• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Catalytic, asymmetric aldol reaction equivalents: Development and mechanistic studies of Lewis acid-catalyzed acyl halide-aldehyde cyclocondensations.
【24h】

Catalytic, asymmetric aldol reaction equivalents: Development and mechanistic studies of Lewis acid-catalyzed acyl halide-aldehyde cyclocondensations.

机译：催化，不对称醛醇缩合反应当量：路易斯酸催化的酰基卤-醛环缩合反应的发展和机理研究。

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

Catalyzed asymmetric acyl halide-aldehyde cyclocondensation (AAC) reactions have been developed as catalyzed direct aldol reaction variants. The AAC reactions utilize acetyl bromide or propionyl bromide in the presence of diisopropylethylamine to generate ketene in situ as an enolate surrogate. Ensuing ketene-aldehyde cyclization occurs in the presence of a substoichiometric amount (10 mol%) of optically active AI(III)-triamine complex 27a affording enantioenriched β-lactones (≥90% ee) as masked aldol adducts. The operational simplicity of these reactions and the use of inexpensive, commercially available reaction components are particularly attractive characteristics.*; Solid state and solution studies of the active catalyst demonstrated that a neutral, pentacoordinate Lewis acid-base adduct derived from 27a is the catalytically active species in the asymmetric AAC reactions. The solid state structure indicates 27a to be a four-coordinate complex adopting a trigonal monopyramidal (tmp) geometry ideally disposed to accept a fifth ligand in a vacant apical site. The ligand, therefore, acts primarily to define a catalytically active coordination geometry rather than assisting in defining electronic properties within the metal complex necessary for catalysis. The ligand-defined catalysis can be interpreted as arising from a combination of ground state destabilization of the distorted metal complex and a stabilization of the transition state leading to Lewis acid-base association for the preorganized tmp catalysts relative to analogous tetrahedral complexes.; The empirical rate expression of the asymmetric AAC reaction of hydrocinnamaldehyde catalyzed by Al(III)-triamine complex 27a was determined. The AAC reaction was first order in catalyst 27a and ketene, but a fractional dependence on aldehyde concentration and a first order dependence on bromide ion concentration were also identified. The observed kinetic behavior of the asymmetric AAC reaction is consistent with a novel mechanism incorporating a chiral acid bromide enolate intermediate. The kinetic observations from a variety of acyl halide aldehyde cyclocondensation reactions suggest that the reaction occurs by competing bromide-dependent and bromide-independent pathways.; *Please refer to dissertation for diagram.
机译：催化的不对称酰基卤-醛环缩合（AAC）反应已开发为催化的直接羟醛反应变体。 AAC反应在二异丙基乙胺的存在下利用乙酰基溴或丙酰基溴来生成烯基酮作为烯醇酸酯替代物。随后的乙烯酮-醛环化反应发生在亚化学计量量（10 mol％）的光学活性AI（III）-三胺络合物 27a 存在下，提供了对映体丰富的β-内酯（≥90％ee）作为被掩盖的羟醛加合物。这些反应的操作简便性以及使用廉价的可商购反应组分特别具有吸引力。活性催化剂的固态和溶液研究表明，衍生自 27a 的中性，五配位路易斯酸碱加合物是不对称AAC反应中的催化活性物质。固态结构表示 27a 是四坐标复合物，采用的是理想的三角形三角锥（tmp）几何形状，可以在空缺的顶端位置接受第五个配体。因此，配体主要起限定催化活性配位几何形状的作用，而不是协助限定催化所必需的金属络合物内的电子性质。配体定义的催化作用可以解释为是由于扭曲的金属配合物的基态失稳和过渡态的稳定（导致相对于类似的四面体配合物的预组织的tmp催化剂的路易斯酸碱缔合）的结合。测定了Al（III）-三胺络合物 27a 催化的氢肉桂醛不对称AAC反应的经验速率表达。 AAC反应在催化剂 27a 和乙烯酮中是一阶的，但也确定了对醛浓度的分数依赖性和对溴离子浓度的一阶依赖性。所观察到的不对称AAC反应的动力学行为与引入手性酸溴化物烯醇酸酯中间体的新机理是一致的。来自各种酰基卤醛醛环缩合反应的动力学观察结果表明，该反应是通过竞争依赖于溴化物和不依赖于溴化物的途径发生的。 *请参考论文的图表。

著录项

  • 作者

    Peelen, Timothy John.;

  • 作者单位

    University of Pittsburgh.;

  • 授予单位 University of Pittsburgh.;
  • 学科 Chemistry Organic.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 239 p.
  • 总页数 239
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 有机化学;
  • 关键词

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