Liu Yanhong, Feng Aili, Zhu Rongxiu, Zhang Dongju
Key Lab of Colloid and Interface Chemistry, Ministry of Education, Institute of Theoretical Chemistry, School of Chemistry and Chemical Engineering, Shandong University Jinan 250100 P. R. China
School of Radiology, Shandong First Medical University & Shandong Academy of Medical Sciences Taian 271016 P. R. China.
Chem Sci. 2023 Mar 29;14(17):4580-4588. doi: 10.1039/d3sc00002h. eCollection 2023 May 3.
This work presents a DFT-based computational study to understand the mechanism, and regio- and enantioselectivities in the synergetic photoredox/copper(i)-catalyzed carbocyanation of 1,3-dienes with alkyl redox-active esters. The calculated results show an unprecedented copper catalytic mechanism, where the reaction follows a catalytic cycle involving Cu-only catalysis, instead of a Cu(i)/Cu(ii)/Cu(iii)/Cu(i) cycle as proposed in the experimental study. Moreover, it is found that the critical step involves the reaction of the cyanocopper(i) species with an allyl cation rather than the cyanocopper(ii) species reacting with an allyl radical as proposed in the experiment, and that the photocatalyst is regenerated single electron transfer from the allyl radical to the oxidized photocatalyst. In the newly proposed photoredox/copper(i) catalysis, the reaction consists of four stages: (i) generation of the copper(i) active catalyst, (ii) formation of an allyl radical with oxidative quenching of the photoexcited species, (iii) generation of an allylcopper complex accompanied by the regeneration of the photocatalyst, and (iv) formation of the allyl cyanide product with the regeneration of the copper(i) active catalyst. The cyanation of the allyl cation is calculated to be the regio- and enantioselectivity-determining step. The excellent regio- and stereoselectivities are attributed to the favorable CH-π interaction between the substrate and catalyst as well as the small distortion of the substrate.
这项工作提出了一项基于密度泛函理论（DFT）的计算研究，以了解1,3 - 二烯与烷基氧化还原活性酯协同光氧化还原/铜（I）催化的碳氰化反应的机理、区域选择性和对映选择性。计算结果显示了一种前所未有的铜催化机理，该反应遵循一个仅涉及铜催化的催化循环，而不是实验研究中提出的Cu（I）/Cu（II）/Cu（III）/Cu（I）循环。此外，研究发现关键步骤涉及氰化亚铜物种与烯丙基阳离子的反应，而不是如实验中所提出的氰化铜（II）物种与烯丙基自由基的反应，并且光催化剂通过烯丙基自由基向氧化态光催化剂的单电子转移而再生。在新提出的光氧化还原/铜（I）催化中，反应包括四个阶段：（i）生成铜（I）活性催化剂；（ii）通过光激发物种的氧化猝灭形成烯丙基自由基；（iii）生成烯丙基铜配合物并伴随光催化剂的再生；（iv）形成烯丙基氰产物并再生铜（I）活性催化剂。烯丙基阳离子的氰化反应被计算为区域选择性和对映选择性的决定步骤。优异的区域选择性和立体选择性归因于底物与催化剂之间有利的CH - π相互作用以及底物的小变形。
