Silica-supported polyphosphoric acid (PPA-SiO2): An efficient and reusable heterogeneous catalyst for ecofriendly organic synthesis

This review discusses the advances in the use of silica-supported polyphosphoric acid (PPA-SiO₂) as a green and reusable heterogeneous catalyst in the preparation of various organic compounds and pharmaceutical intermediates. PPA-SiO₂ could be recovered and reused several times without significant loss of their efficiency. In this review, we attempt to give an overview of the applications of PPA-SiO₂ as a catalyst in condensation, cyclization, and addition reactions for the preparation of various organic compounds.     

高效SnO2纳米片催化剂用于CO氧化

SnO2是一种具有丰富表面缺位氧的n型半导体,其晶格氧亦可还原.另外其熔点高达1630oC,具有较高的热稳定性能.在过去的几十年中, SnO2主要用作气敏材料.而其作为催化材料的性能,特别是用于大气污染治理则鲜见报道.在过去的几年中,本课题组系统研究了SnO2的催化化学,发现利用传统共沉淀法制备的SnO2纳米粉末,在焙烧温度高于500 oC时,其比表面积通常低于20 m2/g,因而限制了其氧化活性.在SnO2晶格中掺杂Fe、Cr、Mn、Ce和Ta等形成固溶体可有效提高其比表面积并产生更多的活性氧物种,因而其对CO和CH4的氧化活性及稳定性大幅度提高.本课题组近期研究结果表明,采用熔盐法制备的高纯SnO2纳米棒单晶比SnO2纳米颗粒和纳米微球等具有更优异的CO氧化活性,260 oC即可完全氧化CO.且在240–260 oC狭窄温度区间发生转化率突跃,表现出类似贵金属的催化行为.值得指出的是, SnO2纳米棒的比表面积(1 m2/g)远低于其他几种形貌的材料,且无活泼氧存在.但研究表明SnO2纳米棒具有优先暴露的(110)活泼晶面,是导致其活性优良的主要原因.另外,我们采用简单共沉淀法成功制备了高比表面介孔Cu-Sn复合氧化物纳米片(196 m2/g),其在140 oC即可将CO完全氧化,且具有优良的抗水失活性能.因此, SnO2的形貌是影响其催化活性的主要因素之一,但迄今未见较系统深入的研究.在上述工作基础上,本文通过水热法,不添加任何有机模板剂,成功制备了厚度约10 nm的介孔SnO2纳米片和纳米棒及纳米颗粒混合物样品;采用常规共沉淀法制备了SnO2纳米颗粒.并将以上三种不同形貌的SnO2纳米材料用于CO氧化.利用SEM、XRD、N2吸附-脱附、H2-TPR和XPS探讨了不同形貌SnO2催化剂的体相结构和表面性质及其对催化性能的影响.与SnO2纳米颗粒相比,介孔SnO2纳米片具有高的比表面积、孔体积及更活泼的氧中心,因此后者CO氧化活性远高于前者.在空速18000 mL/(g·h)时, SnO2纳米片在260 oC即可完全氧化CO.而SnO2纳米颗粒的CO完全氧化温度高于360 oC. SnO2纳米棒和纳米颗粒的混合样品虽然其比表面积和孔体积及表面活性氧的活性仅略高于SnO2纳米颗粒,但XRD定量结果表明,其具有更多的暴露(110)活泼晶面,因而活性也高于SnO2纳米颗粒. SnO2纳米片催化剂的寿命及抗水性能测试结果表明,该催化剂具有良好的稳定性,且水蒸气仅对其活性产生可恢复的影响.进一步优化其性能, SnO2纳米片有可能用于实际汽车尾气状况下的CO催化清除.     

Novel silica-supported molybdic acid (SSMA): an efficient catalyst for the synthesis of new azo dyes

Research on Chemical Intermediates - Silica-supported molybdic acid (SSMA) as a novel and highly efficient catalyst was prepared and characterized by X-ray fluorescence, X-ray diffraction, and...     

Design of chiral tin(IV) aryloxide as a mild Lewis acid catalyst for enantioselective Diels-Alder reaction

A novel Sn(IV) aryloxide Lewis acid has been designed and prepared from SnCl₄ and (S)-3,3′-bis(3,5-bis(trifluoromethyl)phenyl)-1,1′-bi-2-naphthol. The chiral Sn(IV) Lewis acid has been successfully applied to the enantioselective Diels-Alder reaction.     

Silica sulfuric acid: an efficient and reusable catalyst for the one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones

Silica sulfuric acid efficiently catalyzes the three-component Biginelli reaction between an aldehyde, a β-dicarbonyl compound and urea or thiourea in refluxing ethanol to afford the corresponding dihydropyrimidinones in high yields. The catalyst is reusable and can be applied several times without any decrease in the yield of the reactions.     

Palladium(0) nanoparticles: an efficient catalyst for the one-pot synthesis of polyhydroquinolines

A mild, concise, and efficient protocol for the synthesis of polyhydroquinoline via four component reaction of aromatic aldehydes, dimedone, ethyl acetoacetate or ethyl cyanoacetate, and ammonium acetate using Pd-nanoparticles is described. The same phenomenon was observed in the case of arylmethylene bis(3-hydroxy-2-cyclohexene-1-ones), ethyl acetoacetate, ammonium acetate, and Pd-nanoparticles in one-pot. The present method also allows us to synthesize highly functionalized title compounds from simple and readily available inputs.     

A thermal synthesis of a new tin(IV) dithiocarbamate

A new tin dithiocarbamate containing sulphur bridges, di--sulphidobis [bis(N,N-diethyldithiocarbamato)tin(IV)], has been isolated from the thermal decomposition of tetrakis(N,N-diethyldithiocarbamato)tin(IV). A dimeric structure is proposed on the basis of results from mass spectrometry, infrared spectroscopy, thermal analysis and vapour pressure osmometry.

---

Zusammenfassung Ein neues, Schwefelbrücken enthaltendes Zinn-Dithiocarbamat, Di--sulfidobis[bis(N,N-diäthyldithiocarbamato)Zinn(IV)], wurde bei der Zersetzung von Tetrakis(N,N-diäthyl-dithiocarbamato)Zinn(IV) isoliert. Aufgrund der Ergebnisse der Massenspektrometrie, der Infrarotspektroskopie, der Thermoanalyse und der Dampfdruck-Osmometrie wird eine Dimerstruktur vorgeschlagen.

---

Résumé Un nouveau dithiocarbamate d'étain contenant des ponts de soufre, le di--sulfidobis[bis(N,N-diéthyl-dithiocarbamato)é tain(IV)], a été isolé lors de la décomposition thermique du tétrakis(N,N-diethyl-dithiocarbamato) étain(IV). Une structure dimère est proposéeà partir des résultats obtenus par spectrométrie de masse, spectroscopie infrarouge, analyse thermique et osmométrie sous pression de vapeur.

---

—-- [/N,N- (/IV)], [/N,N- (/IV)], , (N,N- ) (IV). - , , .

---

---

The authors gratefully acknowledge the assistance given by Dr. A. G. Wedd with the vacuum sublimation technique. One of us, G. K. B., is grateful for a research scholarship provided by La Trobe University.     

Silica supported phosphomolybdic acid: an efficient heterogeneous catalyst for Friedlander synthesis of quinolines

Silica supported phosphomolybdic acid, an eco-friendly heterogeneous catalyst, has been found to be highly efficient for Friedlander synthesis of quinolines in excellent yields. A variety of ketones afford the quinolines smoothly. The catalyst can be easily recovered and reused.     

A Keggin heteropoly acid as an efficient catalyst for an expeditious, one-pot synthesis of 1-methyl-2-(hetero)arylbenzimidazoles

The Keggin heteropoly acid, silicotungstic acid, H₄SiW₁₂O₄₀, has been demonstrated to be highly efficient for an expeditious, one-pot synthesis of 1-methyl-2-(hetero)arylbenzimidazoles from N-methyl-1,2-phenylenediamine and (hetero)aryl aldehydes in ethyl acetate at room temperature. The catalyst works equally well for N-phenyl-1,2-phenylenediamine.     

Sulfamic acid: an efficient, cost-effective and recyclable solid acid catalyst for the Friedlander quinoline synthesis

o-Aminoaryl ketones undergo smooth condensation with α-methylene ketones in the presence of sulfamic acid (NH₂SO₃H) (SA) under mild reaction conditions to afford the corresponding polysubstituted quinolines in excellent yields. The catalyst can be recovered by simple filtration and can be recycled in subsequent reactions. The method is simple, cost-effective and environmentally benign.     

Zirconium(IV) 4-sulphophenylethyliminobismethylphosphonate as an efficient and reusable catalyst for one-pot synthesis of 3,4-dihydropyrimidones under solvent-free conditions

Zirconium(IV) 4-sulphophenylethyliminobismethylphosphonate (ZSBEDP) was prepared and characterised by elemental analysis, IR, TG-DSC, and XRD. ZSBEDP was found to be an efficient catalyst for the Biginelli reaction of aromatic aldehyde, ethyl acetoacetate, and urea or thiourea under solvent-free conditions so as to give 3,4-dihydropyrimidones in good to excellent yields. The catalyst can be separated by simple filtration and reused without significant loss of its catalytic activity.     

Efficient dehydration of carbohydrates to 5-hydroxymethylfurfural in ionic liquids catalyzed by tin(Ⅳ) phosphonate and zirconium phosphonate

In this work,we synthesized tin(IV)phosphonate(SnBPMA)and zirconium phosphonate(ZrBPMA)by the reaction of SnCl4·5H2O or ZrOCl2·8H2O with N,N-bis(phosphonomethyl)aminoacetic acid,which was synthesized from a biomaterial glycine through a Mannich-type reaction.The SnBPMA and ZrBPMA were very efficient heterogeneous catalysts for the dehydration of fructose to produce 5-hydroxymethylfurfural(HMF),and the SnBPMA had higher activity than the ZrBPMA.The effects of solvents,temperature,reaction time,and reactant/solvent weight ratio on the reaction catalyzed by SnBPMA were investigated.It was demonstrated that the yield of HMF could reach 86.5%with 1-ethyl-3-methylimidazolium bromide([Emim]Br)as solvent,and the SnBPMA and SnBPMA/[Emim]Br catalytic system could be reused five times without considerable reduction in catalytic efficiency.Further study indicated that the SnBPMA and ZrBPMA in[Emim]Br were also effective for the dehydration of sucrose and inulin to produce HMF with satisfactory yields.     

The Pd3(dppm)3(CO)2+ cluster: an efficient electrochemically assisted Lewis acid catalyst for the fluorination and alcoholysis of acyl chlorides

The dicationic palladium cluster Pd3(dppm)3(CO)2+ (dppm = bis(diphenylphosphino)methane) reacts with acid chlorides RCOCl (R = n-C6H13, t-Bu, Ph) to afford quantitatively the chloride adduct Pd3(dppm)3(CO)(Cl)+ and the acyl cation RCO+ as the organic counterpart. The dicationic reactive cluster can be reformed by electrolyzing the chloride complex with a copper anode leaving CuCl as a byproduct. The combination of these two reactions provides an electrocatalytic way to form the acylium from the acid chloride. Indeed, in CH2Cl2, 0.2 M NBu4PF6, or NBu4BF4, the electrolysis of the acid chloride in the presence of a catalytic amount of the cluster (1%) gives in good yields the acid fluoride RCOF, arising from the coupling of the acylium with a F(-) issued from the fluorinated supporting electrolyte. Alternatively, in CH2Cl2 or 0.2 M NBu4ClO4, by operating with an alcohol R'OH as the nucleophile, the electrolysis gives the ester RC(O)OR' as the only final product.     

Direct assembly synthesis of metal complex-semiconductor hybrid photocatalysts anchored by phosphonate for highly efficient CO2 reduction

Hybrid photocatalysts consisting of a ruthenium complex and p-type photoactive N-doped Ta(2)O(5) anchored with an organic group were successfully synthesized by a direct assembly method. The photocatalyst anchored by phosphonate exhibited excellent photoconversion activity of CO(2) to formic acid under visible-light irradiation with respect to the reaction rate and stability.     

Extraction chromatography with bis(2-ethylhexyl)phosphoric acid for separation of tin(IV)

Tin is extracted from 0.01M hydrochloric acid on a silica-gel column impregnated with bis(2-ethylhexyl)phosphoric acid, stripped with 5M hydrochloric acid, and then determined spectrophotometrically as its Pyrocatechol Violet complex at 555 nm. Tin has been separated from several multicomponent mixtures containing arsenic, antimony, bismuth, lead and copper, and determined in various alloys.     

Organotin and tin(IV) derivatives of dimethyldithioarsinic acid

Organotin derivatives of dimethyldithioarsinic (dithocacodylic) acid have been obtained from the appropriate organotin chloride and the sodium salt of the latter. Tin(IV) chloride and NaS₂AsMe₂ · 2 H₂O yielded only two products, namely Cl₂Sn(S₂AsMe₂)₂ and Sn (S₂AsMe₂)₄, regardless of the reagent ratio. Spectroscopic characterization of the compounds (infrared and¹H NMR) provides structural information suggesting that the dimethyldithioarsinato group behaves as monodentate (or anisobidentate) ligand in Me₂Sn(S₂AsMe₂)₂, Bu₂Sn-(S₂AsMe₂)₂ and Cy₃Sn(S₂AsMe₂), as bidentate in Ph₂Sn(S₂AsMe₂)₂, Ph₃Sn(S₂AsMe₂) and Cl₂As(S₂AsMe₂)₂, whereas Sn(S₂AsMe₂)₄ contains both mono- and bidentate ligands, presumably in a six-coordinate structure.     

Nanoporous aluminosilicate catalyst with 3D cage-type porous structure as an efficient catalyst for the synthesis of benzimidazole derivatives

Herein we demonstrate for the first time, the synthesis of benzimidazoles through the coupling of aldehydes with o-phenylenediamine by using highly acidic nanoporous aluminosilicate with 3D structure and cage-type pores as the catalyst. The catalyst resulted in excellent yields in short reaction times presumably due to its high acidity, large pore diameter, high surface area, and cage-type 3D porous structure.