Reusable ammonium salt-tagged NHC-Cu(I) complexes: preparation and catalytic application in the three component click reaction

A series of ammonium salt-tagged SIPr-Cu(I) complexes have been conveniently synthesized and characterized by NMR and HRMS. They are highly active toward the three component click reaction of benzyl bromide, NaN3 and alkyne with water as solvent at rt. Current water soluble NHC-Cu(I) catalyst could be efficiently used at least four times with an 84% isolated yield of the desired triazole in the last run

铜-氮羟基吡啶二甲酰亚胺配合物催化烃类选择氧化

铜-氮羟基吡啶二甲酰亚胺配合物催化烃类选择氧

Chemical equilibrium controlled synthesis of polyoxymethylene dimethyl ethers over sulfated titania

The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers (DMMn) were investigated over sulfated titania in order to reveal the decisive factor controlling the reaction. The results showed that the molar ratio of adjacent DMMn products in equilibrium solution had the same value, which depended absolutely on the reaction temperature. Meanwhile, the reactions had the same DMMn products distributions under varied reaction conditions. The equilibrium constants of the related step-wise reactions for DMMn formation were equal, which were calculated based on the bulk compositions of the reaction solution. And thus, the selectivity to DMMn was mainly controlled by the chemical equilibrium, i.e., thermodynamic control. In brief, the present results provide some guidance for future synthesis of DMMn

Designed SO42-/Fe2O3-SiO2 solid acids for polyoxymethylene dimethyl ethers synthesis: The acid sites control and reaction pathways

The designed model SO42-/Fe2O3-SiO2 catalysts with varied acidic strength and Bronsted acid sites were successfully prepared. The properties of acid sites can be regulated by preparation method and silica incorporation. The S/Fe sample without silica had stronger acid strength, more Bronsted acid sites and higher acid density, which showed the best catalytic performance. NH3-TPD, pyridine-IR and methanol/dimethoxymethane adsorption-desorption techniques were employed to reveal the relationship between acid properties of the catalysts and catalytic activity for the reaction of trioxane with methanol. Further, this reaction is determined by the strength of acid sites on catalyst surface and does not affect by the inner pore diffusion. These findings suggest that the catalytic activity and selectivity can be monitored mainly by acid strength and Bronsted acid sites on the sulfated oxides, while trioxane decomposition process seems to be a vital step and polyoxymethylene hemiacetals are supposed to be the key intermediates. Meanwhile, a large number of acid sites and a higher surface area of the catalysts can also improve the catalytic performance. These results should provide some specific guidance for understanding of the reaction mechanism and the catalyst design. (C) 2014 Elsevier B.V. All rights reserved