Computational investigations of NHC-backbone configurations for applications in organocatalytic umpolung reactions.,Organic & Biomolecular Chemistry

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Computational investigations of NHC-backbone configurations for applications in organocatalytic umpolung reactions.
Organic & Biomolecular Chemistry ( IF 2.9 ) Pub Date : 2020-09-14 , DOI: 10.1039/d0ob01267j
Kortney M Melancon ₁ , Thomas R Cundari ₁

Affiliation

Density functional theory (DFT) and multiconfigurational self-consistent field theory (MCSCF) methods are employed to investigate variation of the electronic properties of various N-heterocyclic carbenes. Alterations to the backbone by increased or decreased conjugation, heteroatom substitution in the NHC ring, and electron-donating or -withdrawing backbone substituents are modeled. The MCSCF calculations show extensive delocalization of both the highest occupied and lowest unoccupied molecular orbitals for NHCs with polymerizable backbone substituents. The free energies of the intermediates and transition structures for benzoin condensation are also shown to be sensitive to substitution of the NHC backbone. Taken together, these results imply great sensitivity of the reactivity of poly(NHC) catalysts to backbone modification at this moiety. Implications with respect to enhancement of poly(NHC)s employed in umpolung catalysis are discussed.

中文翻译：

NHC骨架构型用于有机催化蛋白反应的计算研究。

密度泛函理论（DFT）和多构型自洽场论（MCSCF）方法用于研究各种N杂环卡宾的电子性质的变化。通过增加或减少共轭，NHC环中的杂原子取代以及给电子或吸电子的骨架取代基对骨架进行了建模。MCSCF计算结果显示，具有可聚合主链取代基的NHC的最高占据和最低未占据分子轨道都发生了广泛的离域化。还显示了用于安息香缩合的中间体和过渡结构的自由能对NHC主链的取代敏感。两者合计，这些结果表明聚（NHC）催化剂的反应性对该部分的主链修饰具有很高的敏感性。

更新日期：2020-09-30

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