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，而是由这些物种中的特定原子和官能团等局部结构决定的。本文研究了烯丙基硼化合物，首次从理论上估算了硼中心的电子接受能力和刘易斯酸硬度。这些量已被证明根据助剂的类型而显著变化。理论估算的烯丙基硼化合物对醛的反应活性与从头算MO法精确计算的活化能吻合得很好，与实验结果也吻合得很好。本研究揭示了烯丙基硼化合物反应活性的控制因素，并提供了一个新的反应活性标度，可用于新型硼试剂的设计。 关于我们 利用分子轨道计算和轨道相互作用的概念，研究了2-氯-2-丙烯基乙基碳酸酯的钯和铂络合物中烯丙基碳的亲核取代。在铂配合物的情况下，计算表明金属环丁烷结构和eta^22配位结构在能量上相当，并且eta^22配位结构中的配体交换不容易。因此，亲核取代应该发生在烯丙基碳上，得到烯丙基化的化合物。相比之下，金属环丁烷结构的稳定性不如钯配合物中的η ^22配位结构。取代反应发生在eta^22-络合物中，得到烯烃化合物作为主要产物。在这种情况下，反应发生催化作用。金属环丁烷结构和η ^22-结构的相对稳定性已经通过相互作用轨道的相位和重叠得到了非常清楚的解释。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