Dasgupta Ayan, Stefkova Katarina, Babaahmadi Rasool, Yates Brian F, Buurma Niklaas J, Ariafard Alireza, Richards Emma, Melen Rebecca L
Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom.
School of Natural Sciences-Chemistry, University of Tasmania Private Bag 75, Hobart, Tasmania 7001, Australia.
J Am Chem Soc. 2021 Mar 24;143(11):4451-4464. doi: 10.1021/jacs.1c01622. Epub 2021 Mar 15.
The donor-acceptor ability of frustrated Lewis pairs (FLPs) has led to widespread applications in organic synthesis. Single electron transfer from a donor Lewis base to an acceptor Lewis acid can generate a frustrated radical pair (FRP) depending on the substrate and energy required (thermal or photochemical) to promote an FLP into an FRP system. Herein, we report the C-C cross-coupling reaction of aryl esters with terminal alkynes using the B(CF)/MesP FLP. Significantly, when the 1-ethynyl-4-vinylbenzene substrate was employed, the exclusive formation of C-C cross-coupled products was observed. However, when 1-ethynyl-2-vinylbenzene was employed, solvent-dependent site-selective C-C or C-C cross-coupling resulted. The nature of these reaction pathways and their selectivity has been investigated by extensive electron paramagnetic resonance (EPR) studies, kinetic studies, and density functional theory (DFT) calculations both to elucidate the mechanism of these coupling reactions and to explain the solvent-dependent site selectivity.
受阻路易斯酸碱对（FLPs）的给体-受体能力已在有机合成中得到广泛应用。取决于底物以及将FLP促进到受阻自由基对（FRP）体系所需的能量（热或光化学），从给体路易斯碱到受体路易斯酸的单电子转移可生成受阻自由基对（FRP）。在此，我们报道了使用B(CF)/MesP FLP实现芳基酯与末端炔烃的C-C交叉偶联反应。值得注意的是，当使用1-乙炔基-4-乙烯基苯底物时，观察到仅生成C-C交叉偶联产物。然而，当使用1-乙炔基-2-乙烯基苯时，则产生了溶剂依赖性的位点选择性C-C或C-C交叉偶联。通过广泛的电子顺磁共振（EPR）研究、动力学研究和密度泛函理论（DFT）计算，对这些反应途径的性质及其选择性进行了研究，以阐明这些偶联反应的机理并解释溶剂依赖性的位点选择性。
