Molecular structure of <Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">o</Emphasis>-and <Emphasis Type="Italic">p</Emphasis>-hydroxybenzyl)cytisine

The molecular structures of N-(o-and p-hydroxybenzyl)cytisine were investigated by NMR spectroscopy, x-ray structure analysis, and molecular modeling. It was found that NMR resonances of the OH and aromatic protons in N-(o-hydroxybenzyl)cytisine were doubled because of the presence of two conformers in solution. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 165–168, March–April, 2008.     

Synthesis of new hydrazones based on <Emphasis Type="Italic">o</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-hydroxybenzohydrazides

o- and p-Hydroxybenzohydrazides reacted with various unsaturated aromatic aldehydes to give the corresponding N′-(hydroxybenzoyl)hydrazones. Inhibitory activity of the obtained hydrazones against cathepsin E was evaluated.     

Hypercrosslinked Polycondensation Networks: Copolymers of <Emphasis Type="Italic">p</Emphasis>-Xylylene Dichloride

It was shown that self-condensation of p-xylylene dichloride (p-XDC) and its co-polycondensation with naphthalene, anthracene, benzyl alcohol, and benzhydrol in presence of the Lewis acids in solution leads to the formation of hypercrosslinked polymers characterized by developed porosity and ability to swell in nonpolar and polar media. Swelling and porosity of the polycondensed network do not depend on dilution of the initial monomer mixture or catalyst amount involved in the reaction as opposed to the properties of hypercrosslinked polymer. The similarities and differences of the regularities of formation of structures obtained at intense crosslinking of linear polymers (polystyrene) and polycondensed networks were examined. It was also estimated that copolymers with naphthalene and anthracene demonstrate perfect ability to extract furfural (which is able to participate in strong π–π interactions) even from methanol solution.     

Synthesis of derivatives of <Emphasis Type="Italic">o</Emphasis>-aminoacetophenone and <Emphasis Type="Italic">o</Emphasis>-aminobenzyl alcohol

Oxidation of 2′-hydroxy-8-methylspiro[4H-benz-1,3-oxazin-2-one-6,1′-cyclopentane] or N-mesyl-2-(cyclopent-1-en-1-yl)-6-methylaniline provided the corresponding ketones. The rearrangement of these ketones oximes under treatment with thionyl chloride gave rise to nitriles of 5-(2-amino-3-methylphenyl)-5-oxopentanoic or 5-(2-methanesulfamido-3-methylphenyl)-5-hydroxypentanoic acids. By heating 5-(2-acetylamido-3-methylphenyl)-5-oxopentanoic acid with LiH in THF3-(2,8-dimethylquinol-4-on-3-yl)propanoic acid was obtained.     

Synthesis of <Emphasis Type="Italic">o</Emphasis>(<Emphasis Type="Italic">m</Emphasis>)-carborane-containing azomethines

A method of preparative synthesis of o(m)-carborane-containing azomethines via the condensation of o(m)-carboranyl-C-methylene-4-formylbenzoates with aliphatic, cycloaliphatic, and aromatic amines was developed.     

Nickel catalysis for hydrogenation of <Emphasis Type="Italic">p</Emphasis>-dinitrobenzene to <Emphasis Type="Italic">p</Emphasis>-phenylenediamine

The activity of supported nickel catalysts (5–20% Ni) in the hydrogenation of p-dinitrobenzene to p-phenylenediamine was investigated. The catalysts were obtained by ureainduced precipitation. Activated carbon, alumina, titania, and silica gel were evaluated as supports. The most active catalysts, 5%Ni/TiO₂ and 20%Ni/SiO₂, provided 50–54% yields of p-phenylenediamine at complete dinitrobenzene conversion.     

Conducting materials prepared by the oxidation of <Emphasis Type="Italic">p</Emphasis>-phenylenediamine with <Emphasis Type="Italic">p</Emphasis>-benzoquinone

p-Phenylenediamine was oxidized with p-benzoquinone in the aqueous solutions of methanesulfonic acid (MSA). The conductivity of the products increased with increasing concentration of MSA from 1.5?×?10^?12 S cm^?1 in 0.1 M MSA up to 3.4?×?10^?4 S cm^?1 in 5 M MSA. The low-molecular-weight products are basically composed of one p-benzoquinone and two p-phenylenediamine molecules. Their molecular structure is discussed on the basis of mass, Fourier-transform infrared, Raman, NMR and electron paramagnetic resonance (EPR) spectroscopies. The formation of 2,5-di(p-phenylenediamine)-p-benzoquinone protonated with methanesulfonic acid best complies with the information provided by spectroscopic techniques. Its conversion to hydroquinone tautomer explains the formation of unpaired spins observed by EPR and their potential contribution to the conduction.     

4<Emphasis Type="Italic">p</Emphasis><Superscript>2</Superscript> resonances in photoionization from 4<Emphasis Type="Italic">s</Emphasis>4<Emphasis Type="Italic">p</Emphasis> levels in neutral zinc

In neutral zinc the 4p ² configuration lies above the 3d ¹⁰4s ionization limit and its levels become perturbers in the continuum. Lines have been identified in the Zn I spectrum for the multiplet, whereas no lines have been found for transitions to 4p ^{2 1} D or ¹ S. In this paper, cross sections for photoionization from 4s4p levels are reported that reveal the positions and widths of the 4p ² resonances. Calculations were performed using the multiconfiguration Hartree-Fock (MCHF) and B-spline R-matrix (BSR) method. Results from Breit–Pauli calculations that ignore the background continua are also presented. Included in the latter are energies for the levels and transition data (transition energies, line strengths, f-values, and A-rates) for all E1 transitions between these levels. Transition energies and the agreement in the length and velocity values, particularly for allowed transitions, indicate the accuracy of the computational model. Line widths are compared with other estimates. Contribution to the Serafin Fraga Memorial Issue.     

Photolysis of <Emphasis Type="Italic">p</Emphasis>-benzoquinone and <Emphasis Type="Italic">p</Emphasis>-chloranil in aqueous sodium sulfite solution

Photosubstitution of the sulfo group for hydrogen (chlorine in chloranil) is observed under irradiation of sulfonated derivatives of hydroquinone formed upon dissolving of p-benzoquinone and p-chloranil in aqueous solutions of sodium sulfite. The quantum yield of the photochemical reaction is 0.18 ± 0.02 for p-benzoquinone. The rate constant of the thermal reaction of substitution is 5.5 × 10⁻⁴ l mol⁻¹ s⁻¹. The substitution reaction is sensitized by eosin upon irradiation with visible light. During the course of irradiation of sulfohydroquinones, the formation of a product with an absorption maximum at 235 nm was found. The product decays with a rate constant of 0.005 s⁻¹.     

Oxidation of <Emphasis Type="Italic">p</Emphasis>-Xylene

The review discusses the main procedures for producing terephthalic acid from p-xylene (primarily the Amoco process with the participation of Co, Mn, and Br salts), the oxidation mechanisms, alternative processes, and perspectives.     

Conformational Polymorphism in Racemic 2,4-Di-<Emphasis Type="Italic">o</Emphasis>-Benzoyl-6-<Emphasis Type="Italic">o</Emphasis>-Tosyl <Emphasis Type="Italic">myo</Emphasis>-Inositol 1,3,5-Orthoacetate

The title compound, C₂₉H₂₆O₁₀S, yields two conformational polymorphs concomitantly from dichloromethane-methanol mixture; the major polymorph grows as plates (Form I, monoclinic, P2₁/n) and the minor polymorph grows as needles (Form II, triclinic, P-1). The two forms differ mainly in orientation of the tosyl group. In Form I, sulfonyl oxygen of the tosyl group makes intermolecular C −H…O interactions, whereas the same group in Form II is involved in an intramolecular short dipolar S=O…C=O (sulfonyl-carbonyl) contact. The molecular organization and the influence of various weak non-covalent interactions that stabilize these conformers in the crystal lattices are discussed.     

Compounds of the menthane series. Synthesis of unsaturated primary alcohols with the <Emphasis Type="Italic">o</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-menthane skeletons

Precursors to terpene alcohols of the o- and p-menthane series (o-cimen-7-ol and o- and p-cimen-9-ols) were synthesized, and their reduction with lithium in ethylenediamine was studied. The reduction of o- and p-cimen-9-ols in the presence of isopropyl alcohol selectively afforded the corresponding 1,4-dihydro derivatives. Under analogous conditions, o-cimen-7-ol was converted into a mixture of unsaturated hydrocarbons. The reduction with lithium in ethylenediamine in the absence of isopropyl alcohol in all cases gave mixtures of menthene alcohols.     

Curing reaction of <Emphasis Type="Italic">o</Emphasis>-cresol-formaldehyde epoxy/LC epoxy(<Emphasis Type="Italic">p</Emphasis>-PEPB)/anhydride(MeTHPA)

The curing kinetics of a bi-component system about o-cresol-formaldehyde epoxy resin (o-CFER) modified by liquid crystalline p-phenylene di[4-(2,3-epoxypropyl) benzoate] (p-PEPB), with 3-methyl-tetrahydrophthalic anhydride (MeTHPA) as a curing agent, were studied by non-isothermal differential scanning calorimetry (DSC) method. The relationship between apparent activation energy E _a and the conversion α was obtained by the isoconversional method of Ozawa. The reaction molecular mechanism was proposed. The results show that the values of E _a in the initial stage are higher than other time, and E _a tend to decrease slightly with the reaction processing. There is a phase separation in the cure process with LC phase formation. These curing reactions can be described by the Šesták–Berggren (S–B) equation, the kinetic equation of cure reaction as follows: \frac\textda\textdt = Aexp( - \fracE_\texta RT )a^m ( 1 - a )ⁿ {\frac{{{\text{d}}\alpha }}{{{\text{d}}t}}} = A\exp \left( { - {\frac{{E_{\text{a}} }}{RT}}} \right)\alpha^{m} \left( {1 - a} \right)^{n} .     

New tin(<Emphasis Type="SmallCaps">iv</Emphasis>) <Emphasis Type="Italic">o</Emphasis>-iminosemiquinone complexes

New tin(iv) mono- and bis-o-iminosemiquinone complexes were obtained by the exchange reaction of radical anion lithium salt of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-imino-benzoquinone with tin(iv) organochlorides. The compounds synthesized were characterized by EPR spectroscopy and X-ray diffraction analysis. Substituents on the tin atom were found to affect stability of paramagnetic metal derivatives formed.     

Photolysis of <Emphasis Type="Italic">o</Emphasis>-iodo- and <Emphasis Type="Italic">o</Emphasis>-bromophenols in aqueous solution of sodium sulfite and organic solvents

The photochemical reaction of o-iodo- and o-bromophenol in an aqueous sodium sulfite solution proceeds via both nonchain and chain mechanisms. The formation of the intermediate product, aromatic radical anion, was observed. The quantum yield of the photochemical reaction of o-iodophenol increases, when the electron donor diphenylamine is irradiated. In the photolysis of o-halophenols in organic solvents, free iodine is evolved in addition to aromatic products. The products of the photolysis of o-iodophenol in ethanol and carbon tetrachloride were identified by gas chromatography-mass spectrometry. These are phenol in the case of ethanol and a mixture of o-chlorophenol and hydroxychloro-substituted biphenyls in the case of carbon tetrachloride. The quantum yields were determined for all photochemical reactions studied.     

<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Stability of <Emphasis Type="Italic">s</Emphasis>-, <Emphasis Type="Italic">p</Emphasis>-, and <Emphasis Type="Italic">d</Emphasis>-element diphosphates in water

The mean atomic Gibbs energies of formation of (Δ _f ? _at ⁰ ) of s-, p-, and d-element diphosphates have been calculated using ion increments of the Gibbs energy (Δ _f G ⁰). The diphosphate hydrolysis kinetics is considered, and a correlation between the Δ _f ? _at ⁰ values and the hydrolysis rate constants is presented.     

<Emphasis Type="Italic">N</Emphasis>-aryl-<Emphasis Type="Italic">o</Emphasis>-iminobenzoquinones as novel regulators of radical polymerization

The effect of a number of quinoid compounds on methyl methacrylate polymerization initiated by azo-bis(isobutyronitrile) has been studied. It has been revealed that N-aryl-o-iminobenzoquinones, in contrast to o-benzoquinones, can provide radical polymerization of methyl methacrylate in controllable mode. The efficiency of the compounds as chain growth regulators has been found to depend on their composition and reaction conditions. It has been established that 4,6-di-tert-butyl-N-(2,6-diethylphenyl)-o-iminobenzoquinone and 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone under radical initiation conditions provide the synthesis of poly(methyl methacrylate) with wide-range molecular weight, retaining polydispersity indices about ~1.4–1.8 up to deep conversions.     

Reaction of <Emphasis Type="Italic">o</Emphasis>-aminophenol and <Emphasis Type="Italic">o</Emphasis>-aminobenzyl alcohol with palladium(II) bis(isocyanide) complexes

Reactions of palladium(II) bis-isocyanide complexes cis-[PdCl₂(CNR)₂] (R = 2,6-Me₂C₆H₃, 2-Me-6-ClC₆H₃) with an equimolar amount of chelating N,O-binucleophiles, 2-aminophenol and (2-aminophenyl)-methanol, in acetonitrile at room temperature in 24 h selectively afforded the corresponding open-chain monocarbene complexes. The complexation involved one isocyanide ligand and amino group of the aromatic amine. Neither bis(carbene) complexes (in the reactions with 4 equiv of the nucleophile under harsh conditions) nor C,O-chelate structures were detected. The isolated complexes were characterized by elemental analyses, IR, NMR, and mass spectra, and X-ray diffraction data.     

Propanal hydroamination with <Emphasis Type="Italic">p</Emphasis>-aminobenzoic acid

The propanal hydroamination was studied. It was found that the reaction in ethanol proceeded faster than in 2-propanol. By ¹H and ¹³C NMR method the existence was proved of a tautomeric equilibrium in ethanol solution between 4-(propylideneamino)benzoic acid and its enamine form, 4-(prop-1-en-1-ylamino)benzoic acid.