Theoretical Mechanistic Studies of Rh-Catalyzed C(sp3-H Amination:A Comparison with Co Analogue and Metal Effects

• 作者: Yang Yu Gen Luo Jimin Yang Yi Luo
• 来源期刊: 中国化学（英文版）
• 年，卷（期）: 2020,（12）
• 所属期刊栏目: Concise Reports
• 页码范围: 1526-1532
• 页数: 7页
• 语种: 英文
• DOI: 10.1002/cjoc.202000153

摘要

The mechanism of Rh-catalyzed C(sp3)-H amination has been computationally investigated.The reac-tion mechanism mainly involves sequential C(sp3)—H activation,decarboxylation,nitrene migration insertion,and protonation steps.Competitive con-certed metalation deprotonation(CMD)and external base assisted deprotonation(EBAD)pathways are found for the involved C(sp3)-H activation in both Rh and Co analogous systems.This is different from the previously reported C(sp2)-H activation,where the CMD is dominant.The key mechanistic difference between the two systems is found to be in the C(sp3)-H activation step.In comparison with Rh species,the lower activity of Co complex to-ward the C(sp3)—H activation could be ascribed to smaller atomic size of Co and thus larger steric repulsion between ancillary ligand and substrate along with the CMD pathway.In view of the EBAD pathway,however,the lower activity of Co species could be imputed to the triplet nature of Co center,which is against the electron transfer from the electron-rich carbon atom of the deprotonating C(sp3)-H bond to the Co center.As to the subsequent decarbox-ylation and nitrene insertion steps,compared with the Co system,the relatively lower reactivity of Rh species is partially due to the stronger Rh—N bond,and the higherπ(Rh-N)and π*(Rh-N)orbital energies of the corresponding transition state structure.