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首页> 外文学位 >I. Stereoselective Construction of Polycyclic Architectures: Enantioselective Catalytic Transannular Ketone-Ene Reactions and an Enantioselective Total Synthesis of (+)-Reserpine II. Synthesis of Chiral Bisthioureas for Anion-Abstraction Catalysis.
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I. Stereoselective Construction of Polycyclic Architectures: Enantioselective Catalytic Transannular Ketone-Ene Reactions and an Enantioselective Total Synthesis of (+)-Reserpine II. Synthesis of Chiral Bisthioureas for Anion-Abstraction Catalysis.

机译：I.多环结构的立体选择性构建：对映选择性催化环戊酮-烯反应和（+）-利血平的对映选择性总合成II。用于阴离子提取催化的手性双硫脲的合成。

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摘要

The research presented herein explores three aspects of asymmetric catalysis: (1) the development of new catalytic enantioselective reactions, (2) the application of stereoselective catalysis to natural product total synthesis, and (3) the design and synthesis of new chiral catalysts.;In Chapter 1, an asymmetric transannular ene reaction of electronically unactivated ketones is reported. The transformation is catalyzed by a new chromium(III) tridentate Schiff-base catalyst and provides access to trans-decalinol frameworks in high diastereo- and enantioselectivity.;A convergent total synthesis of indole alkaloid (+)-reserpine is presented in Chapter 2. The synthesis uses two key catalytic asymmetric methods: an oligomeric Co(salen)-catalyzed enantioselective kinetic resolution of terminal epoxides and a catalyst-controlled diastereoselective primary aminothiourea-catalyzed formal aza-Diels-Alder reaction. These methods enabled an enantioselective synthesis of the classic target and addressed the historically problematic C3 stereocenter of the molecule. Through the investigation of various synthetic routes we were able to access two unnatural diastereomers of methyl reserpate: 16-epi-(+)-methyl reserpate and 15,16-di-epi-(+)-methyl reserpate.;Chapter 3 describes the syntheses of rationally designed bisthioureas for anion-abstraction catalysis. Recent mechanistic investigations have led to the identification of productive and nonproductive thiourea dimerization modes in the context of an asymmetric alkylation of alpha-chloroethers. Based on this work, we synthesized covalently tethered thioureas that enforce proximity of the hydrogen bond donor moieties for cooperative electrophile activation while disfavoring nonproductive self-aggregation. Significant enhancements in reactivity are obtained with the bisthioureas relative to analogous monomeric thioureas in the model reaction.
机译：本文提出的研究探索了不对称催化的三个方面：（1）新催化对映选择性反应的发展；（2）立体选择性催化在天然产物全合成中的应用；（3）新手性催化剂的设计和合成。在第一章中，报道了电子未活化酮的不对称环戊烯反应。新型三价铬Schiff碱铬（III）催化催化转化，并提供了高非对映体和对映体选择性的反式萘烷骨架;第2章介绍了吲哚生物碱（+）-利血平的聚合全合成。该合成方法使用两种关键的催化不对称方法：末端环氧化物的低聚Co（salen）催化对映选择性动力学拆分和催化剂控制的非对映选择性伯氨基硫脲催化的正式aza-Diels-Alder反应。这些方法实现了经典靶标的对映选择性合成，并解决了该分子历史上有问题的C3立体中心。通过对各种合成途径的研究，我们能够获得两种非天然非对映异构体，即16-epi-（+）-甲基Reserpate和15,16-di-epi-（+）-Reserpate。;第三章介绍了合理设计的双硫脲的合成用于阴离子吸附催化。最近的机械研究已导致在α-氯醚不对称烷基化的情况下确定生产性和非生产性硫脲二聚化模式。基于这项工作，我们合成了共价束缚的硫脲，该硫脲可强制氢键供体基团的亲和性，以促进亲电试剂的协同活化，同时不利于非生产性自聚集。在模型反应中，相对于类似的单体硫脲，双硫脲获得了显着的反应性增强。

著录项

  • 作者

    Rajapaksa, Naomi Samadara.;

  • 作者单位

    Harvard University.;

  • 授予单位 Harvard University.;
  • 学科 Chemistry Organic.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 209 p.
  • 总页数 209
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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