Efficient deprotection of N-benzyloxycarbonyl group from amino acids by hydroxyapatite-bound Pd catalyst in the presence of molecular hydrogen

Hydroxyapatite-bound Pd catalyst was found to be highly effective for the deprotection of N-benzyloxycarbonyl group from amino acids in the presence of molecular hydrogen. The catalyst was also applicable to the hydrogenolysis of a sterically encumbered core-Z-protected poly(amido amine) dendrimer, affording the dendritic amino compound in 99% yield.     

Ligandless C‐C bond formation via Suzuki–Miyaura reaction in micelles or water–ethanol solution using PdPtZn and PdZn nanoparticle thin films

PdPtZn and PdZn nanoparticle (NP) thin films were synthesized by the reduction of [PdCl₂(cod)], [PtCl₂(cod)] (cod = cis,cis‐1,5‐cyclooctadiene) and [Zn(acac)₂] (acac = acetylacetonate) complexes at an oil–water interface. The structure and morphology of the as‐prepared NPs were characterized with X‐ray diffraction, transmission electron microscopy and energy dispersive analysis of X‐rays. Catalytic activity of the prepared NPs was investigated in the Suzuki–Miyaura cross‐coupling reaction in H₂O–EtOH and various micellar media systems such as cetyltrimethylammonium bromide (cationic surfactant), sodium dodecylsulfate (anionic surfactant) and Pluronic P123 (non‐ionic surfactant). PdPtZn and PdZn thin films exhibited higher catalytic activity compared to Pd thin film in the Suzuki–Miyaura coupling reaction due to the appropriate interaction between palladium, platinum and zinc metals. Copyright © 2015 John Wiley & Sons, Ltd.     

Environmentally friendly one-pot synthesis of alpha-alkylated nitriles using hydrotalcite-supported metal species as multifunctional solid catalysts

A ruthenium-grafted hydrotalcite (Ru/HT) and hydrotalcite-supported palladium nanoparticles (Pd(nano)/HT) are easily prepared by treating basic layered double hydroxide, hydrotalcite (HT, Mg(6)Al(2)(OH)(16)CO(3)) with aqueous RuCl(3)n H(2)O and K(2)[PdCl(4)] solutions, respectively, using surface impregnation methods. Analysis by means of X-ray diffraction, and energy-dispersive X-ray, electron paramagnetic resonance, and X-ray absorption fine structure spectroscopies proves that a monomeric Ru(IV) species is grafted onto the surface of the HT. Meanwhile, after reduction of a surface-isolated Pd(II) species, highly dispersed Pd nanoclusters with a mean diameter of about 70 A is observed on the Pd(nano)/HT surface by transmission electron microscopy analysis. These hydrotalcite-supported metal catalysts can effectively promote alpha-alkylation reactions of various nitriles with primary alcohols or carbonyl compounds through tandem reactions consisting of metal-catalyzed oxidation and reduction, and an aldol reaction promoted by the base sites of the HT. In these catalytic alpha-alkylations, homogeneous bases are unnecessary and the only by-product is water. Additionally, these catalyst systems are applicable to one-pot syntheses of glutaronitrile derivatives.     

Carbon–carbon bond formation between secondary alcohols and aldehydes under ruthenium‐catalyzed redox shuttle

Secondary alcohols are coupled with aldehydes in dioxane in the presence of a catalytic amount of a ruthenium catalyst along with KOH to give coupled ketones or coupled secondary alcohols depending on the molar ratio of secondary alcohols to aldehydes and the presence (or absence) of a sacrificial hydrogen acceptor. Copyright © 2011 John Wiley & Sons, Ltd.     

A heterometal (Pd–Pb) organic framework: synthesis,structure and heterogeneous catalytic application

A heterometallic organic framework {Pb[Pd(bpydc)Cl₂]DMF}_n ( 1 ) (H₂bpydc = 2,2′‐bipyridine‐5,5′‐dicarboxylic acid) was synthesized via a one‐pot solvothermal method and characterized using thermogravimetric analysis, X‐ray photoelectron spectroscopy as well as powder and single‐crystal X‐ray diffraction. The crystal structure of 1 indicates that, in metalloligand Pd(bpydc)Cl₂, every Pd atom adopts a square planar coordination mode with two chloride ions and two nitrogen atoms from bpydc, and the carboxyl groups of Pd(bpydc)Cl₂ connect Pb atoms to form a one‐dimensional chain along the crystallographic a‐axis, which is interlinked via metalloligands to form a two‐dimensional layer structure. This complex is highly active, stable and recyclable as a catalyst for the Suzuki–Miyaura and Heck reactions of a wide range of aryl halides including electron‐rich and electron‐poor aryl iodides/bromides, affording the corresponding products in good to excellent yields. Copyright © 2016 John Wiley & Sons, Ltd.     

Design of catalysts based on electrochemical microcell models

The concept and the strategy for designing catalytic systems on the basis of electrochemical microcell models have been proposed and demonstrated for Wacker-type oxidation of ethylene, selective hydrogenation of nitric oxide into hydroxylamine and partial oxidation of alkenes and alkanes. For designing active and selective catalysts, at least four fundamental catalytic elements are required. These are (1) the oxidation sites (anode), (2) the reduction sites (cathode), (3) proton conducting medium, and (4) electron conducting medium. The catalytic elements (3) and (4) would electrochemically connect the oxidation (anode reaction) on site (1) and the reduction (cathode reaction) on site (2). A mixture of these four catalytic elements generates an unlimited number of microcells which work as catalysts for desired synthetic reactions.     

Characteristic reactions of group 9 transition metal compounds in organic synthesis

Group 9 metal compounds in organic synthesis have two characteristic reactions. The first occurs because the group 9 metals have a high affinity to carbon–carbon or carbon–nitrogen π‐bonds. The first type of characteristic reactions in these group 9 metal compounds includes Pauson–Khand reactions, the Pauson–Khand‐type reactions ([2 + 2 + 1] cyclization), the other cyclizations and coupling reactions. The second occurs because the group 9 metals have a high affinity to carbonyl groups. The second type of characteristic reactions includes carbonylations such as hydroformylations, the carbonylations of methanol, amidocarbonylations and other carbonylations. The first characteristic reactions are applied for the synthesis of fine chemicals such as pharmaceuticals and agrochemicals. However, the second characteristic reactions are utilized not only for fine chemicals but also for important bulk commodity chemicals such as aldehydes, carboxylic acids and alcohols. Copyright © 2009 John Wiley & Sons, Ltd.     

New insights into the palladium-catalysed synthesis of δ-lactones from 1,3-dienes and carbon dioxide

Two-coordinate Pd(0) complexes are shown to be important intermediates in the telomerization of 1,3-dienes and CO₂ using palladium/phosphine catalysts without additives. Only one phosphorus atom is bound to palladium during the C–C bond forming steps, but the second phosphorus atom is crucial in the early stages of the catalytic cycle and for the elimination of the product. A ligand that gave an active palladium catalyst for the coupling of 1,3-butadiene and CO₂ has been designed. Use of a palladium catalyst in the reaction of isoprene with CO₂ allowed for the first time isolation and NMR spectroscopic characterization of the resulting mixture of lactones.     

Reaction mechanism of aerobic oxidation of alcohols conducted on activated-carbon-supported cobalt oxide catalysts

Catalytic performances and the reaction mechanism of Co(3)O(4)/AC (AC=activated carbon) for aerobic oxidation of alcohols carried out in the liquid phase were investigated. Co(3)O(4)/AC shows a high activity for aerobic oxidation of benzyl alcohol, comparable to noble metal catalysts (e.g., Au/AC) even in the absence of additives or promoters (e.g., NaOH). Changing preparation conditions, such as treatment temperature and/or time, can affect the catalytic performances of Co(3)O(4)/AC, due to decomposition of surface groups of the carbon support. Careful studies show that low alcohol conversions are obtained with either Co(3)O(4) or AC alone, which indicates that the high conversion observed over the Co(3)O(4)/AC is due to a synergistic effect between Co(3)O(4) and AC. Parallel experiments using a high-surface-area covalent triazine framework or oxygen-inert carbon nitride as support for the Co(3)O(4) catalyst also show lower conversions, which suggest that the ability of AC (in Co(3)O(4)/AC) to activate molecular oxygen is essential for the reaction. FTIR and XPS spectra taken from catalysts before and after the reaction confirm that oxygen activation proceeds mainly on the carbon support. As a result, it can be assumed that the alcohol dehydrogenation step proceeds on the metal oxide, whereas the oxygen activation step occurs mainly on the carbon support.     

Direct synthesis of Fe(III) immobilized Zr‐based metal–organic framework for aerobic oxidation reaction

A Zr‐based metal–organic framework with bipyridine units (UiO‐67) has been utilized for the immobilization of catalytically active iron species via a post‐synthetic metalation method. UiO‐67 bipyridine MOF was synthesized through a simple solvothermal method and was shown to have a UiO‐type structure. Post‐synthetic metalation of UiO‐67 MOF was performed for the immobilization of the catalytically active FeCl₃. FT‐IR and EDX element map suggested that FeCl₃ is coordinately bonded to the UiO‐67 bipyridine framework. The synthesized UiO‐67‐FeCl₃ catalyst was used for the aerobic oxidation of alcohols and benzylic compounds in the presence of molecular oxygen. In addition, the UiO‐67‐FeCl₃ catalyst can be reused as a solid heterogeneous catalyst without compromising its activity and selectivity.     

Mizoroki–Heck and Suzuki–Miyaura reactions mediated by poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐stabilized magnetically separable palladium catalyst

The purpose of this work was to synthesize and characterize a new magnetic polymer nanosphere‐supported palladium(II) acetate catalyst for reactions requiring harsh conditions. In this regard, an air‐stable, moisture‐stable and highly efficient heterogenized palladium was synthesized by the coordination of palladium(II) acetate with poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐grafted modified magnetic nanoparticles with a core–shell structure. The structure of the newly developed catalyst was characterized using various techniques. The catalytic activity of the resultant nano‐organometallic catalyst was evaluated in Mizoroki–Heck and Suzuki–Miyaura reactions to afford the corresponding coupling products in good to excellent yields. High selectivity as well as outstanding turnover number (14 143, 4900) and turnover frequency (28 296, 7424) values were recorded for the catalyst in Suzuki–Miyaura and Mizoroki–Heck reactions, respectively. Magnetic separation and recycling of the catalyst for at least six runs became possible without any significant loss of efficiency or any detectable palladium leaching.     

An improved preparation of mesoporous silica‐supported Pd as sustainable catalysts for phosphine‐free Suzuki–Miyaura and Heck coupling reactions

An improved and eco‐friendly procedure has been developed to generate mesoporous silica‐supported palladium nanoparticles (SiO₂@PdNP) that could be used as a sustainable heterogeneous Pd catalyst for phosphine‐free Suzuki–Miyaura and Heck coupling reactions with excellent turnover number and turnover frequency. The presence of Pd on the silica surface was detected by X‐ray diffraction and the structural morphology of SiO₂@PdNP was obtained by transmission electron microscopy. The heterogeneous catalytic system is recyclable and leaching of the metal after the reaction is not apparently observed. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of addition of iron on morphology and catalytic activity of PdCu nanoalloy thin film as catalyst in Sonogashira coupling reaction

Palladium‐supported catalysts are complex assemblies with a challenging preparation. Minor changes in their preparation conditions can affect the activity, selectivity and lifetime of these catalysts. PdCuFe nanoparticle (NP) thin films were supported on reduced graphene oxide (RGO) by the reduction of the organometallic complex [PdCl_2‌(cod)] (cod = cis ,cis ‐1,5‐cyclooctadiene), and [Cu(acac)₂] and [Fe(acac)₃] (acac = acetylacetonate) complexes at a toluene–water interface. We have investigated the application of the liquid–liquid interface method for preparing ultrathin films of catalysts and have evaluated the catalytic activity of the prepared NPs for the Sonogashira coupling reaction in micelle media. Also, we have investigated the effect of the addition of iron on the morphology, size and catalytic activity of PdCu/RGO NPs. Our study shows that both of the prepared catalysts (PdCu/RGO and PdCuFe/RGO) are efficient and recoverable catalysts for the Sonogashira carbon–carbon coupling reaction. This method has advantages compared to other routes, such as short reaction times, high to excellent yields, facile and low‐cost method for the preparation of the catalysts, and easy separation and reusability of the catalysts.     

Self-supported heterogeneous titanium catalysts for enantioselective carbonyl-ene and sulfoxidation reactions

A new strategy for the heterogenization of chiral titanium complexes was developed by the in situ assembly of bridged multitopic BINOL ligands with [Ti(OiPr)4] without using a support. The assembled heterogeneous catalysts (self-supported) showed excellent enantioselectivity in both the carbonyl-ene reaction of alpha-methylstyrene with ethyl glyoxylate (up to 98 % ee) and the oxidation of sulfides (up to >99 % ee). The catalytic performance of these heterogeneous catalytic systems was comparable or even superior to that attained with their homogeneous counterparts. The spacers between the two BINOL units of the ligands in the assembled catalysts had significant impact on the enantioselectivity of the carbonyl-ene reaction. This demonstrates the importance of the supramolecular structures of the assemblies on their catalytic behavior. In the catalysis of sulfoxidation, the self-supported heterogeneous titanium catalysts were highly stable and could be readily recycled and reused for over one month (at least eight cycles) without significant loss of activity and enantioselectivity (up to >99.9 % ee). The features of these self-supported catalysts, such as facile preparation, robust chiral structure of solid-state catalysts, high density of the catalytically active units in the solids, as well as easy recovery and simple recycling, are particularly important in developing methods for the synthesis of optically active compounds in industrial processes.     

铜基非贵金属异相催化剂在环境修复中的应用（英文）

近年来,全球经济和工业高速发展带来的环境问题,不仅严重影响着经济社会的可持续发展,更极大地危害着人类健康.石油化工、医药生产和交通运输等过程产生的气、液、固相污染物可直接或间接造成臭氧层空洞、光化学烟雾及水体污染等重大环境问题.气相污染物中,CO和可挥发性有机物(VOCs)不仅具有生物毒性,更是形成光化学烟雾等大气污染的主要前驱体.NO_x和SO2会造成酸雨的形成,极大地破坏生态系统.工业废水中难分解的有机污染物可对环境造成持续性破坏.而不完全燃烧产生的碳烟颗粒物不仅影响气候和大气环境,同时可导致心血管疾病高发,危害人体健康.源头控制是环境污染治理的关键,而催化净化是当前污染物源头控制最有效的技术之一.因此,设计和开发稳定、高效的环境修复催化剂是科学家们面临的一个关键问题.传统贵金属(Pt,Rh,Pd)催化剂虽然催化活性高,但是存在价格昂贵且易中毒等不足.而过渡金属及其氧化物因具有高活性、价格低廉和高储量等特点有望成为贵金属的替代催化剂.铜是具有3d轨道的过渡金属,有活泼的物理化学性质,是工业中大量应用的有色金属.铜基氧化物因高氧化还原电势和低环境危害被广泛应用于热催化、电催化和光催化.基于文献报道,铜基催化剂主要分为三类:铜氧化物(CuO_x),负载型铜氧化物(CuO_x/support)和固溶体铜氧化物(CuO_x-X).本篇综述首先探讨了铜氧化物的价态、晶体结构、形貌、暴露晶面以及载体与催化剂活性之间的内在联系,阐明铜基催化剂结构与性能的构效关系及高效催化剂的设计原则;继而全面总结了近年来不同类型的铜基材料在催化净化环境污染物中的应用,主要介绍了以下5类反应:CO的催化氧化,NO_x的选择性催化还原(SCR),VOCs的完全燃烧,废水中有机污染物降解,以及碳烟颗粒物催化燃烧.我们深入阐述铜氧化物的催化活性位点和催化机制;分析负载型铜基催化剂的比表面积、分散度、协同作用和界面作用对催化剂的活性和稳定性的影响;阐明固溶体催化剂的独特原子组成设计与性能关系,为高效催化剂设计提供思路.此外,本综述对铜基催化剂在环境催化中的研究现状以及尚未解决的问题进行了剖析与展望.通过铜氧化物表面调控,复合催化剂的界面调控,具有更高稳定性和抗中毒性的高效催化剂有望开发成功,而团簇及单原子铜催化剂也有望在此领域有所突破.     

Iron oxide on carbon‐based supports as efficient catalysts for organic compounds oxidation

For the first time, iron oxide on carbon aerogel, amine functionalized carbon nanotube, black carbon and carboxylic acid functionalized carbon nanotube in the presence of H₂O₂ was reported as an efficient and stable catalyst for the selective oxidation of sulfides and alcohols. The catalysts were characterized by scanning electron microscopy, energy‐dispersive spectroscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. In the next step, catalytic reactivity toward sulfide to sulfoxide and alcohol to aldehyde/ketone oxidation in the presence of H₂O₂ was studied and discussed.     

Palladium nanoparticles deposited on a graphene–benzimidazole support as an efficient and recyclable catalyst for aqueous‐phase Suzuki–Miyaura coupling reaction

Graphene oxide was functionalized with benzimidazole for palladium immobilization. The resultant graphene–benzimidazole‐supported palladium composite (G‐BI‐Pd) was characterized using infrared and Raman spectroscopies, transmission electron microscopy and energy‐dispersive X‐ray spectroscopy. G‐BI‐Pd showed excellent catalytic activity and fast reaction kinetics in the aqueous‐phase Suzuki–Miyaura reaction of aryl iodides and bromides with phenylboronic acid under relatively mild conditions (5–25 min, 80 °C). The catalyst can be used several times without any significant loss of its catalytic activity.     

Ruthenium complexes bearing bidentate Schiff base ligands as efficient catalysts for organic and polymer syntheses

A concise overview is given on mononuclear and dinuclear, bidentate Schiff base ruthenium complexes with different additional ligands and on their applications in various chemical transformations such as Kharasch addition, enol-ester synthesis, alkyne dimerization, olefin metathesis and atom transfer radical polymerization. These new ruthenium complexes, conveniently prepared from commonly available ruthenium compounds, are very stable, exhibit a good tolerance towards organic functionalities, air and moisture and display high activity and chemoselectivity in chemical transformations. Relevant features of coordination chemistry connected with the reaction mechanism and chemoselectivity are also fully described. Since the nature of Schiff bases can be changed in a variety of ways, appealing routes for designing and preparing novel ruthenium complexes can be foreseen in the future.     

Palladium chloride anchored on organic functionalized MCM‐41 as a catalyst for the Heck reaction

Palladium chloride was grafted to amino‐functionalized MCM‐41 to prepare heterogeneous catalysts. XRD, N₂ adsorption–desorption isotherms, IR, ¹³C and ²⁹Si cross‐polarization magic‐angle spinning NMR spectroscopy and XPS techniques were employed to characterize the catalytic materials. The heterogeneous palladium catalyst exhibited excellent catalytic activity for the Heck vinylation of iodobenzene with methyl acrylate, giving 92% yield of methyl cinnamate in the presence of N‐methylpyrrolidone (NMP) and triethylamine (Et₃N). The stability of the heterogeneous catalyst was also studied in detail. The catalytic tests showed that the palladium leaching correlated to solvent, base and palladium loading. The heterogeneous catalyst exhibited excellent stability towards loss of activity and palladium leaching was not observed during six recycles in the presence of toluene and Na₂CO₃. Copyright © 2007 John Wiley & Sons, Ltd.     

Silica‐supported terpyridine palladium(II) complex as an efficient and reusable catalyst for Heck and Suzuki cross‐coupling reactions

Silica‐supported terpyridine palladium(II) was prepared and used as an effective and recyclable catalyst in Mizoroki–Heck and Suzuki–Miyaura coupling reactions. The catalyst was very effective for the Mizoroki–Heck reaction of aryl halides with olefins and conversion was in most cases excellent. The catalyst showed good thermal stability (up to 230 °C) and could be recovered and reused for four reaction cycles. The Suzuki coupling of aryl iodides with aryl boronic acids in the presence of the catalyst was also investigated and the reaction proceeded with a short reaction time and excellent conversion. Copyright © 2013 John Wiley & Sons, Ltd.