Tungstate Sulfuric Acid: A Novel and Efficient Solid Acidic Reagent for the Oxidation of Thiols to Disulfides and the Oxidative Demasking of 1,3-Dithianes

Tungstate sulfuric acid in combination with various oxidants was found to be an efficient reagent for the conversion of thiols to disulfides at r.t. in good to excellent yields. The selective oxidative deprotection of 1,3-dithianes to their parent carbonyl compounds at r.t. was also observed with this reagent.     

A novel theoretical model for calculating the effective diffusivity of gases in a porous pellet composed of two different grains

Effective diffusivity of gases is an important property when modeling the physicochemical processes occurring in a pellet. Calculating effective diffusivity in a pellet composed of a mixture of particles is a difficult task. In this paper, a theoretical model is presented in order to describe the diffusion of gases in a porous pellet made up of a mixture of two kinds of solid grain. Solid grains can either be fully dense and thus non-porous or contain pores, with a grain being sub-divided into sub-grains. The results predicted by the model have been evaluated and validated by use of experimental data obtained by reduction of cuprous sulfide in the presence of lime. Finally, the effects of structural properties and operating conditions on the effective diffusivity of the gases in the pellet have been evaluated.     

A new and green approach for regiospecific synthesis of novel chromeno-triazolopyrimidin using tungstic acid immobilized MCM-41 as a reusable catalyst

A novel, eco-friendly and fast route has been developed for the synthesis of new and known triazolo[1,5-a]pyrimidin fused chromone derivatives via a one pot three-component reaction of 3-amino-1,2,4-triazoles, aromatic aldehydes and 4-hydroxycoumarin in aqueous medium at room temperature. These reactions are catalyzed by MCM-41-HWO₄ as a safe and recyclable mesoporous solid acid. It combines successfully the synergistic effect of green chemistry with nanocatalysis. The yields are high and the products were characterized by ¹H NMR, ¹³CNMR spectra and elemental analysis.     

Alternative two-step route to khellactone analogues using silica tungstic acid and sodium hydrogen phosphate

A series of coumarins was synthesised via the silica tungstic acid-catalysed Pechmann reaction; some of these were employed for known three-component reactions with aromatic aldehydes and malononitrile in the presence of sodium hydrogen phosphate (Na₂HPO₄) as a basic catalyst, affording a variety of potentially anti-HIV active khellactone analogues.     

One-Pot Synthesis of Dihydropyrimidine-Thione Derivatives Using Tungstate Sulfuric Acid (TSA) as a Recyclable Catalyst

Abstract

An efficient, simple, and environmentally benign procedure for the one-pot synthesis of 3,4-dihydropyrimidine-2-(1H) thione derivatives that entails the three-component condensation of appropriate aryl aldehydes, β-dicarbonyls, and thiourea in the presence of catalytic amount of tungstate sulfuric acid under solvent-free conditions was reported. This method has many advantages including excellent yields, short reaction time, and simple work-up procedure.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: 1H, 13C NMR and Mass Spectra for 5b, 5g, 5j, 5i, 5l (S2-S16). Additional Characterization Data (S17-18).     

One‐pot Synthesis of Benzamidonaphtho[2,1‐b]furans and Benzamidobenzo[b]furans as Novel Polycyclic Heteroaromatic Compounds

An operationally simple, green and efficient procedure for one‐pot synthesis of novel polycyclic heteroaromatic compounds such as benzamidonaphtho[2,1‐b]furans and benzamidobenzo[b]furans has been developed from the reaction of arylglyoxals, benzamide, and phenols. The reactions were mediated with low amounts of yttrium nitrate hexahydrate as a suitable Lewis acid catalyst without using solvent.     

Silica‐supported ICl as a novel heterogeneous system for the rapid oxidation of urazoles to triazolinediones

ICl–SiO₂ as a new reactive system was prepared by the treatment of iodine monochloride with an activated silica gel in chloroform. ICl–SiO₂ in a heterogeneous system efficiently oxidized urazoles to the corresponding triazolinediones under mild conditions in high yields at room temperature. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:389–393, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20444