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Kinetic study on michael-type reactions of β-nitrostyrenes with cyclic secondary amines in acetonitrile: Transition-state structures and reaction mechanism deduced from negative enthalpy of activation and analyses of LFERs

Title
Kinetic study on michael-type reactions of β-nitrostyrenes with cyclic secondary amines in acetonitrile: Transition-state structures and reaction mechanism deduced from negative enthalpy of activation and analyses of LFERs
Authors
Um I.-H.Kang J.-S.Park J.-Y.
Ewha Authors
엄익환박종윤
SCOPUS Author ID
엄익환scopusscopus; 박종윤scopus
Issue Date
2013
Journal Title
Journal of Organic Chemistry
ISSN
0022-3263JCR Link
Citation
vol. 78, no. 11, pp. 5604 - 5610
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
A kinetic study is reported for the Michael-type reactions of X-substituted β-nitrostyrenes (1a-j) with a series of cyclic secondary amines in MeCN. The plots of pseudo-first-order rate constant kobsd vs [amine] curve upward, indicating that the reactions proceed through catalyzed and uncatalyzed routes. The dissection of kobsd into Kk2 and Kk 3 (i.e., the rate constants for the uncatalyzed and catalyzed routes, respectively) revealed that Kk3 is much larger than Kk2, implying that the reactions proceed mainly through the catalyzed route when [amine] > 0.01 M. Strikingly, the reactivity of β-nitrostyrene (1g) toward piperidine decreases as the reaction temperature increases. Consequently, a negative enthalpy of activation is obtained, indicating that the reaction proceeds through a relatively stable intermediate. The Brønsted-type plots for the reactions of 1g are linear with βnuc = 0.51 and 0.61, and the Hammett plots for the reactions of 1a-j are also linear with ρX = 0.84 and 2.10 for the uncatalyzed and catalyzed routes, respectively. The reactions are concluded to proceed through six-membered cyclic transition states for both the catalyzed and uncatalyzed routes. The effects of the substituent X on reactivity and factors influencing βnuc and ρX obtained in this study are discussed. © 2013 American Chemical Society.
DOI
10.1021/jo4007442
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자연과학대학 > 화학·나노과학전공 > Journal papers
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