Abstract：
The development of the merger of a Ni(II) catalyst with an appropriate photocatalyst under visible-light irradiation provides a new strategy for realizing direct functionalization of C(sp3 )-H bonds. Mechanistically, whether the reduction of Ni catalyst to form a Ni(0) species is necessary in the dual catalysis still remains under debate. Herein, DFT calculations were carried out to gain a mechanistic insight into the enantioselective acylation of α-amino C(sp3 )-H bonds to furnish α-amino ketones via photoredox and Ni dual catalysis. A feasible mechanistic pathway for the Ni catalysis via the Ni(I)-Ni(III)-Ni(II)-Ni(III)-Ni(I) cycle is suggested with the sequential elementary steps of oxidative addition, single electron reduction, radical addition, and reductive elimination in leading to the final product, whereas a nickel catalytic cycle, Ni(I)-Ni(0)-Ni(II)-Ni(III)-Ni(I), might not be feasible for the photoredox and Ni dual-catalyzed acylation of α-amino C(sp3 )-H bonds. The origin of the stereoselectivity for this reaction is also discussed, which could be attributed to the minimization of the steric hindrance between the alkyl moiety of radical part and phenyl group of the chiral ligand.
摘要：
Ni(II)催化剂与合适的光催化剂在可见光照射下的结合为实现C(sp3)-H键的直接官能化提供了一种新的策略。机械上,在双重催化中是否需要还原Ni催化剂以形成Ni（0）物种仍然存在争议。在这里，进行了DFT计算，以从机理上了解α-氨基C（sp3）-H键的对映选择性酰化，以通过光氧化还原和Ni双重催化提供α-氨基酮。通过连续的氧化添加基本步骤，提出了通过Ni（I）-Ni（III）-Ni（II）-Ni（III）-Ni（I）循环进行Ni催化的可行机理，单电子还原，自由基加成,和还原性消除导致最终产品。同时,镍催化循环，Ni(I)-Ni(O)-Ni(II)-Ni(III)-Ni(I),对于α-氨基C（sp3）-H键的光氧化还原和Ni双催化酰化可能不可行。还讨论了该反应的立体选择性的起源，这可能归因于自由基部分的烷基部分与手性配体的苯基之间的空间位阻最小化。
