade, affording a chiral syn-1,3-diol structure with simultaneous construction of two stereogenic centers. The use of trifluoromethyl ketones is crucial
Metal-Free Asymmetric 1,3-Dipolar Cycloaddition of N-Arylmaleimides to Azomethine Ylides Catalyzed by Chiral Tertiary Amine Thiourea
作者:Jian-Fei Bai、Liang-Liang Wang、Lin Peng、Yun-Long Guo、Jun-Nan Ming、Fei-Ying Wang、Xiao-Ying Xu、Li-Xin Wang
DOI:10.1002/ejoc.201100205
日期:2011.8
The first metal-freeasymmetric 1,3-dipolar cycloaddition of N-arylmaleimides to azomethine ylides catalyzed by chiral tertiary amine thiourea to form multiply substituted pyrrolidines in excellent yields (up to 89 %) and enantioselectivities (up to 96 % ee) is presented. This procedure allows a rapid diversity-oriented synthesis of chiral pyrrolidine derivatives with high optical purity.
cyanation of acylsilanes involving the in‐situ formation of chiralacylsilane cyanohydrins followed by their kinetic resolution via organocatalytic cycloetherification is described. The highly enantio‐ and diastereoselective cycloetherification was crucial for achieving a high efficiency in the kinetic resolution. Consequently, acylsilane cyanohydrins containing a tetrasubstituted chiral carbon atom
Organocatalytic asymmetric conjugate addition of malonates to 3-nitro-2H-chromenes
作者:Shao-zhen Nie、Zhi-peng Hu、Yi-ning Xuan、Jin-jia Wang、Xue-ming Li、Ming Yan
DOI:10.1016/j.tetasy.2010.07.015
日期:2010.8
The conjugateaddition of malonates to 3-nitro-2H-chromenes has been studied in the presence of a number of chiral organocatalysts. A bifunctional thiourea-tertiary amine was found to be an efficient catalyst for the reaction. Good yields and enantioselectivities were obtained for a variety of substituted 3-nitro-2H-chromenes. Diethyl malonate and diisopropyl malonate were applicable for the reaction