Intramolecular general base catalysis of aminolysis by ethylenediamine

Jencks, William P.; Salvesen, Karin

doi:10.1039/c29700000548

Cited by 3 publications

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“…Among the diamines, the reactivity of 1,3‐diaminopropane is higher than 1,2‐diaminopropane. Enhanced reactivity was observed in the reactions of diamines with phenyl acetate 7 and acetylimidazole 42 when compared to simple primary amines, which has been attributed to the existence of intramolecular general base catalysis. In the present case, the reaction of 1,3‐diaminopropane proceeds in a similar manner with a transition state as shown as Structure II, similar to the one already proposed (7).…”

Section: Resultsmentioning

confidence: 99%

Structure‐reactivity correlation in the aminolysis of 4‐fluorophenyl acetate in aqueous medium

Rajarathnam

Jeyakumar

Nadar

2002

Int J of Chemical Kinetics

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The reaction of the title substrate with a series of amines of varying pK a , viz. ammonia, ethanolamine, glycine, 1,2-diaminopropane, 1,3-diaminopropane, n-butylamine, piperidine, hydrazine, imidazole, and hydroxylamine is subjected to a kinetic study in aqueous medium, 25 • C, ionic strength 0.1 M (KCl). Pseudo-first-order rate coefficients (k obs ) are found throughout under amine excess at various pH values for each amine. For amines, excluding hydrazine, ammonia, and hydroxylamine the reaction follows clean second-order kinetics and the plots of (k obs − k H ) against free amine concentration are linear at constant pH. The macroscopic nucleophilic substitution rate coefficients (k N ) are obtained as the slopes of these plots and found to be pH independent. For hydrazine, ammonia, and hydroxylamine, a rate dependence on more than first power of the amine is observed, accordingly, the rate constants for the assisted paths have been disseminated for these amines besides k N . The Brönsted-type plot (logk N against amine pK a ) is linear with a slope value of β = 1.02. The magnitude of the slope value is consistent with a stepwise mechanism through a zwitterionic tetrahedral addition intermediate whose breakdown to products is rate-determining (k 2 step). A remarkable reactivity difference is observed among the diamines, the reason for which is discussed in detail.

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Section: Resultsmentioning

confidence: 99%

Structure‐reactivity correlation in the aminolysis of 4‐fluorophenyl acetate in aqueous medium

Rajarathnam

Jeyakumar

Nadar

2002

Int J of Chemical Kinetics

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N‐acylation of 1,3‐dimethyl‐6‐aminouracils. A reversal in the regiospecificity of an electrophilic substitution induced by an intramolecular proton‐transfer

Bernier

Hénichart

Warin

1984

Journal of Heterocyclic Chem

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Electrophilic reactions of 1,3‐dimethyl‐6‐aminouracil lead to 5‐substituted derivatives. The introduction of a dialkylaminoalkylamino chain in the 6‐position of 1,3‐dimethyluracil modifies the regiospecificity of the acylation reaction to give N‐6 acylated compounds. This reversal in acylation is induced by an intramolecular proton‐transfer which introduces a change in the electron density of the enamine system. The cyclic transition state and the spatial conformation of the final products substantiate the proposed mechanism, on the basis of X‐ray and 1H nmr data.

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Neighbouring Group Participation

Capon¹

1975

Proton-Transfer Reactions

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Intramolecular general base catalysis of aminolysis by ethylenediamine

Abstract: The aminolysis of acetylimidazole by ethylenediamine shows a rate enhancement of more than lo3 compared to glycine, which is attributed to intramolecular general base catalysis ; the reaction with acetylimidazolium ion shows no significant rate enhancement.

Cited by 3 publications

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Structure‐reactivity correlation in the aminolysis of 4‐fluorophenyl acetate in aqueous medium

Structure‐reactivity correlation in the aminolysis of 4‐fluorophenyl acetate in aqueous medium

N‐acylation of 1,3‐dimethyl‐6‐aminouracils. A reversal in the regiospecificity of an electrophilic substitution induced by an intramolecular proton‐transfer

Neighbouring Group Participation

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