Kinetics and Mechanism of Cyclization of Substituted 2-(Benzoylamino)alkanamides in Strongly Basic Medium

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Title:Kinetics and Mechanism of Cyclization of Substituted 2-(Benzoylamino)alkanamides in Strongly Basic Medium
Creators:
Sedlák, Miloš
Kaválek, Jaromír
Mitaš, Petr
Macháček, Vladimír
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 63, 3, pp. 394-406
Uncontrolled Keywords:2-Phenylimidazol-4(5<i>H</i>)-ones, Reaction kinetics, Mechanism of cyclization, Solvent effect, Dissociation constants

Abstract

The cyclization reaction of substituted 2-(benzoylamino)alkanamides <strong>1a</strong>-<strong>1i</strong> giving the corresponding substituted 2-phenylimidazol-4(5<i>H</i>)-ones <strong>2a</strong>-<strong>2i</strong> has been studied. The equilibrium constants of reactions of compounds <strong>1d</strong>-<strong>1f</strong> and 2-[(4-nitrobenzoyl)amino]-2,3-dimethylbutanenitrile (<strong>3</strong>) with methoxide have been determined in methanol-dimethyl sulfoxide media. For compound <strong>1d</strong> and <i>N</i>-methyl derivatives <strong>1a</strong>-<strong>1c</strong>, the cyclization rate constants have been measured in dependence on methoxide concentration in media of varying contents of dimethyl sulfoxide. The cyclization reaction mechanism involves formation of anion in a rapid pre-equilibrium and subsequent rate-limiting step: either formation of a cyclic intermediate or splitting off of OH<sup>-</sup> ion from this intermediate. The product formed in the given medium is immediately transformed into its conjugate base. A change in reaction medium affects the reactions of all the compounds in the same way. The ratio of concentration of substrate to that of its anion at low methoxide concentrations is affected by the solvent composition (MeOH-DMSO). At higher methoxide and DMSO concentrations the reaction rate distinctly decreases, which can be interpreted by the transformation of reactive anion into non-reactive dianion. The corresponding <i>N</i>-methylbenzoylamino compounds are cyclized faster by a factor of 400 as compared with compounds having no methyl group at the benzamide group.

Title:Kinetics and Mechanism of Cyclization of Substituted 2-(Benzoylamino)alkanamides in Strongly Basic Medium
Creators:
Sedlák, Miloš
Kaválek, Jaromír
Mitaš, Petr
Macháček, Vladimír
Uncontrolled Keywords:2-Phenylimidazol-4(5<i>H</i>)-ones, Reaction kinetics, Mechanism of cyclization, Solvent effect, Dissociation constants
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:63
Number:3
Page Range:pp. 394-406
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc19980394UNSPECIFIED
ID Code:1307
Item Type:Article
Deposited On:06 Feb 2009 17:08
Last Modified:06 Feb 2009 16:08

Citation

Sedlák, Miloš; Kaválek, Jaromír; Mitaš, Petr; Macháček, Vladimír (1998) Kinetics and Mechanism of Cyclization of Substituted 2-(Benzoylamino)alkanamides in Strongly Basic Medium. Collection of Czechoslovak Chemical Communications, 63 (3). pp. 394-406. ISSN 0010-0765

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