Exploration of Methods for the Design of Reactive Molecules and the Control of Stereoselectivity

分子和反应中间体的物理性质和化学活性不是由分子的稳定结构决定的，而是由这些物质中的特定原子和官能团等局部结构决定的。在本研究中，我们研究了烯丙基硼化合物，并首次从理论上估计了硼中心的电子接受能力和路易斯酸硬度。根据助剂类型的不同，这些量有明显的变化。理论估计的烯丙基硼化合物对醛类化合物的反应活性与用从头算MO方法精确计算的活化能和实验结果吻合得很好。本研究揭示了控制烯丙基硼化合物反应性的因素，并为新型硼试剂的设计提供了新的反应性尺度。利用分子轨道计算和轨道相互作用的概念，进一步研究了2-氯-2-丙烯乙基碳酸酯钯和铂配合物中烯丙基碳的亲核取代。以铂配合物为例，计算表明金属环丁烷结构与eta^22配位结构在能量上具有可比性，而eta^22配位结构中的配体交换不容易。因此，亲核取代应发生在烯丙基碳上，从而得到烯丙基化化合物。相反，钯配合物中的金属环丁烷结构不如eta^22配位结构稳定。在eta^22配合物中发生取代反应，得到主要产物烯烃化合物。在这种情况下，反应是催化发生的。金属环丁烷结构和eta^22结构的相对稳定性已经用相互作用轨道的相位和重叠非常清楚地解释了。少

The physical properties and chemical activities of molecules and reaction intermediates are not determined by the stable structure of molecules, but by the local structures, such as the specific atoms and functional groups, in those species. In this study, we have investigated allyl boron compounds and have estimated, for the first time, theoretically the electron-accepting ability and Lewis acidic hardness of the boron center. These quantities have been shown to change markedly depending on the type of auxiliary. The theoretically estimated reactivity of allyl boron compounds toward aldehydes has been demonstrated to give an excellent agreement with the activation energies calculated accurately by the ab initio MO method and to agree well also with the experimental results. We have revealed in this study the factors that should control the reactivity of allyl boron compounds and have provided a new reactivity scale which can be utilized for the design of novel boron reagents.We have s … More tudied next the nucleophilic substitutions of the allyl carbons in palladium and platinum complexes of 2-chloro-2-propenyl ethyl carbonate, utilizing molecular orbital calculations and the concept of orbital interactions. In the case of platinum complexes, the calculations have shown that the metallacyclobutane structure and the eta^22-coordinated structure are comparable in energy and exchange of ligands in the eta^22-coordinated structure is not facile. Accordingly, the nucleophilic substitution should occur at the allyl carbon to give an allylated compound. In contrast, the metallacyclobutane structure is less stable than the eta^22-coordinated structure in the palladium complex. Substitution reaction takes place in the eta^22-complex to give an alkene compound as the major product. The reaction takes place catalytically in this case. The relative stability of the metallacyclobutane structure and the eta^22-structure has been interpreted very clearly in terms of the phase and overlap of the interaction orbitals. Less