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首页> 外文期刊>Organometallics >DFT Study on the Mechanism and Regioselectivity of Gold(I)-Catalyzed Synthesis of Highly Substituted Furans Based on 1-(1-Alkynyl)cyclopropyl Ketones with Nucleophiles
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DFT Study on the Mechanism and Regioselectivity of Gold(I)-Catalyzed Synthesis of Highly Substituted Furans Based on 1-(1-Alkynyl)cyclopropyl Ketones with Nucleophiles

机译：DFT研究金（I）催化1-（1-炔基）环丙基酮与亲核试剂合成高取代度呋喃的机理和区域选择性

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The mechanism and regioselectivity of gold(I)-catalyzed synthesis of highly substituted furans based on 1-(1-alkynyl)cyclopropyl ketones with nucleophiles have been investigated using density functional theory calculations done at the BH and HLYP/6-31G(d, p) (SDD for Au) level of theory. Solvent effects on these reactions have been explored by calculations that included a polarizable continuum model (PCM) for the solvent (dichloromethane). Our calculations suggest that the first step of the cycle is the cyclization of the carbonyl oxygen onto the triple bond to form a new and stable five-membered resonance structure of an oxonium ion and a carbocation intermediate. Furthermore, the seven-membered carbocation intermediate proposed by Zhang and Schmalz was found and characterized as a transition structure on the potential energy surface. The attack of the carbonyl oxygen to the gold-coordinated alkynes results in the formation of a resonance structure intermediate, which upon subsequent trapping with alcohols followed by migration of a hydrogen atom results in the formation of the final products and regeneration of the catalyst. The key reaction step is the attack of the oxygen atom of the CH3OH on the C-C sigma bond of the cyclopropane moiety to yield new organogold intermediates through formation of a C-O bond and cleavage of a C-C bond. The cleavage of the C-C bond is strongly favored kinetically in the case of the C-1-C-2 bond and required only 19.8 kcal/mol of energy, while the activation energy for cleavage of the C-1-C-3 bond was found to be 31.8 kcal/mol and indicates that the ring-opening cycloisomerization for cyclopropyl ketones has high regioselectivity. Our computational results are consistent with the experimental observations of Zhang and Schmalz for the gold(I)-catalyzed synthesis of highly substituted furans based on 1-(1-alkynyl)cyclopropyl ketones with nucleophiles.
机译：使用BH和HLYP / 6-31G（d， p）（Au的SDD）理论水平。通过计算探索了溶剂对这些反应的影响，其中包括溶剂（二氯甲烷）的可极化连续体模型（PCM）。我们的计算表明，循环的第一步是将羰基氧环化到三键上，形成氧离子和碳正离子中间体的新的稳定的五元共振结构。此外，发现了Zhang和Schmalz提出的七元碳正离子中间体，并将其表征为势能表面上的过渡结构。羰基氧对金配位的炔烃的侵蚀导致形成共振结构中间体，该中间体随后被醇捕集，随后氢原子迁移导致最终产物的形成和催化剂的再生。关键的反应步骤是CH3OH的氧原子攻击环丙烷部分的C-C sigma键，通过形成C-O键和C-C键断裂，生成新的有机金中间体。在C-1-C-2键的情况下，强烈希望在动力学上支持CC键的裂解，并且仅需要19.8 kcal / mol的能量，而用于裂解C-1-C-3键的活化能为分子量为31.8kcal / mol，表明环丙基酮的开环环异构化具有很高的区域选择性。我们的计算结果与Zhang和Schmalz在金（I）催化的基于1-（1-炔基）环丙基酮与亲核试剂的高取代呋喃的合成反应中的实验观察结果一致。

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