Showing papers on "Palladium published in 2010"

Auxiliary-Assisted Palladium-Catalyzed Arylation and Alkylation of sp2 and sp3 Carbon-Hydrogen Bonds

Abstract: We have developed a method for auxiliary-directed, palladium-catalyzed β-arylation and alkylation of sp3 and sp2 C−H bonds in carboxylic acid derivatives. The method employs a carboxylic acid 2-methylthioaniline- or 8-aminoquinoline amide substrate, aryl or alkyl iodide coupling partner, palladium acetate catalyst, and an inorganic base. By employing 2-methylthioaniline auxiliary, selective monoarylation of primary sp3 C−H bonds can be achieved. If arylation of secondary sp3 C−H bonds is desired, 8-aminoquinoline auxiliary may be used. For alkylation of sp3 and sp2 C−H bonds, 8-aminoquinoline auxiliary affords the best results. Some functional group tolerance is observed and amino- and hydroxy-acid derivatives can be functionalized. Preliminary mechanistic studies have been performed. A palladacycle intermediate has been isolated, characterized by X-ray crystallography, and its reactions have been studied.

Core-protected platinum monolayer shell high-stability electrocatalysts for fuel-cell cathodes.

Abstract: More than skin deep: Platinum monolayers can act as shells for palladium nanoparticles to lead to electrocatalysts with high activities and an ultralow platinum content, but high platinum utilization. The stability derives from the core protecting the shell from dissolution. In fuel-cell tests, no loss of platinum was observed in 200?000 potential cycles, whereas loss of palladium was significant.

Emergence of palladium(IV) chemistry in synthesis and catalysis.

Abstract: Palladium-catalyzed bond-forming processes (e.g., C-C, C-X, C-Y; X ) F; Y ) NR2, OR, SR, etc.) represent essential tools for the synthetic chemist. A fascinating myriad of adventurous and unique Pd-catalyzed transformations are routinely found as key steps in target-oriented syntheses, affording complex natural products, functional advanced materials, fluorescent compounds, pharmaceutical lead compounds, and other high-value commercial products. Innovative Pd catalyst design, the identification of new synthetic methodologies, and the acquirement of detailed mechanistic insight, spanning both homogeneous and heterogeneous fields, underpin the numerous developments seen in this area over the past 40 years. Most commonly, Pd-catalyzed bond-forming processes involve Pd0/PdII complexes as intermediates. In recent times, the involvement of PdIV complexes have been implicated in many new synthetic methodologies, for which important advances have been made in the last 5 years or so. While observing the emergence of catalytic PdIV chemistry, particularly in organic synthesis, we identified the need to comprehensively review this area, which draws on aspects from both inorganic (organometallic) and organic chemistry fields. The historical background to organopalladium(IV) chemistry is therefore detailed. We have selected a wide range of diverse transformations where PdIV complexes are believed to act as key intermediates. It is clear that catalytic reaction manifolds involving PdIV intermediates offer new * Corresponding author. E-mail: ijsf1@york.ac.uk. Telephone: +44 (0)1904 434091. Fax: +44 (0)1904 432516. Chem. Rev. 2010, 110, 824–889 824

From Noble Metal to Nobel Prize: Palladium-Catalyzed Coupling Reactions as Key Methods in Organic Synthesis

Abstract: Palladium is known to a broad audience as a beautiful, but expensive jewellery metal. In addition, it is nowadays found in nearly every car as part of the automotive catalysts, where palladium is used to eliminate harmful emissions produced by internal combustion engines. On the other hand, and not known to the general public, is the essential role of palladium catalysts in contemporary organic chemistry, a topic which has now been recognized with the Nobel Prize for Chemistry 2010. Have a look at any recent issue of a chemical journal devoted to organic synthesis and you will discover the broad utility of palladium-based catalysts. Among these different palladium-catalyzed reactions, the so-called cross-coupling reactions have become very powerful methods for the creation of new C C bonds. In general, bond formation takes place here between less-reactive organic electrophiles, typically aryl halides, and different carbon nucleophiles with the help of palladium. Remember the situation 50 years ago, when palladium began to make its way into organic chemistry. At that time C C bond formation in organic synthesis was typically achieved by stoichiometric reactions of reactive nucleophiles with electrophiles or by pericyclic reactions. Ironically, however, oxidation catalysis was the start of today s carbon–carbon bond-forming methods: The oxidation of olefins to carbonyl compounds, specifically the synthesis of acetaldehyde from ethylene (Wacker process) by applying palladium(II) catalysts, was an important inspiration for further applications. Probably also for Richard Heck, who worked in the 1960s as an industrial chemist with Hercules Corporation. There, in the late 1960s, he developed several coupling reactions of arylmercury compounds in the presence of either stoichiometric or catalytic amounts of palladium(II). Some of this work was published in 1968 in a remarkable series of seven consecutive articles, with Heck as the sole author! Based on the reaction of phenylmercuric acetate and lithium tetrachloropalladate under an atmosphere of ethylene, which afforded styrene in 80% yield and 10% trans-stilbene, he described in 1972 a protocol for the coupling of iodobenzene with styrene, which today is known as the “Heck reaction”. A very similar reaction had already been published by Tsutomo Mizoroki in 1971. However, Mizoroki didn t follow up on the reaction and died too young from cancer. The coupling protocol for aryl halides with olefins can be considered as a milestone for the development and application of organometallic catalysis in organic synthesis and set the stage for numerous further applications. Hence, palladium-catalyzed coupling reactions were disclosed continuously during the 1970s (Scheme 1). One of the related reactions is the Sonogashira coupling of aryl halides with alkynes, typically in the presence of catalytic amounts of palladium and copper salts.

Mechanistically Driven Development of Iridium Catalysts for Asymmetric Allylic Substitution

Abstract: Enantioselective allylic substitution reactions comprise some of the most versatile methods for preparing enantiomerically enriched materials. These reactions form products that contain multiple functionalities by creating carbon−nitrogen, carbon−oxygen, carbon−carbon, and carbon−sulfur bonds. For many years, the development of catalysts for allylic substitution focused on palladium complexes. However, studies of complexes of other metals have revealed selectivities that often complement those of palladium systems. Most striking is the observation that reactions with unsymmetrical allylic electrophiles that typically occur with palladium catalysts at the less hindered site of an allylic electrophile occur at the more hindered site with catalysts based on other metals. In this Account, we describe the combination of an iridium precursor and a phosphoramidite ligand that catalyzes enantioselective allylic substitution reactions with a particularly broad scope of nucleophiles. The active form of this iridium...

A Highly Active Heterogeneous Palladium Catalyst for the Suzuki–Miyaura and Ullmann Coupling Reactions of Aryl Chlorides in Aqueous Media

Abstract: A new heterogeneous palladium catalyst is prepared by impregnation of palladium(II) nitrate on a metal-organic framework, MIL-101, giving highly dispersed palladium nanoparticles.

Palladium(II)-catalyzed oxidative C-H/C-H cross-coupling of heteroarenes.

Abstract: An efficient methodology for the synthesis of unsymmetrical biheteroaryl molecules has been developed via Pd(II)-catalyzed oxidative C−H/C−H cross-coupling of heteroarenes. An inversion in reactivity and selectivity has been achieved successfully to perform the desired heterocoupling. This process allows the heterocoupling of not only electron-rich N-containing heteroarenes (e.g., xanthines, azoles, and indolizines) but also electron-poor pyridine N-oxides with various thiophenes or furans.

Shape-Controlled Synthesis of Single-Crystalline Palladium Nanocrystals

Abstract: A versatile method for selectively synthesizing single-crystalline rhombic dodecahedral, cubic, and octahedral palladium nanocrystals, as well as their derivatives with varying degrees of edge- and corner-truncation, was reported for the first time. This is also the first report regarding the synthesis of rhombic dodecahedral palladium nanocrystals. All the nanocrystals were readily synthesized by a seed-mediated method with cetyltrimethylammonium bromide as surfactant, KI as additive, and ascorbic acid as reductant. At the same ascorbic acid concentration, a series of palladium nanocrystals with varying shapes were obtained through manipulation of the concentration of KI and the reaction temperature. The formation of different palladium facets were correlated with their growth conditions. In the absence of KI, the 100 palladium facets are favored. In the presence of KI, the concentration of KI and the reaction temperature play an important role on the formation of different palladium facets. The 110 palladium facets are favored at relatively high temperatures and medium KI concentrations. The 111 palladium facets are favored at relatively low temperatures and medium KI concentrations. The 100 palladium facets are favored at either very low or relatively high KI concentrations. These correlations were explained in terms of surface-energy and growth kinetics. These results provide a basis for gaining mechanistic insights into the growth of well-faceted metal nanostructures.

Biphasic Pd−Au Alloy Catalyst for Low-Temperature CO Oxidation

Abstract: Low-temperature CO oxidation over a compositional series of Pd−Au nanoalloy catalysts supported on silica fume was studied. Except for the pure metals, these materials invariably showed biphasic separation into palladium- and gold-rich components. Performance was optimal for a catalyst of bulk composition Pd4Au1, a mixture of Pd90Au10 (72.5 at. %) and Pd31Au69 (27.5 at. %), that was remarkably active at 300 K and more stable than a pure Au catalyst. For bulk materials dominated by Pd (Pd:Au = 16:1; 8:1; 4:1), the palladium-rich alloy fraction frequently adopted hollow sphere or annular morphology, while the gold-rich crystals were often multiply twinned. Quantitative powder X-ray diffraction (XRD) showed that under the synthesis conditions used, the Au solubility limit in Pd crystals was ∼12 at. %, while Pd was more soluble in Au (∼31 at. %). This was consistent with X-ray photoelectron spectroscopy (XPS), which revealed that the surfaces of Pd-rich alloys were enriched in gold relative to the bulk compos...

Controlled selectivity for palladium catalysts using self-assembled monolayers

Abstract: The selective reaction of one part of a bifunctional molecule is a fundamental challenge in heterogeneous catalysis and for many processes including the conversion of biomass-derived intermediates. Selective hydrogenation of unsaturated epoxides to saturated epoxides is particularly difficult given the reactivity of the strained epoxide ring, and traditional platinum group catalysts show low selectivities. We describe the preparation of highly selective Pd catalysts involving the deposition of n-alkanethiol self-assembled monolayer (SAM) coatings. These coatings improve the selectivity of 1-epoxybutane formation from 1-epoxy-3-butene on palladium catalysts from 11 to 94% at equivalent reaction conditions and conversions. Although sulphur species are generally considered to be indiscriminate catalyst poisons, the reaction rate to the desired product on a catalyst coated with a thiol was 40% of the rate on an uncoated catalyst. Interestingly the activity decreased for less-ordered SAMs with shorter chains. The behaviour of SAM-coated catalysts was compared with catalysts where surface sites were modified by carbon monoxide, hydrocarbons or sulphur atoms. The results suggest that the SAMs restrict sulphur coverage to enhance selectivity without significantly poisoning the activity of the desired reaction.

Palladium-catalyzed ortho-arylation of O-phenylcarbamates with simple arenes and sodium persulfate.

Abstract: By palladium catalysis, the C−H bond functionalization of O-phenylcarbamates with simple arenes has been achieved using sodium persulfate (Na2S2O8), an inexpensive, easy-to-handle, and environmentally friendly oxidant. This oxidative cross-coupling involves two aromatic C−H bonds undergoing concomitant oxidation to furnish a new biaryl C−C linkage. Excellent reaction efficiencies and regioselectivities were observed with a range of electron-rich, electron-neutral, and electron-deficient arenes; minimal homocoupling of either component was observed. When two reactive C−H bonds are present on the O-phenylcarbamate, selective diarylation can be achieved via quadruple C−H bond functionalization. This work represents a rare example of using O-carbamates as directing groups for catalytic C−H bond activation. Additionally, a palladacycle obtained from an O-phenylcarbamate was prepared and fully characterized. This trifluoroacetate-bridged bimetallic Pd complex exhibits clean conversion to the ortho-arylation pro...

Metal–support interactions in Pt/Al2O3 and Pd/Al2O3 catalysts for CO oxidation

Abstract: Platinum and palladium catalysts supported on γ-Al2O3 were studied by XRD, UV–vis DRS, HRTEM, TPR-H2, XPS together with measurements of their catalytic properties. The properties of the catalysts denoted as Pt(Pd)/Al2O3(X)-Y (X—the calcination temperature of support, °C; Y—the calcination temperature of catalyst, °C) were studied as a function of the temperatures used for calcination of the support and/or the catalyst in oxygen or in a reaction mixture of CO + O2. It was found that the deposition of Pt or Pd on γ-Al2O3 did not alter the structure of the support. Two types of the Pt and Pd particles were typically present on the γ-Al2O3 surface: individual particles with dimensions of 1.5–3 nm and agglomerates about 100 nm in size. In the catalysts calcined at relatively low temperatures (Pt/Al2O3(550)-450), platinum was present in the form of metal clusters. However, in the Pd/Al2O3(550)-450 catalyst, the palladium particles were almost completely decorated with a thin layer of an aluminate phase. These structures are not reduced in hydrogen in the temperature range of −15 to 450 °C, and are stable to treatment in a reaction mixture of CO + O2. Pd deposition on the γ-Al2O3-800 support was found to result in stabilization of the active component in two main forms, Pdo and PdO, with varying degrees of interaction due to the decoration effect. Calcination at the low temperature of 550 °C led to the formation of a so-called “core–shell structure”, where a palladium metal core is covered with a thin shell of an aluminate phase. Depending on the calcination temperature of the catalyst in the range of 450–1000 °C, the morphological form of the active component was converted from the “core-shell” state to a state consisting of two phases, Pdo and PdO, with a gradual decrease of the Pdo/PdO ratio, weakening the interaction with the support and the growth of palladium particles. Under the action of the reaction mixture, the Pd/Al2O3(800)-(450,600,800,1000) catalysts underwent changes in the Pdo/PdO ratio, which regulates the light-off temperature. After catalyst calcination at the highest temperature used in this study, 1200 °C, the palladium particles became much larger due to the loss of the palladium interaction with the support. Only the metal phase of palladium was observed in these catalysts, and their catalytic activity decreases substantially.

Pd(II)-Catalyzed C−H Activation/Aryl−Aryl Coupling of Phenol Esters

Abstract: Although nitrogen-containing group-directed cyclopalladation reactions have been well-known, Pd(II) insertion into C−H bonds promoted by coordination of an oxygen-only group to the palladium remains rather rare. In the present study, the first cyclopalladation complex formed from a simple phenol ester was characterized by X-ray crystallography. A promising protocol for the ortho C−H activation/aryl−aryl coupling of phenol esters that was not sensitive to moisture or air was then established. The utility of the reaction was demonstrated for the synthesis of useful phenol derivatives.

Green synthesis of palladium nanoparticles using broth of Cinnamomum camphora leaf

Abstract: The development of dependable, environmentally benign processes for the synthesis of nanoscale materials is an important aspect of nanotechnology. In the present study, we report one-pot biogenic fabrication of palladium nanoparticles by a simple procedure using broth of Cinnamomum camphora leaf without extra surfactant, capping agent, and/or template. The mean size of palladium nanoparticles, ranging from 3.2 to 6.0 nm, could be facilely controlled by merely varying the initial concentration of the palladium ions. The polyols components and the heterocyclic components were believed to be responsible for the reduction of palladium ions and the stabilization of palladium nanoparticles, respectively.

Shape control of platinum and palladium nanoparticles for catalysis

Abstract: Platinum and palladium are important catalysts for a wide variety of industrial processes. With the increasing demands of these materials, the development of high-performance catalysts is an important area of research, and as a result, shape control synthesis has become one of the leading research focuses. This minireview surveys the different approaches in solution-phase synthesis that have been successfully adopted for achieving shaped platinum and palladium nanoparticles that are enclosed with specific crystallographic facets. In addition, catalytic studies of the shaped nanoparticles are highlighted, in which promising results have been reported in terms of enhanced activity and selectivity. The future outlook discusses the aspects in synthesis and catalysis to be considered for the development of highly efficient and effective catalysts.

Electro-oxidation of glycerol at Pd based nano-catalysts for an application in alkaline fuel cells for chemicals and energy cogeneration

Abstract: Carbon supported Pd, Pt, Au and bimetallic PdAu and PdNi nano-catalysts with different compositions were synthesized. Their catalytic activity toward glycerol electro-oxidation was evaluated in alkaline medium. Physical and electrochemical methods where used to characterize the structure and the surface of the catalysts. It was shown that the PdxAu1−x/C catalysts were alloys, which present an increase of crystallite (XRD) and particle (TEM) sizes with increasing Au atomic fraction. Their surfaces were palladium rich whatever the Pd atomic ratio. The structure of the Pd0.5Ni0.5/C catalyst is much more difficult to understand, but it seems to be composed of a palladium phase in interaction with a Ni(OH)2 phase. The onset potential of glycerol oxidation is ca. 0.15 V lower on Pt/C than on Pd/C and Au/C. All PdxMe1−x/C catalysts presented lower onset potential than monometallic Au/C and Pd/C ones, but higher than Pt/C. For bimetallic catalysts, the order of activity at low potentials is: Pd0.3Au0.7/C > Pd0.5Au0.5/C > Pd0.5Ni0.5/C. Electrochemical experiments and in situ infrared spectroscopy measurements have shown that glycerol electro-oxidation mechanism is dependent on the catalyst, leading to different reaction products. Adsorbed CO species are detected on monometallic Pt and on Pd rich catalysts, but not on Au and Pd0.3Au0.7 catalysts, indicating that they are not able to break the C–C bond. The formation of hydroxypyruvate ion, which is a costly chemical product, is detected on pure gold catalyst.

Room Temperature Palladium-Catalyzed Decarboxylative ortho-Acylation of Acetanilides with α-Oxocarboxylic Acids

Abstract: A novel Pd-catalyzed decarboxylative ortho-acylation of acetanilides with α-oxocarboxylic acids is realized at room temperature. This reaction provides efficient access to o-acyl acetanilides under mild conditions.

A practical heterogeneous catalyst for the Suzuki, Sonogashira, and Stille coupling reactions of unreactive aryl chlorides.

Abstract: Transition-metal-catalyzed coupling reactions have contributed greatly to the straightforward and facile construction of carbon–carbon bonds. Significant progress in this area has been achieved with a variety of homogeneous palladium catalysts. However, homogeneous catalysis suffers from the problematic separation of the expensive catalyst from the product for re-use. Moreover, the homogeneous palladium catalysts tend to lose their catalytic activity because of palladium metal aggregation and precipitation. These problems are of particular environmental and economic concern in large-scale syntheses. Heterogenization of the existing homogeneous palladium catalysts could be an attractive solution to this problem. There has been considerable interest in the development of heterogeneous catalytic systems that can be efficiently re-used whilst keeping the inherent activity of the catalytic center. Aryl iodides and bromides have been widely employed as substrates in heterogeneous coupling reactions. From a practical point of view, the use of aryl chlorides is highly desirable because they are readily available and inexpensive. However, they are much more difficult to activate than aryl iodides and bromides. The activation of aryl halides is particularly challenging for heterogeneous catalysts, and although there have been many reports of heterogeneous reactions in the literature, successful examples using deactivated aryl chlorides are quite rare. Therefore, the development of high-performance catalysts for practical catalytic coupling reactions is of ongoing interest. Magnetite Fe3O4 nanoparticles have recently emerged as promising supports for immobilization because Fe3O4-supported catalysts can be separated from the reaction medium by an external permanent magnet. This circumvents time-consuming and laborious separation steps, and allows for practical continuous catalysis. In particular, Fe3O4 nanoparticles coated with a thin layer of silica have beneficial properties, such as invariant catalytic activity and stability. We have previously reported the use of a (b-oxoiminato)(phosphanyl)palladium complex as an efficient catalyst in coupling reactions. In this context, we have prepared triethoxysilyl-functionalized palladium complex 2, which can be anchored easily onto the surface of the silica. Commercially available Fe3O4 nanoparticles, with an average diameter of 20 nm, were coated with a thin layer of silica using a sol-gel process to give silica-coated Fe3O4 (3 ; SiO2@Fe3O4). [13] The silica shell has plenty of hydroxyl groups for potential derivatization with different functional groups, and also protects the magnetite core from abrasion under harsh shaking conditions. The silylated palladium complex 2 was successfully immobilized on the surface of robust SiO2@Fe3O4 (3) (Scheme 1). Schiff-base condensation of 2,4-pentanedione with (3-aminopropyl)triethoxysilane under microwave heating afforded 1 in only 3 min in quantitative yield. Deprotonation of 1 with EtOTl in tetrahydrofuran, followed by treatment with [Pd2(m-Cl)2Me2(PPh3)2], [14] led to the formation of 2. Magnetic-nanoparticle-supported (b-oxoiminato)(phosphanyl)palladium complex 4 was obtained by reaction

Silver-Catalyzed Late-Stage Fluorination

Abstract: Carbon−fluorine bond formation by transition metal catalysis is difficult, and only a few methods for the synthesis of aryl fluorides have been developed. All reported transition-metal-catalyzed fluorination reactions for the synthesis of functionalized arenes are based on palladium. Here we present silver catalysis for carbon−fluorine bond formation. Our report is the first example of the use of the transition metal silver to form carbon−heteroatom bonds by cross-coupling catalysis. The functional group tolerance and substrate scope presented here have not been demonstrated for any other fluorination reaction to date.

A Universal Approach to the Synthesis of Noble Metal Nanodendrites and Their Catalytic Properties

Abstract: A universal approach is presented for high-yield synthesis of Au, Pt, and Pd nanoflowers using the surfactant sodium N-(4-n-dodecyloxybenzoyl)-L-isoleucinate (SDBIL). The pH-dependent self-assembly using SDBIL is critical for nanoflower growth. The Pt and Pd nanoflowers show superior catalytic activity for Suzuki–Miyaura and Heck coupling reactions over spherical counterparts.

Palladium Nanoparticle-Graphene Hybrids as Active Catalysts for the Suzuki Reaction

Abstract: Graphene has been successfully modified with palladium nanoparticles in a facile manner by reducing palladium acetate [Pd(OAc)2] in the present of sodium dodecyl sulfate (SDS), which is used as both surfactant and the reducing agent. The palladium nanoparticle–graphene hybrids (Pd–graphene hybrids) are characterized by highresolution transmission electron microscopy, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy. We demonstrate that the Pd–graphene hybrids can act as an efficient catalyst for the Suzuki reaction under aqueous and aerobic conditions, with the reaction reaching completion in as little as 5 min. The influence of the preparation conditions on the catalytic activities of the hybrids is also investigated.

Aryl−CF3 Bond-Forming Reductive Elimination from Palladium(IV)

Abstract: This communication describes oxidatively induced Ar-CF(3) bond-forming reductive elimination from new Pd(II) complexes of general structure (L approximately L)Pd(II)(Ar)(CF(3)). The electrophilic fluorinating reagent N-fluoro-2,4,6-trimethylpyridinium triflate promotes these reactions in good to excellent yields. The palladium(IV) intermediate ((t)Bu-bpy)Pd(IV)(CF(3))(F)(OTf)(C(6)H(4)F) has been isolated, characterized, and demonstrated to undergo high yielding Ar-CF(3) coupling upon thermolysis. This work provides an attractive conceptual framework for the development of Pd(II/IV)-catalyzed arene trifluoromethylation reactions.

A Highly Efficient Palladium/Copper Cocatalytic System for Direct Arylation of Heteroarenes: An Unexpected Effect of Cu(Xantphos)I

Abstract: Heteroarenes are important structural moieties in many chemical industry fields. A highly efficient Pd/Cu-catalyzed C−H arylation method for a range of heterocycles has been discovered. It was found that the key to the success of this transformation is a combination of a palladium catalyst and a well-defined copper cocatalyst. The efficiency and low loadings of catalyst (0.25 mol %) and cocatalyst (1 mol %) together with the mild reaction conditions demonstrate this method to be practically useful and mechanistically interesting.

Palladium-Catalyzed Aminosulfonylation of Aryl Halides

Abstract: The palladium-catalyzed three-component coupling of aryl iodides, sulfur dioxide, and hydrazines to deliver aryl N-aminosulfonamides is described. The colorless crystalline solid DABCO·(SO2)2 was used as a convenient source of sulfur dioxide. The reaction tolerates significant variation of both the aryl iodide and hydrazine coupling partners.

Palladium-catalyzed benzylic addition of 2-methyl azaarenes to N-sulfonyl aldimines via C-H bond activation.

Abstract: An efficient protocol for the generation of amines by palladium-catalyzed nucleophilic benzylic addition of 2-methyl-substituted azaarenes to N-sulfonyl aldimines under neutral conditions via C−H bond activation has been developed. This reaction represents a very efficient methodology for the synthesis of heterocycle-containing amines and thus opens a new way to access amines through C−H bond activation.

C-H activation.

Abstract: Synthesis in the Key of Catellani: Norbornene-Mediated ortho C-H Functionalization.- Mechanistic Considerations in the Development and Use of Azine, Diazine and Azole N-Oxides in Palladium-Catalyzed Direct Arylation.- Palladium and Copper Catalysis in Regioselective, Intermolecular Coupling of C-H and C-Hal Bonds.- Pd-Catalyzed C-H Bond Functionalization on the Indole and Pyrrole Nucleus.- Remote C-H Activation via Through-Space Palladium and Rhodium Migrations.- Palladium-Catalyzed Aryl-Aryl Bond Formation Through Double C-H Activation.- Palladium-Catalyzed Allylic C-H Bond Functionalization of Olefins.- Ruthenium-Catalyzed Direct Arylations Through C-H Bond Cleavages.- Rhodium-Catalyzed C-H Bond Arylation of Arenes.- Cross-Dehydrogenative Coupling Reactions of sp3-Hybridized C-H Bonds.- Functionalization of Carbon-Hydrogen Bonds Through Transition Metal Carbenoid Insertion.- Metal-Catalyzed Oxidations of C-H to C-N Bonds.

Cationic palladium(II) catalysis: C-H activation/Suzuki-Miyaura couplings at room temperature.

Abstract: Cationic palladium(II) catalyst realized facile C−H activation of aryl urea with arylboronic acids at room temperature This reaction is extremely mild to carry out aromatic C−H activations through

A P,N‐Ligand for Palladium‐Catalyzed Ammonia Arylation: Coupling of Deactivated Aryl Chlorides, Chemoselective Arylations, and Room Temperature Reactions

Abstract: A new air-stable P,N-ligand is used in the palladium-catalyzed cross-coupling of ammonia to a variety of aryl chlorides with high chemoselectivity.

Experimental evidence for the nanocage effect in catalysis with hollow nanoparticles.

Abstract: Five different hollow cubic nanoparticles with wall length of 75 nm were synthesized from platinum and/or palladium elements. The five nanocatalysts are pure platinum nanocages (PtNCs), pure palladium nanocages (PdNCs), Pt/Pd hollow shell-shell nanocages (NCs) (where Pd is defined as the inner shell around the cavity), Pd/Pt shell-shell NCs, and Pt-Pd alloy NCs. These are used to catalyze the reduction of 4-nitrophenol with sodium borohydride. The kinetic parameters (rate constants, activation energies, frequency factors, and entropies of activation) of each shell/shell NCs are found to be comparable to that of pure metal NCs made of the same metal coating the cavity in the shell-shell NCs. These results strongly suggest that the catalytic reaction takes place inside the cavity of the hollow nanoparticles. Because of the nanoreactor confinement effect of the hollow nanocatalysts, the frequency factors obtained from the Arrhenius plots are found to be the highest ever reported for this reduction reaction. This is the reason for enhanced rate of this reaction inside the cavity. The importance of mechanism of the homogeneous and the heterogeneous nanocatalytic reactions occurring on the external surface of a solid nanoparticle are contrasted with those occurring on the nanocavity surface.