Premium
Copper‐Catalyzed Aerobic Autoxidation of N ‐Hydroxycarbamates Probed by Mass Spectrometry
Author(s) -
Xie Xiaobo,
Zhang Long,
He Qing,
Hou Jian,
Xu Changming,
Zhang Ning,
Luo Sanzhong,
Nie Zongxiu
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201501750
Subject(s) - chemistry , autoxidation , catalysis , photochemistry , copper , enamine , mass spectrometry , diamine , ligand (biochemistry) , denticity , combinatorial chemistry , medicinal chemistry , organic chemistry , biochemistry , receptor , chromatography , crystal structure
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.