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首页> 外文学位 >Discovery and development of novel reactions: Catalytic, asymmetric aldol-Tishchenko, Claisen, and diboration reactions.
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Discovery and development of novel reactions: Catalytic, asymmetric aldol-Tishchenko, Claisen, and diboration reactions.

机译：新型反应的发现和发展：催化反应，不对称的Aldol-Tishchenko反应，Claisen反应和硼氢化反应。

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摘要

It was discovered that 10 mol% of Cr(ClO4)*6H2O could catalyze the intramolecular Cannizzaro reaction with iso-propanol. A series of high-throughput screenings led to the identification of a chiral Cu(II)-box complex as a potential chiral Lewis acid catalyst for the reaction. Selectivities remained low (33% e.e.), although catalyst loading could be lowered to 1 mol% without detrimental effects on product yields or selectivity. A cross-over experiment helped determine that hydride shift probably occurs in an intramolecular fashion.; Utilization of a chiral metal alkoxide library screening led to the discovery that an optimized yttrium (III)/salen complex could catalyze the aldol-Tishchenko reaction between iso-butyraldehyde and several aromatic aldehydes. The 1, 3-diol monoesters were prepared in up to 70% yield and 74% e.e. A postulated mechanism for the reaction was described, as well as a proposed model for asymmetric induction. Further studies on alpha, beta-unsaturated aldehydes were performed, including a focused screening of chiral metal alkoxides that all contained at least one acidic proton.; A library of chiral catalysts was screened for their effectiveness in the reductive ester enolate Claisen rearrangement of allylic acrylates. The results of the screen and the discovery that silyl ketene acetal was the reactive intermediate were presented. Use of a rhodium(I)/Me-Duphos catalyst allowed for selective formation of the (E)-silyl ketene acetal with allylic acrylates and therefore, a highly diastereoselective and mild Ireland-Claisen rearrangement under base-free conditions was discovered. Catalyst loading could be dropped to 0.5 mol% with no detrimental effects. Also, it was shown that the reaction is chemoselective as ester functionality survives the reaction untouched.; Finally, the discovery of a catalytic, enantioselective diboration of simple alkenes is discussed. It was discovered that 5 mol% of a rhodium(I)/( S)-Quinap catalyst complex and bis(catecholatodiboron) could perform the diboration of simple unfunctionalized alkenes. The products were isolated as the 1, 2-diols with yields of up to 76%, diastereomeric ratios >50:1, and >98% e.e. Further functionalization of the diborane intermediate was highlighted through transformation to the bis(pinacol) ester and homologation to the 1, 4-diol.
机译：发现10mol％的Cr（ClO4）* 6H2O可以催化与异丙醇的分子内Cannizzaro反应。一系列高通量筛选导致鉴定出手性Cu（II）-box配合物作为潜在的手性路易斯酸催化剂。选择性仍然很低（e.e.为33％），尽管催化剂的加入量可以降低到1mol％，而对产物的产率或选择性没有不利的影响。交叉实验有助于确定氢化物转移可能以分子内方式发生。利用手性金属醇盐文库筛选导致发现优化的钇（III）/ salen配合物可以催化异丁醛与几种芳香醛之间的aldol-Tishchenko反应。制备1，3-二醇单酯的产率最高为70％，e.e。为74％。描述了假定的反应机理，以及提出的不对称诱导模型。对α，β-不饱和醛进行了进一步的研究，包括重点筛选所有都含有至少一个酸性质子的手性金属醇盐。筛选了手性催化剂库在烯丙基丙烯酸酯的还原性酯烯醇化克莱森重排中的有效性。提出了筛选结果，并发现了甲硅烷基烯酮缩醛为反应性中间体。使用铑（I）/ Me-Duphos催化剂可以与烯丙基丙烯酸酯选择性地形成（E）-硅烷基烯酮缩醛，因此，在无碱条件下发现了高度非对映选择性和温和的爱尔兰-克莱森重排。催化剂的负载量可以降至0.5mol％，而没有不利影响。另外，还表明该反应是化学选择性的，因为酯官能度在未反应的条件下仍然存在。最后，讨论了对简单烯烃的催化，对映选择性的硼化反应的发现。发现5mol％的铑（I）/（S）-Quinap催化剂配合物和双（儿茶酚二硼）可以进行简单的未官能化烯烃的二硼化。分离出产物为1，2-二醇，产率高达76％，非对映异构体比率＞ 50∶1，＞ 98％e.e。通过转化成双（频哪醇）酯和同化为1，4-二醇，突出了乙硼烷中间体的进一步官能化。

著录项

  • 作者

    Miller, Steven Paul.;

  • 作者单位

    The University of North Carolina at Chapel Hill.;

  • 授予单位 The University of North Carolina at Chapel Hill.;
  • 学科 Chemistry Organic.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 313 p.
  • 总页数 313
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 有机化学;
  • 关键词

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