Kinetics and mechanism of the cyclization of ω-(p-nitrophenyl)-hydantoic acid amides: steric hindrance to proton transfer causes a 104-fold change in rateElectronic supplementary information (ESI) available: Observed first-order rate coefficients, constants for solvent and buffer catalysis for the cyclization reactions. See http://www.rsc.org/suppdata/ob/b2/b211040g/

Angelova, Violina T.; Kirby, Anthony J.; Koedjikov, Asen H.; Pojarlieff, Ivan G.

doi:10.1039/b211040g

Cited by 11 publications

(1 citation statement)

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“…The pK a values of the carboxy groups of the three (1-arylureido)acetic acids 2a-2c and of (3-arylureido)acetic acid (4) were determined by potentiometric titration at 25°C in a water jacket vessel under nitrogen 9 . The pH-meter used was a Radiometer pHM 84 Research pH-meter with a GK2401C electrode standardized at pH 7.00 and 4.01.…”

Section: Pk a Measurementsmentioning

confidence: 99%

σI Values for Arylureido Groups

Blagoeva

Koedjikov

Pojarlieff

et al. 2004

Collect. Czech. Chem. Commun.

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Section: Pk a Measurementsmentioning

confidence: 99%

σI Values for Arylureido Groups

Blagoeva

Koedjikov

Pojarlieff

et al. 2004

Collect. Czech. Chem. Commun.

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Synthesis of new substituted 5‐methyl‐3,5‐diphenylimidazolidine‐2,4‐diones from substituted 1‐(1‐cyanoethyl‐1‐phenyl)‐3‐phenylureas

Sedlák¹,

Keder²,

Hanusek³

et al. 2005

Journal of Heterocyclic Chem

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The reaction of substituted phenyl isocyanates with 2-amino-2-phenylpropanenitrile and 2-amino-2-(4-nitrophenyl)propanenitrile has been used to prepare substituted 1-(1-cyanoethyl-1-phenyl)-3-phenylureas. In anhydrous phosphoric acid the first products to be formed from 1-(1-cyanoethyl-1-phenyl)-3-phenylureas are phosphates of 4-methyl-4-phenyl-2-phenylimino-5-imino-4,5-dihydro-1,3-oxazoles, which on subsequent hydrolysis give the respective ureidocarboxylic acids. On prolongation of the reaction time, the phosphates of 4-methyl-4-phenyl-2-phenylimino-5-imino-4,5-dihydro-1,3-oxazoles rearrange to give phosphates of 5-methyl-4-imino-3,5-diphenylimidazolidin-2-ones, and these are subsequently hydrolysed to the respective substituted 5-methyl-3,5-diphenylimidazolidin-2,4-diones. The ureidocarboxylic acids were also prepared by alkaline hydrolysis of 5-methyl-3,5-diphenylimidazolidin-2,4-diones. The 5-methyl-3,5-diphenylimidazolidin-2,4-diones and ureidocarboxylic acids were characterised by their 1 H and 13 C NMR spectra. Structure of the 5-methyl-5-(4-nitrophenyl)-3-phenylimidazolidine-2,4-dione was verified by X-ray d i ffraction. The alkaline hydrolysis of individual imidazolidine-2,4-diones was studies spectrophotometrically in sodium hydroxide solutions at 25 °C. The rate-limiting step of the base catalysed hydrolysis consists in decomposition of the tetrahedral intermediate. The reaction is faster if electron-acceptor substituents are present in the 3-phenyl group of imidazolidine-2,4-dione cycle. The pK a values of individual 5-methyl-3,5-diphenylimidazolidine-2,4-diones have been determined kinetically.

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A large gem‐dimethyl effect in the cyclization of ω‐phenylhydantoic acids: computational modeling of the gem‐dimethyl effect on the acid‐ or base‐catalyzed cyclization of hydantoic acids and esters

Ivanov¹,

Pojarlieff²,

Blagoeva³

et al. 2004

J of Physical Organic Chem

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The rates of the cyclization of methyl‐substituted 5‐phenylhydantoic acids were measured in acid solutions. A particularly strong gem‐dimethyl effect (GDME) was observed with the N‐methyl compounds amounting to an acceleration of six powers of ten for the 2,2,3‐trimethyl derivative. The variations in the free energies of activation for the cyclization of hydantoic acids and esters were modeled by the strain energies of the tetrahedral intermediates and of the reactants calculated by the MM3 force field. The neutral tetrahedral intermediate T0 was used for reaction series involving acid catalysis and the negatively charged intermediate T− for base catalysis. Very good agreement with the experimental GDME was obtained for the acid‐catalyzed cyclizations of the complete series of the N‐methyl‐substituted substrates, showing that the accelerations result from a greater strain increase in the reactants. The results with T− are closely parallel, indicating that the loss of GDME observed under base catalysis with 2,2,3‐trimethylhydantoate esters is not due to intramolecular strain in T−. A linear correlation (slope 1.22, r = 0.934) is obtained for a plot of the free energy variations against strain energies for the reaction series of 5‐phenylhydantoic acids when the data for the strongly deviating parent acid is excluded. Excellent LFERs are obtained between the reaction series of esters and acids. The observed large rate enhancements induced by N‐substituents explain the switches to cyclization routes in synthetic reactions. Copyright © 2004 John Wiley & Sons, Ltd.

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Cited by 11 publications

References 15 publications

σI Values for Arylureido Groups

σI Values for Arylureido Groups

Synthesis of new substituted 5‐methyl‐3,5‐diphenylimidazolidine‐2,4‐diones from substituted 1‐(1‐cyanoethyl‐1‐phenyl)‐3‐phenylureas

A large gem‐dimethyl effect in the cyclization of ω‐phenylhydantoic acids: computational modeling of the gem‐dimethyl effect on the acid‐ or base‐catalyzed cyclization of hydantoic acids and esters

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