A mild,simple and efficient method for selectiveα-monobromination of 1,3-diketones and β-ketoesters using pyridinium bromochromate

Pyridinium bromochromate has been found to be a highly efficient and selective reagent for theα-monobromination of 1,3-diketones andβ-keto-esters in the absence of base,Lewis acid,or other catalyst.The products were formed in high to excellent yields under mild reaction conditions and in short reaction times.     

高效可回收催化剂In(OTf)_3用于无溶剂条件下Pechmann缩合反应(英文)

In(OTf)3 plays the role of a Lewis acid catalyst in the Pechmann condensation of phenols with β-ketoesters under solvent-free conditions to give coumarin derivatives. This novel and inexpensive method has advantages such as short reaction time, excellent product yields, and avoids the use of organic solvents in agreement with green chemistry principles. Catalyst loadings can be as low as 1 mol% to give high yields of the corresponding coumarins at 80 °C. The catalyst can be recovered after the reaction, and reused with only a slight decrease in the yield.     

聚乙二醇固载的双辛可宁生物碱配体催化的烯烃的对映选择性双羟基化反应

The recyclable PEG-bound bi-cinchona alkaloid ligand has been successfully applied to the homogeneous catalytic asymmetric dihydroxylation of various alkenes; good yields and excellent enantioselectivities were obtained, The ligand could be easily recovered and reused for 10 times without any apparent loss of its catalyst efficiency.     

Knoevenagel condensation catalysed by poly（vinyl chloride） supported tetraethylenepentamine （PVC-TEPA）

Poly(vinyl chloride) supported tetraethylenepentamine (PVC-TEPA) has been found to be an efficient catalyst for the Knoevenagel condensation. A wide range of aromatic aldehydes easily undergo condensations with ethyl cyanoacetate and malononitrile in the commercial 95% ethanol in refluxing using PVC-TEPA as catalyst to afford the desired products of good purity in moderate to excellent yields. A recycling study confirmed that the catalyst could be reused, the yield of the desired condensation product were not reduced. The merits of this protocol are environmentally benign, simple operation, convenient work-up and good yields. Furthermore, the catalyst can easily be recovered and reused at five times with comparable yields.     

Zinc oxide nanoparticles:A highly efficient and readily recyclable catalyst for the synthesis of xanthenes

A novel and efficient route for the synthesis of 1,8-dioxooctahydroxanthenes and 14-aryl-14H-dibenzo[a,j]xanthenes is described through one-pot multi-component reaction of dimedone and 2-naphthol with various aryl aldehydes using ZnO nanoparticles under solvent-free conditions.This method provides a novel and improved pathway for the synthesis of xanthenes in the terms of excellent yields,short reaction times,reusability and low catalyst loading.     

磺化碳催化Biginelli反应一锅法合成3,4-二氢-2(1H)-酮和硫酮(英文)

A sulfonated carbon material was shown to be a highly efficient,eco-friendly,and recyclable solid acid catalyst for the Biginelli reaction of β-ketoester,aldehyde,and urea or thiourea under solvent-free conditions.It gave 3,4-dihydropyrimidin-2(1H)-ones and-thiones in good to excellent yields.This method has the advantages of a simple procedure with easy work-up,short reaction time,and high yields.The catalyst can be recycled after a simple work-up and was reused four times without substantial reduction in activity.     

Reduction of Sulphur-containing Aromatic Nitro Compounds with Hydrazine Hydrate over Iron(III) Oxide-MgO Catalyst

Sulphur-containing aromatic amines were prepared efficiently in good to excellent yields by reduction of the corresponding sulphur-containing aromatic nitro compounds with hydrazine hydrate in the presence of iron(III) oxide-MgO catalyst. The catalyst exhibited high activity and stability for the reduction of sulphur-containing aromatic nitro compounds. The yields of sulphur-containing aromatic amines were up to 91-99 % at 355 K after reduction for 1-4 h over this catalyst.     

Reduction of Sulphur-containing Aromatic Nitro Compounds with Hydrazine Hydrate over Iron（Ⅲ） Oxide-MgO Catalyst

Sulphur-containing aromatic amines were prepared efficiently in good to excellent yields by reduction of the corresponding sulphur-containing aromatic nitro compounds with hydrazine hydrate in the presence of iron（Ⅲ） oxide-MgO catalyst. The catalyst exhibited high activity and stability for the reduction of sulphur-containing aromatic nitro compounds. The yields of sulphur-containing aromatic amines were up to 91-99 % at 355 K after reduction for 1-4 h over this catalyst.     

Sevelamer as an efficient and reusable heterogeneous catalyst for the Knoevenagel reaction in water

A catalyst system of Sevelamer, a phosphate-binding drug, has been prepared and used in the Knoevenagel reaction of aromatic aldehydes in water to produce substituted electrophilic alkenes. The products were obtained in excellent yields. Several novel, related catalytic systems showed promising catalytic properties for aromatic and heterocyclic aldehydes. The Sevelamer catalyst can be recovered using simple filtration and reused numerous times（up to 15 times） in the aqueous Knoevenagel reaction without any significant lowering of activity.     

碘催化的亚胺Diels-Alder反应：有效地合成四氢喹啉衍生物

Iodine was found to be an efficient catalyst for the imino Diels-Alder reaction of N-arylimine with enol ethers toprovide tetrahydroquinolines in good yields.The influence of the loading of iodine,reaction solvent,the structure ofimine and enol ethers was studied.One pot synthesis of tetrahydroquinolines from aldehyde,aniline and enol etherscatalyzed by iodine was also applicable and provided tetrahydroquinolines in comparable yields.Mild reaction con-ditions,facile experimental procedure,low price of iodine and good yield of products render this new method at-tractive for practical synthesis of many tetrahydroquinoline derivatives.     

磷酸锆铁催化无溶剂条件下醇和苯酚乙酰化(英文)

Iron zirconium phosphate(ZPFe) nanoparticles were found to function as an efficient catalyst for the acetylation of a wide range of alcohols and phenols using acetic anhydride, generating good to excellent yields under solvent-free conditions. The steric and electronic properties of various sub-strates had a significant influence on the reaction conditions required to achieve the acetylation. The catalyst used in the current study was characterized by inductively coupled plasma-optical emission spectrometry, X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, and transmission electron microscopy. These analyses revealed that the interlayer distance in the catalyst increased from 7.5 to 9.3  when Fe3+ was intercalated between the layers, whereas the crystallinity of the material was reduced. This nanocatalyst could also be recovered and reused at least six times without any discernible decrease in its catalytic activity. This new method for the acetylation of alcohols and phenols has several important advantages, including mild and environ-mentally friendly reaction conditions, as well as good to excellent yields and a facile work-up.     

Pincer iridium（Ⅲ）-catalyzed enantioselective C（sp3）-H functionalization via carbenoid C–H insertion of 3-diazooxindoles with 1,4-cyclohexadiene

The asymmetric carbenoid C–H insertion of 3-diazooxindoles into 1,4-cyclohexadiene has been accomplished in the presence of chiral bis(imidazoline) NCN pincer iridium(Ⅲ) complexes as the catalysts. With a catalyst loading of 0.5 mol%, the reactions proceeded smoothly at 0℃ to afford a variety of chiral 3-substituted oxindoles in good yields with moderate to excellent enantioselectivities(up to 99% ee). The protocol exhibits good functional group tolerance with respect to 3-diazooxindoles and is ...     

Pincer iridium（Ⅲ）-catalyzed enantioselective C（sp3）-H functionalization via carbenoid C–H insertion of 3-diazooxindoles with 1,4-cyclohexadiene

The asymmetric carbenoid C–H insertion of 3-diazooxindoles into 1,4-cyclohexadiene has been accomplished in the presence of chiral bis(imidazoline) NCN pincer iridium(Ⅲ) complexes as the catalysts. With a catalyst loading of 0.5 mol%, the reactions proceeded smoothly at 0℃ to afford a variety of chiral 3-substituted oxindoles in good yields with moderate to excellent enantioselectivities(up to 99% ee). The protocol exhibits good functional group tolerance with respect to 3-diazooxindoles and is ...     

无溶剂条件下铜磷酸锆催化醇类和酚类化合物乙酰化(英文)

Copper zirconium phosphate nanoparticles have been used as an efficient catalyst for the acetyla-tion of a wide range of alcohols and phenols with acetic anhydride in good to excellent yields under solvent-free conditions. The steric and electronic properties of the different substrates had a signif-icant influence on the reaction conditions required to achieve the acetylation. The catalyst used in the current study was characterized by inductively-coupled plasma optical emission spectroscopy,energy dispersive spectroscopy, X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, and transmission electron microscopy. These analyses revealed that the interlayer distance in the catalyst increased from 7.5 to 8.0  when Cu2+ was intercalated between the layers, whereas the crystallinity of the material was reduced. This nanocatalyst could also be recovered and reused at least six times without any discernible decrease in its catalytic activity. This new method for the acetylation of alcohols and phenols has several key advantages, including mild and environmentally friendly reaction conditions, as well as good to excellent yields and a facile work-up.     

Enantioselective organocatalytic synthesis of the chiral chromenes by domino oxa-Michael-aldol reaction

The proline based chiral organocatalyst has been found to be an efficient catalyst for enantioselective domino oxa-Michael-aldol reaction. This catalytic system provided the synthesis of substituted 2-aryl-2H-chromenes-3-carbaldehyde in good to high yields (73%–97%) with excellent enantioselectivity (up to 97%) and reasonable reaction times. The atom economy, high yield and mild reaction conditions are some of the important features of this protocol.     

Acetylation of alcohols and phenols under solvent-free conditions using iron zirconium phosphate

Iron zirconium phosphate (ZPFe) nanoparticles were found to function as an efficient catalyst for the acetylation of a wide range of alcohols and phenols using acetic anhydride, generating good to excellent yields under solvent‐free conditions. The steric and electronic properties of various sub‐strates had a significant influence on the reaction conditions required to achieve the acetylation. The catalyst used in the current study was characterized by inductively coupled plasma‐optical emission spectrometry, X‐ray diffraction, N2 adsorption‐desorption, scanning electron microscopy, and transmission electron microscopy. These analyses revealed that the interlayer distance in the catalyst increased from 7.5 to 9.3 ? when Fe3+was intercalated between the layers, whereas the crystallinity of the material was reduced. This nanocatalyst could also be recovered and reused at least six times without any discernible decrease in its catalytic activity. This new method for the acetylation of alcohols and phenols has several important advantages, including mild and environ‐mentally friendly reaction conditions, as well as good to excellent yields and a facile work‐up.     

Palladium particles from oxime-derived palladacycle supported on Fe3O4/oleic acid as a catalyst forthe copper-free Sonogashira cross-coupling reaction

An oxime-derived palladacycle was synthesized using4-bromobenzoxime and pyridine in CHCl3, and characterized by FT-IR and1H NMR spectroscopy. This Pd complex was supported on Fe3O4/oleic acid and shown to be an efficient catalyst for the copper-free Sonogashira cross-coupling reaction of various aryl halides with phenylacetylene in air and in ethanol or mixed aqueous medium. The oxime-derived palladacycle gave highly active palladium nanoparticles for the organicsynthesis. The coupling products were obtained in high yields with low Pd loading and theheterogeneous catalyst can be separated by an external magnet andreused six times without loss of its activity. The characterization of the catalyst wascarried out by XRD, SEM and TEM. Both TEM and XRD revealed that the palladium nanoparticles were well dispersed with diameters from 5 to 10 nm and average size 9.97 nm.     

一种高效简易的聚(4-乙烯基三溴化吡啶)催化乙醇合成乙酸盐的方法(英文)

Poly(4-vinylpyridinium tribromide) is an efficient catalyst for the conversion of various alcohols to their corresponding acetate derivatives with acetic anhydride.This method has some advantages such as mild reaction conditions,good to excellent yields,and ease of work-up.     

An Environmentally Benign System for Synthesis of β-Hydroxylketones： L-Histidine Asymmetrically Catalyzed Direct Aldol Reactions in Aqueous Micelle and Water-like Media

The first histidine catalyzed direct aldol reactions of ketones with nitrobenzaldehydes in water and in poly（ethylene glycol） （PEG） were reported. It reveals that histidine is a good aldol catalyst for synthesis of β-hydroxylketones in water and in PEG, giving good to excellent yields of the respective products. Better enantioand regioselectivity were achieved using low molecular weight PEG as the media. The results show that histidine and PEG-200 or -300 may constitute a promising environmentally benign system for asymmetric synthesis of β-hydroxylketones.     

溴化镁催化的1,2,3,4-四氢吡啶酮无溶剂合成研究

An efficient and environmentally friendly procedure for the one-pot synthesis of tetrahydropyrimidinones from aldehydes, β-diketones and urea/thiourea by using magnesium bromide as an inexpensive and easily available catalyst under solvent-free conditions was described. Compared with the classical Biginelli reaction conditions, this new method has the advantage of good to excellent yields (74%-94%) and short reaction time (45-90 min). The structure of the Biginelli reaction product from β-diketone, salicylaldehyde and urea has been proposed to possess an oxygen-bridge by cyclization (intramolecular Michael-addition).