Ambient-pressure hydrogenation of ketones and aldehydes by a metal-ligand bifunctional catalyst [Cp*Ir(2,2′-bpyO)(H2O)] without using base

An efficient catalytic system for hydrogenation of ketones and aldehydes using a Cp*Ir complex [Cp*Ir(2,2′-bpyO)(H₂O)] bearing a bipyridine-based functional ligand as catalyst has been developed. A wide variety of secondary and primary alcohols were synthesized by the catalyzed hydrogenation of ketones and aldehydes under facile atmospheric-pressure without a base. The catalyst also displays an excellent chemoselectivity towards other carbonyl functionalities and unsaturated motifs. This catalytic system exhibits high activity for hydrogenation of ketones and aldehydes with H₂ gas.     

A Convenient and Selective Palladium‐Catalyzed Aerobic Oxidation of Alcohols

An efficient procedure for the oxidation of primary and secondary alcohols to aldehydes and ketones, respectively, with molecular oxygen under ambient conditions has been achieved. By applying catalytic amounts of Pd(OAc)₂ in the presence of tertiary phosphine oxides (O?PR₃) as ligands, a variety of substrates are selectively oxidized without formation of ester byproducts. Spectroscopic investigations and DFT calculations suggest stabilization of the active palladium(II) catalyst by phosphine oxide ligands.     

超临界二氧化碳中功能化聚乙二醇稳定的钯纳米粒子催化醇的选择氧化反应

 以超临界二氧化碳 (scCO2)/聚乙二醇 (PEG) 两相为反应介质, 双齿氮配体功能化聚乙二醇稳定的 Pd 纳米颗粒作为催化剂, 进行了醇的需氧氧化反应. 系统研究了催化剂制备条件和反应条件对苯甲醇需氧氧化反应的影响. 结果表明, 以氢气为还原剂制备的 Pd 纳米粒子的催化活性最高. 反应结束后, 可以利用 scCO2 直接进行原位萃取得到产物, 实现了催化剂与产物的有效分离和催化剂的循环使用. 反应中没有检测到钯的流失. 催化剂经过 5 次循环利用后转化率仍可达 98%.     

An Efficient Selective Oxidation of Alcohols with Zinc Zirconium Phosphate under Solvent‐free Conditions

Zinc zirconium phosphate (ZPZn) nanoparticles have been used as an efficient catalyst for the selective oxidation of a wide range of alcohols to their corresponding ketones or aldehydes using H₂O₂ as an oxidizing agent without any organic solvent, phase transfer catalyst, or additive. The steric factors associated with the substrates had a significant influence on the reaction conditions. The results showed that this method can be applied for chemoselective oxidation of benzyl alcohols in the presence of aliphatic alcohols. The catalyst used in the current study was characterized by ICP‐OES, XRD, N₂ adsorption‐desorption, NH₃‐TPD, Py‐FTIR, SEM, and TEM. These analyses revealed that the interlayer distance in the catalyst increased from 7.5 to 8.7 Å when Zn²⁺ was intercalated between the layers, whereas the crystallinity of the material was reduced. This nanocatalyst could also be recovered and reused at least seven times without any discernible decrease in its catalytic activity. This new method for the oxidation of alcohols has several key advantages, including mild and environmentally friendly reaction conditions, excellent yields and a facile work‐up.     

3-BocNH-ABNO-catalyzed aerobic oxidation of alcohol at room temperature and atmospheric pressure

A transition-metal-free catalytic system has been developed for selective transformation of alcohol to aldehydes or ketones. The reactions were performed with 3-(tert-butoxycarbonylamino)-9-azabicyclo[3.3.1]nonane N-oxyl (3-BocNH-ABNO) as the catalyst, NaNO₂ as the co-catalyst, molecular oxygen as the terminal oxidant, and AcOH as the solvent under room temperature. This catalytic system exhibited broad functional group tolerance. A series of alcohol substrates, including primary and secondary benzylic alcohols, heteroaromatic analogues, primary and secondary aliphatic alcohols, could be converted into their corresponding aldehydes and ketones in good conversions and selectivities.     

Na4H3[SiW9Al3(H2O)3O37]·12H2O/H2O: a new system for selective oxidation of alcohols with H2O2 as oxidant

This work describes a catalytic system consisting of both Na₄H₃[SiW₉Al₃(H₂O)₃O₃₇]·12H₂O(SiW₉Al₃) and water as solvents (a small quantity of organic solvents were used as co-solvent for a few substrates) that can be good for selective oxidation of alcohols to ketones (aldehydes) using 30% H₂O₂ without any phase-transfer catalyst under mild reaction conditions. The catalyst system allows easy product/catalyst separation. Under the given conditions, the secondary hydroxyl group was highly chemoselectively oxidized to the corresponding ketones in good yields in the presence of primary hydroxyl group within the same molecule, and hydroxides are selectively oxidized even in the presence of alkene. Benzylic alcohols were selectively oxidized to the corresponding benzaldehydes in good yields without over oxidation products in solvent-free conditions. Nitrogen, oxygen, sulfur-based moieties, at least for the cases where these atoms are not susceptible to oxidation, do not interfere with the catalytic alcohol oxidation.     

Manganese oxide nanoparticles supported on graphene oxide as an efficient nanocatalyst for the synthesis of 1,2,4-oxadiazoles from aldehydes

The easy synthesis of graphene oxide (GO)-supported manganese dioxide (MnO₂) nanoparticles as a stable heterogeneous nanocatalyst (MnO₂@GO) is described. This catalyst was investigated in the synthesis of 1,2,4-oxadiazoles from amidoximes and aldehydes via a cyclization and oxidation process. The nanocomposite was prepared and characterized using various techniques. The catalytic application of the nanocomposite was examined in the reaction of a variety of aldehydes with aliphatic and aromatic amidoximes. The stable and robust catalyst was recycled for seven consecutive runs without a significant decrease in the catalytic activity.     

Synthesis,structural characterization and alcohol oxidation activity of a new mononuclear manganese(II) complex

A manganese(II) complex of 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) has been synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR, and UV–Vis spectroscopic techniques. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted by this catalyst using oxone (2KHSO₅·KHSO₄·K₂SO₄) as an oxidant under biphasic reaction conditions (CH₂Cl₂/H₂O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature. Easy preparation, mild reaction conditions, high yields of the products, short reaction times, no further oxidation to the corresponding carboxylic acids, high selectivity and inexpensive reagents make this catalytic system a useful oxidation method for aliphatic and benzylic alcohols.     

MgBr2 supported on Fe3O4@SiO2 ~ urea nanoparticle: An efficient catalyst for ortho‐formylation of phenols and oxidation of benzylic alcohols

Urea was successfully immobilized on the surface of chloropropyl‐modified Fe₃O₄@SiO₂ core–shell magnetic nanoparticles, then supported by MgBr₂ and acts as a unique catalyst for oxidation of benzylic alcohols to aldehydes and ketones, and ortho‐formylation of phenols to salicylaldehydes. The prepared catalyst was characterized by FT‐IR, transmission electron microscopy, scanning electron microscopy, X‐ray powder diffraction, dispersive X‐ray spectroscopy, CHN and TGA. It was found that Fe₃O₄@SiO₂ ~ urea/MgBr₂ showed higher catalytic activity than homogenous MgBr₂, and could be reused several times without significant loss of activity.     

Br?nsted-acidic ionic liquid [HO3S(CH2)4MIM][HSO4] as efficient and reusable catalyst for one-pot synthesis of β-acetamido ketones

Abstract  

Efficient and convenient synthesis of β-acetamido ketones has been achieved by one-pot reaction of acetophenone, aryl aldehydes, acetyl chloride, and acetonitrile in the presence of 3-methyl-1-(4-sulfonylbutyl)imidazolium hydrogensulfate [HO₃S(CH₂)₄MIM][HSO₄], a Br?nsted-acidic ionic liquid, as a green and reusable catalyst in solvent-free media at room temperature. The catalyst could be recycled and reused without noticeable decrease in catalytic activity.     

Ceria/vinylpyridine polymer nanocomposite: an ecofriendly catalyst for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones

The three-component condensation of aldehydes, β-ketoesters and urea has been carried out in water using ceria (cerium oxide, CeO₂) nanoparticles supported on poly(4vp-co-dvb) as a catalyst for the preparation of 3,4-dihydropyrimidin-2(1H)-ones in good yields. The catalyst was recovered easily and reused without loss of its activity.     

通过CeOx修饰提高金纳米颗粒在CO氧化反应中的催化活性和耐久性

CO催化氧化是一个重要的经典反应,与许多应用息息相关,包括痕量CO气体检测、汽车尾气净化和安全防护等,吸引了人们广泛的研究兴趣.负载型Au纳米颗粒在CO氧化等许多反应中有着与众不同的催化活性,具有广泛的应用前景,但依然存在着稳定性差、易团聚失活的问题.人们通过应用多孔载体隔离Au纳米颗粒,在Au纳米颗粒表面覆盖金属氧化物、二氧化硅或碳,以及对Au纳米粒子进行封装等方法解决这些问题.尤其是利用金属氧化物与Au纳米粒子间的强相互作用对其进行覆盖或封装,有效地提高了Au催化材料的稳定性.但以上策略操作流程复杂,不利于应用.本文发展了一种简单有效的方法,通过EDTA的络合作用引入CeOx对Au纳米粒子进行修饰,得到的CeOx@Au/SiO2催化剂活性和耐久性明显提升.采用X射线衍射(XRD)和高分辨透射电子显微镜(HRTEM)证明了CeOx成功地修饰在Au纳米颗粒上.且通过EDTA引入CeOx所制备的CeOx@Au/SiO2催化剂结构明显不同于直接加入纳米CeO2所得到的CeOx-Au/SiO2的结构.EDTA的络合作用能有效地连结Ce与Au物种,经焙烧消除EDTA后,加强了CeOx与Au间相互作用,最终在Au纳米粒子表面形成丰富的CeOx颗粒与原子级厚度的CeOx层.进一步应用X射线光电子能谱(XPS)和氢气程序升温还原(H2-TPR)等手段研究了CeOx修饰对Au纳米粒子的影响.XPS结果表明,CeOx@Au/SiO2催化剂带正电的Au+和Au3+的浓度明显高于一般的Au/SiO2和直接加入CeO2制备得到的CeOx-Au/SiO2催化剂.H2-TPR同样表明,CeOx修饰调变了Au纳米粒子的氧化还原性.这些均对其在CO催化氧化反应中的催化活性具有重要影响将CeOx@Au/SiO2催化剂用于CO催化氧化反应中,160°C时,CO转化率达98.8％,至180°C后实现了CO的完全转化.而一般的Au/SiO2催化剂在160°C时CO转化率仅为4.0％,CO的完全转化则需340°C.直接加入纳米CeO2所得到的CeOx-Au/SiO2催化剂,其催化活性略有提升,CO完全转化所需的温度为300°C.这充分证明了通过CeOx修饰Au纳米粒子,能有效提升其催化活性.原位漫反射红外光谱(DRIFT)结果表明,CeOx修饰促进了CO在Au表面的吸附,并能形成[Au(CO)2]δ+物种;同时还观察到大量的单齿CO32? 物种信号,反映了CeOx@Au/SiO2催化剂表面存在丰富的活性氧物种.通入O2后,观察到了大量CO32?物种信号和气相CO2,印证了催化剂表面发生的CO催化氧化过程,也表明其具有非常高的催化活性.考察了CeOx@Au/SiO2催化剂的耐久性,发现经50 h CO氧化反应,催化剂依然能有效保持活性.相比之下,Au/SiO2催化剂经10 h反应后,开始明显失活.由此可见,CeOx@Au/SiO2催化剂具有相当高的耐久性.在600°C将催化剂焙烧3 h,发现Au/SiO2催化剂中Au纳米粒子存在明显团聚现象,而CeOx@Au/SiO2催化剂的Au纳米粒子依然均匀分布在载体表面,且粒径未发生明显变化.     

Selective oxidation of alcohols over copper zirconium phosphate

The catalytic activity of copper zirconium phosphate (ZPCu) in the selective oxidation of alcohols to their corresponding ketones or aldehydes, using H₂O₂ as an oxidizing agent, was studied. The oxidation reaction was performed without any organic solvent, phase-transfer catalyst, or additive. Steric factors associated with the substrates influenced the reaction. The catalyst was characterized using X-ray diffraction, inductively coupled plasma atomic emission spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. It was shown that the interlayer distance increased from 0.74 to 0.80 nm and the crystallinity was reduced after Cu²⁺ intercalation into the layers. This catalyst can be recovered and reused three times without significant loss of activity and selectivity.     

Investigation of catalytic properties of two new orthopalladated complexes supported on montmorillonite: Synthesis,characterization and application in aerobic oxidation of alcohols

Two new complexes, [Pd(L₁)(C,N)]NO₃ ( 1 ) and [Pd(L₂)(C,N)]NO₃ ( 2 ) (L₁ = 5‐nitro‐1,10‐phenanthroline, L₂ = 4‐methyl‐1,10‐phenanthroline, C,N = benzylamine), have been synthesized and characterized using infrared and NMR spectroscopies and elemental analysis. Montmorillonite (MMT‐K10 clay) was used as a solid support for incorporating the cationic part of complexes 1 and 2 to produce catalysts 1 and 2 , respectively, as heterogeneous catalysts. Catalyst 1 was identified using powder X‐ray diffraction and scanning and transmission electron microscopies, and the content of palladium obtained from inductively coupled plasma analysis. By changing the electron‐donating group on the L₁ ligand with an electron‐withdrawing one, a minor improvement was observed in the catalytic properties. Catalyst 1 showed better efficiency for oxidation of benzyl alcohol in comparison with catalyst 2 , so catalyst 1 was used for the aerobic oxidation of alcohols to corresponding aldehydes or ketones without over‐oxidation (with and without bubbling of air). This catalytic system showed high activity towards alcohols under mild conditions. Finally, the reusability of catalyst 1 was investigated with multiple reuses of the supported catalyst in subsequent alcohol oxidation reactions.     

Synthesis and characterization of sulfamic acid supported on Fe3O4 nanoparticles: A green,versatile and magnetically separable acidic catalyst for oxidation reactions and Knoevenagel condensation

Sulfamic acid immobilized on diethylenetriamine functionalized Fe₃O₄ nanoparticles (SA‐DETA‐Fe₃O₄) was successfully prepared and characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), vibrating sample magnetometer (VSM), thermo gravimetric analysis (TGA), X‐Ray diffraction (XRD) and scanning electron microscopy (SEM). The sulfamic acid was found as a magnetically separable and highly active catalyst for the oxidative coupling thiols, oxidation of sulfides. Furthermore, the SA‐DETA‐Fe₃O₄ showed the high catalytic activity in Knoevenagel condensation of aromatic aldehydes with active methylene compounds (malononitrile and ethyl cynoacetate). The nanosolid catalyst could be easily recovered by a simple magnetic separation and reused for many cycles without deterioration in catalytic activity.     

Porous chitosan–MnO2 nanohybrid: a green and biodegradable heterogeneous catalyst for aerobic oxidation of alkylarenes and alcohols

A porous chitosan–manganese dioxide (PC–MnO₂) nanohybrid was synthesized using an in situ reduction method, in which potassium permanganate solution and nanoporous chitosan acted as precursor and reducing agent. The chemical and structural properties of PC–MnO₂ were characterized using scanning and transmission electron microscopies, X‐ray diffraction, thermogravimetric analysis and Fourier transform infrared spectroscopy. Highly dispersed MnO₂ nanoparticles in a matrix of porous chitosan showed high catalytic activity for selective aerobic oxidation of alkylarenes and alcohols without using any bases or expensive oxidants. Short reaction time, ease of product separation by filtration and recyclability of the catalyst make it environmentally and economically favoured for the synthesis of versatile aldehydes and ketones. Copyright © 2015 John Wiley & Sons, Ltd.     

HAlMCM-41介孔分子筛催化1,3-苯并二噁茂烷合成的研究

研究了HAlMCM-41分子筛催化邻苯二酚与环己酮、丁酮、丙酮、丙醛、丁醛、异丁醛、戊醛、正己醛、正辛醛、苯甲醛、二苯甲酮等十余种醛(酮)的缩合反应. 考察了反应时间、酚与醛(酮)的配比、HAlMCM-41分子筛用量、硅铝比、催化剂重用次数等因素对邻苯二酚与醛(酮)反应的影响. 结果表明, 当邻苯二酚与醛(酮)物质的量比为1∶1.4, 催化剂用量为3.5 g/mol邻苯二酚, 反应4 h, 分子筛n(SiO₂)/n(Al₂O₃)为15时, 选择性一般在99.4%以上, 转化率也一般在85.6%以上, 因此, HAlMCM-41分子筛对邻苯二酚与醛(酮)的反应有较好的催化性能.     

Aerobic oxidation of alcohols to aldehydes and ketones using ruthenium(III)/Et3N catalyst

A simple, efficient method for oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones has been developed. Using RuCl₃/Et₃N as catalyst, the oxidation of benzyl alcohol with oxygen could be achieved with 332 h⁻¹ turnover frequency in the absence of solvent. The influence of versatile N‐containing additives on the catalytic efficiency has been discussed. The presence of minor water would substantially promote the catalytic efficiency, and its role in catalysis has been investigated in detail. The insensitive Hammett correlations of the substituted benzyl alcohols, the normal substrate isotope effect (k_H/k_D = 3.5 at 335 K), and the linear relationship between O₂ pressure and turnover frequency imply that the reoxidation of the Ru(III) hydride intermediate to the active species shares the rate‐determining step with the hydride transfer in the catalytic cycle. Copyright © 2011 John Wiley & Sons, Ltd.     

Fe3O4@L‐arginine magnetic nanoparticles: A novel and magnetically retrievable catalyst for the synthesis of 1′3‐diaryl‐2N‐azaphenalene

The catalytic activity of l ‐arginine‐coated nano‐Fe₃O₄ particles (Fe₃O₄@l ‐arginine) proves they are a novel magnetic catalyst without the use of heat and reflux for the synthesis of 1,3‐diaryl‐2‐N‐azaphenalene derivatives and n‐acyl‐1,3‐diaryl‐2‐N‐azaphenylene derivatives in a one‐pot pseudo‐five‐component condensation reaction of compounds of 2,7‐naphthalene diol, aldehydes, and ammonia derivatives (ammonium acetate or ammonium hydrogen phosphate) and solvent (water and alcohol) with high yield and short reaction times, economical, and simple workup. The structure and magnetic properties of the obtained nanoparticles were characterized via Fourier transform infrared spectroscopy (IR) and field emission scanning electron microscopy (FE‐SEM). The results demonstrated that the average size of the synthesized magnetite nanoparticles is about 21 nm. In addition, the heterogeneous catalyst can be easily recovered magnetically and can be reused for further runs without significant loss of its catalytic activity.     

Nano indium oxide: an efficient catalyst for the synthesis of 1,2-disubstituted benzimidazoles in aqueous media

Synthesis of 1,2-disubstituted benzimidazoles has been developed by the condensation of diamine with aldehydes using nano In₂O₃ as an efficient catalyst under mild reaction conditions in aqueous media. The procedure is applicable to aryl, aliphatic, heteroaryl aldehydes. In₂O₃ nanoparticles are recyclable without the loss of significant catalytic activity.