The condensation of aromatic aldehydes, cyclopentanone and urea promoted by nano Al2O3-SO3H and HCl (aq) as heterogeneous and homogeneous catalysts, respectively, have been developed for the synthesis of some arylidene heterobicyclic compounds. In this synthesis, we have used two methods with sonication and thermal condition that have several advantages such as excellent yields and short reaction times. The ultrasonic device used in this study includes an ultrasonic bath equipped with a thermal system designed and built in our laboratory. پرونده مقاله

An organic–inorganic hybrid nanocomposite was prepared by immobilizing β-cyclodextrin (β-CD) and amino groups onto mesoporous MCM-41 via surfactant-templated sol-gel procedure and post-modification method. The heterogeneous hybrid nanocomposite, MCM-41-β-CD/NH2, was characterized by SEM, TEM, XRD, TGA, BET and FT-IR. The potential application of this covalently linked basic catalyst was also investigated as an efficient, heterogeneous and recyclable stationary micro-vessel and basic heterogeneous catalyst in Biginelli multicomponent condensation reaction. High yield, high efficiency and reusability are among the advantages of this environmentally friendly method. The nano catalyst can be easily separated from the reaction mixture and reused after washing for several runs without less in activity. پرونده مقاله

Fe3O4@SiO2/bipyridinium chloride nanocomposite, Fe3O4@SiO2/BiPy+22Cl-, as a magnetically separable and recyclable heterogeneous catalyst was used for the one-pot synthesis of pyranopyrazole and octahydroquinazoline derivatives via multi-components cyclocondensation reaction under solvent free conditions. The catalyst was recovered by simple magnetic decantation and can be recycled several times with no significant loss of its catalytic activity. The results showed that the desired products were obtained with high efficiency, rapid, simple, and eco-friendly. پرونده مقاله

3,4-Dihydropyrimidinones are an important class of heterocycles due to their pharmaceutical and therapeutic properties. The most efficient method for synthesis of these 3,4-dihydropyrimidinones, first reported by Biginelli, involves three component, one-pot condensation of a β-ketoester with an aldehyde and urea under strongly acidic conditions. The major drawbacks associated with this protocol, is poor to moderate yields, when using substituted aromatic and aliphatic aldehydes. Several improved methods for this protocol have been reported, can overcome the drawback of the classical protocol. This project aims investigating tributyl hexadecyl phosphoniuom bromide(TBHDPB) as a novel and efficient catalyst for synthesis of 3,4dihydropyrimidinones/thiones in milder reaction conditions. Optimization of the reaction conditions was attempted. The effect of temperature and solvent was studied. The best results were obtained in ethanol at 80 oC. The best catalytic activity of TBHDPB was optimized to be 10 mol% ( 0.1 mmol , 0.051g). Under optimal conditions, all reactions were completed within 45-80 min. All pure products were obtained in excellent yields (60-90%). The products were characterized by comparison of melting points and 1HNMR with those prepared in accordance with the literature procedures. The remarkable advantages of the present methodology over the literatures method, including the easily and inexpensive available catalyst, simple experimental procedures, shorter reaction times, excellent yields, easy work up and purification of products by non-chromatographic methods. پرونده مقاله

The methodology involves preparing polyvinyl sulfuric acid as a solid acid by simple mixing of polyvinyl alcohol with chlorosulfonic acid in CH2Cl2 at room temperature. The catalytic ability of the solid acid was investigated for the facile conversion of benzylic alcohols to the unsymmetrical ethers with aliphatic alcohols in the presence of the solid acid. Results show that the solid acid is an appropriate catalytic agent for these condensation reactions. The silica was also extracted from low-cost rice husk and the amorphous silicagel nanoparticles was prepared with solgel method. The polyvinyl sulfuric acid was supported on nano rice husk silica. Then the catalytic effect of this system was investigated for synthesis of unsymmetrical ethers which consisted of a combination of high acidic power for this solid acid and high- surface area of nanoparticles. Results show that totally catalytic effect of polyvinyl sulfuric acid supported on nano silica is more suitable than polyvinyl sulfuric acid. The reason for this is in its ability to produce the end products in shorter reaction times while having high isolated yields. پرونده مقاله

In the present study, application of porous acidic catalyst functionalized with an imidazole ionic liquid ([SBA-Im]HSO4) as a phase transfer catalyst for the facile preparation of benzyl thiocyanates and azides in water has been described. The catalyst has been characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). The polymeric phase transfer catalyst, easily recovered by simple filtration, shows no appreciable loss of activity when recycled several times.In the present study, application of porous acidic catalyst functionalized with an imidazole ionic liquid ([SBA-Im]HSO4) as a phase transfer catalyst for the facile preparation of benzyl thiocyanates and azides in water has been described. The catalyst has been characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). The polymeric phase transfer catalyst, easily recovered by simple filtration, shows no appreciable loss of activity when recycled several times. پرونده مقاله

The present study, for the first time, presents a feasible protocol for the preparation of β-cyclodextrin/ imidazolium based dicationic ionic liquid, [βCD/Im](OTs)2, and its application as an efficient and eco-friendly microvessel and host ionic liquid system for the regioselective ring opening of the epoxides in water. No evidence for the formation of diol by-products or side reactions, such as isomerization, epimerization and rearrangements was observed and 1,2-disubstituted products, β-azidoalcohols, β-cyanohydrins, and β-thiocyanohydrins, obtained in pure form. Short reaction time, easy reaction conditions, simple work-up procedure, high yield, reusability, and use of an eco-friendly catalyst are some of the striking features of the present protocol. پرونده مقاله

An environmentally benign procedure for the synthesis of vicinal nitrohydrins via the regioselective ring opening reaction of epoxides with nitrite anion using silica-bound 3-{2-[poly(ethylene glycol)]ethyl}-substituted 1-methyl-1H-imidazol-3-ium bromide as an effective heterogeneous phase transfer catalyst was described. Short reaction time, high yield of products, simple work-up procedure, and recyclability of the catalyst were some of the striking features of the present protocol. The recovered catalyst could be reused five times without any loss in its catalytic activity and selectivity. پرونده مقاله

For the first time B-podands have been studied as an efficient and powerful catalysts in the ring opening of epoxides with azide anion in water. The reaction afforded the corresponding 1,2-azidoalcohols with high regioselectivity under mild reaction conditions and in a highly atom economic fashion. پرونده مقاله