Ultrasound assisted the chemoselective 1,1-diacetate protection and deprotection of aldehydes catalyzed by poly(4-vinylpyridinium)hydrogen sulfate salt as a eco-benign, efficient and reusable solid acid catalyst

Ultrasonic assisted synergetic green synthesis of polycyclic imidazo(thiazolo)pyrimidines by using Fe3O4@clay core-shell

A practical and green approach for the ultrasound-enhanced one-pot multicomponent synthesis of tetraheterocyclic imidazo(thiazolo)pyrimidines is described via the condensation of an 2-aminobenzimidazole or 2-aminobenzothiazole, dimedone and various aldehydes in the presence of Fe₃O₄@clay as an environmentally benign and reusable core/shell nanocomposite catalyst in relatively quantitative yields. This novel eco-friendly protocol includes several advantages such as avoiding hazardous solvents, reusability of the catalyst, easy work-up, short reaction times, room temperature and mild reaction conditions. Furthermore, ultrasonic irradiation and synergistic catalyst showed considerable superiority vs. traditional heating or stirring conditions.

Ultrasonic treatment of CoFe2O4@B2O3-SiO2 as a new hybrid magnetic composite nanostructure and catalytic application in the synthesis of dihydroquinazolinones

New hybrid magnetic composite nanostructure are prepared via ultrasonic treatment by glass-ceramic method, characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), energy-dispersive X-ray (EDX), element distribution image (EDX mapping), thermal gravimetric analysis (TGA)/differential thermal analysis (DTA) and N₂ adsorption-desorption by Brunauer-Emmett-Teller (BET) analyses. Then, the catalytic activity of the prepared CoFe₂O₄@B₂O₃-SiO₂ nanoparticles was tested in the synthesis of 2-substituted-3-(phenylamino)-dihydroquinazolin-4(1H)-ones in deep eutectic solvent (DES) based on choline chloride as an eco-friendly and recyclable media. This novel protocol offers several advantages such as high yields (70-93%), short reaction times (10-20min), environmentally-friendly reaction media, easily isolation of the products, simple preparation and recoverability of the nanocatalysts (at least 5 times), recyclability of the solvents from the reaction mixture without use of hazardous volatile organic solvent. The catalyst was readily recycled by the use of an external magnetic field and could be reused several times without significant loss of activity or mass. The saturation magnetization of CoFe₂O₄@B₂O₃-SiO₂ nanoparticles was 8.97emug^-1. Their average size distribution was about 12.5nm. DES was a mixture of choline chloride and urea that was recovered from the filtrate by evaporating the water under vacuum.

Ultrasound mediated, iodine catalyzed green synthesis of novel 2-amino-3-cyano-4H-pyran derivatives

An efficient synthesis of a novel series of twelve substituted 2-amino-3-cyano-4H-pyran derivatives was achieved by a one-pot three-component cyclocondensation reaction of heteroaryl aldehydes, malononitrile and active methylene compounds catalyzed by iodine in aqueous medium under ultrasound irradiation. In comparison with conventional methods, our protocol is convenient and offers several advantages, such as shorter reaction time, higher yields, milder conditions and environmental friendliness. We have herein successfully demonstrated the synergistic outcome of multi-component reaction (MCR) and sonication to offer a facile route for the design of these derivatives.

Ultrasound assisted the green synthesis of 2-amino-4H-chromene derivatives catalyzed by Fe3O4-functionalized nanoparticles with chitosan as a novel and reusable magnetic catalyst

Fe3O4 nanoparticles were prepared by chemical coprecipitation method. Subsequently immobilization of chitosan on Fe3O4 nanoparticles was accomplished and afforded magnetic Fe3O4-chitosan nanoparticles. Synthesized nanoparticles was found to be a magnetic and heterogeneous catalyst for a one-pot and efficient synthesis of 2-amino-4H-chromenes by condensation of aldehydes with malononitrile and resorcinol under ultrasound irradiation as an ecofriendly method. This convenient procedure allowed us to achieve products under ultrasound irradiation in short time and excellent yield without using of harmful catalyst. The present method will permit a further increase of the diversity within the 2-amino-4H-chromene family.

An Eco-Friendly Improved Protocol for the Synthesis of Bis(3-indolyl)methanes Using Poly(4-vinylpyridinium)hydrogen Sulfate as Efficient, Heterogeneous, and Recyclable Solid Acid Catalyst

Highly efficient and eco-friendly protocol for the synthesis of bis(3-indolyl)methanes by the electrophilic substitution reaction of indole with aldehydes catalyzed by poly(4-vinylpyridinium)hydrogen sulfate was described. Excellent yields, shorter reaction times, simple work-up procedure, avoiding hazardous organic solvents, and reusability of the catalyst are the most obvious advantages of this method.