(4R-cis)-2,4,5-triphenyl-1,3,2-oxazaborolidine | 1057661-63-8

• 分子结构分类: 有机化合物 - 苯丙烷和聚酮 - 二苯乙烯类
• 英文名称: (4R-cis)-2,4,5-triphenyl-1,3,2-oxazaborolidine
• 英文别名: (4R,5S)-2,4,5-triphenyl-1,3,2-oxazaborolidine
• CAS: 1057661-63-8
• 化学式: C₂₀H₁₈BNO
• 分子量: 299.18
• InChiKey: HQJXFGQLSRREHW-UXHICEINSA-N

物化性质

• 沸点：
  418.0±55.0 °C(Predicted)
• 密度：
  1.14±0.1 g/cm3(Predicted)

计算性质

• 辛醇/水分配系数(LogP)：
  3.48
• 重原子数：
  23
• 可旋转键数：
  3
• 环数：
  4.0
• sp3杂化的碳原子比例：
  0.1
• 拓扑面积：
  21.3
• 氢给体数：
  1
• 氢受体数：
  2

反应信息

• 作为产物：
  描述：

  苯硼酸酐 、 (1S,2R)-2-氨基-1,2-二苯基乙醇 以 甲苯 为溶剂， 以88%的产率得到(4R-cis)-2,4,5-triphenyl-1,3,2-oxazaborolidine
  参考文献：
  名称：

  A combined synthetic and ab initio study of chiral oxazaborolidines structure and enantioselectivity relationships

  摘要：

  Investigations into the relationship of oxazaborolidine structure to the enantioselectivity obtained in the reduction of prochiral ketones revealed the intrinsic power of the molecular recognition element in the catalytic reduction. This molecular recognition, two-point binding of borane and the ketonic oxygen atom by the oxazaborotidine, assembles a trimolecular complex which provides high enantiomeric excess. Enantiomeric excess was demonstrated to be dependent on the extent to which one oxazaborolidine face was precluded from attaining two-point binding and on nonbonded interactions that developed during formation of the borane-oxazaborolidine complex. As a result, erythro-substituted oxazaborolidines were demonstrated to be useful catalysts for enantioselective reduction of prochiral ketones. Ab initio molecular orbital calculations have been used to locate possible complexes and transition state assemblies that correspond to catalyst-borane and the trimolecular complex on a proposed reduction pathway. Geometry optimizations were carried out at the 3-21G, 6-31G(d), and MP2/6-31G(d) levels of theory. Correlation energies were computed via Moller-Plesset perturbation theory to the second order (MP2). Relative activation energies establish correctly the observed enantioselectivity of the two best oxazaborolidine catalysts in this study. Additionally, the diminished enantioselectivity of N-methyl-substituted catalysts was traced to conformational changes in the exo transition state. Though the relative energies obtained from the various levels of theory are similar, absolute complexation and activation energies are found to vary considerably with the level of theory employed. The existence of key intermediates was found to depend on the level of theory.

  DOI：

  10.1021/ja00098a012

文献信息

• A combined synthetic and ab initio study of chiral oxazaborolidines structure and enantioselectivity relationships
  作者：George J. Quallich、James F. Blake、Teresa M. Woodall

  DOI：10.1021/ja00098a012

  日期：1994.9

  Investigations into the relationship of oxazaborolidine structure to the enantioselectivity obtained in the reduction of prochiral ketones revealed the intrinsic power of the molecular recognition element in the catalytic reduction. This molecular recognition, two-point binding of borane and the ketonic oxygen atom by the oxazaborotidine, assembles a trimolecular complex which provides high enantiomeric excess. Enantiomeric excess was demonstrated to be dependent on the extent to which one oxazaborolidine face was precluded from attaining two-point binding and on nonbonded interactions that developed during formation of the borane-oxazaborolidine complex. As a result, erythro-substituted oxazaborolidines were demonstrated to be useful catalysts for enantioselective reduction of prochiral ketones. Ab initio molecular orbital calculations have been used to locate possible complexes and transition state assemblies that correspond to catalyst-borane and the trimolecular complex on a proposed reduction pathway. Geometry optimizations were carried out at the 3-21G, 6-31G(d), and MP2/6-31G(d) levels of theory. Correlation energies were computed via Moller-Plesset perturbation theory to the second order (MP2). Relative activation energies establish correctly the observed enantioselectivity of the two best oxazaborolidine catalysts in this study. Additionally, the diminished enantioselectivity of N-methyl-substituted catalysts was traced to conformational changes in the exo transition state. Though the relative energies obtained from the various levels of theory are similar, absolute complexation and activation energies are found to vary considerably with the level of theory employed. The existence of key intermediates was found to depend on the level of theory.