The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310014, China.
J Am Chem Soc. 2023 Jul 12;145(27):14705-14715. doi: 10.1021/jacs.3c02649. Epub 2023 Jun 26.
Mechanistic investigations of the Ni-catalyzed asymmetric reductive alkenylation of -hydroxyphthalimide (NHP) esters and benzylic chlorides are reported. Investigations of the redox properties of the Ni-bis(oxazoline) catalyst, the reaction kinetics, and mode of electrophile activation show divergent mechanisms for these two related transformations. Notably, the mechanism of C(sp) activation changes from a Ni-mediated process when benzyl chlorides and Mn are used to a reductant-mediated process that is gated by a Lewis acid when NHP esters and tetrakis(dimethylamino)ethylene is used. Kinetic experiments show that changing the identity of the Lewis acid can be used to tune the rate of NHP ester reduction. Spectroscopic studies support a Ni-alkenyl oxidative addition complex as the catalyst resting state. DFT calculations suggest an enantiodetermining radical capture step and elucidate the origin of enantioinduction for this Ni-BOX catalyst.
报道了镍催化的 - 羟基邻苯二甲酰亚胺（NHP）酯和苄基氯化物不对称还原烯丙基化的机理研究。对 Ni-双（恶唑啉）催化剂的氧化还原性质、反应动力学和亲电试剂活化方式的研究表明，这两种相关转化的机理不同。值得注意的是，当使用苄基氯化物和 Mn 时，C(sp) 活化的机理为 Ni 介导的过程，而当使用 NHP 酯和四（二甲氨基）乙烯时，该机理变为受路易斯酸控制的还原剂介导过程。动力学实验表明，改变路易斯酸的种类可以用来调节 NHP 酯的还原速率。光谱研究支持 Ni-烯丙基氧化加成配合物作为催化剂的静止状态。DFT 计算表明，确定对映体的自由基捕获步骤，并阐明了这种 Ni-BOX 催化剂的对映体诱导的起源。
