Chiral amine organocatalysts for the syn-aldol reaction involving substituted benzaldehydes and hydroxyacetone
摘要:
A new series of cyclohexanediamine organocatalysts that contain the primary amine functionality has been designed, synthesized and tested as catalysts for the asymmetric aldol reaction involving hydroxyacetone and a variety of substituted benzaldehydes. High enantioselectivites and diasteroselectivites were obtained using catalyst la for these reactions. A key step in this reaction for the formation of the syn-product is the formation of a stable intramolecular hydrogen bonded Z-enamine isomer, which in addition to the steric bulk of the catalyst, serve to dictate the course of the stereochemical outcome of the reaction. (C) 2011 Elsevier Ltd. All rights reserved.
A highly efficient asymmetric Michael addition of α,α-disubstituted aldehydes to maleimides catalyzed by primary amine thiourea salt
作者:Feng Yu、Zhichao Jin、Huicai Huang、Tingting Ye、Xinmiao Liang、Jinxing Ye
DOI:10.1039/c0ob00154f
日期:——
The first highlyefficientMichaeladdition of challenging α,α-disubstituted aldehydes to maleimides catalyzed by a simple bifunctional primary amine thiourea catalyst/benzoic acid system has been successfully developed to generate quaternary carbon centers in high yields (up to 99%) with excellent enantioselectivities (91–99%).
The first intermolecular asymmetric Michael addition of nitrogen-nucleophiles to alpha,beta-unsaturated carboxylic acids was achieved through a new type of arylboronic acid equipped with chiral aminothiourea. The use of BnONH2 as a nucleophile gives a range of enantioenriched beta-(benzyloxy)amino acid derivatives in good yields and with high enantioselectivity (up to 90% yield, 97% enantiomeric excess
The iridium/f-diaphos L1, L5 or L12 catalyzed asymmetric hydrogenation of 2-imidazolyl aryl/alkyl ketones to afford two enantiomers of the desired chiral alcohols with high conversions (up to 99% yield) and moderate to excellent enantioselectivities (61% - >99% ee) was realized for the first time. This protocol could be easily conducted on a gram-scale with a TON of 9700.
铱/ f-二磷L1、L5或L12催化 2-咪唑基芳基/烷基酮的不对称氢化,得到所需手性醇的两种对映异构体,具有高转化率(高达 99% 的产率)和中等至优异的对映选择性(61% - >99% ee ) 首次实现。该协议可以在 TON 为 9700 的克级上轻松执行。