Formylation or methylation: what determines the chemoselectivity of the reaction of amine, CO2, and hydrosilane catalyzed by 1,3,2-diazaphospholene?

	Formylation or methylation: what determines the chemoselectivity of the reaction of amine, CO2, and hydrosilane catalyzed by 1,3,2-diazaphospholene?
	Lu, Yu 1; Gao, Zhong-Hua 2; Chen, Xiang-Yu 2; Guo, Jiandong 1; Liu, Zheyuan 1; Dang, Yanfeng 1; Ye, Song 2; Wang, Zhi-Xiang 1
刊名	CHEMICAL SCIENCE
	2017-11-01
卷号	8 期号:11 页码:7637-7650
英文摘要	DFT computations have been performed to gain insight into the mechanisms of formylation/methylation of amines (e. g. methylaniline (1a)/2,2,4,4-tetramethylpiperidine (2a)) with CO2 and hydrosilane ([Si]H-2, [Si] = Ph2Si), catalyzed by 1,3,2-diazaphospholene ([NHP] H). Different from the generally proposed sequential mechanism for the methylation of amine with CO2, i. e. methylation proceeds via formylation, followed by further reduction of formamide to give an N-methylated amine, the study characterized a competition mechanism between formylation and methylation. The chemoselectivity originates from the competition between the amine and [NHP] H hydride to attack the formyloxy carbon of [Si](OCHO) 2 (the insertion product of CO2 into [Si]H-2). When the attack of an amine (e.g. 1a) wins, the transformation affords formamide (1b) but would otherwise (e.g. 2a) result in an N-methylated amine (2c). The reduction of formamide by [Si] H-2 or [NHP] H is highly unfavorable kinetically, thus we call attention to the sequential mechanism for understanding the methylation of amine with CO2. In addition, the study has the following key mechanistic findings. The activation of CO2 by [NHP] H establishes an equilibrium: [NHP]H + CO2 reversible arrow [NHP]OCHO % [NHP]+ + HCO2-. The ions play catalytic roles to promote formylation via HCO2- or methylation via [NHP]+. In 1a formylation, HCO2- initiates the reaction, giving 1b and silanol byproducts. However, after the initiation, the silanol byproducts acting as hydrogen transfer shuttles are more effective than HCO2- to promote formylation. In 2a methylation, [NHP](+) promotes the generation of the key species, formaldehyde and a carbocation species (IM17(+)). Our experimental study corroborates our computed mechanisms.
语种	英语
内容类型	期刊论文
源URL	[http://ir.iccas.ac.cn/handle/121111/41287]
专题	化学研究所_分子识别与功能实验室
作者单位	1.Univ Chinese Acad Sci, Sch Chem & Chem Engn, Beijing 100049, Peoples R China 2.Chinese Acad Sci, Inst Chem, Beijing 100190, Peoples R China
推荐引用方式 GB/T 7714	Lu, Yu,Gao, Zhong-Hua,Chen, Xiang-Yu,et al. Formylation or methylation: what determines the chemoselectivity of the reaction of amine, CO2, and hydrosilane catalyzed by 1,3,2-diazaphospholene?[J]. CHEMICAL SCIENCE,2017,8(11):7637-7650.
APA	Lu, Yu.,Gao, Zhong-Hua.,Chen, Xiang-Yu.,Guo, Jiandong.,Liu, Zheyuan.,...&Wang, Zhi-Xiang.(2017).Formylation or methylation: what determines the chemoselectivity of the reaction of amine, CO2, and hydrosilane catalyzed by 1,3,2-diazaphospholene?.CHEMICAL SCIENCE,8(11),7637-7650.
MLA	Lu, Yu,et al."Formylation or methylation: what determines the chemoselectivity of the reaction of amine, CO2, and hydrosilane catalyzed by 1,3,2-diazaphospholene?".CHEMICAL SCIENCE 8.11(2017):7637-7650.