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ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 31, Number 1
BKCSDE 31(1)
January 20, 2010 |
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Title |
Synthesis and Aminolysis of N,N-Diethyl Carbamic Ester of HOBt Derivatives
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Author |
Sherine Nabil Khattab, Seham Yassin Hassan, Ezzat Awad Hamed, Fernando Albericio*, Ayman El Faham* |
Keywords |
N,N-diethyl carbamic esters, 1-Hydroxybezotriazole, Aminolysis, Acylation/Nucleophilic substitution, Linear free energy relationship
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Abstract |
The reaction of N,N-diethyl carbamates of 1H-[1,2,3]triazolo[4,5-b]pyridin-1-ol (4-HOAt) 7, 3H-[1,2,3]triazolo[4,5- b]pyridin-3-ol (7-HOAt) 8, 1H-benzo[d][1,2,3]triazol-1-ol (HOBt) 9, 6-chloro-1H-benzo[d][1,2,3]triazol-1-ol (Cl- HOBt) 10, 6-(trifluoromethyl)-1H-benzo[d][1,2,3]triazol-1-ol (CF3-HOBt) 11, and 6-nitro-1H-benzo[d][1,2,3]triazol- 1-ol (NO2-HOBt) 12 with morpholine and piperidine in CH3CN underwent acyl nucleophilic substitution to give the corresponding carboxamide derivatives. The reactants and products were identified by elemental analysis, IR and NMR. We measured the kinetics of these reactions spectrophotometrically in CH3CN at a range of temperatures. The rates of morpholinolysis and piperidinolysis were found to fit the Hammett equation and correlated with σ-Hammett values. The values were 1.44 - 1.21 for morpholinolysis and 1.95 - 1.72 for piperidinolysis depending on the temperature. The Brønsted-type plot was linear with a βlg = ?0.49 ± 0.02 and ?0.67 ± 0.03. The kinetic data and structure-reactivity relationships indicate that the reaction of 9-12 with amines proceeds by a concerted mechanism. The deviation from linearity of the correlation ΔH# vs. ΔS# and plot of logkpip vs. logkmorph and Brønsted-type correlation indicate that the reactions of amines with carbamates 7 and 8 is attributed to the electronic nature of their leaving groups.
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75 - 81 |
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