Strong Preference of the Redox-Neutral Mechanism over the Redox Mechanism for the Ti<sup>IV</sup>
Catalysis Involved in the Carboamination of Alkyne with Alkene and Diazene
作者:Jiandong Guo、Yu Lu、Ruihua Zhao、Zheyuan Liu、Wasihun Menberu、Zhi-Xiang Wang
DOI:10.1002/chem.201800339
日期:2018.5.11
electronic structures indicate that the catalytic cycles proceed through redox-neutral mechanisms. The alternative redox mechanisms (e.g., by N-H or C-H reductive elimination) are substantially less favorable. We concluded that electronically, the TiIV catalysis intrinsically favors the redox-neutral mechanism, because a redox pathway would involve TiII structures either in the triplet ground state or in the
钛催化通常更喜欢氧化还原中性机理。然而,据报道钛可以以类似于还原消除的方式促进键的形成。因此,已经考虑了涉及TiIV / TiII循环的氧化还原催化循环。例如,通过研究由[TiIV] = NPh亚氨基络合物催化的炔烃与烯烃和偶氮苯的碳氨化反应,我们进行了DFT计算,以了解“异常”催化的发生方式,从而使我们能够澄清是否催化作用确实遵循TiIV / TiII的氧化还原机理。该反应首先通过将炔烃加成到[TiIV] = NPh键上而形成氮杂多环己烯,然后插入烯烃。氮杂双环己烯可以进行Cα-Cγ偶联,以提供双环[3.1.0]亚胺或β-H消除,产生[TiIV] -H氢化物,然后对其进行Cα=Cβ或Cγ=Cδ插入,分别得到α,β-或β,γ-不饱和亚胺。几何结构和电子结构均表明催化循环通过氧化还原中性机理进行。替代的氧化还原机制(例如,通过NH或CH的还原消除)基本上不利。我们得出的结论是,在电子学上,T