- Preparation of N'-[2-(5,6-dimethylbenzothiazolyl)]-N-furfuryloxamide with plant growth regulatory activity
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The reaction of the N-furfuryloxamic acid sodium salt (12) with 1,1'-oxalyldiimidazole (ODI) yielded the imidazolide (13) as an intermediate, and this directly reacted with 2-aminothiazole derivatives (14) or 2-aminobenzothiazole derivatives (15) under es
- Kitagawa,Tsutsui
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- Kinetics and mechanism of the nucleophilic substitution reaction of imidazole with bis(2,4,6-trichlorophenyl) oxalate and bis(2,4-dinitrophenyl) oxalate
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The kinetics of the imidazole-catalyzed decomposition of bis(2,4,6-trichlorophenyl) oxalate (TCPO) and bis(2,4-dinitrophenyl) oxalate (DNPO) was investigated by the stopped-flow technique. Pseudo-first-order rate constants were determined as a function imidazole concentration in the temperature range 6-45 °C by fitting the temporal changes in absorbance throughout the 245 to 345 nm wavelength range for TCPO and at 420 nm for DNPO. The reaction proceeds by release of two molecules of substituted phenol and formation of 1,1′-oxalyldiimidazole (ODI) for both esters. The identity of ODI was confirmed in the reaction of imidazole with TCPO by its UV absorbance spectrum and 13C-NMR spectrum. The reaction of imidazole with TCPO has a second-order dependence on imidazole concentration and an observed negative activation energy of -6.2 ± 0.3 kJ/mol, whereas the DNPO reaction has a first-order dependence on imidazole concentration and an observed positive activation energy of 12.0 ± 0.6 kJ/mol. The differences in the temperature dependence and order of the reaction with respect to imidazole for the two oxalate esters are explained by a shift in the rate-determining step from addition to the acyl group for DNPO to imidazole-catalyzed release of the phenol leaving group for TCPO. These kinetics results are useful in interpreting the initial reaction steps in peroxyoxalate chemiluminescence.
- Hadd, Andrew G.,Birks, John W.
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- Stopped-Flow Kinetics Investigation of the Imidazole-Catalyzed Peroxyoxalate Chemiluminescence Reaction
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The stopped-flow technique was used to study the temperature-dependent kinetics of the imidazole- catalyzed peroxyoxalate reaction in order to further elucidate the reaction mechanism. Pseudo- first-order rate constants were obtained from the chemiluminescence intensity vs time profiles for the sequential reaction model X → Y → Z over a wide range of initial concentrations of each of the following reagents: bis(2,4,6-trichlorophenyl) oxalate (TCPO), imidazole (ImH), and hydrogen peroxide. These measurements were complemented by UV absorbance measurements of the kinetics of the step X → Y. For both reaction conditions pseudo-flrst-order in TCPO ([ImH], [H2O2] [TCPO]) and pseudo-first-order in H2O2 ([ImH][TCPO][H2O2]), the first step of the reaction is nucleophilic substitution by two imidazole molecules to form 1,1′-oxalyldiimidazole (ODI). Under conditions of excess TCPO in the concentration range 0.075-0.25 mM, the Y → Z reaction probed the subsequent reaction of ODI with H2O2 to form the imidazoyl peracid intermediate, ImC(O)C(O)OOH, For excess H2O2 concentrations in the range 2.5-15 mM, the reaction of H2O2 with ODI is fast, and the Y → Z step of the sequential reaction model describes subsequent reactions of the imidazoyl peracid. An important unexpected finding necessary for interpreting the kinetics of this reaction is that under conditions of a large excess of H2O2 the faster rise of the chemiluminescence signal corresponds to the second step of the reaction (Y → Z), and the slower fall of the signal corresponds to the first step (X → Y). Lutidine and collidine, amine bases of similar aqueous pKa as imidazole, displayed very little catalytic effect on the PO-CL reaction in comparison to imidazole, corroborating the conclusion that nucleophilic catalysis with formation of ODI as an intermediate constitutes the principal reaction pathway under conditions of both excess oxalate ester and excess H2O2. Imidazole quenches the quantum yield of the reaction, a result that can be well explained by catalysis of the decomposition of the key energy-transfer intermediate.
- Hadd, Andrew G.,Robinson, Alex L.,Rowlen, Kathy L.,Birks, John W.
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- Study of the characteristics of three high-energy intermediates generated in peroxyoxalate chemiluminescence (PO-CL) reactions
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Perylene emission intensity generated from peroxyoxalate chemiluminescence (PO-CL) reactions was studied as a function of time and order of reagent addition. Based on 1H-NMR analyses, kinetics of UV absorbance and emission intensity vs. time profiles, we
- Lee, Ji Hoon,Rock, James C.,Park, Seung Bum,Schlautman, Mark A.,Carraway, Elizabeth R.
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- Preparation and plant growth-regulatory activity of N'-substituted N- furfuryloxamides
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N'-Substituted N-furfuryloxamides (4) were prepared via condensation of potassium methyl oxalate (8) with furfurylamine (5f) using 1,1'- oxalyldiimidazole (6), followed by hydrolysis of the resulting amide-ester (10), and finally condensation with aliphatic or aromatic amines (5). The prepared compounds (4) were examined for activity as plant growth regulators using two kinds of plant seeds, namely, those of rape, Brassica campestris L. (Dicotyledoneae) and leek, Allium tuberosum ROTTLER (Monocotyledoneae). N'- Benzyl- and N'-phenyl-N-furfuryloxamides (4b and 4c) and N,N'- difurfuryloxamide (4f) inhibited root growth in seedlings of both species.
- Kitagawa, Tokujiro,Tsutsui, Chinatsu,Hayashi, Kumi,Yamano, Aiko
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p. 514 - 517
(2007/10/03)
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- Kinetic studies on the peroxyoxalate chemiluminescent reaction: imidazole as a nucleophilic catalyst
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The peroxyoxalate system undergoes one of the most efficient chemiluminescence reactions and is the only one supposed to involve an intermolecular chemically induced electron exchange luminescence (CIEEL) mechanism, with proven high efficiency.In this work we report kinetic results on the reaction of bis(2,4,6-trichlorophenyl) oxalate (TCPO) with hydrogen peroxide, catalysed by imidazole (IMI), in the presence of chemiluminescence activators.The kinetics were followed by measurement of the intensity of light emission and the 2,4,6-trichlorophenol (TCP) release, observed as an absorption change.From the dependence of the observed rate constants on the concentrations of TCPO, imidazole, hydrogen peroxide and activator, we attribute rate constants to three elementary steps in the proposed simplified mechanistic scheme.The initial step consists of attack of the nucleophilic imidazole on TCPO.A bimolecular (k1(2) = 1.4 +/- 0.1 dm3 mol-1 s-1) and a trimolecular 1(3) = (9.78 +/- 0.08) 102 dm6 mol-2 s-1> rate constant can be attributed to this step.The imidazolide subsequently suffers imidazole-catalysed peroxide attack, leading to a peracid derivative; trimolecular rate constants k2(3) = (1.86 +/- 0.06) 104 dm6 mol-2 s-1 and k2(3)' = (8.7 +/- 0.2) 103 dm6mol-2s-1 can be obtained for this step from the peroxide and the imidazole dependence, respectively.The cyclization of the peracid affords the reactive intermediate, which we believe to be 1,2-dioxetanedione; a rough estimate of k3 ca. 0.2 s-1 (at = 1.0 mmol dm3) is obtained for this step.Finally, the interaction of the activator with the reactive intermediate, probably involving the CIEEL sequence and leading ultimately to light emission, is extremely fast and cannot be observed kinetically.
- Stevani, Cassius V.,Lima, Decio F.,Toscano, Vicente G.,Baader, Wilhelm J.
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p. 989 - 996
(2007/10/03)
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- Neutral hydrolysis and imidazole-catalysed decomposition of bis(4-nitrophenyl) oxalate. 1,1'-Oxalyldiimidazole as an intermediate
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Neutral hydrolysis and imidazole-catalysed decomposition of a peroxyoxalate chemiluminescence reagent type compound, bis(4-nitrophenyl) oxalate (4-NPO), have been studied in acetonitrile and in acetonitrile-water mixtures.For comparison, the rate coeffici
- Neuvonen, Helmi
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p. 945 - 950
(2007/10/02)
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- An experimental estimation of aromaticity relative to that of benzene. The synthesis and NMR properties of a series of highly annelated dimethyldihydropyrenes: Bridged benzannulenes
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The synthesis of 13 trans-dimethyldihydropyrenes (bridged [14]annulenes) fused to one or more benzene, naphthalene, phenanthrene, phenalene, or quinoxaline rings and 6 cis-dihydropyrene derivatives from benzenoid precursors using either a thiacyclophane route or an electrocyclic addition of a furan to an annulyne followed by deoxygenation is reported. Their 1H NMR spectra are studied in detail to obtain correlations between 3JH,H coupling constants and the internal methyl proton chemical shifts and also between the latter and the more distant external annulene ring proton shifts. These linear correlations are then used to obtain a relationship between the relative aromaticity of benzene and the fused ring in question, such that the aromaticity of the fused ring can be estimated relative to that of a benzene ring simply from a measurement of chemical shift in the fused annulene.
- Mitchell, Reginald H.,Iyer, Vivekanantan S.,Khalifa, Nasr,Mahadevan, Ramanathan,Venugopalan, Santhanagopalan,Weerawarna, Sirimevan Ananda,Zhou, Pengzu
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p. 1514 - 1532
(2007/10/02)
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- New General Synthesis of Organophosphorus P-F Compounds via Reaction of Azolides of Phosphorus Acids with Acyl Fluorides: Novel Route to 2-Deoxynucleosidyl Phosphorofluoridates and Phosphorodifluoridates
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Tetra- and tri-coordinate P-N-imidazole derivatives and their structural analogous react smoothly with acyl fluorides to give the corresponding P-F compounds an almost quantitative yield.This method has been successfully applied to produce 2-deoxynucleosidyl phosphorofluoridates and phosphorodifluoridates.
- Dabkowski, Wojciech,Michalski, Jan,Wasiak, Jacek,Cramer, Friedrich
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p. 817 - 820
(2007/10/02)
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- 1,1'-OXALYLDIIMIDAZOLE, A NEW REAGENT FOR ACTIVATION OF CARBOXYLIC ACID
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Carboxylic acids and their salts are converted into the 1-acylimidazoles by the title reagent.This reaction is applied for esterification of fatty acids.
- Murata, Shizuaki
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p. 1819 - 1820
(2007/10/02)
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