• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >Evidence That Protons Can Be the Active Catalysts in Lewis Acid Mediated Hetero-Michael Addition Reactions
【24h】

Evidence That Protons Can Be the Active Catalysts in Lewis Acid Mediated Hetero-Michael Addition Reactions

机译：质子可以在路易斯酸介导的杂-迈克尔加成反应中成为活性催化剂的证据

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

The mechanism of Lewis acid catalysed hetero-Michael addition reactions of weakly basic nucleophiles to alpha,beta-unsaturated ketones was investigated.Protons,rather than metal ions,were identified as the active catalysts.Other mechanisms have been ruled out by analyses of side products and of stoichiometric enone-catalyst mixtures and by the use of radical inhibitors.No evidence for the involvement of pi-olefin-metal complexes or for carbonyl-metal-ion interactions was obtained.The reactions did not proceed in the presence of the non-coordinating base 2,6-di-tert-butylpyridine.An excellent correlation of catalytic activities with cation hydrolysis constants was obtained.Different reactivities of mono-and dicarbonyl substrates have been rationalised.A ~1H NMR probe for the assessment of proton generation was established and Lewis acids have been classified according to their propensity to hydrolyse in organic solvents.Bronsted acid-catalysed conjugate addition reactions of nitrogen,oxygen,sulfur and carbon nucleophiles are developed and implications for asymmetric Lewis acid catalysis are discussed.
机译：研究了路易斯酸催化弱碱性亲核试剂与α，β-不饱和酮的杂-迈克尔加成反应的机理。确定了质子而不是金属离子为活性催化剂。通过副产物分析排除了其他机理以及没有化学计量的烯酮-催化剂混合物和自由基抑制剂的使用。没有获得有关π-烯烃-金属配合物或羰基-金属-离子相互作用的证据。配位了2,6-二叔丁基吡啶碱，得到了良好的催化活性与阳离子水解常数的相关关系，合理化了单和二羰基底物的不同反应性。建立了〜1H NMR探针来评估质子的生成路易斯酸和路易斯酸根据其在有机溶剂中的水解倾向进行了分类。布朗斯台德酸催化的氮，氧共轭加成反应氧，硫和碳亲核试剂的开发，并讨论了不对称路易斯酸催化的意义。

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