Reactions of <Emphasis Type="Italic">N</Emphasis>-alkyl- and <Emphasis Type="Italic">N</Emphasis>-aryltrihalogenoacetamides with phosphorus pentachloride

In the study of reactions of N-alkyl- and N-aryltrihalogenoacetamides with PCl₅, it was demonstrated for the first time that 3-alkyl(aryl)-2,2,2,4 tetrachloro-4-trihalomethyl-1,3,2-λ⁵-oxazaphosphetanes are intermediates in the synthesis of trihaloacetimidoyl chlorides. According to quantum-chemical calculations, acyclic N-tetrachlorophosphoranes, which are the primary products in the reactions of trihaloacetamides with PCl⁵, undergo rapid cyclization into the corresponding phosphorates and subsequent 1,3-chlorotropic migration gives rise to oxazaphosphetanes with the five-coordinate P atom.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 739-744, March, 2005.     

Kinetics and Mechanism of Oxidation of Some Substituted Benzhydrols by <Emphasis Type="Italic">N</Emphasis>-Bromosuccinimide

N-bromosuccinimide (NBS) oxidation of some substituted benzhydrols (4-Cl-, 4-Me-, 4-OMe-, 4-NO²⁻, 4,4′-dimethyl-, 4,4′-dichloro-, 4,4′-dimethoxy-, and 4-methyl-2-nitro-) yields corresponding benzophenones in the presence of Hg(OAc)₂. The reaction is first-order in [NBS], [substrate], and [H⁺]. A study on the primary kinetic hydrogen isotope effect and solvent isotope effect suggest that C-H and O-H stretching frequencies are affected in the transition state. Activation parameters for the rate-determining step have been evaluated. The results are in accord with the linear free energy relationship (LFER). The linear plot of log(k _obs/k ₀) vs. σ⁺ (ρ = −0.69)and Bunnett plots support the existence of proton-transfer in the rate-determining step. Rate behavior in different solvent compositions suggests dipolar-dipolar interaction in the absence of acid and ion-dipolar interaction in the presence of acid. Two different mechanisms have been suggested: cyclic transition state with unprotonated N-bromosuccinimide (NBS) in the absence of acid and noncyclic transition state with protonated NBS in the presence of acid.__________From Kinetika i Kataliz, Vol. 46, No. 3, 2005, pp. 360–365.Original English Text Copyright © 2005 by Hiran, Malkani, Rathore.This article was submitted by the authors in English.     

Discoloration of cellulose solutions in <Emphasis Type="Italic">N</Emphasis>-methylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide (Lyocell). Part 1: Studies on model compounds and pulps

N-Methylmorpholine-N-oxide monohydrate (NMMO) is used as solvent for cellulose in the Lyocell process as a modern industrial fiber-making technology. Undesired chemical side reactions and byproduct formation in the system cellulose/NMMO/water are known to cause detrimental effects, such as chromophore formation and discoloration of the resulting fibers. A detailed kinetic study on the influence of carbonyl structures on chromophore formation in NMMO melts was carried out employing UV spectroscopy. Different sugar model compounds, such as reducing or non-reducing sugars, and sugars with additional oxidized functions, were applied. The chromophore formation rate differed widely for various reducing sugar model compounds, with pentoses generally reacting faster than hexoses, and carbohydrates with protected reducing end being largely inert. The effect of carbonyl groups on chromophore generation has been studied further using oligomers and oxidized pulps with different contents of carbonyl groups. As in the case of model compounds, also for the pulps a linear correlation between carbonyl content and chromophore formation rate was established. A distinct effect of hemicelluloses was observed.     

Substitution effects in <Emphasis Type="Italic">N</Emphasis>-pyrazole and <Emphasis Type="Italic">N</Emphasis>-imidazole derivatives along the periodic table

A theoretical study of the monosubstitution effects of all the atoms of the second and third row of the periodic table on the pyrazole and imidazole rings has been carried out by means of B3LYP/6-31+G(d,p) DFT calculations. The geometric and electronic properties, calculated using the atoms in molecules methodology, electrostatic potential, and frontier orbitals have been analyzed. Some of the results have been rationalized based on the electronegativity of the substituents. In addition, the different parameters obtained have been compared with aromaticity indexes (HOMA and NICS). A comparison with the results obtained for the corresponding N-pyrrole derivatives has been carried out.     

Reductive Acylamination of Pyridine <Emphasis Type="Italic">N</Emphasis>-Oxide with Aminopyridines and Their <Emphasis Type="Italic">N</Emphasis>-<Emphasis Type="Italic">p</Emphasis>-Tolylsulfonyl Derivatives

Pyridine N-oxide reacts with 2- and 3-aminopyridines and their N-p-tolylsulfonyl derivatives in alkaline medium in the presence of p-toluenesulfonyl chloride to give N-p-tolylsulfonyl-2,2′- and 2,3′-dipyridylamines, respectively, as a result of reductive acylamination. In the reactions with 4-aminopyridine and 4-p-tolylsulfonyl-aminopyridine, their N-p-tolylsulfonyl- and N,N-bis(p-tolylsulfonyl) derivatives are formed, while reductive acylamination does not occur.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005, pp. 128–130.Original Russian Text Copyright © 2005 by Solekhova, Kurbatov.     

Synthesis of new <Emphasis Type="Italic">N</Emphasis>-aminoglycosides based on halo-substituted <Emphasis Type="Italic">p</Emphasis>-phenylenediamines and <Emphasis Type="Italic">p</Emphasis>-aminophenols

Condensation of the monosaccharides D-glucose and D-galactose with synthesized halo-substituted p-phenylenediamines and 4-amino-2,6-dibromophenol was studied. It was found that glycosylation occurred only at the 4-amino group that was sterically unhindered by the halogen atom. The position of the aglycon in the glycoside was established by PMR spectroscopy.     

<Emphasis Type="Italic">N</Emphasis>-arylsulfinyl-1,4-benzoquinonimines

Stable N-arylsulfinyl-1,4-benzoquinonimines were synthesized by acylation of the corresponding 1,4-benzoquinone monooximes with arenesulfenyl chlorides. The process involves transformation of sulfur(II) into sulfur(IV).Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 9, 2004, pp. 1340–1343.Original Russian Text Copyright © 2004 by Avdeenko, Pirozhenko, Stanovskii, Konovalova, Yusina.This study was performed under financial support by the ES INTAS program (grant no. 00 157–1999) and by the Ministry of Education and Science of Ukraine.     

Ethylenebis(<Emphasis Type="Italic">N</Emphasis>-methylimidazolium) Chlorochromate (<Emphasis Type="Italic">EBMICC</Emphasis>): An Efficient and Selective Reagent for the Oxidation of Thiols to Disulfides

Summary. Ethylenebis(N-methylimidazolium) chlorochromate was prepared by addition of N-methylimidazole to 1,2-dibromoethane to form the corresponding dibromide salt and subsequent treatment of this salt with CrO₃ in 6N HCl solution. It is a stable yellow-orange solid, which oxidized thiols to the corresponding disulfides at room temperature. Selective oxidation of thiols in the presence of sulfides and hydroxyl groups was also achieved with this reagent.     

Structure and photochromism of 2-(<Emphasis Type="Italic">N</Emphasis>-acyl-<Emphasis Type="Italic">N</Emphasis>-arylaminomethylene)benzo[<Emphasis Type="Italic">b</Emphasis>]thiophen-3(2<Emphasis Type="Italic">H</Emphasis>)-ones

It was shown by electron absorption spectroscopy and X-ray diffraction analysis that steric strains in photochromic 2-(N-acyl-N-arylaminomethylene) benzo[b]thiophen-3(2H)-one molecules ortho-substituted in the N-phenyl ring increase the quantum yield of the N→O photoinduced rearrangement in accord with an increase in the steric constant of the ortho-substituent.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2151–2155, October, 2004.     

Kinetic characterisation of arylamine <Emphasis Type="Italic">N</Emphasis>-acetyltransferase from <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis>

Background  

Arylamine N-acetyltransferases (NATs) are important drug- and carcinogen-metabolising enzymes that catalyse the transfer of an acetyl group from a donor, such as acetyl coenzyme A, to an aromatic or heterocyclic amine, hydrazine, hydrazide or N-hydroxylamine acceptor substrate. NATs are found in eukaryotes and prokaryotes, and they may also have an endogenous function in addition to drug metabolism. For example, NAT from Mycobacterium tuberculosis has been proposed to have a role in cell wall lipid biosynthesis, and is therefore of interest as a potential drug target. To date there have been no studies investigating the kinetic mechanism of a bacterial NAT enzyme.     

UV/Vis Spectroscopic Properties of <Emphasis Type="Italic">N</Emphasis>-(2′-Hydroxy-4′-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethyl-aminobenzylidene)-4-nitroaniline in Various Solvents and Solid Environments

Summary.  N-(2′-Hydroxy-4′-N,N-dimethylaminobenzylidene)-4-nitroaniline [HDBN] has been used as a model for investigating intra- and intermolecular D–A (donor–acceptor) interactions in various environments by means of UV/Vis spectroscopy. UV/Vis spectra of HDBN have been measured in various solvents, ethanolic solutions of different pH, adsorbed on silica, and in the solid state. A bathochromic shift of ν_max is observed with increasing the dipolarity/polarizability and HBD (hydrogen bond donor) capacity of the solvent, which is described by means of a multiple LSE (linear solvation energy) relationship in terms of the empirical Kamlet-Taft solvent polarity parameters. The adsorption of HDBN on Aerosil^? 300-silica particles in non-HBA (hydrogen bond acceptor) solvents is explained in the same sense. Mobile protons and sol–gel entrapping cause a hypsochromic shift due to protonation of the lone electron pair of the 4′-N,N-dimethylamino group. Hydroxide ions attack the 2′-hydroxy group which causes a bathochromic shift. A strong intramolecular hydrogen bond between the 2′-hydroxyl hydrogen and the imine nitrogen atom is present in the solid-state structure causing an unprecedented bathochromic shift. Corresponding author. E-mail: stefan.spange@chemie.tu-chemnitz.de Received July 8, 2002; accepted (revised) September 30, 2002     

Structural analysis of <Emphasis Type="Italic">w</Emphasis>/<Emphasis Type="Italic">o</Emphasis>/<Emphasis Type="Italic">w</Emphasis> multiple emulsions by means of DSC

Summary The properties of the inner and the external aqueous phases, were studied in w/o/w multiple emulsions with light microscopic image analysis and differential scanning calorimetry (DSC). The importance of multiple emulsions lies in the presence of these aqueous phases, making them available for sustained, controlled drug delivery systems. Differentiation of these two aqueous phases, studying the effect of manufacturing technology on droplet structure, quantitative determination of phase volumes and any changes occurring during storage are essential when planning w/o/w emulsions. The present study uses microscopic observations combined with DSC measurements in order to identify the formed structure, at developmental stage in case of different components, preparation methods, and stirring rates. These tools are beneficial during manufacturing as in process controls, or to ensure product quality.     

Competitive complexation in the copper(II) chloride-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylformamide-Aerosil system

Competitive complexation in the copper(II) chloride-N,N-dimethylformamide (DMF)-Aerosil system was studied by IR spectroscopy. It was found that adsorption from organic solutions containing copper(II) chloride and DMF resulted in the formation of the following three types of DMF complexes: self-associates of DMF, DMF complexes with surface hydroxyl groups, and DMF complexes with Cu(II) ions. The removal of DMF resulted in the sequential degradation of, initially, self-associates; next, complexes with silanol groups; and, finally, complexes with copper ions.Translated from Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 917–920.Original Russian Text Copyright © 2004 by Golubeva, Zubareva.     

<Emphasis Type="Italic">O</Emphasis>- and <Emphasis Type="Italic">N</Emphasis>-Alkylation of <Emphasis Type="Italic">N</Emphasis>-halosuccinimides in ionic reactions with 1-phenyltricyclo [4.1.0.0<Superscript>2,7</Superscript>]heptane

N-Bromo and N-chlorosuccinimides add to 1-phenyltricyclo[4.1.0.0^2,7]heptane in CH₂Cl₂ with cleavage of the C(1)-C(7) bond to give isomeric 1 : 1 Markownikoff-type endo, anti-adducts of the norpinane structure in a ∼3 :7 ratio corresponding to N and O alkylation of succinimide.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No.2, pp. 457–460, February, 2005     

Synthesis of 4<Emphasis Type="Italic">E</Emphasis>,7<Emphasis Type="Italic">Z</Emphasis>-tridecadien-1-ylacetate,a component of the <Emphasis Type="Italic">Phthorimaea opercucella</Emphasis> sex pheromone

A new synthetic approach to 4E,7Z-tridecadien-1-ylacetate, a component of the Phthorimaea opercucella (Zeller) potato moth sex pheromone, was developed using a highly stereoselective Claisen rearrangement and Wittig reaction. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 235–236, May–June, 2007.