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This paper presents the synthesis and application of a novel catalyst for carbon–carbon bond formations, comprising palladium immobilized on 2-(5-hydroxyquinolin-8-yl)-1H-benzo[d]imidazole-5-carboxylic acid modified superparamagnetic iron oxide nanoparticles (Pd@HQBI-SPION). The synthesis involved the attachment of HQBI ligands to SPION using APTES, followed by the immobilization of palladium. Characterization techniques, including FTIR, TEM, and magnetic measurements, confirmed the successful synthesis and structural integrity of Pd@HQBI-SPION. The catalytic activity of Pd@HQBI-SPION was evaluated in various carbon–carbon bond formation reactions, demonstrating high efficiency and reusability. 8 different derivatives bearing several electron withdrawing and electron donating functionalities were used as starting materials and the products were obtained in high isolated yields (75–97%). The catalyst exhibited excellent performance in one-pot synthesis of phenanthroline-dimedone polycyclic derivatives via C-alkylation followed by intramolecular O-alkylation of phenanthroline with dimedone. The products are obtained in high to excellent yields is described. This protocol presents a highly selective synthetic method for the construction of polycyclic aromatic compounds containing nitrogen and oxygen atoms. [ABSTRACT FROM AUTHOR]

Indole is a promising heteroarene in many natural products and pharmaceuticals; therefore, various synthetic methods for indole functionalizations have arisen in recent years. Herein, we report a Pd-catalyzed deoxygenative coupling for the N-vinylation of indoles by employing vinyl ethers. The vinylated indoles could be readily prepared in good to excellent yields with N1-regioselectivity regardless of the electronic characteristics and substitution patterns of indole substrates. Some indole-based pharmaceutical molecules, such as gramine, evodiamine, rutaecarpine, and melatonine, are also successfully vinylated. Moreover, carbazoles and indazoles are shown to participate. Additionally, vinylated indole can readily transform into structurally interesting indole derivatives. [ABSTRACT FROM AUTHOR]

Developing environmentally benevolent and sustainable approaches is a vital objective of research in any field. By upholding these parameters and strategizing the methodology, herein we report the development of a new heterogeneous nanocatalyst based on Schiff base functionalized Pd(II) complex onto titania-coated magnetic nanoparticles [Pd@SB/Fe3O4–TiO2]. The developed catalytic system is well characterized with various techniques such as FE-SEM, TEM, XPS, XRD, TGA, BET, FTIR, VSM, CHN, EDX, and ICP-AES analysis. The catalytic activity of [Pd@SB/Fe3O4–TiO2] for the Suzuki coupling reaction to synthesize biaryls and for the hydrogenation reaction of aromatic nitro compounds to synthesize aromatic amines under sustainable reaction conditions was tested which revealed excellent results. Pd@SB/Fe3O4–TiO2 showed remarkably higher activity than the homogeneous PdCl2 and Pd(OAc)2, which might be due to the presence of electronic synergism between support and Pd. Schiff base functionalization provides excellent support to the palladium as leaching of the metal was not observed. The magnetic core of the catalyst ascertains its easy recoverability, thereby maintaining the sustainability of the reaction. The magnetic catalyst was easily separable with the help of an external magnet and showed very good recyclability for up to six cycles with no appreciable loss in catalytic efficiency. Furthermore, the reported catalyst remains unchanged even after six consecutive runs as established by the FTIR, XPS, and XRD analysis of the recovered catalyst. [ABSTRACT FROM AUTHOR]

A novel fluorescent supramolecular polymer (named N3T) has been synthesized resoundingly, which can effectively identify trace amounts of Pd2+ in solution, and then a self-assembled supramolecular catalyst catalyst N3T-Pd was obtained. The N3T-Pd with spherical structure could be used for C–C coupling reactions in an eco-friendly aqueous medium. The catalyst was characterized by NMR, FT-IR, XPS, SEM and fluorescence spectra. The N3T-Pd has prominent stability and recyclability without any decrease of catalytic activity after least five cycles. Notably, the reaction degree of Pd2+ with the supramolecular polymer can be conformed by the fluorescence intensity of the supramolecular polymer. With that, the N3T detection limit (LOD) of Pd2+ was measured by fluorescent titration. Surprisingly, N3T can ultrasensitive detection of Pd2+, the limit of detection was 1.9 × 10−7 M. The self-assembly supramolecular palladium catalyst N3T-Pd has been developed as a novel and efficient catalyst for ligand-free C–C cross-coupling reactions in aqueous at room temperature. [ABSTRACT FROM AUTHOR]

The aminocarbonylation of ethyl 2-substituted 5-iodobenzoate has been investigated in the presence of a series of amine nucleophiles, providing an efficient synthetic route for producing various 5-carboxamide and 5-glyoxylamide derivatives of 2-(N-substituted) ethylbenzoates. It was shown, after detailed optimization study, that the formation of amides and α-ketoamides is strongly influenced by the reaction conditions. Performing the reactions of ethyl 2-substituted 5-iodobenzoate with nitrogen nucleophiles at 1 atm of carbon monoxide pressure in the presence of [Pd(η3-C3H5)(μ-Cl)]2 as a palladium source and DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) as the base, the corresponding 2-ketocarboxamides were formed as major products (up to 60%). We have characterized the cytotoxicity (MTT test) and SAR of a new class of 2-(N-substituted) ethylbenzoate 5-amides and 5-(α-keto)amides. 5-Glyoxylamido derivatives 9a,b, 14a,d exhibited remarkably good cytotoxic potential on MCF-7 and T98G cancer cell lines. In addition, all the synthesized compounds were found to be non-toxic against normal cells (DF-2). The readily available nitrogen substituted 5-glyoxylamido-2-(N-acetylamino)ethylbenzoates 14a,d may serve as lead molecules for the future research regarding the identification of new anticancer agents. These novel compounds were confirmed to be cyclin-dependent kinase 6 and 9 (CDK6 and 9) inhibitors through in silico molecular modeling studies for the mode of action. [ABSTRACT FROM AUTHOR]

An efficient and stable palladium species catalyst immobilized on functionalized hyper–cross-linked polymers (HCPs-Pd) has been successfully developed and applied in the Suzuki–Miyaura coupling reaction of diverse types of aromatic halides with aryl boronic acid in this work. The results demonstrated that HCPs-Pd exhibited high catalytic activity, which benefited from the microporous structure of the catalyst guaranteed high dispersibility of active palladium, and high specific surface area, large pore volume, good chemical stability. Under optimal reaction conditions, 93.0% of biphenyl yield in the Suzuki–Miyaura reaction with bromobenzene (C6H5Br) and phenylboronic acid (C6H7BO2) as raw material was obtained. The good stability of the HCPs-II-Pd catalyst was verified by five cycles experiments. Perhaps this work provides new insights into the high-yield preparation of aromatic biphenyl compounds employing HCPs-Pd as an efficient and stable catalyst in the Suzuki–Miyaura reaction. [ABSTRACT FROM AUTHOR]

In the palladium-catalyzed cross-coupling of potassium pentafluorophenyltrifluoroborate with aryl chlorides in the presence of the precursor of SIMes carbene, the yields of pentafluorobiphenyls decrease, whereas the yield of 2,3,4,5,6-pentafluoro-4'-methylbiphenyl from 4-bromotoluene under the same conditions increases. An explanation for this phenomenon and for the intensification of the side hydrodeboration reaction of the initial borate has been proposed. [ABSTRACT FROM AUTHOR]

Pyrolysis of cellulose powder granules impregnated with an aqueous solution of saccharose and palladium nitrate gave granular Pd/C carbons with 1–9 wt % metal. It was shown by X-ray diffraction analysis and electronic microscopy that palladium is present in the carbon matrix in the form of Pd(0) nanoparticles with sizes of 10–30 nm in the main fraction (~95%). Palladium nanoparticles are localized inside the saccharose carbonizate layer and on its surface. An IR spectral study showed that pyrolysis of the cellulose–saccharose powder composite in the presence of palladium nitrate leads to the appearance of ester groups in the carbonizate. An increase in the palladium nitrate content in the cellulose powder leads to lower yields of the carbonizate and larger metal nanoparticles in carbon. The specific catalytic activity of nanoparticles in the model decomposition reaction of hydrogen peroxide was found to be the same for all palladium-containing carbons. [ABSTRACT FROM AUTHOR]

In this work, comparative testing of the activity of low-percentage palladium and palladium-nickel catalysts supported on activated diatomite with a commercial nickel catalyst from BASF was carried out in the process of hydrogenation of polyalphaolefins (PAO-4). It has been found that palladium catalysts carry out the process under milder conditions, demonstrate higher activity compared to nickel catalysts, significantly reduce the process time, and provide a higher degree of hydrogenation. The activity of bimetallic catalysts is lower than that of monometallic palladium catalysts. Furthermore, Ni exhibits a reaction temperature of at least 150 °C, while Pd is at least 110 °C. If nickel is a single-use catalyst, then when palladium is used 5 times remains an excellent catalytic activity. Catalyst activity is related to the form of adsorbed hydrogen, and on Pd catalyst hydrogen is weakly bound form, while on Ni hydrogen is strongly bound form. The physicochemical characteristics of catalysts and polyalphaolefin oils also have been determined. [ABSTRACT FROM AUTHOR]

In this work, two palladium-based catalysts with either ZSM-5 or Zeolite Y as support material are tested for their performance in selective catalytic reduction of NOx with hydrogen (H2-SCR). The ligh-toff measurements in synthetic exhaust gas mixtures typical for hydrogen combustion engines are supplemented by detailed catalyst characterization comprising N2 physisorption, X-ray powder diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR) and ammonia temperature programmed desorption (NH3-TPD). Introducing 10% or 20% TiO2 into the catalyst formulations reduced the surface area and the number of acidic sites for both catalysts, however, more severely for the Zeolite Y-supported catalysts. The higher reducibility of the Pd particles that was uncovered by H2-TPR resulted in an improved catalytic performance during the light-off measurements and substantially boosted NO conversion. Upon exposition to humid exhaust gas, the ZSM-5-supported catalysts showed a significant drop in performance, whereas the Zeolite Y-supported catalyst kept the high levels of conversion while shifting the selectivity from N2O more toward NH3 and N2. The 1%Pd/20%TiO2/HY catalyst subject to this work outperforms one of the most active and selective benchmark catalyst formulations, 1%Pd/5%V2O5/20%TiO2-Al2O3, making Zeolite Y a promising support material for H2-SCR catalyst formulations that allow efficient and selective NOx-removal from exhaust gases originating from hydrogen-fueled engines. [ABSTRACT FROM AUTHOR]

The effect of MOFs-derived Ce0.3Ni0.7Ox carrier (CN-M) on Pd dispersion states for three-way catalytic (TWC) performance of natural gas vehicles (NGVs) comparing with Ce0.3Ni0.7Ox carrier (CN-C) prepared by citric acid complexation method has been studied. The results showed that the Pd/CN-M catalyst displayed better Pd dispersion (46.3%) and much higher activity for the conversions of CO, NO and CH4. Both T50 and T90 of CO conversion over Pd/CN-M were lower ca. 100 °C than that over Pd/CN-C catalyst, T50 and T90 of NO conversion were same trend with lower degree ca. 150 °C, the CH4 conversion of Pd/CN-M was also much better than that of Pd/CN-C. After thermal aging, the conversions of CO, NO and CH4 of Pd/CN-M had a finite shift with 20–50 °C to high temperature. It showed unique structure, smaller crystal particles, higher metal dispersion, stronger reducibility, and higher adsorbed oxygen (Oα) on Pd/CN-M catalyst in comparison to Pd/CN-C, and dispersion thermal stabilization of Pd particles on Pd/CN-M catalyst was better than that on Pd/CN-C. This work maybe provides a new method for preparing TWCs with high active for NGVs. [ABSTRACT FROM AUTHOR]

The main pathways of liquid-phase hydrogenation of 5-ethenylbicyclo[2.2.1]hept-2-ene (5-vinyl-2-norbornene, VNE) in the presence of PK-25 palladium catalyst (Pd/γ-Al2O3, 0.25% Pd) were studied. All the reaction products were identified, and the material balance was examined. The effect of the prevalent adsorption of the norbornene double bond on the Pd active site (AS) was confirmed. The parallel-consecutive scheme of the process mechanism, based on the set of experimental and theoretical data, was suggested. It involves the successive substrate hydrogenation and significant role of the isomerization of the vinyl group into the ethylidene group in intermediates on AS in a hydrogen atmosphere. The reaction is zero-order in a wide interval of initial VNE concentrations. An adequate kinetic model of the process, based on the Langmuir–Hinshelwood approach and the concept of multiple adsorption of substrates on one AS, was developed. Five steps, including two parallel steps, significantly contribute to the reaction rate. Their rate constants and the adsorption constants of AS complexes with unsaturated compounds were estimated. [ABSTRACT FROM AUTHOR]

Eliminating hydrogen from CO via preferential oxidation is an important process in Coal to Ethylene Glycol technology for achieving target products with high yield. During the reaction, applied Pd–Cl/alumina catalyst inevitably experienced structural reconstruction stem from reaction conditions. The deactivation behavior of catalyst was clarified via spectroscopic and microscopic observations. It proposed that surface evolutions about metal sintering should be primarily responsible for the degradation of catalytic efficiency. Owing to chlorine effusion, dependent ferrous contamination and Pd aggregation was emerged on catalyst during the operation. The detachment of coordinative chlorine from active sites in the form of hydrogen chloride favored the accessing of adsorbate on Pd sites which further accelerated the coalescence of clusters. Despite the textural perturbation about porosity and surface area was negligible, on the other hand, the elimination of surface hydroxyls may contribute much for surface passivation and undermined Pd–Cl-Al interfacial interactions. Diagram illustrated the surface evolutions of catalyst during the operation in hydrogen preferential oxidation. [ABSTRACT FROM AUTHOR]

Liquid-phase hydrogenation of 5-vinylbicyclo[2.2.1]hept-2-ene (5-vinyl-2-norbornene, VNE) existing as a mixture of endo- and exo-isomers in the presence of a palladium catalyst (0.25% Pd/γ-Al2O3, or PC-25) is a complex consecutive-parallel process proceeding via the formation of (endo/exo)-2-vinylnorbornanes. Subsequent hydrogenation of the latter is preceded by quantitative isomerization of the vinyl group to the ethylidene one. The mechanism of the phenomenon was studied experimentally and theoretically. It was established that isomerization of 2-vinylnorbornanes to 2-ethylidenenorbornanes requires the presence of palladium (as the active component of the catalyst) and hydrogen in the reaction system. All reaction products were identified and the material balance of the process was studied. According to DFT PBE/SBK quantum chemical calculations, migration of the multiple bond in 2-vinylnorbornanes on the Pd(111) face of the model cluster Pd21(H)2 is of allylic character. [ABSTRACT FROM AUTHOR]

Liquid-phase hydrogenation of bicyclo[2.2.1]hepta-2,5-diene (norbornadiene, ND) proceeds in the presence of an industrial palladium catalyst Pd/γ-Al2O3 (PK-25) in an n-heptane solution at 76°C via consecutive formation of bicyclo[2.2.1]hept-2-ene (norbornene, NE) and bicyclo[2.2.1]heptane (norbornane, NA), as well as tricyclo[2.2.1.02,6]heptane (nortricyclane, NT) as a minor product. The reaction products were identified, the main routes were determined, and the material balance was studied. Preferable adsorption of ND at the active palladium site over adsorption of other components of the system was confirmed. A parallel-serial scheme of the process mechanism was proposed based on the sum of experimental and theoretical data. Zero order kinetics was observed in a wide range of initial substrate concentrations. The apparent rate constants of each stage were measured. A detailed kinetic model was developed based on the Langmuir–Hinshelwood approach, assuming multiple adsorption of substrates at a single active site of the heterogeneous catalyst. The model adequately describes the available experimental data using the proposed mechanism of ND hydrogenation. The possibility of a "cocktail" mechanism for the given reaction was discussed. [ABSTRACT FROM AUTHOR]

A series of 3-amino-5-(1,4-dioxo-1,4-dihydronaphthalen-2-ylamino)benzoic acid derivatives were synthesized by the Michael addition of 1,4-naphthoquinone and 3,5-diaminobenzoic acid followed by the Suzuki coupling reaction. The derivatives of compound 2 were integrated, exposing it to benzolyation by an assortment of acid chlorides. Among the synthesized compounds, compounds 3b, 3c and 3d displayed better IC50 value of cytotoxicity (against HeLa) when compared with other derivatives. All the IC50 esteems were compared with the standard drug doxorubicin. DPPH and ABTS evaluation procedures are employed to assess the antioxidant activity. The compound 3d exhibited the highest inhibition of 75% and 77% in the DPPH and ABTS antioxidant activity evaluation, respectively. [ABSTRACT FROM AUTHOR]

Ferrocene derivatives have been synthesized by the Suzuki cross-coupling reaction of ferroceneboronic acid with various aryl/heteroaryl halides. The reactions yield ferrocenyl derivatives with overall yields varying between 35 and 98%. The derivatives have been characterized by 1H NMR, 13C NMR, IR, HRMS and elemental analysis. The structure–property relationship has been investigated based on UV/Vis spectroscopy and cyclic voltammetry. Cyclic voltammetry studies revealed when the side group of ferrocenes were an electron-donating, lower oxidation was displayed. On the other hand, the strong electron-withdrawing group had a higher oxidation potential. [ABSTRACT FROM AUTHOR]

The catalytic hydrodechlorination (HDC) of chlorophenols (CPs) to high-value and more eco-friendly cyclohexanone is attractive for the treatment of wastewater. The HDC performance of Pd catalyst can be improved by the modification with an appropriate element. La modification on Pd/CNTs catalyst, would provide solid Lewis acid, promote the active Pd dispersion, and induce the partial oxidation of Pd, minimizing the apparent activation energy of phenol during HDC greatly. A broad scope of CPs was degraded completely at mild conditions over Pd–La(1:1)/CNTs catalyst, with the deep hydrogenation of phenol (> 99.5%) and high selectivity of cyclohexanone (cyclohexanone yield > 68%). Moreover, this new La modified Pd/CNTs catalyst exhibited excellent catalytic stability, making it to be a promising candidate for hydrodechlorination of wastewater containing CPs. [ABSTRACT FROM AUTHOR]

Carbonylation, one of the most powerful approaches to the preparation of carbonylated compounds, has received significant attention from researchers active in various fields. Indeed, impressive progress has been made on this subject over the past few decades. Among the various types of carbonylation reactions, asymmetric carbonylation is a straightforward methodology for constructing chiral compounds. Although rhodium-catalyzed enantioselective hydroformylations have been discussed in several elegant reviews, a general review on palladium-catalyzed asymmetric carbonylations is still missing. In this review, we summarize and discuss recent achievements in palladium-catalyzed asymmetric carbonylation reactions. Notably, this review's contents are categorized by reaction type. [ABSTRACT FROM AUTHOR]

Pd–Ag/Al2O3 catalysts (Pd = 0.03 wt% with Ag = 0.18 wt% in bimetallic samples) were prepared by sequential impregnation using acidic and basic colloidal oxide solutions. The catalysts were evaluated for selective hydrogenation of acetylene to ethylene (T = 60 °C, p = 10 bar, H2/C2H2 = 1.5 mol/mol, GHSV = 4000 h−1). The colloidal solutions were characterized by HR-TEM, the fresh catalysts by CO chemisorption, CO-TPD and FE-SEM and the spent catalysts by TGA and FTIR techniques. The HR-TEM images showed fairly narrow size distributions of PdO nanoparticles (1.9–3.4 and 1.3–4.4 nm in acidic and basic solutions, respectively). However, the Pd particles on unpromoted catalysts were much larger (19–51 nm) indicating considerable sintering during the preparation steps due to low melting point of PdO and its weak interaction with the support. The FE-SEM results illustrated that the colloidal method is capable of producing egg-shell distribution of Pd with penetration depths (7–15 μm) comparable to those achieved by conventional impregnation although due to a different mechanism. On the mono-metallic colloid-based samples, the acetylene conversions (96%) and ethylene selectivities (65–68%) were much larger than those of the sample prepared by conventional impregnation (90 and 24%, respectively). Upon Ag addition, the acetylene conversion was decreased to 40 and 56%, while ethylene selectivity was increased to 92 and 95% for acidic and basic samples, respectively. For the conventional bimetallic sample, the conversion and selectivity were increased to 95 and 86%, respectively. The results illustrated a better performance of the colloid-based catalysts with basic mode showing superior performance. The coke deposited on spent catalyst was found to be of soft type, that is, the one with high H/C ratio. [ABSTRACT FROM AUTHOR]

The rate and directions of transformations during the liquid-phase hydrogenation of furfural with molecular hydrogen in the presence of the 5%Pd/C catalyst (at 423 K, 3 MPa) depend substantially on the chemical nature of the solvent. The main products of the catalytic transformations in alcohols are alkyl furyl ethers. Hydrogenation in solvent environment of aromatic hydrocarbons and 1,4-dioxane (nonpolar solvents), as well as in ethyl acetate and DMF (polar aprotic solvents) leads to the predominant formation of furfuryl alcohol, and its highest selectivity (up to 92%) is achieved with the use of DMF. [ABSTRACT FROM AUTHOR]

The liquid-phase hydrogenation of 5-ethenylbicyclo[2.2.1]hept-2-ene (5-vinyl-2-norbornene, VNE) in the presence of the palladium catalyst Pd/γ-Al2O3 (PC-25) in an n-heptane medium at 76 °C was studied. The hydrogenation proceeds via a complicated mechanism through (exo/endo)-2-vinylnorbornanes and (Z/E)-2-ethylidenenorbornanes to form (exo/endo)-2-ethylnorbornanes. The reaction products were identified, the main reaction routes were determined, and the material balance was studied. The isomerization of (exo/endo)-2-vinylnorbornanes to (Z/E)-2-ethylidenenorbornanes with the conversion close to 100% was found for the reaction in a hydrogen atmosphere. The molar ratios of the stereoisomers of the substrate and of the intermediate and final hydrogenation products are retained at all steps of the process. The parallel-sequential mechanism was proposed for the process. The zero kinetic time order with respect to VNE was established in a wide range of its initial concentrations. [ABSTRACT FROM AUTHOR]

Bis[(E)-2-bromovinyl] selenide enters cross coupling with terminal acetylenes in the presence of a Pd/CuI catalyst at room temperature. The reaction involves both the bromine atom and the selanyl function and leads to both substituted bis(but-1-en-3-ynyl) selenides and enediynes with complete retention of the configuration of the parent selenide. [ABSTRACT FROM AUTHOR]

The catalytic activity of chitosan-containing palladium catalysts in the hydrogenation reaction of n-hex-2-yne was studied. The most active was the catalyst with [Pd]:[chitosan] molar ratio = 1:1.3. The hydrogenation rate on this catalyst was five times higher than that of similar catalyst with [Pd]:[chitosan] ratio = 1:3.3. Modification of the active catalyst with silver resulted in increasing the selectivity of the process for cis-hex-2-ene up to 96%. [ABSTRACT FROM AUTHOR]

The gas- and liquid-phase hydrogenation of bicyclo[2.2.1]hepta-2,5-diene (norbornadiene) in the presence of the Pd/γ-Al2O3 (PK-25) industrial palladium catalyst in an n-heptane medium at 75–200°С is studied. The reaction products are identified, the main reaction routes are established, and the material balance is studied. The effect of preferable adsorption of norbornadiene compared to other components of the system on the palladium active site is confirmed. A relationship between possible modes of norbornadiene coordination and the product structure is considered. A parallel-sequential scheme is proposed for the mechanism of the process on the basis of the obtained experimental and theoretical data. [ABSTRACT FROM AUTHOR]

Zirconia supported palladium catalysts were synthesized in the inert solvent by an in-situ reduction route. The preparative parameters, such as the reducing agents and the way of pre-nucleation, were regulated for the purpose of tuning the interaction between the support and the active metal (SMI). When a high dispersion of palladium is obtained by reducing agent of 1,2-hexadecanediol, a strong SMI between the active metal and zirconia is built up. This depresses the catalytic performance of the Pd/PdOx composite active phase for methane combustion. Conversely, the ratio of palladium species (Pd/PdOx) is apt to be optimized in the case of sample reduced by 2,5-di-tert-butyl-p-diphenol (DTBHQ). Furthermore, the catalysts involved a pre-nucleation step will result in a much weaker SMI, which leads to a decrease of catalytic activity for methane combustion. It is proved that an appropriate SMI is a key factor for the oxidation activity of supported palladium catalysts. The reduction of palladium component by 2,5-di-tert-butyl-p-diphenol (DTBHQ) launched until 200 °C. This would result in an active phase (Pd/PdOx) with less strong metal-support interaction (SMSI). Therefore, the ignition temperature of the methane oxidation is lowered by 100 °C. [ABSTRACT FROM AUTHOR]

An efficient Pd-catalyzed C–N bond formation for the synthesis of different pyrazole derivatives using XPhos as a ligand and KOH as a base is presented. The developed procedure can be successfully applied for the synthesis of 5-N-aryl-1,3-disubstituted 1H-pyrazol-5-amines. Contrary to previously described procedures, this one proceeds in one step utilizing commercially available aminopyrazoles and aryl halides. Thus, a series of 5-N-aryl-1,3-disubstituted 1H-pyrazol-5-amines were obtained with satisfactory yields under optimized reaction conditions. [ABSTRACT FROM AUTHOR]

In this work, the modification of chitosan using 2-acetyl pyridine has been used to prepare an intermediate, chitosan pyridyl imine (CPI), in first step and then in second step it is further reacted with Pd(OAc)2 to develop chitosan pyridyl imine palladium (CPIP) complex catalyst in a very simplistic way. The formed CPIP has been extensively characterized with respect to raw chitosan utilizing methods including FT-IR, pyrolysis GC–MS, XRD, XPS, FE-SEM, EDS, TGA-DTG and DSC. TG-DSC study suggested that the catalyst is thermally stable up to 300 °C. This catalyst shows an excellent activity in the reduction of toxic pollutant nitrobenzene to less toxic aniline. CPIP complex has also been found to give magnificent results in Suzuki–Miyaura and Heck cross-coupling reactions, and therefore, using this green catalyst, the toxic phosphine ligand can be excluded from cross-coupling reactions. This study furnishes an economic and eco-friendly catalyst for organic transformation in sustainable chemistry. [ABSTRACT FROM AUTHOR]

The effect of pectin, gellan, and chitosan on the activity, stability, and styrene selectivity of supported palladium catalysts for the selective hydrogenation of phenylacetylene was determined. It was shown that a positive effect is achieved as a result of the formation of palladium nanoparticles with a size of 1-4 nm, which are distributed relatively uniformly over the surface of the carriers, when polysaccharides are added in the catalytic system. [ABSTRACT FROM AUTHOR]

The applicability of a new carbon material—carbon foam with a cellular structure synthesized from the pyrolysis products of hydrocarbon gases—as a catalyst support was demonstrated. The modification of the carbon foam by the deposition of nanoglobular carbon particles on its surface made it possible to obtain a nonporous material with a specific surface area of <1 m2/g and an open-cell structure. Dispersed palladium particles uniformly distributed over the support surface were formed using a hydrolytic deposition method. It was found that the resulting catalyst with palladium immobilized on cellular carbon is promising for the selective hydrogenation of acetylene to ethylene. [ABSTRACT FROM AUTHOR]

A series of N-heterocyclic carbene (NHC)–palladium catalysts have been synthesized and applied to catalyze the Suzuki coupling reaction efficiently between aryl sulfonates and arylboronic acids with the potassium phosphate heptahydrate as a base. The desired yields are obtained even with less reactive aryl tosylates or aryl mesylates as substrates. This method was applied successfully to the synthesis of the (R)-2-(t-butoxycarbonylamino)-3-(biphenyl-4-yl)-propan-1-ol which is the key intermediate of sacubitril, a component of the newly approved antihypertensive drug "Entresto." [ABSTRACT FROM AUTHOR]

Schiff-base modified Pd nanoparticles (NPs) supported on silica with an average size of ca. 2 nm have been synthesized via a one-pot aldimine condensation followed by impregnation-reduction of a palladium precursor, and the sample exhibits an excellent catalytic activity and selectivity in hydrogenation of 2-butyne-1,4-diol (BYD) to 2-butene-1,4-diol (BED). Under the mild reaction conditions (50 °C, 2 MPa H2, and 4 h) and additive-free, 95.2% BYD conversion has been achieved with ca. 100% BED selectivity over the Pd/SiO2–Schiff catalyst, and the Pd/SiO2–Schiff catalyst presents an excellent catalytic stability. The above results are much better than that of commercial Lindlar catalyst, and the improved catalytic performance is attributed to the strong metal–support interaction derived from the coordination of nitrogen sites (Schiff-base) to Pd NPs, based on catalyst characterization results. Featured by additive-free and high selectivity, hydrogenation of 2-butyne-1,4-diol to 2-butene-1,4-diol over the Pd/SiO2–Schiff catalyst has been developed, aiming for green production of fine chemicals. [ABSTRACT FROM AUTHOR]

The model of selectivity to methyl pelargonate was developed for the hydrocarbomethoxylation of 1-octene catalyzed by the Pd(PPh3)2Cl2—PPh3—p-toluenesulfonic acid system (378 K). The ratio of the rate of methyl pelargonate formation to the sum of the rates of formation of three isomeric esters (reaction products) was accepted as the differential selectivity of the reaction. The model represents a system of equations relating the differential selectivity of the reaction to the CO pressure and concentrations of methanol, PPh3, and p-toluenesulfonic acid. The model adequately depicts the experimental data in a wide range of 1-octene conversions up to 95.5%. The regularities of a change in the reaction selectivity were substantiated using the hydride multiroute mechanism of hydrocarbomethoxylation of 1-octene. [ABSTRACT FROM AUTHOR]

The results of studies on selective hydrogenation of acetylene to ethylene over bimetallic palladium-containing catalysts were summarized. Regular and specific features of the catalyst action in gas-phase hydrogenation of traces of acetylene in the acetylene-ethylene mixture produced by pyrolysis of petroleum feedstock, as well as in liquid-phase hydrogenation of mixtures enriched in acetylene and hydrogen were analyzed. The advantages of ethylene production by liquid-phase hydrogenation of acetylene were shown, and ways of increasing the selectivity to ethylene in this process were considered. [ABSTRACT FROM AUTHOR]

A series of bimetallic Pd–Zn catalysts supported on the carbon material Sibunit was synthesized for selective hydrogenation of acetylene. XRD, XPS, XAFS and TEM data revealed that the structure and dispersion of bimetallic particles in Pd–Zn/Sibunit samples depend on the molar ratio Pd:Zn. The active component of the Pd–Zn(1:0.25)/Sibunit sample is a substitutional solid solution. In the catalysts with Pd:Zn ≤ 1, the interaction proceeds more completely with the transformation of FCC lattice of the solid solution into the tetragonal structure of intermetallic phase with the composition close to PdZn, whereas an excess of zinc forms the individual ZnO phase. It was found that an increase in the zinc content in Pd–Zn/Sibunit catalysts from Pd:Zn = 1:0 to 1:4 leads to dispergation of the deposited mono- and bimetallic particles from dav = 7.2 to 2.0 nm. The formation of the PdZn intermetallic compound with increasing the zinc content from Pd:Zn = 1:0 to 1:1 is accompanied by a gradual increase in selectivity to ethylene from 42% for Pd/Sibunit to 67% for Pd–Zn(1:1)/Sibunit (the reaction temperature is 95 °C), and also by a decrease in activity. The introduction of a zinc excess (Pd:Zn < 1), on the contrary, decreases the hydrogenation selectivity to ~ 62%, presumably owing to a high dispersion of bimetallic particles. [ABSTRACT FROM AUTHOR]

Understanding the need for simple, robust and low effluents, in chemical processes, we have developed an elegant protocol for the catalytic reduction of aldehydes and ketones to corresponding alcohols which are used in synthetic fragrance applications using cinchona alkaloid-derived palladium catalyst. This system holds good for very low catalyst loading surfaces with the formation of fewer impurities and negligible decomposition under moderate pressure. The conversions and yields range from moderate to good (60-80%). [ABSTRACT FROM AUTHOR]

Tin dioxide was assessed as a substitute for part of platinum-group metals in a catalytic converter, and the activity of various Pd and PdPt catalysts was compared on conventional alumina support and SnO2 in wet lean methane combustion. Remarkably, Pd-only catalysts supported on SnO2 revealed higher activity compared with PdPt/Al2O3. The catalysts benefit from the strong metal-support interactions and high oxygen mobility in SnO2 with dual Sn4+/Sn2+ valency. SnO2 can thus be considered a potential replacement of Pt in a catalytic converter for a natural gas vehicle under lean burn conditions. This potentially decreases the price of the converter and eliminates the need for scarce and expensive Pt. [ABSTRACT FROM AUTHOR]

Catalytic properties of Pd/Al2O3 and Pd-Ga/Al2O3 in selective liquid-phase hydrogenation of acetylene in a flow under pressure and the effect exerted on them by introduction of CO into the feed were studied. The presence of CO in the reaction mixture ensures the reaction with the predominant formation of ethylene. Introduction of gallium into the catalyst formulation prevents the catalyst deactivation. Simultaneous action of these factors allows reaching high yield of the target product in combination with long operation life of the catalyst. [ABSTRACT FROM AUTHOR]

In the course of the experiments nanostructured catalysts have been developed for hydrogenation of ClO3− ions. Different nitrogen doped carbon nanotube (N-BCNT) coated catalyst pellets have been synthetized by the catalytic chemical vapour deposition (CCVD) method. These core-shell structured pellets were used as supports of palladium catalysts. The catalysts were examined by scanning electron microscopy (SEM), energy dispersed X-ray spectrometry (EDX) and X-ray diffractometry (XRD). The catalytic activity of these Pd/BCNT pellets were tested in hydrogenation of chlorate in a continuous flow system. The hydrogenation process was followed by using of a miniaturized spectrophotometric cell developed by us. The catalysts proved to be efficient, because of the higher chlorate hydrogenation 90.5% chlorate conversion could be reached.Graphical Abstract: [ABSTRACT FROM AUTHOR]

The synthesis of palladium and palladium-silver catalysts using supercritical fluid CO2-impregnation (static conditions) was studied. It was shown that the highest amount of metal is impregnated onto a support in a temperature range of 318-323 K and a pressure range of 19.0-23.0 MPa. The activities of palladium catalysts prepared according to the proposed procedure were comparable with those of currently produced industrial samples. [ABSTRACT FROM AUTHOR]

It is shown that modification of zinc oxide with polyethylene glycol leads to an increase in the catalytic activity of 1% Pd/ZnO nanocomposites in the low-temperature selective hydrogenation of acetylenic alcohols. This effect is due to the formation of palladium nanoparticles 2-4 nm in size in the polymer layer attached to the surface of the zinc oxide. [ABSTRACT FROM AUTHOR]

Polyacrylamide grafted onto silica nanoparticles (nano-SiO2-g-PAAm) was prepared through “grafting to” approach via controlled reversible addition-fragmentation chain transfer (RAFT) polymerization system with defined molecular weight and graft density. Modification of the nano-SiO2-g-PAAm with ethanolamine and subsequent reaction with chlorodiphenylphosphine (ClPPh2) was produced polymer-grafted silica with phosphinite functionality which was converted to Pd catalyst through the reaction with Pd(OAc)2. The catalyst was characterized using ICP, FT-IR, TGA, SEM, and DLS methods properly. Dispersion of palladium nanoparticles (PdNPs) in the polymer matrix (10-15-nm range) and existence of Pd in zero oxidation state was verified by TEM and XRD techniques. The catalyst demonstrated activity in the Mizoroki-Heck cross-coupling reaction of varied iodoarenes including electron poor, electron rich, and ortho substituted and heterocycles with olefins efficiently. Reusing of the Pd catalyst was performed at least five times in repeating runs without considerable palladium leaching and change of the catalyst function and structure.Organic-inorganic hybrid catalytic system composed of modified polyacrylamide brushes grafted onto nano-sized silica supported Pd nanoparticles was prepared via RAFT polymerization method through “grafting to” approach. This heterogeneous catalyst was applied in the Mizoroki-Heck reaction of various iodoarenes appropriately. The catalyst was reused at least five times in repeating sequences. [ABSTRACT FROM AUTHOR]

A template consisting of Pd(OAc)2 immobilized on imine-functionalized microporous covalent triazine polymer network (Pd/TATAE) was synthesized and found to be an efficient and recyclable heterogeneous solid catalyst for Mizoroki-Heck C-C coupling of styrene with substituted aryl halides under mild reaction conditions and without addition of any ligand or additives. Furthermore, Pd/TATAE could be recycled for nine consecutive cycles with minor loss of catalytic activity. Finally, the Pd/TATAE catalyst showed good catalytic activity with excellent yield of 96 % and high turnover number of 3349. [ABSTRACT FROM AUTHOR]

The study addresses the effect of the reduction conditions of palladium polynuclear hydroxo complexes (PHC) supported on the Sibunit carbon material on the dispersion of the metal particles and the activity of 0.5%Pd/Sibunit catalysts in the selective hydrogenation of sodium 2,4,6-trinitrobenzoate to 1,3,5-triaminobenzene in an aqueous solution (temperature of 323 or 343 K, pressure of 0.5 MPa). The palladium PHC were reduced using the most common methods pertaining to catalyst preparation: liquid-phase reduction with sodium formate and reduction in a hydrogen flow at elevated temperature. It was found that high-temperature reduction in the gas phase gives rise to Pd particles with a markedly lower dispersion compared with the sample obtained under mild liquid-phase reduction conditions. The catalytic activity of the sample containing large Pd particles proved to be higher than the activity of the catalyst obtained by reduction with sodium formate. [ABSTRACT FROM AUTHOR]

The effect of polymers on the formation of nanosized palladium catalysts for the selective hydrogenation of acetylenic alcohols to give alkenols was studied. Various physicochemical methods such as TEM and XPS were used to show that palladium nanoparticles with diameter 1-4 nm stabilized by polyethylene glycol or pectin on a ZnO support display enhanced catalyst activity and selectivity. [ABSTRACT FROM AUTHOR]

Supported palladium nanocatalysts have been reported to be active in selective hydrogenation of acetylene. In this work, non-thermal radio frequency plasma modification has been applied to Pd/AlO catalysts for selective hydrogenation of acetylene in the presence of excess ethylene. High ethylene selectivity, good acetylene conversion activity and high TOF were obtained on the plasma-treated catalysts. To understand the plasma effect, the catalysts were characterized by differential scanning calorimetry in hydrogen (H-DSC), pulse H chemisorption, X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption with ethylene (CH-TPD) experiments. XPS and H-DSC results confirmed that the Pd precursor could be effectively reduced to the metallic state during the room temperature plasma treatment. Plasma treatment also improved the dispersion of Pd particles with strong interaction between AlO support and PdO and Pd nitrate precursors. In addition, CH-TPD indicated that plasma treatment could lead to an enhanced catalytic performance on selective hydrogenation of acetylene. It demonstrates that the non-thermal RF plasma treatment is an effective way to manipulate surface properties and the interaction between metals and supports of supported Pd catalysts for selective hydrogenation. [ABSTRACT FROM AUTHOR]

The kinetics describing the formation of the system Pd/thin layer of MgO (100) surface was investigated by applying programs developed on the basis of Fortran Software. The simulation is based on studies related to nucleation, crystallite growth, coalescence and diffusion of clusters on the surface of thin films. The density of Pd islands is obtained by simulating the deposition of 1 × 10 atoms cm s in 150 s. The density of clusters first increases to reach a plateau. Then, it either remains some time at a nearly constant value or decreases slowly after the saturation regime gives way to the coalescence stage. This phenomenon is explained via island migration process at the surface. The coalescence time strongly depends on the deposition temperature, the coalescence occurs when the substrate temperature is high. Also, the surface coverage decreases when the substrate temperature increases. The coalescence is pronounced at a low surface coverage. It involves the migration on the surface, defined as the dynamic coalescence and precedes the process of the formation of immobile islands that predominates at high extents of surface coverage. [ABSTRACT FROM AUTHOR]

In this work, we have found that the pair palladium acetate/hydrogen peroxide promoted a rare oxidative cyclization of β-citronellol, resulting in the selective formation of a novel monoterpene derivative (i.e., (Z)-4,8,8-trimethyl-3,4,5,8-tetrahydro-2H-oxocine). The activity of different palladium-catalysts was assessed. Palladium acetate was the most active and selective catalyst, providing the oxocine derivative with high selectivity and conversion ( ca. 79 and 83%, respectively) after 4 h reaction. The high atom efficiency, the use of green oxidant and the short reaction time comprise the main aspects of this process. Graphical Abstract: [ABSTRACT FROM AUTHOR]

The potential of ozone (O) for preparation of supported metal catalyst remained unexplored. In this work, a two-step preparation method comprising ion-exchange and room temperature ozone treatment was developed to prepare a zeolite (silicalite-1) supported palladium catalyst. The fundamental preparation chemistry was examined by diffuse reflectance UV-Vis spectroscopy, IR and Raman spectroscopy, X-ray powder diffraction (XRD), and scanning transmission electron microscopy (STEM). While conventional thermal calcination produced PdO particles mostly on the external surface of silicalite-1 crystals, ozone treatment produced PdO clusters mostly within the zeolite crystals. Compared with thermal calcination, room temperature ozone treatment can significantly suppress the migration of palladium species outward to the external surface of the zeolite crystals. PdO/silicalite-1 catalyst prepared with this method exhibited good catalytic activity and stability for catalytic methane combustion. The methane combustion started at about 250 °C; the T and T (the temperatures at which methane conversion reaches 50 and 90% respectively) were 345 and 403 °C, respectively. The conversion decreased slightly from 100 to 96.1% after 24 h of reaction at 500 °C. Deactivation is due to some growth of PdO crystallite revealed by Raman spectroscopy and still could not be detected by XRD. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Pd/Sibunit and Pd-M/Sibunit (M = Ga, Zn, or Ag) catalysts have been synthesized, and their catalytic properties in liquid-phase acetylene hydrogenation have been investigated. Doping of the palladium catalyst with a metal M leads to the formation of the PdGa, PdZn, or PdAg bimetallic compound. The bimetallic particles are much smaller (1.6-2.0 nm) than the monometallic palladium particles (4.0 nm). Doping with zinc raises the ethylene selectivity by 25% without affecting the activity of the catalyst. Specific features of the effect of each of the dopants on palladium are reported. [ABSTRACT FROM AUTHOR]