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- Title
Differentiation between enamines and tautomerizable imines in the oxidation reaction with TEMPO.
- Authors
Jie, Xiaoming; Shang, Yaping; Chen, Zhe-Ning; Zhang, Xiaofeng; Zhuang, Wei; Su, Weiping
- Abstract
Enamine and imine represent two of the most common reaction intermediates in syntheses, and the imine intermediates containing α-hydrogen often exhibit the similar reactivity to enamines due to their rapid tautomerization to enamine tautomers. Herein, we report that the minor structural difference between the enamine and the enamine tautomer derived from imine tautomerization results in the different chemo- and regioselectivity in the reaction of cyclohexanones, amines and TEMPO: the reaction of primary amines furnishes the formal oxygen 1,2-migration product, α-amino-enones, while the reaction of secondary amines under similar conditions generates exclusively arylamines via consecutive dehydrogenation on the cyclohexyl rings. The 18O-labeling experiment for α-amino-enone formation revealed that TEMPO served as oxygen transfer reagent. Experimental and computational studies of reaction mechanisms revealed that the difference in chemo- and regioselectivity could be ascribed to the flexible imine-enamine tautomerization of the imine intermediate containing an α-hydrogen. Tautomerization of imines into enamines is the basis of their similar reactivity; however, minor structural changes may lead to different outcomes. Here, the authors show that the reaction of cyclohexanone and amines in presence of TEMPO affords either α-amino-enones or arylamines depending on the intermediate imine structure.
- Publication
Nature Communications, 2018, Vol 9, Issue 1, p1
- ISSN
2041-1723
- Publication type
Article
- DOI
10.1038/s41467-018-07534-x