Homogeneous Palladium Catalysts Research Articles

Synthesis of condensation polymers catalyzed by palladium-graphite

Palladium-graphite (PdGr) was applied to polycondensations as a heterogeneous palladium catalyst. Catalytic activities of PdGr for the Heck reaction and a carbonyl insertion reaction were investigated using the model reactions. Polycinnamamide was synthesized through the Heck reaction of N, N′-(3,4′-oxydiphenylene)bis(acrylamide) and bis(4-iodophenyl) ether catalyzed by PdGr. The polymerization proceeded efficiently in the presence of tributylamine, but required a long reaction time compared with the case of homogeneous catalysts. The resulting polymer was almost white in color, which means that it was less contaminated by palladium metal. The removal and recycling of PdGr were much easier than the case of homogeneous catalysts. Aramid was also synthesized through the carbonyl insertion reaction of m-diiodobenzene and bis(4-aminophenyl) ether catalyzed by PdGr. The rate of carbon monoxide consumption for the polymerization catalyzed by PdGr was almost equal to that catalyzed by the homogeneous palladium catalyst. In both cases, the structures of the resulting polymers were identical to those prepared by homogeneous palladium catalysts.

Metal-assisted reactions. Part 25. Heterogeneous and homogeneous catalytic transfer hydrogenolysis of allyloxytetrazoles to yield alkenes or alkanes

Transfer hydrogenolysis of 5-allyloxy-l-phenyltetrazoles using either a heterogeneous or a homogeneous palladium catalyst and a hydrogen donor leads to cleavage of the allyloxy C–O bond to yield an alkane or an alkene and 1-phenyltetrazolone, depending on the catalyst used.

ChemInform Abstract: Chemoselective Hydrogenation of the Double Bond of Vinyl Epoxides with Homogeneous Palladium and Iridium Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chemoselective hydrogenation of the double bond of vinyl epoxides with homogeneous palladium and iridium catalysts

The selective hydrogenation of the double bond of vinyl epoxides is catalyzed by either the species generated by treatment of the binuclear palladium complex, [(Bu t 2PH)PdPBu t 2] 2 with oxygen, or by the cationic iridium(I) complex, [Ir(COD)(PPh 3)(PhCN)]BF 4, to produce the corresponding saturated epoxides at room temperature, and with good selectivity.

Direct and carbonylative vinylation of steroidal triflates in the presence of homogeneous palladium catalysts

The palladium-catalyzed vinylation of several steroid 2-enyl- and 3,5-dienyl-3 triflates and estrone-3-triflate was systematically examined using vinyltributylstannane as a vinylating agent. In carbon monoxide atmosphere the insertion of a CO molecule took place and unsaturated ketones were obtained. In this way new steroid derivatives containing unsaturated side chain were produced, which can serve as starting material for further functionalization of the steroid skeleton.

Investigations of the progress of an organic chemical reaction by precision calorimetry. Part 2

The application of calorimetry to the dimerization of isoprene yielded various results that depend on the homogeneous palladium catalyst, its composition, the solvent selected and, not least, the concentration of isoprene. The influences of all the variables were optimized with respect to the turnover and the ratio of the two main products that are the head-head or head-tail configurations of dimeric isoprene. The products are of interest in perfumery.

Efficient palladium catalysts for the carbonylation of alkynes

A class of highly efficient homogeneous palladium catalysts has been developed for the carbonylation of alkynes. One application of interest is the selective production of methyl methacrylate by methoxycarbonylation of propyne. The essential feature of the new catalyst systems is that they are formed by the combination of a ligand containing a 2-pyridylphosphine moiety with a palladium(II) species and a proton source containing weakly coordinating anions. High turn-over numbers of more than 40000 mol (mol Pd) −1 h −1 and selectivities towards methyl methacrylate of up to 99.95% can be obtained under mild conditions. It is suggested that the 2-pyridylphosphine ligand plays an essential role both as a chelating PN ligand in the selectivity-determining step and as a monocoordinated ligand in the rate-determining step of the catalytic cycle.

Hydrogenation of liquid carboxylated nitrile rubber

AbstractHydrogenation of liquid carboxylated nitrile rubber (L‐XNBR) was carried out using homogeneous palladium and rhodium catalysts. It was observed that the six‐membered cyclic palladate complex of 2‐benzoylpyridine, 1, reduces the carbon‐carbon double bonds without affecting the nitrile and carboxyl functionality. The intrinsic viscosity of the polymers remains unchanged during hydrogenation. The glass transition temperature is marginally lowered for the hydrogenated products. A great extent of decarboxylation was obtained for samples hydrogenated in presence of the rhodium complex, 2.

Efficient palladium catalysts for the copolymerization of carbon monoxide with olefins to produce perfectly alternating polyketones

A class of highly efficient homogeneous palladium catalyst systems has been developed for the production of perfectly alternating copolymers of carbon monoxide with ethylene. Mixtures of carbon monoxide, ethylene and propene are converted into the corresponding alternating carbon monoxide/olefin terpolymers in which C 3 units randomly replace ethylene units along the chain. The essential features of the new catalyst systems are that they are formed by the combination of an equimolar quantity of a suitable bidentate phosphine ligand with a palladium(II) species in which the counter anions are weakly coordinating. For a series of diphenylphosphinoalkanes of general formula Ph 2P(CH 2) m PPh 2 the most efficient catalyst system for the production of high-molecular-weight polyketones is that with m = 3. High rates with conversions of more than one million molecules of carbon monoxide and ethylene per palladium center are obtained. In methanol, the majority of the polymer chains produced are polyketo-esters of general formula H(CH 2CH 2CO) n OMe; analyses of methanol-soluble oligomer fractions shows that diesters MeOCO(CH 2CH 2CO) n OMe and diketones H(CH 2CH 2CO) n CH 2CH 3 are also formed. Two interlinked catalytic cycles are invoked to account for the formation of polyketones with keto-ester, diester and diketone end groups.

Synthesis of 9-Organyl-1,2 and 1,7-Dicarba-closo-dodecaboranss(12) via the Cross-Coupling Reactions Between Organozinc Compounds and 9-Iodo-1,2- or 1,7-Dicarba-closo-dodecaboranes

Abstract 9-Alkyl-, 9-aryl-, and 9-ethynyl-1,2- or 1,7-dicarba-closo-dodecaboranes were prepared via the cross-coupling reaction between alkyl-, aryl-, or ethynylzinc compounds and 9-iodo-1,2- or 1,7-dicarba-closo-dodecaboranes in the presence of homogeneous palladium catalysts.

Enantioselective telomerization: I. Telomerization of butadiene with formaldehyde, β-dicarbonyl compounds, nitroalkanes, and enamines

Enantioselective telomerization reactions catalyzed by homogeneous palladium catalysts are described. Applying the concept of chiral bidentate phosphorus ligands and low temperatures proved useful in telomerizing butadiene with formaldehyde, with a β-dicarbonyl compound and with a nitroalkane. Excess of enantiomers up to 41% could be obtained. With a chiral enamine as nucleophile ee values of 72% have been observed.

Hydrogenation of nitrile rubber using a new homogeneous palladium (II) catalyst: Synthesis and characterization

Journal of Applied Polymer ScienceVolume 41, Issue 5-6 p. 1357-1363 NoteFree Access Hydrogenation of nitrile rubber using a new homogeneous palladium (II) catalyst: Synthesis and characterization Susmita Bhattacharjee, Susmita Bhattacharjee Indian Institute of Technology, Kharagpur 721 302, IndiaSearch for more papers by this authorAnil K. Bhowmick, Anil K. Bhowmick Indian Institute of Technology, Kharagpur 721 302, IndiaSearch for more papers by this authorB. N. Avasthi, B. N. Avasthi Indian Institute of Technology, Kharagpur 721 302, IndiaSearch for more papers by this author Susmita Bhattacharjee, Susmita Bhattacharjee Indian Institute of Technology, Kharagpur 721 302, IndiaSearch for more papers by this authorAnil K. Bhowmick, Anil K. Bhowmick Indian Institute of Technology, Kharagpur 721 302, IndiaSearch for more papers by this authorB. N. Avasthi, B. N. Avasthi Indian Institute of Technology, Kharagpur 721 302, IndiaSearch for more papers by this author First published: 1990 https://doi.org/10.1002/app.1990.070410544Citations: 21AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume41, Issue5-61990Pages 1357-1363 ReferencesRelatedInformation

Recovery of Dunaliella salina cells following hydrogenation of lipids in specific membranes by a homogeneous palladium catalyst

Unsaturated fatty acyl chains of Dunaliella salina membrane lipids can be catalytically reduced by the homogeneous hydrogenation catalyst palladium di(sodium alizarine monosulphonate), Pd(QS) 2, under conditions permitting full recovery of the cells within 24 h. The hydrogenation is accomplished by incubation of cells with the hydride form of Pd(QS) 2 under 1 atmosphere of H 2 and for 2 min or less. Following this protocol, hydrogenation reduces only those fatty acids located in the plasma membrane and other membranes located near the cell surface. The limited reactivity in vivo is due to the fact the Pd(QS) 2 permeates into the living cells more slowly than it does into liposomes prepared from extracted Dunaliella membrane lipids. While Dunaliella is completely unaffected by exposure to the oxygenated, inactive catalyst, hydrogenated cells cease growth for approximately 12 h, during which time the hydrogenated acyl chains are being enzymatically retroconverted to their original unsaturated form. When the lipid composition approaches its prehydrogenation values, growth resumes, presumably due to the restoration of normal membrane functions. The system shows promise for studying the metabolic regulation of membrane microviscosity.

ChemInform Abstract: Palladium‐Catalyzed Triethylammonium Formate Reduction of Aryl Triflates. A Selective Method for the Deoxygenation of Phenols.

Abstract Phenols can be selectively deoxygenated by reduction of the corresponding aryl triflates with triethylammonium formate in the presence of a homogeneous palladium catalyst.

Palladium-catalyzed triethylammonium formate reduction of aryl triflates. A selective method for the deoxygenation of phenols

Phenols can be selectively deoxygenated by reduction of the corresponding aryl triflates with triethylammonium formate in the presence of a homogeneous palladium catalyst.

Influence of the basicity of amines on the direction and structural selectivity of their telomerization with butadiene in the presence of palladium complexes

1. The telomerization of o-, m-, and p-substituted anilines with butadiene in the presence of homogeneous palladium catalysts has been investigated. 2. The direction, selectivity, and structural specificity of the telomerization of anilines with butadiene can be controlled not only by varying the basicity and structure of the starting anilines, but also by changing the nature and structure of the catalyst components.

New method for dehydrogenation of 1,4-dihydropyridines to pyridines using homogeneous complex palladium catalysts

1. We were the first to study the dehydrogenation of 1,4-dihydropyridines using catalytic amounts of homogeneous Pd catalysts and it was shown that 2,6-dimethyl-3,5-dicarbethoxy-1,4-dihydropyridine and its 4-substituted alkyl-(CH3-C4H9) and aryl- (C6H5, o-C6H4OH, CH=CH-C6H5, p-C6H4-OCH3) derivatives are easily converted to the corresponding pyridines under the influence (10 h, 100°) of the catalyst: Pd(acac)2-P(C4H9)3-Al(C2H5)3-CF3CO2H (1∶3∶3∶10). 2) When substituted 1,4-dihydropyridines are dehydrogenated in the presence of 1,5-cyclooctadienes the latter undergo simultaneous selective hydrogenation to the corresponding cyclooctenes.

Study of isomerization and hydrogenation reactions of olefins in the presence of a palladium catalyst based on dimethyl sulfoxide

1. A homogeneous palladium catalyst based on dimethyl sulfoxide accelerates the transformation of pentenes at 20° and hydrogen pressures close to atmospheric. 2. The migration of the C=C bond of 1-pentene proceeds at a faster rate than does its hydrogenation, cis-2-Pentene is converted much more rapidly to the trans-isomer than to n-pentane. 3. Apparently the observed processes proceed with the involvement of coordinated hydrogen: isomerization is not observed in its absence.

Dimerization and polymerization of allene by a homogeneous palladium catalyst

Dimerization and polymerization of allene by a homogeneous palladium catalyst