The synthesis of a potential anti-cancer agent containing the caffeine and 1,2,4-benzotriazine moieties

The potential anti-cancer agent 6 has been synthesised from 4-(4-chlorobutoxy)-2-nitroaniline, 15b by the conversion of the nitroaniline to the benzotriazine N-oxide 16 . Theophylline has been reacted with 16 to give the N-oxide 9 and this has been oxidised to the required N,N'-dioxide, 6 . The compound 6 has been found to be ineffective as a radiosensitizer.     

Influence of phenylenediamine additions on the morphology and on the catalytic effect of polyaniline

The influence of para‐, ortho‐, and meta‐phenylenediamine (p‐, o‐, and m‐PDA) additions on the electrochemical synthesis of polyaniline has been investigated by the use of cyclic voltametry. It has been found that small additions (1 and 5 mmol L^?1) of PDA monomers influence significantly the polymerization rate. Whereas p‐PDA increases the polymerization rate, the addition of o‐ or m‐PDA slows it down. Therefore, a different number of potential cycling is necessary to obtain similar thickness of layers. The layers exhibit very different morphology, which changes from “spaghetti‐like” for polyaniline to “sponge‐like” for p‐PDA, to “pebble‐like” for o‐PDA and to “cauliflower‐like” for m‐PDA additions, respectively. The catalytic effect of the synthesized polymer layers has been tested. It has been found that all the layers exhibit catalytic effect in lowering the redox potential of hydroquinone/quinone tested reaction, but the rate of the electrocatalytic reaction varies depending on the PDA monomer added. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1599–1608, 2004     

A calorimetric study of the acid dissociation of the conjugate acids of poly(N-vinylimidazole) and polyallylamine

Thermodynamic parameters for acid dissociation of the conjugate acids of poly(N-vinylimidazole) and polyallylamine have been determined in the presence of sodium chloride and sodium nitrate. Even though the plots of ΔG ⁰ against the degree of dissociation, α, are highly dependent on the added salt concentration levels, the concentration effect has never been observed for the corresponding ΔH ⁰ versus α plots. The effect on the ΔG ⁰ versus α plots has been attributed to the entropy change of the counterions between a polyelectrolyte phase and a bulk solution phase. The α dependency of ΔH ⁰ is affected remarkably by the kinds of cationic polymers and counter-anions. Each ΔH ⁰ value at completely neutralized conditions is quite close to the corresponding ΔH ⁰ value of the monomer analog. The difference in the ΔH ⁰ values at fully charged conditions has been explained by the heats due to The ion-pair formation of chloride anion to the conjugate acids of poly(N-vinylimidazole) and polyallylamine has been supported by ³⁵Cl NMR measurement. It has also been suggested that chloride anions bind the basic polymer molecules even at fully neutralized conditions. Received: 2 June 1999/Accepted in revised form: 19 July 1999     

Solvent and Substituent Effects on the Spectra of Some Substituted Thioureas

A study on the effect of a number of solvents, covering a broad polarity range i.e. from dioxane (D=2.20) to acetonitrile (D=38.0), has been made on the electronic transitions of N-aryl, N′-2-(5-halo-pyridyl) thioureas (where aryl= -C₂H₅ or O-CH₃-C₆H₅-, and halo= -Cl, -Brand -I). Two intense absorption maxima in the regions 270-285 nm (assigned for thiocarbonyl π-π* transition) are exhibited by all the substituted thioureas studied. The excitation energies and oscillator strengths of these transitions have been calculated. A correlation between ‘E_T’ and ‘Z’ (an empirical measure of solvent polarity) has been attempted. Solvent sensitivities of these compounds have also been calculated. The effect of halo-substituents, in the pyridine ring, on the spectra of these substituted thioureas has also been studied. It has been proposed that there is a delocalization of electrons between the pyridine ring and the thiourea unit of these compounds. This delocalization of electronic charge is affected by the substitution of the halo-groups in the pyridine ring at para position to the thiourea unit which is reflected in the intensities and shifting of the absorption maxima.     

Synthesis and surface-active properties of the fatty acid N-methylethylolamides and their phosphate derivatives

N-Methylethylolamides have been synthesized on the basis of vegetable oils (corn, coconut, canola, olive, cotton-seed, and palm) and modified with orthophosphoric acid. The structure of the synthesized N-methylethylolamides and their phosphate derivatives has been identified by IR and NMR spectroscopies. Surface activity of the N-methylethylolamides and their derivatives at the water–air border has been determined and their colloidal-chemical parameters (maximum surface excess concentration and minimum area per molecule at the aqueous solution–air interface, surface pressure at the critical micellization concentration (CMC), standard thermodynamic parameters of adsorption and micellization) have been calculated. The character of influence of the surfactants structure on their colloidal-chemical parameter has been clarified. The petroleum-collecting and petroleum-dispersing capacities of the synthesized surfactants have been studied on the surface of the water of various mineralization degrees.     

Mirror reflection symmetry and the phase relations for partially and almost filled shells of equivalent atomic electrons

The mirror reflection symmetry which consists in the correlation of the substitution j → ?j ?1 with the reflection of the coordinate system and of m → ?m with the reflection of the space with respect to the xy-plane has been applied to the quasi-spin formalism. The phases of the wave functions of the shell of equivalent atomic electrons treated as partially filled, as they relate to those when the same shell is treated as almost filled, have been established. The mirror reflection symmetry has been generalized for the supplementary quantum numbers used for distinguishing the terms of the same kind. The phases of the coefficients of fractional parentage of almost filled shell enabling us to determine them from those of partially filled shell have been specified. Corresponding phase relations for the matrix elements of operators have also been considered.     

Semiempirical quantum-chemical calculations on the conformations of methyl formate and methyl thiolformate

The cis, trans, and gauche conformations of the methyl esters of formic and thiolformic acids have been investigated by different semiempirical methods. Total geometry optimization (CNDO/2, MINDO/3) and bond angle optimization (PCILO, NDDO) have been performed for the O-alkyl ester. The S-alkyl ester has been studied by the MINDO/3 method at the total geometry optimization level and by CNDO/2 and PCILO methods at the bond angle optimization level. The influence of sulphur d orbitals on the optimized molecular geometry as well as on the magnitude and direction of the dipole moment vector has been investigated in the CNDO/2 framework. The total energy differences of the conformers are compared to the experimental and ab initio results. CNDO/2 and NDDO energy partitioning have been performed to obtain information on the origin of the cis—trans energy difference and of the rotation barrier. The extent of the lone-pair delocalization has been studied in the different conformations using localized molecular orbitals. Calculations have been performed on the staggered and eclipsed positions of the methyl group in the planar conformations of both esters.     

Spectrophotometric Determination of Dissociation Constants of Thiovioluric Acid and the Stability Constant of its Fe(II) Complex

Spectrophotometric studies of Fe(II)-thiovioluric acid system indicates the presence of a 1:2 complex in the pH range 4.0–6.5. The apparent equilibrium constant (K′₁) has been determined by general absorbance-extinction concentration scheme. The first and second dissociation constants of the acid have been studied at an ionic strength of 0.1 M while the third dissociation constant has been determined at I = 1 M. The effects of sudden pH change and buffer compositions on the dissociations have also been investigated. The stability constant of the complex has been calculated from the apparent equilibrium constant at ionic strength of 0.1 M. The stability constant works out to be 15.67 at pH 5.5.     

Dependence of the catalytic activity of organoaluminum compounds and some of their complexes on their composition

The influence of the acidity of organoaluminum compounds and their complexes on the catalytic activity in polymerization of trioxane has been studied. It is found that the catalytic activity of organoaluminum compounds of the type R_nALX_3?n depends on n as well as the nature of R or X. Catalytic activity of the complexes also depends on the type of cocatalyst used. The change of electroconductivity in the course of formation of some initiator complexes has been studied and an attempt has been made to determine the relation between conductivity and polymerization activity.     

Comparative identification of irradiated herbs by the methods of electron paramagnetic resonance and thermoluminescence

Non irradiated and γ-irradiated dry herbs savoury (Savoury), wild thyme (Thymus serpollorium) and marjoram (Origanum) with absorbed dose of 8 kGy have been investigated by the methods of elecrtron paramagnetic resonance (EPR) and thermoluminescence (TL). Non-irradiated herbs exhibit only one weak siglet EPR signal whereas in irradiated samples its intensity increase and in addition two satelite lines are recorded. This triplet EPR spectrum is attributed to cellulose free radical generated by irradiation. It has been found that upon keeping the samples under the normal stock conditions the life-time of the cellulose free radical in the examined samples is ∼60–80 days. Thus the conclusion has been made that the presence of the EPR signal of cellulose free radical is unambiguous indication that the sample under study has been irradiated but its absence can not be considered as the opposite evidence. In the case when EPR signal was absent the method of TL has been used to give the final decision about the previous radiation treatment of the sample.     

Composition of the coats and kernels of the seeds ofNepeta pannonica andLavandula vera

The lipid compositions of the coats and kernels of the seeds ofNepeta pannonica andLavandula vera have been studied. It has been established that the lipids of the seed coats of the two species of plants differ substantially in their composition. The lipids of the kernels ofNepeta have been found to contain free fatty acids with chain lengths of from C₂₀ to C₃₅. Ursolic acid and its acetate have been isolated from extracts of the seed coats ofLavandula, and dimethyladipic acid from the seed oil of this species. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 614–620, September–October, 1980.     

Kinetics and mechanism of the oxidation of glycine by N-bromosuccinimide

A systematic kinetic study on the oxidation of glycine by N-bromosuccinimide (NBS) in presence of mercuric acetate in acetic acid—water media has been made. Near first order dependence inNBS and glycine and near inverse first order dependence in hydrogen ion concentrations have been observed. A negligible ionic strength effect and a positive dielectric effect have been observed. Various rate parameters have been computed and hydrocyanic acid identified as the end product. On the basis of the kinetic data, a mechanism of the reaction has been proposed.With 3 Figures     

Preparation and polymerization of a diisocyanate from the Diels-Alder adduct of levopimaric acid and acrylic acid

Starting from tetrahydroabietic acid the model compounds tetrahydroabietoyl chloride, 2-aminoethyltetrahydroabietate hydrochloride, and 2-isocyanatoethyltetrahydroabietate have been prepared. Carbamate and urea derivatives of the isocyanate have been prepared. A Diels-Alder adduct of levopimaric acid and acrylic acid has been prepared and converted to its diacid chloride. The β-aminoethyl ester hydrochloride has been synthesized and converted to a diisocyanate which has been polymerized with poly(tetramethylene glycol) and also with p-phenylenediamine. Dimerex resin, a technical polymerized rosin, has been similarly converted to a diisocyanate. This isocyanate has not proven to be useful as a polymer-forming intermediate.     

Quantum-chemical investigation of the silicon and carbon coordination bond in their isostructural compounds

Ab initio calculations within the minimal basis set of STO -4LGTO have been carried out on molecules of type H₃MX (M = Si, C; X = H, NH₂, OH, F). The influence of the MH₃-group inversion on the electronic structure of these compounds has been investigated and illustrated by MO electron density maps. The ability of the central atom to form an additional bond has been estimated with the help of calculations on the complexes of these molecules with the hydrogen negative ion. The complexes of type [H₄SiX]^? have been found to be more stable than their unbonded components. The [H₄CX]^? complex formation has not proved to be advantageous.     

The Accuracy of Senum and Yang's Approximations to the Arrhenius Integral

The accuracy of the integral of the Arrhenius equation, as determined from the 1^st to the 4^th degree rational approximation proposed by Senum and Yang, has been calculated. The precision of the 5^th to 8^th rational approximations, here proposed for the first time, has also been analyzed. It has been concluded that the accuracy increases by increasing the order of the rational approximation. It has been shown that these approximations to the Arrhenius equation integral would allow an accuracy better than 10⁻⁸ % in the E/RT range generally observed for solid state reactions. Moreover, it has been demonstrated that errors closed to 10⁻² % can be obtained even for E/RT=1, provided that high enough degrees of rational approximation have been used. Thus, it would be reasonable to assume that high degree rational approximations for the Arrhenius integral could be used for the kinetic analysis of processes, like adsorption or desorption of gases on solid surfaces, which can take place at low temperatures with very low values of E/RT. This revised version was published online in August 2006 with corrections to the Cover Date.     

Specific and random processes in the fragmentation of cyclohexanol

The mass spectra of cyclohexanol and eleven deuterated analogues have been studied. Detailed mechanisms, consistent with peak intensity and defocused metastable abundance data, have been proposed for the loss of water from the molecular ion and for the subsequent loss of a methyl radical. The importance of specific eliminations and the absence of any processes involving complete hydrogen atom scrambling in these fragmentations has been demonstrated. Scrambling has also been shown to be absent in the formation of the base peak m/e 57, the [C₃H₅O]⁺ ion.     

Kinetics and mechanism of the oxidation of diols by pyridinium bromochromate

The kinetics of oxidation of four vicinal diols, four nonvicinal diols, and one of their monoethers by pyridinium bromochromate (PBC) have been studied in dimethyl sulfoxide. The main product of oxidation is the corresponding hydroxyaldehyde. The reaction is first-order with respect to each the diol and PBC. The reaction is acid-catalyzed and the acid dependence has the form: k_obs=a+b[H⁺]. The oxidation of [1,1,2,2-²H₄]ethanediol exhibited a primary kinetic isotope effect (k_H/k _D=6.70 at 298 K). The reaction has been studied in 19 organic solvents including dimethyl sulfoxide and the solvent effect has been analyzed using multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 285–290, 1998.     

Generation and Rearrangement of N,O‐Dialkenylhydroxylamines for the Synthesis of 2‐Aminotetrahydrofurans

A new diastereoselective route to 2‐aminotetrahydrofurans has been developed from N,O‐dialkenylhydroxylamines. These intermediates undergo a spontaneous C?C bond‐forming [3,3]‐sigmatropic rearrangement followed by a C?O bond‐forming cyclization. A copper‐catalyzed N‐alkenylation of an N‐Boc‐hydroxylamine with alkenyl iodides, and a base‐promoted addition of the resulting N‐hydroxyenamines to an electron‐deficient allene, provide modular access to these novel rearrangement precursors. The scope of this de novo synthesis of simple nucleoside analogues has been explored to reveal trends in diastereoselectivity and reactivity. In addition, a base‐promoted ring‐opening and Mannich reaction has been discovered to covert 2‐aminotetrahydrofurans to cyclopentyl β‐aminoacid derivatives or cyclopentenones.     

Photoionisation and fragmentation of the stereoisomers of 4-t-butylcyclohexyl acetate and 4-t-butylcyclohexyl methyl ether

The fragmentation of the stereoisomers of 4-t-butylcyclohexyl acetate and 4-t-butylcyclohexyl methyl ether has been studied by photoionisation mass spectrometry at 1216 Å and 584 Å. Deuterium substitution and high resolution mass spectrometry have been used to gain further insight into the fragmentation pathways.     

Crystal structure and Hirshfeld surface analysis of the anhydrous form of the nucleoside analogue entecavir

The nucleoside analogue entecavir {systematic name: 2‐amino‐9‐[(1S,3R,4S)‐4‐hydroxy‐3‐hydroxymethyl‐2‐methylenecyclopentyl]‐1,9‐dihydro‐6H‐purin‐6‐one}, C₁₂H₁₅N₅O₃, is an antihepatitis B virus drug that has been approved in the US, EU and several countries worldwide. We report here the single‐crystal structure of the anhydrous form and compare it with that of the previously reported monohydrate form [Jiang & Liu (2009). Acta Cryst. E 65 , o2232]. Hirshfeld surface analysis has been employed to understand and visualize the subtle packing differences between the two crystalline forms. The results show that, compared to the previously reported hydrated form, the anhydrous crystal has significantly different intermolecular interactions and packing patterns.