• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >Polymer-supported enantioselective bifunctional catalysts for nitro-Michael addition of ketones and aldehydes
【24h】

Polymer-supported enantioselective bifunctional catalysts for nitro-Michael addition of ketones and aldehydes

机译：聚合物负载的对映选择性双功能催化剂，用于酮和醛的硝基-迈克尔加成

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

Introduction of an L-amino acid as a spacer and a urea-forming moiety in a polymer-supported bifunctional urea-primary amine catalyst, based on (1R, 2R)-(+)-1,2-diphenylethylenediamine, significantly improves the catalyst's activity and stereoselectivity in the asymmetric addition of ketones and aldehydes to nitroolefins. Yields and enantioselectivities, unprecedented for immobilized catalysts, were obtained with such challenging donors as acetone, cyclopentanone, and α,α-disubstituted aldehydes, which usually perform inadequately in this reaction (particularly when a secondary-amine-based catalyst is used). Remarkably, though in the examined catalysts the D-amino acids as spacers were significantly inferior to the L isomers, for the chosen configuration of the diamine (match-mismatch pairs) the size of the side chain of the amino acid hardly influenced the enantioselectivity of the catalyst. These results, combined with the reactivity profile of the catalysts with substrates bearing two electron-withdrawing groups and the behavior of the catalysts' analogues based on tertiary (rather than primary) amine, suggest an enamine-involving addition mechanism and a particular ordered C-C bond-forming transition state as being responsible for the catalytic reactions with high enantioselectivity.
机译：在基于（1R，2R）-（+）-1,2-二苯基乙二胺的聚合物负载双官能尿素伯胺催化剂中引入L-氨基酸作为间隔基和形成脲的部分，可显着改善催化剂的酮和醛不对称加成到硝基烯烃中的活性和立体选择性。用丙酮，环戊酮和α，α-二取代醛等具有挑战性的给体获得了固定化催化剂前所未有的收率和对映选择性，这通常在该反应中表现不佳（特别是在使用仲胺基催化剂时）。值得注意的是，尽管在所研究的催化剂中，作为间隔基的D-氨基酸明显劣于L异构体，但对于二胺的选择构型（匹配-不匹配对），氨基酸侧链的大小几乎不会影响其对映选择性。催化剂。这些结果，再加上催化剂与带有两个吸电子基团的底物的反应性分布以及基于叔胺（而非伯胺）的催化剂类似物的行为，表明存在涉及烯胺的加成机理和特定的有序CC键形成过渡态是负责高对映选择性的催化反应的原因。

著录项

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