The Catalytic Performance of Preyssler's Anion, [NaP5W30O110]14−, in the Oxidation of Benzyl Alcohols

Under mild conditions, monosubstituted benzyl alcohols were oxidized to benzaldehydes and benzoic acids in the presence of sodium 30-tungstopentaphosphate (Preyssler's anion), [NaP₅W₃₀O₁₂₀]^14? , and hydrogen peroxide as an oxidant. This polyanion with high hydrolytic stability (pH = 0–12), high thermal stability, and high acidic strength shows good activities. The effects of various parameters on the yield of the products, including a catalyst type, a nature of the substitutents, and temperature, were studied. Comparison between Keggin's heteropolyacids, H₃[PW₁₂O₄₀], H₃[PMo₁₂O₄₀], H₄[SiW₁₂O₄₀], and H₄[SiMo₁₂O₄₀], and Preyssler's anion shows that this polyanion reacts similar to Keggin's acids whitout any degradation of the structure.     

Triphenylphosphine-Catalyzed Preparation of Sterically Congested,Electron-Poor N-Vinylimidazole Derivatives from Acetylenic Esters and Imidazole-Containing NH-Acids

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and alkyl acetylenecarboxylates (or ethyl 3-phenyl-2-propynoate), by azathioprine or imidazole leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce phosphorus ylides. Dipotassium hydrogen phosphate, potassium dihydrogen phosphate, and potassium iodide were found to catalyze the conversion of the phosphorus ylides to electron-poor N-vinyl imidazoles in solvent-free conditions under thermal (90°C, 1 h) conditions. The structural analysis of the products indicated that the reaction is regio- and stereoselective.     

A New and Efficient Procedure for the Production of 1,1-Diacetate from Corresponding Aldehydes Promoted by Silica Chromate (SiO2-O-CrO2-O-SiO2)

Abstract

A wide range of aromatic aldehydes has been selectively converted to 1,1-diacetates using silica chromate (SiO₂?O?CrO₂?O?SiO₂) under solvent-free conditions at room temperature in moderate to good yields. This protocol is mild and efficient compared to other reported methods.

GRAPHICAL ABSTRACT     

One-Pot Green Synthesis of Novel Polysubstituted 1,2-Dihydronaphtho[2,1-b]furans

A simple and highly efficient one-pot protocol for the synthesis of novel polysubstituted 1,2-dihydronaphtho[2,1-b] furans has been developed by three-component coupling reaction of 2-aminopyridines, naphthols, and glyoxal in the presence of guanidinium chloride as a polyfunctional organocatalyst under solvent-free conditions. The protocol avoids the use of expensive catalysts, toxic solvents, and chromatographic separation and provides a wide range of novel dihydronaphthofurans in good to excellent yields.     

Silica‐Supported bis (Trimethylsilyl) Chromate: Oxidation of Thiols to Their Corresponding Disulfides

An efficient and convenient method for the oxidation of thiols mediated by silica‐supported bis (trimethylsilyl) chromate (BTSC) in acetonitrile is reported.     

New and General Nitrogen Heterocycle Synthesis: Use of Heteropoly Acids as a Heterogeneous Recyclable Catalyst

An efficient synthetic method of six- and five-member nitrogen heterocyclic compounds was developed. Nitrogen heterocyclic compounds were prepared by condensation of the β-dicarbonyl compounds with the corresponding β- or γ-amino alcohols, subsequent cyclization, and spontaneous aromatization in the presence of a catalytic amount of Keggin-type heteropoly acids under very mild conditions.     

H6P2W18O62-18H2O,a Green and Reusable Catalyst for the Three-Component,One-Pot Synthesis of 4,6-Diarylpyrimidin-2(1H)-ones Under Solvent-Free Conditions

Three-component, one-pot synthesis of 4,6-diarylpyrimidin-2(1H)-ones and 9-phenyl-8-oxa-10,12-diaza-tricyclo[7.3.1.0^2,7]trideca-2(7),3,5-trien-11-one by condensing acetophenone derivatives, aldehydes, and urea in the presence of trimethylsilyl chloride using a catalytic amount of H₆P₂W₁₈O₆₂-18H₂O under solvent-free conditions is reported.     

Determination of cocaine and methadone in urine samples by thin-film solid-phase microextraction and direct analysis in real time (DART) coupled with tandem mass spectrometry

The use of thin-film solid-phase microextraction (SPME) as the sampling preparation step before direct analysis in real time (DART) was evaluated for the determination of two prohibited doping substances, cocaine and methadone, in urine samples. Results showed that thin-film SPME improves the detectability of these compounds: signal-to-blank ratios of 5 (cocaine) and 13 (methadone) were obtained in the analysis of 0.5 ng/ml in human urine. Thin-film SPME also provides efficient sample cleanup, avoiding contamination of the ion source by salt residues from the urine samples. Extraction time was established in 10 min, thus providing relatively short analysis time and high throughput when combined with a 96-well shaker and coupled with DART technique.

Complexation of 4′-Nitrobenzo-15-crown-5 with Zn<Superscript>2+</Superscript>, Mn<Superscript>2+</Superscript>, Cr<Superscript>3+</Superscript> and Sn<Superscript>4+</Superscript> Cations in Acetonitrile–Ethanol Binary Mixtures

The complexation reactions of 4′-nitrobenzo-15-crown-5 (4′NB15C5) with Zn²⁺, Mn²⁺, Cr³⁺ and Sn⁴⁺ cations were studied in acetonitrile–ethanol (AN–EtOH) binary solvent mixtures at different temperatures by the electrical conductometry method. The stability constants of the resulting 1:1 complexes were determined from computer fitting of the conductance versus mole ratio data. The results show that the selectivity order of 4′NB15C5 for the metal cations in the AN–EtOH (mol-%AN=76) binary solvent at 298.15 K is: Cr³⁺>Mn²⁺≈Zn²⁺>Sn⁴⁺, but the selectivity order changes with the composition of the mixed solvents. A nonlinear relationship was observed between the stability constants (log ₁₀ K _f) of these complexes and the composition of the AN–EtOH binary solvents. The corresponding thermodynamic parameters (DH_c^o, DS_c^o)(\Delta H_{\mathrm{c}}^{\mathrm{o}}, \Delta S_{\mathrm{c}}^{\mathrm{o}}) were obtained from the temperature dependence of the stability constants using van’t Hoff plots. The results show that the values and also the sign of these parameters are influenced by the nature and composition of the mixed solvents.     

Preparation and preliminary evaluation of [<Superscript>67</Superscript>Ga]-tetra phenyl porphyrin complexes as possible imaging agents

[⁶⁷Ga]labeled tetraphenyl porphyrin ([⁶⁷Ga]-TPP) was prepared using freshly prepared [⁶⁷Ga]GaCl₃ and tetraphenyl porphyrin (TPPH₂) for 30–60 min at 25 °C (radiochemical purity: >97 ± 1% ITLC, >98 ± 0.5% HPLC, specific activity: 13–14 GBq/mmol). Stability of the complex was checked in final formulation and human serum for 24 h. The partition coefficient was calculated for the compound (log P 1.89). The biodistribution of the labeled compound in vital organs of wild-type rats was studied using scarification studies and SPECT imaging up to 24 h. A detailed comparative pharmacokinetic study performed for ⁶⁷Ga cation and [⁶⁷Ga]-TPP. The complex is mostly washed out from the circulation through kidneys and can be an interesting tumor imaging/targeting agent due to low liver uptake and rapid excretion through the urinary tract.