Mechanism of BPh3-Catalyzed N-Methylation of Amines with CO2 and Phenylsilane: Cooperative Activation of Hydrosilane
Mechanism of BPh3-Catalyzed N-Methylation of Amines with CO2 and Phenylsilane: Cooperative Activation of Hydrosilane
复制标题
BPh3 催化 CO2 和苯基硅烷对胺进行 N-甲基化反应的机理：氢硅烷的协同活化
DOI：
10.1002/chem.202202210
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Tadashi Ema
中科院分区：
文献类型：
--
作者：
Manussada Ratanasak;Takumi Murata;Taishin Adachi;Jun-ya Hasegawa;Tadashi Ema
在CO2和PhSiH3存在下，BPh3催化仲胺的N-甲基化和N，N-二甲基苯胺或1-甲基吲哚的C-亚甲基化(芳环之间的亚甲基桥形成)；这些反应在30-40 °C的无溶剂条件下进行。相比之下，B(C6F5)3活性很低或没有活性。11B 核磁共振谱表明生成了[HBPh3]−。用密度泛函理论方法研究了BPh_3催化N-甲基苯胺(1)与CO2和PhSiH_3的N-甲基化反应的详细机理。BPh3促进两种底物(N-甲基苯胺和二氧化碳)转化为两性离子氨基甲酸酯，得到三组分物种[Ph(Me)(H)N+CO2−⋅⋅⋅BPh3]。氨基甲酸酯和BPh3分别作为亲核剂和Lewis酸激活PhSiH3生成[HBPh3]−，用于生成关键的二氧化碳衍生物种，如甲酸硅酯和双(硅基)缩醛，对1的N-甲基化至关重要。密度泛函理论计算还提出了与水有关的其他生成[HBPh3]−物种的机制。
BPh3catalyzes the N‐methylation of secondary amines and the C‐methylenation (methylene‐bridge formation between aromatic rings) ofN,N‐dimethylanilines or 1‐methylindoles in the presence of CO2and PhSiH3; these reactions proceed at 30–40 °C under solvent‐free conditions. In contrast, B(C6F5)3shows little or no activity.11B NMR spectra suggested the generation of [HBPh3]−. The detailed mechanism of the BPh3‐catalyzed N‐methylation ofN‐methylaniline (1) with CO2and PhSiH3was studied by using DFT calculations. BPh3promotes the conversion of two substrates (N‐methylaniline and CO2) into a zwitterionic carbamate to give three‐component species [Ph(Me)(H)N+CO2−⋅⋅⋅BPh3]. The carbamate and BPh3act as the nucleophile and Lewis acid, respectively, for the activation of PhSiH3to generate [HBPh3]−, which is used to produce key CO2‐derived species, such as silyl formate and bis(silyl)acetal, essential for the N‐methylation of1. DFT calculations also suggested other mechanisms involving water for the generation of [HBPh3]−species.