Conventional Palladium Catalyst Research Articles

Basketing nanopalladium into calix[4]pyrrole as an efficient catalyst for Mizoroki-Heck reaction

An approach to synthesize calix[4]pyrrole protected palladium nanoparticles (PdNPs) employed for catalytic Mizoroki-Heck C-C coupling reaction is reported. The nanoparticles are synthesized in water using novel calix[4]pyrrole tetrahydrazide (CPTH) as a reducing as well as stabilizing agent which is a proficient “one-pot” synthesis discouraging the need of an external stabilizer. CPTH-PdNPs have been characterized and studied by UV–Vis spectroscopy, Fourier transform infrared, transmission electron microscopy, energy‐dispersive X‐ray and powder X‐ray diffraction. The synthesized palladium nanoparticles with a size range of 5–9nm show an efficient catalytic activity for Heck cross-coupling reactions giving good yields within short reaction time in comparison with conventional palladium catalyst. Also, a good degree of recyclability is shown by the nanocatalyst with five consecutive catalytic cycles. CPTH-PdNPs also exhibit a potential antimicrobial activity against gram-negative bacteria which shows the biological applicability of the synthesized CPTH-PdNPs.

Catalytic activity of recyclable resorcinarene-protected antibacterial Pd nanoparticles in C-C coupling reactions

Novel tetra-methoxy resorcinarene tetra-hydrazide (TMRTH) has been synthesized and used as a reducing agent and a capping agent for the synthesis of water-dispersible stable palladium nanoparticles (PdNPs). The TMRTH-PdNPs were characterized by UV-Vis spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and powder X-ray diffraction. The synthesized nanoparticles are polydispersible with a size of 5 ± 2 nm and were found to be recyclable over five cycles maintaining a catalytic activity in the Suzuki-Miyuara cross-coupling reaction. The nanocatalyst was superior in catalytic performance to conventional palladium catalysts with respect to reaction time, catalyst loading and recyclability. TMRTH-PdNPs show promise for their use in biological applications as they exhibit good antibacterial activity against gram-positive bacteria.

Copper-catalyzed distannylation of alkynes

A copper(I)-phosphine complex has been found to facilely promote the distannylation of alkynes with the aid of a base, where a catalytically generated Cu-Sn species serves as a key intermediate. The broad versatility of the copper catalysis has been demonstrated by the facile distannylation of unfunctionalized aliphatic alkynes, being hardly achievable with the conventional palladium catalysts.

Palladium-Catalyzed Alkynylation of Aryl and Hetaryl Halides: A Journey from Conventional Palladium Complexes or Salts to Palladium/Carbon

Palladium-catalyzed alkynylation of aryl and hetaryl -halideshas found wide application in the areas of synthetic, heterocyclic,and medicinal chemistry. Attempts to introduce the stable and potentiallyrecyclable palladium/carbon has provided an attractivealternative to the homogeneous palladium catalytic process. Thepresent article provides a personal account of the outcome of theuse of conventional palladium catalysts versus palladium/carbon,especially under Sonogashira conditions. 1 Introduction 1.1 The Focus on Palladium/Carbon 1.2 The Origin of the Research 2 Copper-Free Sonogashira Coupling: An Unusual Observation 3 Palladium-Mediated Synthesis of 3-Substituted (Thio)flavones:The Role of ( S)-Prolinol and Copper 4 Palladium/Carbon in Water 4.1 Synthesis of Benzo[ B]furans 4.2 2-Aminoethanol as an Alternative Base: Synthesis of Aryl- andHetaryl-Substituted Alkynes 4.3 Synthesis of Indoles 5 Palladium/Carbon in Organic Solvents 5.1 Synthesis of Isocoumarins and Phthalides 5.2 Synthesis of Thieno[2,3- C]pyranones 5.3 Synthesis of Alkynylpyrimidines 5.4 Synthesis of Furoquinolines and Pyrroloquinolines 5.5 Synthesis of 2 H-1,2-Benzothiazine1,1-Dioxides 6 Alkynylation of b-Chloroacroleins 7 Synthesis of Substituted Benzenes Fused with Carbocycles/Heterocycles:Palladium Salts versus Palladium/Carbon 8 Palladium/Carbon in the Union of Organic Azide andTerminal Alkynes 9 Conclusions: Towards Fulfilling the Requirements for Commercialization

Selective catalytic low pressure hydrogenation of acetophenone on Pd/ZnO/ZnAl2O4

A PdZn alloy-based catalyst was prepared by impregnation with a Pd salt of the oxides obtained by the thermal decomposition of a Zn–Al hydrotalcite. Two samples were obtained by carrying out the reduction at 373 and 673 K, that were characterized by chemical analysis, powder XRD and TEM. The catalytic activity was tested in the low pressure hydrogenation of acetophenone. The results were compared with those obtained using a conventional palladium catalyst.

New synthetic reactions catalyzed by cobalt complexes

Abstract Without suffering from β-elimination, cobalt complexes allow cross-coupling reactions of alkyl halides with Grignard reagents. A combination of a cobalt complex and trimethylsilylmethyl Grignard reagent effects Mizoroki-Heck-type reaction of alkyl halide with styrene, which conventional palladium catalysts have never made possible. Cobalt exhibits intriguing catalytic activities on hydrophosphination and allylzincation of alkynes. Silylmethylcobalt reagent is a powerful tool for the synthesis of highly silylated ethenes.

Multiple Vinylation of Tribenzotriquinacenes and Fenestrindanes at Their Aromatic Peripheries by Use of Nájera’s Catalyst

AbstractHighly efficient six‐ and eightfold Heck cross‐coupling reactions were carried out with two related convex‐concave and saddle‐shaped hydrocarbons bearing several ortho‐dibromo functionalities at the molecular periphery, viz. the hexabromotribenzotriquinacene 3a and the octabromofenestrindane 4a. In contrast to conventional palladium catalysts, use of Nájera’s oxime‐derived palladacycle catalyst 7 effected exhaustive vinylation with styrene or methyl acrylate in high yield and without concomitant formation of partial cross coupling or reduction products. The hexavinyltribenzotriquinacenes and octavinylfenestrindanes thus obtained are of interest as potential building blocks for novel organic networks. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Ni direct electroless metallization of polymers by a new palladium-free process

Ni films were electrolessly deposited on the surface of different polymer substrates without having to use the conventional palladium catalyst to initiate the redox reaction leading to metallization. With this in view, the surface to be coated was seeded with Ni(+2) species from an organo-nickel precursor. After reduction of the Ni(+2) ions to the Ni(0) oxidation state, it was possible to use the remarkable autocatalytic property of nickel to deposit a metallic film on the polymer by merely immersing in a Ni plating bath. The reduction of Ni(+2) species, less easy than that of Pd(+2) species commonly used in the authors' laboratory in the case of the tin-free process, was performed in the present work either using a chemical path or by plasma treatment in a non-oxidizing atmosphere (H 2 or Ar), then checked by XPS. This method was experimented on various polymer substrates using two different industrial Ni plating baths. Adhesion of Ni films evaluated by the Scotch® tape test mainly depends on the phosphorus content of the plating bath used, i.e. on the amount of stresses generated in the film which depends on the quantity of phosphorus present, the latter originating from the plating bath reducer. Both the nature of the polymer surface treatment and especially the route used to perform the Ni(+2) reduction play an important part in the interfacial stresses generated and therefore on film adhesion.

Characterisation of Mg/Al hydrotalcite with interlayer palladium complex for catalytic oxidation of toluene

The synthesis, characterisation and catalytic behaviour of palladium compound derived from Mg/Al hydrotalcite were investigated in the toluene total oxidation. The hydrotalcite sample was prepared by co-precipitation of the corresponding chlorides (MgCl 2, AlCl 3 and H 2PdCl 4) with boiled fresh water and under N 2 atmosphere. Under these conditions, the layered double hydroxide [Mg 0.75Al 0.25(OH) 2] 0.25+ PdCl 2 (OH) 2 0.125−x 2− (CO 3) x 2−· nH 2O was formed. Palladium species were inserted as [PdCl 2(OH) 2] 2− complex coming from the partial substitution of Cl with OH. The space interlayer was imposed by CO 3 2− present also as balancing anion. This new hydrotalcite is less stable than classical hydrotalcite Mg/Al without Pd since its destruction took place at a lower temperature. The palladium hydrotalcite calcined at 290 °C exhibited the best catalytic behaviour (activity and selectivity) in the total oxidation of toluene compared with a conventional palladium catalyst.

無電解ニッケルめっきの有孔度の低減と環境を配慮した評価法

An electro-graph test using zinc instead of cadmium was evaluated as a alternative porosity measurement method. This technique was effective in the porosity evaluation of electroless nickel plating on copper substrate.Pinholes of electroless nickel deposits produced on copper substrate by the conventional palladium catalyst process have been compared to direct electroless nickel plating on copper using DMAB as a second reducing agent.Results confirmed that fewer pinholes are produced on electroless nickel films when not using the palladium catalyst process than with films treated using the conventional palladium catalyst process. The direct electroless nickel plating films displayed excellent corrosion resistance.

Novel syntheses of ( Z)-alkene and alkane base-modified nucleosides

The syntheses of 5-( Z)-(3-aminoallyl)- and 5-(3-aminopropyl)-substituted 2′-deoxyuridine and 2′-deoxycytidine are reported. These compounds were derived from the corresponding 5-propargylamine derivative. [Hobbs, F. W. J. Org. Chem. 1989, 52, 3420.] The catalyst we have employed for these reductions is a NiCl 2/NaBH 4 system, which we have found to be superior to the more conventional palladium-catalysts previously reported with similar compounds.

Zum mechanismus der heck-reaktion: Katalysator-deaktivierung durch PC-bindungsbruch

The conventional palladium catalysts used in Heck reactions —Pd(OAc)2 + n P(aryl)3—suffer from extensive PC-bond cleavage at temperatures that would be necessary to activate aryl chlorides and electron-rich aryl bromides (> 120°C). This type of catalysts is, thus,not suitable to perform Heck reactions with non-activated substrates, especially with the technically interesting aryl chlorides.

Cationic palladium complexes as highly active catalysts in the telomerization of isoprene with diethylamine

Cationic palladium complexes such as [Pd(dppe)(py) 2][BF 4] 2, dppe = Ph 2PCH 2CH 2PPh 2, are active catalysts for the telomerization of isoprene with diethylamine to give under mild conditions N, N-diethyl(dimethyl-2,7-octadienyl) amines. In contrast to neutral palladium complexes, which favour tail-to-tail coupling of the isoprene units, the head-to-head and tail-to-head linkage prevails with these systems. Experiments with N-deuteriodiethyl-amine revealed that the hydrogen of the nucleophile adds selectively to C-6 of the octadienyl chain, as has been observed earlier for conventional palladium catalysts