Palladium catalysis dehydrogenation

DEHYDROGENATION Anthraquinone. Chloranil. 2,3-DichIoro-5,6-dicyano-1,4-benzoquinone. Diethyl azodicarboxylate. Manganese dioxide. Palladium catalysis. Potassium hydride. Palladium-on-carbon. N,N,N, N -Tetramethylethylenediamine. Trifluoroacetic acid. 

With palladium catalysis, refluxing in nitrobenzene or xylene dehydrogenates 3-substituted 5,6,7,8-tetrahydropyrido[4,3-rf]pyrimidin-4(3//)-ones to yield the corresponding aromatic compounds. Thus, the 3-phenyl compound is dehydrogenated by heating in nitrobenzene with palladium on carbon at 125 130°C for 17 hours.509... 

Similar 1 1 and/or 1 2 coupling reactions of benzamides with alkynes were reported by Guimond s, Rovis s, and Li s groups [35]. Later, ruthenium- [36], palladium- [37], and nickel-catalyzed [38] versions for isoquinolinone synthesis were disclosed. Shi et al. reported similar lactam formation through dehydrogenative annu-lation of an indolecarboxamide 91 with 2c under palladium catalysis (Scheme 25.45) [39],... 

A number of transition metal complexes will catalyze the dehydrogenative coupling of organotin tin hydrides, R SnI I, to give the distannanes, RjSnSnRj.443 These metals include palladium,449 gold,450, hafnium,451 yttrium, and ruthenium.452 The catalyst that is most commonly used is palladium, often as Pd(PPh3>4, and the most active catalysts appear to be the heterobimetallic Fe/Pd complexes, in which both metals are believed to be involved in the catalysis.443... 

New applications of dichlorodicyanobenzoquinone (DDQ) for the dehydrogenation of ketones include the conversion of a 4,7-dien-3-one into the 4,6,8(14)-trienone, which is further dehydrogenated to the l,4,6,8(14)-tetraenone with acidic catalysis.The dehydrogenation of a 4-en-6-one with DDQ affords the 2,4-dien-6-one. Selective 1,2-dehydrogenation of 5a-cholestan-3-one has been achieved with palladium acetylacetonate and oxygen.Possible alternative mechanisms are discussed. 

The mechanism which can be proposed for the observed reduction is similar to the one indicated for the reduction of a haloarene by an alcohol, catalyzed by the palladium (ref. 12). In the case of a palladium(O) catalysis, the different steps of this mechanism are shown in the following Scheme 3, involving in particular the dehydrogenation of the amine [the same reactions performed without any amine leads to exclusive formation of the reduction product 7 in a very low yield (< 5%). 

Supported metal clusters play an important role in nanoscience and nanotechnology for a variety of reasons [1-6]. Yet, the most immediate applications are related to catalysis. The heterogeneous catalyst, installed in automobiles to reduce the amount of harmful car exhaust, is quite typical it consists of a monolithic backbone covered internally with a porous ceramic material like alumina. Small particles of noble metals such as palladium, platinum, and rhodium are deposited on the surface of the ceramic. Other pertinent examples are transition metal clusters and atomic species in zeolites which may react even with such inert compounds as saturated hydrocarbons activating their catalytic transformations [7-9]. Dehydrogenation of alkanes to the alkenes is an important initial step in the transformation of ethane or propane to aromatics [8-11]. This conversion via nonoxidative routes augments the type of feedstocks available for the synthesis of these valuable products. 

The main part of the compound (decahydroazulene) decomposes and azulene forms, evidently, by dehydrogenation by the doublet mechanism. Thus, although the aromatic nature affects catalysis to a certain degree, it cannot by itself bring about a smooth dehydrogenation such as occurs in the case of cyclohexane. In order that catalysis take place, a structural correspondence is also necessary. Bicyclo[5.3.0]decane, contrary to cyclohexane, has no elements of symmetry common with with the lattice A1 of palladium and cannot superimpose on it. 

Liang W. Q., Hughes R. 2005. The catalytic dehydrogenation of isobutane to isobutene in a palladium/silver composite membrane reactor. Catalysis Today 104 238-243. 

Dittmeyer, R., Hollein, V. and Daub, K. (2001) Membrane reactors for hydrogenation and dehydrogenation processes based on supported palladium. Journal of Molecular Catalysis A Chemical, 173, 135-184. 

Lin, W.-H., Chang, H.-F. (2004). A study of ethanol dehydrogenation reaction in a palladium membrane reactor. Catalysis Today, 97, 181—188. 

Cui, T., Fang, J., Zheng, A., Jones, F., Reppond, A. (2000). Fabrication of microreactors for dehydrogenation of cyclohexane to benzene. Sensors and Actuators B Chemical, 71,228—231. Dittmeyer, R., Hollein, V., Daub, K. (2001). Membrane reactors for hydrogenation and dehydrogenation processes based on supported palladium. Journal of Molecular Catalysis A, 173, 135-184. 

Matsuda, T., Koike, I., Kubo, N., Kikuchi, E. (1993). Dehydrogenation of isobutane to isobutene in a palladium membrane reactor. Applied Catalysis A, General, 96, 3. 

Stoltz BM (2004) Palladium catalyzed aerobic dehydrogenation from alcohols to indoles and asymmetric catalysis. Chem Lett 33 362-367... 

Quicker, R, Hollein, V. and Dittmeyer, R. (2000) Catalytic dehydrogenation of hydrocarbons in palladium composite membrane reactors. Catalysis Today, 56, 21-34. 

Ai, M., 2002. Catalytic activity of palladium-doped iron phosphate in the oxidative dehydrogenation of lactic add to pyruvic acid. Applied Catalysis A 232,1-6. 

Markus, H., Plomp, A.J., Sandberg, T., Nieminen, V., Bitter, J.H. and Murzin, D.Y.Yu (2007) Dehydrogenation of hydroxymatairesinol to oxomatairesinol over carbon nanofibre-supported palladium catalysts. Journal of Molecular Catalysis A-Chemical, 274, 42. 

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