Tungsten hexachloride nanoparticles loaded on montmorillonite K-10: a novel solid acid catalyst in the synthesis of symmetrical and unsymmetrical azines

In the present investigation, we have developed a novel technique to prepare azines using nano-WCl₆ loaded on Montmorillonite K10 clay as a highly active catalyst. A variety of aldehydes and ketones were efficiently converted to the corresponding azines using catalytic amounts of nanosized WCl₆/Mont. K10 under mild conditions. The nanostructures of WCl₆ loaded on Mont. K10 as solid acid catalyst have been prepared by solid dispersion method. The advantages of this catalyst are rapid completion of the reactions, simplicity of performance, lack of pollution and mild and green reaction conditions. The morphologies, structure, and chemical components of parent and modified clay were successfully characterized using SEM, FT-IR, CV, XRD and EDX measurements.     

Pyrroles and pyrazolines from the ring closure of azines

Alkyl substituted pyrroles and pyrazolines are obtained in good yields by catalytic ring closure of azines, using nickel or cobalt (II) halides as catalysts. The specificity of the reaction is determined by the structure of the azines and a notable exception is discussed.     

Selective Protection of Carbonyl Compounds as Azines and Their Facile Regeneration

Carbonyl compounds with freshly prepared hydrazinium formate successfully yielded the corresponding azines in excellent yields. In turn, azines were deprotected to the corresponding carbonyls using triethylammonium chlorochromate chemoselectively.     

Analysis of azines and diazines by HPLC on bonded alkyl stationary phases. Pyridine and quinoline in environmental samples

Summary Several heterocyclic compounds have been investigated by HPLC on RP-8 and RP-18 with methanol-water mixtures as mobile phase. The chromatographic systems developed showed good selectivity for determination of azines and diazines. Pyridine and quinoline have been determined in environmental samples and in food. Samples for analysis were preconcentrated by solid phase extraction on-column with octadecyl silane packing.     

2,2,2‐Trifluoroacetophenone as an Organocatalyst for the Oxidation of Tertiary Amines and Azines to N‐Oxides

A cheap, mild and environmentally friendly oxidation of tertiary amines and azines to the corresponding N‐oxides is reported by using polyfluoroalkyl ketones as efficient organocatalysts. 2,2,2‐Trifluoroacetophenone was identified as the optimum catalyst for the oxidation of aliphatic tertiary amines and azines. This oxidation is chemoselective and proceeds in high‐to‐quantitative yields utilizing 10 mol % of the catalyst and H₂O₂ as the oxidant.     

The structure of azines derived from C‐formyl‐1H‐imidazoles in solution and in the solid state: tautomerism,configurational and conformational studies

The structures of three azines derived from 2‐formylimidazole, 4(5)‐formylimidazole, and 4(5)‐formyl‐5(4)‐methylimidazole have been determined in solution and in the solid state. Density Functional Theory (DFT) Polarizable Continuum Model (PCM) calculations (geometries, energies, and chemical shifts), NMR [solution and cross polarization magic‐angle spinning (CPMAS)], and X‐ray crystallography [azine of 4(5)‐formylimidazole] have been used. The configuration around the central C = N bonds has been determined and some insights about prototropic tautomerism and conformation have been gained. Copyright © 2013 John Wiley & Sons, Ltd.     

Cyclazines and topological resonance energies

The resonance energies and magnetic properties of cyclazines such as pyrido[2,1,6-cd]quinolizine ( 1 ) and pyrido[2,1,5-de]quinolizine ( 6 ) were calculated by means of Aihara's TRE. Consequently, cycl[3.2.2]azines and cycl[3.3.3]azines were predicted to be aromatic, while cycl[4.3.2]azines were predicted to be anti-aromatic.     

Experimental measurements and theoretical calculations of the chemical shifts and coupling constants of three azines (benzalazine, acetophenoneazine and cinnamaldazine)

Three azines, two of them doubly labeled with (15)N, have been studied by multinuclear magnetic resonance in solution and in the solid state. The spectral parameters obtained by iterative analyses have been compared with DFT/B3LYP calculated values (absolute shieldings and coupling constants). The agreement is generally good. Some anomalies have been discussed in relation to the structure of these compounds.     

Synthesis of chiral ferrocenylazines. Negishi cross-coupling or S N H reactions?

Preparation of new hetaryl-containing planar chiral ferrocene by a nucleophilic substitution of hydrogen in azines was performed using a lithium derivative of (S)-ferrocenyl-p-tolylsulfoxide as s nucleophilic reagent     

MRINDO/S-CI calculation of the electronic spectra of azines

An MRINDO/S calculation completed by singly excited configuration interaction was performed on the azines vic-triazine, as-triazine, vic-tetrazine, and as-tetrazine. The importance of outer (Rydberg) atomic orbitals is stressed and it is found that a few transitions of these azines lead to an excited state with considerable Rydberg character. Ionization potentials of the azines are also interpreted. Received: 23 June 1998 / Accepted: 27 July 1999 / Published online: 15 December 1999     

Thermodynamic characteristics of adsorption of nitrogen-containing heterocycles on graphitized thermal carbon black derived from molecular statistical calculation. 1. Azines

Thermodynamic characteristics of adsorption (TCA) for six-membered aromatic nitrogen-containing heterocycles (azines), viz., pyridine, pyridazine, pyrimidine, and 1,3,5-triazine, on graphitized thermal carbon black (GTC) were experimentally determined and theoretically calculated. The best coincidence of the experiment and calculation is achieved using atom-atomic potential functions of intermolecular interactions, which allow for a decreased -electron density in the aromatic system. The N atoms in the azine molecules are nonequivalent in terms of the adsorption behavior. The GTC surface very selectively adsorbs azines with different molecular structures, and this selectivity can be used for separation and chromatographic analysis of these compounds. The dependence of TCA of azines on the degree of aromaticity of their molecules has been established for the first time.     

Synthesis of trichloromethyl-substituted azines from dichloromethyl-substituted azines and carbon tetrachloride under interphase catalysis conditions

The reactions of 2- and 3-dichloromethylpyridines and dichloromethylpyrazine with carbon tetrachloride in the presence of aqueous or solid alkali and an interphase catalyst lead to the corresponding trichloromethyl-substituted azines. The CCl₄-solid KOH-18-crown-6 system, in the use of which trichloromethyl-substituted heterocycles were obtained in preparative yields, was the most effective.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 50–53, January, 1990.     

The reactions of n-benzoylperoxycarbamic acid with azines and imines

N-Benzoylperoxycarbamic acid (BPC) was found to react generally with imines and azines to form oxaziridines rather than N-oxides. The imine products were stable, but those found from azines apparently were unstable and converted to ketones or aldehydes plus diazo compounds.     

Microwave-assisted synthesis of substituted fluoroazines using KF·2H2O

This Letter describes a new microwave-assisted fluorination of azines using hydrated potassium fluoride in untreated DMSO under atmospheric conditions. It is thought that microwave irradiation promotes desolvation of the fluorine anion leading to halide nucleophilic substitution.     

Preparation of rapidly disintegrating tablets containing itraconazole solid dispersions

The disintegratability of tablets prepared from two types of solid dispersions containing the water-soluble polymer TC-5 and the enteric polymer HP-55 as an excipient were compared. The disintegratability was better in the tablets of solid dispersions containing non-water-soluble HP-55 than those containing TC-5. In consideration of the dissolubility of solid dispersions containing HP-55, the mean diameter of the solid dispersion (coating powder) must be controlled to 120 microm or less, but as this markedly increases the adhesion/aggregation tendency of the particles (angle of repose: 47 degrees ), control of the adhesion/aggregation tendency emerged as another problem. Therefore, surface-modification was performed in a high-speed agitating granulator using 0.1% light anhydrous silicic acid as a surface modifier, and marked improvement in the flowability was observed. This made continuous tableting using a rotary tablet machine possible even with the poorly flowable solid dispersions. Also, in tableting of the solid dispersions, no recrystallization of amorphous itraconazole by the tableting pressure was observed, and the tablets maintained satisfactory dissolubility. Moreover, it was possible to obtain the rapidly disintegrating tablets with very satisfactory properties, i.e., a tablet hardness of 30 N or higher and a disintegration time of 30 s or less, by the addition of croscarmellose as a disintegrant at 2% to the surface-modified solid dispersion and selection of the tableting pressure at 4.5 kN.     

Sulfoxidations in the solid phase

The asymmetric oxidation of a sulfide in the solid phase using two distinct scaffolds as models is described.     

Mechanoformation of ammonium perchlorate-potassium perchlorate solid solutions

Ammonium perchlorate-potassium perchlorate mixtures, upon pelletization, form a series of homogeneous solid solutions as manifested by X-ray powder diffractograms. Scanning electron microscopic studies throw light on the mechanism of the solid-solution formation. Solid solutions of ammonium perchlorate-potassium perchlorate have also been obtained by a modified cocrystallization technique. The thermal and combustion behavior of the solid solutions have also been studied, using the DTA technique and the Crawford strand burner.     

Regeneration of carbonyl compounds by cleavage of CN bonds under mild and completely heterogeneous conditions

Oximes, hydrazones, semicarbazones and azines are converted to the corresponding carbonyl compounds using a combination of Zr(HSO₄)₄ and wet SiO₂ in good to high yields under completely heterogeneous conditions.     

Synthesis of 1-azacycl[3.2.2]azine and 1-azabenzo[h]cycl[3.2.2]azine

1-Azacycl[3.2.2]azines were synthesized from 2-methylthioimidazo[1,2-a]pyridines, 2a and 2b , by using [2 + 8] cycloaddition reaction with dimethyl acetylenedicarboxylate as the key step. Synthesis of 1-azabenzo-[h]cycl[3.2.2]azine was also described.