Nucleophilicity versus Brønsted Basicity Controlled Chemoselectivity: Mechanistic Insight into Silver- or Scandium-Catalyzed Diazo Functionalization,ACS Catalysis

当前位置： X-MOL 学术 › ACS Catal. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

Nucleophilicity versus Brønsted Basicity Controlled Chemoselectivity: Mechanistic Insight into Silver- or Scandium-Catalyzed Diazo Functionalization
ACS Catalysis ( IF 11.3 ) Pub Date : 2019-12-30 , DOI: 10.1021/acscatal.9b02040
Fenru Liu ₁ , Lei Zhu ₁ , Tao Zhang _{1,

2} , Kangbao Zhong ₁ , Qin Xiong ₁ , Boming Shen ₁ , Shihan Liu ₁ , Yu Lan _{1,

2} , Ruopeng Bai ₁

Affiliation

Diazo compounds are popular carbenoid precursors that can react with various transition metals to afford carbene species for further transformations. In this study, density functional theory calculations were used to reveal the mechanisms of silver- and scandium-catalyzed alkylation of diazo compounds to construct compounds with tertiary or quaternary carbon centers. The results show that, with a silver(I) salt as the catalyst, the reaction starts with carbenation of silver(I) to afford a Fisher-type silver carbene. Nucleophilic addition of silver carbene complex yields an enolate intermediate, which is followed by annulation/retro-aldol reaction to give a dialkylation product. Meanwhile, scandium(III) salt behaves as Lewis acid to generate free carbene, which is followed by conjugate addition of free carbene to produce an enolate intermediate. Subsequent 1,4-proton transfer to a synthesized monoalkylation product is more favorable than nucleophilic addition process. Computational studies show that formation of mono- or dialkylation products from enolate intermediates results from competition between the nucleophilicity and Brønsted basicity of the α-carbon in the enolate intermediate, which is mainly controlled by the transition-metal catalyst. The global nucleophilicity and Laplacian of the electron density were evaluated to reveal factors affecting the nucleophilicity and Brønsted basicity.

中文翻译：

亲核性与布朗斯台德碱度控制的化学选择性：对银或Scan催化的重氮官能团的机理研究

重氮化合物是流行的类胡萝卜素前体，可以与各种过渡金属反应，提供卡宾类化合物，用于进一步的转化。在这项研究中，使用密度泛函理论计算来揭示银和compounds催化的重氮化合物烷基化反应的机理，以构建具有叔碳原子或季碳原子中心的化合物。结果表明，以银（I）盐为催化剂，反应从银（I）的碳酸化开始，得到费舍尔型银卡宾。卡宾银配合物的亲核加成产生烯醇化物中间体，随后进行环化/复古-醛醇缩合反应，得到二烷基化产物。同时，scan（III）盐起路易斯酸的作用，生成游离卡宾，然后共轭添加游离卡宾以生成烯醇式中间体。随后的1，4-质子转移到合成的单烷基化产物比亲核加成过程更有利。计算研究表明，由烯醇化物中间体形成单烷基化或二烷基化产物的原因是烯醇化物中间体中α碳的亲核性与布朗斯台德碱度之间的竞争，这主要是由过渡金属催化剂控制的。对电子密度的整体亲核性和拉普拉斯算术进行了评估，以揭示影响亲核性和布朗斯台德碱度的因素。计算研究表明，由烯醇化物中间体形成单烷基化或二烷基化产物的原因是烯醇化物中间体中α碳的亲核性与布朗斯台德碱度之间的竞争，这主要是由过渡金属催化剂控制的。对电子密度的整体亲核性和拉普拉斯算术进行了评估，以揭示影响亲核性和布朗斯台德碱度的因素。计算研究表明，由烯醇化物中间体形成单烷基化或二烷基化产物的原因是烯醇化物中间体中α碳的亲核性与布朗斯台德碱度之间的竞争，这主要是由过渡金属催化剂控制的。对电子密度的整体亲核性和拉普拉斯算术进行了评估，以揭示影响亲核性和布朗斯台德碱度的因素。

更新日期：2019-12-31

点击分享查看原文

点击收藏

阅读更多本刊最新论文本刊介绍/投稿指南11