• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >Enantioselective conjugate addition of nitro compounds to α,β-unsaturated ketones: An experimental and computational study
【24h】

Enantioselective conjugate addition of nitro compounds to α,β-unsaturated ketones: An experimental and computational study

机译：对α，β-不饱和酮的硝基化合物的对映选择性的缀合物添加：实验和计算研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

A series of chiral thioureas derived from easily available diamines, prepared from α-amino acids, have been tested as catalysts in the enantioselective Michael additions of nitroalkanes to α,β-unsaturated ketones. The best results are obtained with the bifunctional catalyst prepared from L-valine. This thiourea promotes the reaction with high enantioselectivities and chemical yields for aryl/vinyl ketones, but the enantiomeric ratio for alkyl/vinyl derivatives is very modest. The addition of substituted nitromethanes led to the corresponding adducts with excellent enantioselectivity but very poor diastereoselectivity. Evidence for the isomerization of the addition products has been obtained from the reaction of chalcone with [D_3]nitromethane, which shows that the final addition products epimerize under the reaction conditions. The epimerization explains the low diastereoselectivity observed in the formation of adducts with two adjacent tertiary stereocenters. Density functional studies of the transition structures corresponding to two alternative activation modes of the nitroalkanes and α,β-unsaturated ketones by the bifunctional organocatalyst have been carried out at the B3LYP/3-21G* level. The computations are consistent with a reaction model involving the Michael addition of the thiourea-activated nitronate to the ketone activated by the protonated amine of the organocatalyst. The enantioselectivities predicted by the computations are consistent with the experimental values obtained for aryl- and alkyl-substituted α,β-unsaturated ketones.
机译：从α-氨基酸制备的易于使用的含有易用的二胺的一系列手性硫脲已在氨基烷烃的催化剂中被测试为NITROALKANES至α，β-不饱和酮的催化剂。通过由L-缬氨酸制备的双官能催化剂获得最佳结果。该硫脲促进了芳基/乙烯基酮的高对映射性和化学产率的反应，但烷基/乙烯基衍生物的对映比非常适度。加入取代的硝基甲烷基因导致相应的加合物，具有优异的对映选择性，但非对映选择性非常差。从Chalcone与硝基甲烷的反应中获得了添加产物的异构化的证据，这表明最终加成产物在反应条件下夹杂化。该缩放解释了在形成具有两个相邻的三级立体封闭体的加合物中观察到的低的非对映选择性。在B3LYP / 3-21G *水平下，在B3LYP / 3-21G *水平上进行了对应于二烷烃和α，β-不饱和酮的两种替代活化模式的过渡结构的密度官能研究。计算与涉及迈克尔的反应模型一致，迈克尔将硫脲活化的氮酸盐添加到由有机催化剂的质子化胺激活的酮中。计算预测的映射性与芳基和烷基取代α，β-不饱和酮的实验值一致。

著录项

  • 来源
    《Chemistry: A European journal》 |2011年第21期|共8页
  • 作者

    Manzano R.; Andrés J.M.; álvarez R.; Muruzábal M.D.; De Lera A.R.; Pedrosa R.;

  • 作者单位

    Centro de Innovación en Química y Materiales Avanzados (CINQUIMA) Universidad de Valladolid Dr. Mergelina s/n 47011 Valladolid Spain;

    Centro de Innovación en Química y Materiales Avanzados (CINQUIMA) Universidad de Valladolid Dr. Mergelina s/n 47011 Valladolid Spain;

    Departamento de Química Orgánica Facultad de Química Universidade de Vigo Lagoas Marcosende 36310 Vigo Spain;

    Centro de Innovación en Química y Materiales Avanzados (CINQUIMA) Universidad de Valladolid Dr. Mergelina s/n 47011 Valladolid Spain;

    Departamento de Química Orgánica Facultad de Química Universidade de Vigo Lagoas Marcosende 36310 Vigo Spain;

    Centro de Innovación en Química y Materiales Avanzados (CINQUIMA) Universidad de Valladolid Dr. Mergelina s/n 47011 Valladolid Spain;

  • 收录信息
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 应用化学;
  • 关键词

    density functional calculations; Michael addition; nitroalkanes; organocatalysis; thioureas;

    机译：密度函数计算;迈克尔加法;Nitroalkanes;有机成分分析;硫脲;

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号