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首页> 外文学位 >Density functional theory investigation into mechanisms of metal ion-promoted and base-promoted phosphorothioate cleavage reactions and Lanthanide ion catalysts for kinetic resolution of amino acid esters.
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Density functional theory investigation into mechanisms of metal ion-promoted and base-promoted phosphorothioate cleavage reactions and Lanthanide ion catalysts for kinetic resolution of amino acid esters.

机译：密度泛函理论研究金属离子促进和碱促进的硫代磷酸酯裂解反应机理以及镧系元素离子催化剂用于氨基酸酯的动力学拆分。

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摘要

Described here are chiral Ln3+ complexes of Schiff-base ligands and their use as catalysts for the kinetic resolution of the 4-nitrophenyl esters of N-Boc glutamine and phenylalanine through an enantioselective methanolysis/ethanolysis reaction. Catalysts were screened in various solvents and temperatures to optimize the selectivity value k2L/k2 D or k2D/k2L. The greatest selectivity at 25°C determined was 7.1, however, reducing reaction temperature increases selectivity and after kinetic resolution at -40°C a product mixture with >99% e.e. with ~80% of the desired product remaining.;The detailed mechanism of base-promoted hydrolysis and methanolysis of O,O'-dimethyl O-aryl phosphorothioates and phosphates was examined computationally. Generally, with increased leaving group acidity, the reactions showed a tendency toward being concerted (a single transition state) and while substrates with leaving groups with lower acidity tend to involve 5-coordinate phosphorane intermediates. Bronsted beta lg values are also computed, and found to be similar to experimentally determined values.;The mechanism of palladacycle-promoted phosphorothioate methanolysis is also modeled computationally, showing a change in rate determining step from substrate binding ( pssKa of leaving group phenol 13). The calculations also predict the existence of a stable metal-bound 5-coordinate thiophosphorane intermediate which has been tentatively verified experimentally by others. The preliminary results of a computational investigation into the mechanism for the methanolytic cleavage of a series of N-methyl N-aryl thiobenzamides catalyzed by a similar palladacycle complex is also presented, showing metal-assisted nucleophilic attack and leaving group departure.;A computational method is presented for the prediction of the Bronsted parameter betaeq, for a phosphorothioyl group transfer in methanol by comparing relative free energy values of starting materials and phenolate products for a series of related substrates. Direct comparison of starting material and anionic leaving group free energies results in a poor approximation of betaeq, however given that the beta eq value for the equilibrium of phenol and phenoxide is -1, the comparison of computed free energies of neutral starting material with neutral phenol product provides betaeq approximations that are satisfactorily close to the experimentally derived values.
机译：本文描述了席夫碱配体的手性Ln3 +配合物及其通过对映选择性甲醇分解/乙醇分解反应作为动力学拆分N-Boc谷氨酰胺和苯丙氨酸的4-硝基苯基酯的催化剂的用途。在各种溶剂和温度下筛选催化剂，以优化选择性值k2L / k2 D或k2D / k2L。在25℃下确定的最大选择性为7.1，然而，降低反应温度增加了选择性，并且在-40℃下动力学拆分后，具有＞ 99％e.e的产物混合物。通过计算研究了碱促进O，O'-二甲基O-芳基硫代磷酸酯和磷酸酯的水解和甲醇分解的详细机理。通常，随着离去基团酸度的增加，反应显示出趋于一致的趋势（单一过渡态），而具有离酸基团的底物具有较低酸度的底物倾向于涉及5-配位的膦烷中间体。还计算了布朗斯台德的1g lg值，发现其与实验确定的值相似。 。该计算还预测了稳定的金属结合的5-配位硫代磷烷中间体的存在，该中间体已被其他人尝试性地验证。还提供了计算研究的初步结果，该计算研究是由类似的palladacycle配合物催化的一系列N-甲基N-芳基硫代苯甲酰胺的甲醇裂解反应的机理，表明金属辅助的亲核攻击和离开基团的离开。通过比较一系列相关底物的原料和酚盐产物的相对自由能值，提出了用于预测布朗斯台德参数betaeq的方法，用于预测甲醇中硫代硫酰基的转移。直接比较原料和阴离子离去基团的自由能会导致betaeq的近似值很差，但是，考虑到苯酚和酚盐平衡的beta eq值为-1，比较中性原料和中性酚的自由能产品提供的betaeq近似值令人满意地接近于实验得出的值。

著录项

  • 作者

    Maxwell, Christopher Ian.;

  • 作者单位

    Queen's University (Canada).;

  • 授予单位 Queen's University (Canada).;
  • 学科 Chemistry Organic.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 238 p.
  • 总页数 238
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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