The supramolecular structures and reactivities of some complexes of chiral crown ethers with borane ammonia

Whereas 1 1 crystalline complexes have been isolated between borane ammonia and methyl 4,6-O-benzylidene-2,3-dideoxy--d-galactopyranosido [2,3-b]-1,4,7,10,13,16-hexaoxacyclo-octadecane (1), methyl 4,6-O-benzylidene-2,3-dideoxy--d-mannopyranosido [2,3-b] (methyl 4,6-O-benzylidene-2,3-dideoxy--d-mannopyranosido [2,3-k]-1,4,7,10,13,16-hexaoxacyclo-octadecane (3), and (1R,2R,7R,24R)-3,5,8,11,14,17,20,23,26,28-decaoxatricyclo-[21.4.0.0^2,7]octacosane (4), the hosts, methyl, 4,6-O-benzylidene-2,3-dideoxy--d-mannopyranosido[2,3-b] 1,4,7,10,13,16-hexaoxacyclo-octadecane (2) and 1,4 1,4 3,6 3,6-tetra-anhydro-2,2 5,5-bis-O-oxydiethylenedi-d-mannitol (5) have yielded 2 1 (guest:host) crystalline complexes with borane ammonia as guest. X-ray analyses of the supramolecular structures of BH₃NH₃ ·1, (BH₃NH₃)₂ ·2, BH₃NH₃ ·3, BH₃NH₃ ·4, and (BH₃NH₃)₂ ·5 have been carried out and BH₃NH₃ ·1, BH₃NH₃ ·2, and (BH₃NH₃)₂ ·5 have been shown to reduce acetophenone with enantiomeric excesses of 5, 13, and 10% respectively. Supplementary Data relating to this article (atomic coordinates of the hydrogen atoms and thermal parameters) are deposited with the British Library as Supplementary Publication No. SUP 82017 (74 pages).Dedicated to Professor H. M. Powell.     

Photochromism and Photoisomerization in Some 2,3,4,4,5,6-Hexasubstituted 4H-Thiopyrans

Photochromism and photoisomerization reactions of some new 2,3,4,4,5,6-hexasubstituted 4H-thiopyrans are described.     

KINETIC STUDY ON PHOTOISOMERIZATION OF SOME TETRA- AND HEXASUBSTITUTED 4H-THIOPYRANS

Abstract

The effects of phenyl and methyl groups at 3,5-positions of tetrasubstituted 4H-thiopyrans 1a and 1b on photoisomerization are investigated from a kinetic point of view using ¹H-NMR spectroscopy. On irradiation of 1a-1d in benzene-d₆ solution the hexasubstituted 4H-thi-opyrans 1c and 1d, unlike those of the tetrasubstituted analogues 1a and 1b, give the isomeric 2H-thiopyrans 3c and 3d with no detectable signals for intermediates in ¹H-NMR spectra. The photoisomerization of hexasubstituted 4H-thiopyrans 1c and 1d occur with relative rate constants lower than the corresponding tetrasubstituted model compounds 1a and 1b. Moreover, the kinetic comparison of 1a with 1b reveal that the presence of two phenyl groups at 4-position of tetrasubstituted 4H-thiopyran increases the relative rate constant of photoisomerization.     

Separation of trace amounts palladium by SiO2/TiO2/Ce nanoparticles prior to flame atomic absorption spectrometry determination in anodic slime and wastewater samples

In the present work, a new SiO₂/TiO₂/Ce, nanoparticle was synthesed using sol-gel method and evaluated as an adsorbent for preconcentration trace amounts of Pd(II) ions. The characterization of the nanoparticles has been studied by transmission electron microscope and X-ray diffraction. The preconcentration method is based on palladium adsorption onto the surface of nanoparticle at pH 8.5. The main factors affecting Pd(II) adsorption, such as pH of sample solution, concentration and volume of eluent, sample volume, interfering of the coexisting ions and flow rate of sample and eluent were investigated and optimized. At optimum conditions, linearity was maintained between 4.0 to 1000.0 ng mL^?1. Detection limit based on 3S_b/m was 2.3 ng mL^?1. Seven replicate determinations of a solution containing of 12.5 µg palladium gave a relative standard deviation ±1.7%. According to the Langmuir linear model, the maximum adsorption capacity of palladium was found to be 34.5 mg g^?1. Finally, the feasibility of the proposed method for Pd(II) determination was assessed by analysis of certified reference materials, anodic slime and wastewater samples and satisfactory results were obtained.      

An Efficient Solvent-free Synthetic Technique of 4,4’-Diaminotriarylmethane Leuco Materials

An efficient, versatile and solvent-free synthetic technique of diaminotriarylmethanes was reached by treating N,N-dimethylaniline with some arylaldehydes over zirconium(IV) oxide chloride (ZrOCl2•8H2O), in which ZrOCl2•8H2O has good activity, easy availability, recovery as well as reusability.     

New Facile Route to Synthesize Furo[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine and Furo[3,2-e][1,2,4]triazolo[1,5-c]pyrimidine Derivatives

A new facile route for synthesis of 3-(aryl)-8,9-diphenylfuro[3,2-e][1,2,4]triazolo pyrimidines derivative from the same starting material, 2-amino-4,5-diphenylfuran-3-carbonitrile, has been developed through heterocyclization of the corresponding arylidene-hydrazono-5,6-diphenylfuro[2,3-d]pyrimidine and N-(arylmethylene)-4-imino-5,6-diphenylfuro[2,3-d]pyrimidin-3(4H)-amine under refluxing condition with acetic anhydride followed by air oxidation. The products were obtained in good yield with an easy workup along with the purification of products by a nonchromatographic method. This general synthetic procedure can be extended to the preparation of a wide range of isomeric triazoles using 2-amino 3-carbonitrile bifunctional derivatives.     

Haloperidol imprinted polymer: preparation,evaluation, and application for drug assay in brain tissue

Several molecularly imprinted polymers (MIPs) were prepared in the present work, and their binding properties were evaluated in comparison with a nonimprinted polymer (NIP). An optimized MIP was selected and applied for selective extraction and analysis of haloperidol in rabbit brain tissue. A molecularly imprinted solid-phase extraction (MISPE) method was developed for cleanup and preconcentration of haloperidol in brain samples before HPLC-UV analysis. Selectivity of the MISPE procedure was investigated using haloperidol and some structurally different drugs with similar polarity that could exist simultaneously in brain tissue. The extraction and analytical process was calibrated in the range of 0.05–10 ppm. The recovery of haloperidol in this MISPE process was calculated between 79.9 and 90.4 %. The limit of detection (LOD) and the limit of quantification (LOQ) of the assay were 0.008 and 0.05 ppm, respectively. Intraday precision and interday precision values for haloperidol analysis were less than 5.86 and 7.63 %, respectively. The MISPE method could effectively extract and concentrate haloperidol from brain tissue in the presence of clozapine and imipramine. Finally, the imprinted polymer was successfully applied for the determination of haloperidol in a real rabbit brain sample after administration of a toxic dose. Therefore, the proposed MISPE method could be applied in the extraction and preconcentration before HPLC-UV analysis of haloperidol in rabbit brain tissue.     

One-pot and efficient synthesis of triazolo[1,2-a]indazole-triones via reaction of arylaldehydes with urazole and dimedone catalyzed by silica nanoparticles prepared from rice husk

A novel synthesis of triazolo[1,2-a]indazole-1,3,8-trione derivatives by reaction of urazole, dimedone and aromatic aldehydes under conventional heating and microwave irradiation and solvent-free conditions using silica nanoparticles prepared from rice husk ash as catalyst is described. The new method features high yields, multicomponent reactions and environmental friendliness.     

Syntheses of thiopyrylium-tungsten complexes

Hexacarbonyltungsten reacts with 2,4,6-triphenylthiopyrylium perchlorate and 2,6-dianisyl-4-phenylthiopyrylium perchlorate in diglyme to afford cationic thiopyrylium salts, 2,4,6-[H₂(C₆H₅)₃C₅SW(CO)₃]⁺ClO₄ ⁻ and 2,6,4-[H₂(C₆H₅)(C₆H₄OCH₃)₂C₅SW(CO)₃]⁺ClO₄ ⁻. Both compounds were characterized by physico-chemical and spectroscopic methods. The HMQC, DEPT-45, and COSY experiments were used to assign carbon and proton signals in the ¹H and ¹³C NMR spectra.