title: Copper-catalyzed aerobic autoxidation of N-hydroxycarbamates probed by mass spectrometry.
abstract: We present herein a mechanistic investigation by nanoelectrospray ionization mass spectrometry of copper-catalyzed aerobic oxidative processes involved in the N-nitrosocarbonyl aldol reaction of N-hydroxycarbamates. Protonated amine and copper as charge-tags aided the detection of reaction intermediates, which verified the enamine mechanism together with a competing enol process. Our experimental results reveal that the copper-catalyzed aerobic oxidation of N-hydroxycarbamates may proceed through an autoxidation catalytic mechanism in which a CbzNHO(.) radical abstracts a hydrogen from the bound N-hydroxycarbamate to release the nitroso intermediate through a bimolecular hydrogen-atom transfer. In this process, the chiral diamine also works as a ligand for copper to facilitate the aerobic oxidative step. The dual role of the chiral vicinal diamine as both an aminocatalyst and a bidentate ligand was finally uncovered.
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190 (P.R. China).
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Xie
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, The Chinese Academy of Sciences, Beijing, 100190 (P.R. China).
authors.forename: Long
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190 (P.R. China).
authors.forename: Qing
authors.initials: Q
authors.lastname: He
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190 (P.R. China).
authors.forename: Jian
authors.initials: J
authors.lastname: Hou
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, The Chinese Academy of Sciences, Beijing, 100190 (P.R. China).
authors.forename: Changming
authors.initials: C
authors.lastname: Xu
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190 (P.R. China).
authors.forename: Ning
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, The Chinese Academy of Sciences, Beijing, 100190 (P.R. China). luosz@iccas.ac.cn.
authors.forename: Sanzhong
authors.initials: S
authors.lastname: Luo
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190 (P.R. China). znie@iccas.ac.cn.|National Center for Mass Spectrometry in Beijing (BNLMS), Beijing 100190 (P.R. China). znie@iccas.ac.cn.
authors.forename: Zongxiu
authors.initials: Z
authors.lastname: Nie
keywords: autoxidation; copper; mass spectrometry; reaction mechanisms; reactive intermediates