Simple synthesis of imidazo[1,2-A]pyridine derivatives bearing 2-aminonicotinonitrile or 2-aminochromene moiety

A simple and general method for the synthesis of new imidazopyridines bearing an aminopyridinyl, chromenyl, or quinolinyl moiety in the C2 position was developed. The Knoevenagel reaction between imidazo[1,2-a]pyridine-2-carbaldehyde 1 and malononitrile resulted in the formation of starting material 2. Subsequently, intramolecular cyclization between the cyano group of 2 and acetophenones, naphtols, hydroxyquinolines, or phenols, gave 3, 4, 5, and 6 compounds, respectively. This is a simple, reproducible, and environmentally friendly method of synthesizing substituted imidazopyridines using water as a solvent or under solvent-free conditions.     

RADIAL CONTRACTION OF THE FIRST KIND OF DUMBBELL DOMAINS SUBJECTED TO A STATIC BIAS FIELD

On the basis of the "exercise" experiment and the phenomenon of "self-shrink", the behavior of "less-stable" IDs (first kind of dumbbell domains) in radial contraction under an "exercise" bias field, (H_b)_e, was statistically investigated in detail. It was found that the histograms of their stripe-to-bubble transition field, H_sb after exercise, become narrower and shift towards the side of lower H_sb with the increase of (H_b)_e. It illustrates how the less-stable IDs lose part of their vertical Bloch lines under different (H_b)_e. In addition, it was also found that the curve of the upper boundary of these histograms, (H_sb)_max vs. (H_b)_e, consists of two segments of straight lines. This discontinuity was proved to be due to self shrink, and the crosspoint of these two lines is just the lower limit of the self-shrink region. Furthermore, a series of photographs were taken to show the effect of radial contraction on less-stable IDs intuitively.     

Cryoscopic studies in molten salts. Dissociation state of some alkali isopolymolybdates and some related molybdenum(VI) compounds in molten K2Cr2O7and KNO3

The dissociation state of the solutes M₂MoO₄, M₂Mo₃O₁₀, M₂Mo₄O₁₃, M₂Mo₅O₁₆ (MRb or Cs), Na₂CrO₄·MoO₃, K₂CrO₄·2 MoO₃, Cr₂Mo₃O₁₂ and V₂MoO₈ was studied cryoscopically in molten K₂ Cr₂O₇ and KNO₃ solvents. The freezing point depression, ΔT, of the solvents was obtained by measuring the cooling curves of the binary salt mixtures over unlimited range of solute concentration. The number of foreign ions obtained ν, showed that the solutes were either simply dissociated in the melt into the probable stable species (MoO₄)^2?, (Mo₃O₁₀)^2?, (Mo₄O₁₃)^2? and (Mo₅O₁₆)^2? or, in some cases after reactions and rearrangements, into (CrMo₂O₁₀)^2? heteropolyions. The solute V₂MoO₈, on the other hand, was found to dissolve without any apparent dissociation. An agreement between the experimental and calculated values of activity, a, based on the Temkin and Random Mixing models and that of Van't Hoff's equation support the proposed simple dissocia- tion scheme for K₂Cr₂O₇Cs₂MoO₄ system.     

Synthesis and Chemistry of 4-Aroyl-3-oxo- and 3-Chloropyridazine Derivatives

4H,5H-6-Phenyl (1a) and 6-p-phenoxyphenyl (1b) pyridazin-3(2H)-ones were reacted with aromatic aldehydes to give 4-arylmethylpyridazm-3(2H)-ones (2a-g), Oxidation of (2a-g) with various oxidising agents (selenium dioxide in ethanol or chromium trioxide in acetic acid) gave 4-aroyl-6-arylpyridazin-3(2H)-ones (3a-g). Chlorination of (3a-g) with phosphorous oxychloride afforded 4-aroyl-6-aryl-3-chloropyridazine (4a-g). 1H-3-Aryl-5-phenylpyrazolo[3,4-c]pyridazines (5a-d) were obtained by heating (4a-d) with excess hydrazine hydrate. Hydroxyamination of (3e-g) with iydroxylamine gave aryl-4(6-p-phenoxyphenyl-2,3-dihydro-3-oxo)pyridazinyl oxime (6a-c). Silylation of oximes (6b & 6c) gave (7a & 7b) as acyclic compound instead of the expected seven - membered - ring compound (8).     

Lithium-sulfoxide-lithium exchange for the asymmetric synthesis of atropisomers under thermodynamic control

Ortholithiation and reaction with (-)-menthyl p-toluenesulfinate introduces a sulfoxide substituent ortho to the stereogenic Ar-CO axis of an aromatic amide. The sulfoxide exerts a powerful conformational bias on the axis, such that after rapid equilibration at ambient temperature essentially only one of two diastereoisomeric Ar-CO atropisomers is populated. Sulfoxide-lithium exchange by treatment with t-BuLi regenerates the ortholithiated amide in an enantiomerically pure and conformationally stable form. Rapid electrophilic trapping of the organolithium therefore generates highly enantiomerically enriched atropisomeric tertiary aromatic amides. The overall process, involving temporary substitution of lithium to sulfoxide to lithium, amounts to a dynamic resolution under thermodynamic control.     

New external reagents for the simultaneous microdetermination of carbon,hydrogen and mercury

Non-conventional, extremely cheap and readily available materials, namely zinc plates, pumice granules or polystyrene foam cubes, have been utilized as new external mercury-retentive agents at room temperature for the simultaneous gravimetric microdetermination of mercury, carbon and hydrogen by the rapid straight empty-tube method of Korshun and Klimova. A standard Pregl absorption tube charged with the reagent is connected between the combustion tube and the water-absorption tube. Satisfactory results are obtained for carbon, hydrogen and mercury, and compare reasonably well with those found by using the traditional silver wool or gold sponge under similar conditions. Sulphur or halogen can also be determined simultaneously, as usual.     

Solubilization and Separation of Dicarboxylic Acids by Surfactant Micelles and Polyelectrolytes

Semi‐equilibrium dialysis (SED) and micellar enhanced ultra filtration (MEUF) methods are used to determine the extent of solubilization of water‐insoluble compounds by surfactant and polyelectrolyte. In this study, solubilization of ortho‐, meta‐ and para‐phthalic acids (OPA, MPA and TPA), 1,4‐ and 2,6‐naphthalene dicarboxylic acids (1,4‐NDCA and 2,6‐NDCA) into hexadecylpyridinium chloride (CPC), and the behavior of these acids to bind to the polyelectrolyte ionizable groups were investigated at 25 °C, using SED and MEUF methods. Polydimethyldiallylammonium chloride (PDMDAAC) is used in this study. It was found that the solubilization of organic acids decreases with increasing the solute mole fractions in micelles. Also, the best separation occurs at the lowest concentration of the phthalate ions and high concentrations of either CPC or PDMDAAC. The results support the idea of charge interaction between the anionic dicarboxylate groups and cationic surfactant or polyelectrolyte. The results also show that the presence of a second phenyl ring does not greatly affect the solubilization behavior of the acids.