Palladium-catalyzed dehydrogenation of benzylic alcohols in molten ammonium salts, a recyclable system (original) (raw)
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Molecules
For the creation of adaptable carbonyl compounds in organic synthesis, the oxidation of alcohols is a crucial step. As a sustainable alternative to the harmful traditional oxidation processes, transition-metal catalysts have recently attracted a lot of interest in acceptorless dehydrogenation reactions of alcohols. Here, using well-defined, air-stable palladium(II)–NHC catalysts (A–F), we demonstrate an effective method for the catalytic acceptorless dehydrogenation (CAD) reaction of secondary benzylic alcohols to produce the corresponding ketones and molecular hydrogen (H2). Catalytic acceptorless dehydrogenation (CAD) has been successfully used to convert a variety of alcohols, including electron-rich/electron-poor aromatic secondary alcohols, heteroaromatic secondary alcohols, and aliphatic cyclic alcohols, into their corresponding value-added ketones while only releasing molecular hydrogen as a byproduct.
Palladium-based catalysts for the synthesis of alcohols
Journal of Molecular Catalysis A: Chemical, 2003
The present work intends to illustrate the effects of precursor and support composition on the structure and performance of Pd-based catalysts for the synthesis of methanol and higher oxygenated compounds. The power of the XRD technique and the reaction itself, as characterisation tools, was evidenced.
Palladium-catalyzed oxidation of primary alcohols: Highly selective direct synthesis of acetals
Applied Catalysis A: General, 2007
Selective direct synthesis of symmetric acetals through a tandem aerobic oxidation-acetalization of primary alcohols, using a chloride-free Pd(OAc) 2 /Cu(OAc) 2 /p-TsOH system as an efficient bifunctional catalyst, has been developed. The reactions occur in neat alcohols with no use of other solvent under mild conditions (50-80 8C, 1-10 atm). p-Toluenesulfonic acid exerts a great accelerative and catalyst stabilizing effect, showing a synergism with Cu(OAc) 2. Bimetallic Pd-Cu catalysis is suggested in these reactions. Under similar conditions, a secondary alcohol, propanol-2, reacts more slowly giving mainly acetone. Conventional palladium catalytic systems, such as PdCl 2 /CuCl 2 , Pd(OAc) 2 /LiNO 3 , and Pd(OAc) 2 /pyridine, showed no or very low activity in the oxidation of neat n-butanol.
Journal of Catalysis, 2007
Deuteration in combination with multinuclear NMR spectroscopy was applied to elucidate the pathway of the C-O bond scission of 1-(4isobutylphenyl) ethanol (4-IBPE) to 4-isobutylethylbenzene (4-IBEB) over Pd/SiO 2 , Pd/C, and unsupported Pd black. Information about the pathway was obtained by determining the positions at which deuterium was incorporated by means of 1 H, 2 H, and 13 C NMR spectroscopy. The C-O bond scission of 4-IBPE over Pd/SiO 2 and Pd black occurred exclusively by direct hydrogenolysis, whereas both hydrogenolysis and the dehydration-hydrogenation route were observed over Pd/C. The latter was attributed to the acidic nature of the carbon support. Spillover of dissociatively adsorbed hydrogen from the metal surface to the support does not play an important role in the direct hydrogenolysis of 4-IBPE over Pd.
Advanced Synthesis & Catalysis, 2013
A simple method has been developed for the reductive deoxygenation of aromatic ketones and benzylic alcohols in the presence of polymethylhydrosiloxane (PMHS). The reductive deoxygenation of aromatic ketones and benzylic alcohols, including secondary alcohols, to the corresponding methylene hydrocarbons has been achieved in good to excellent yields using palladium chloride (PdCl 2) as catalyst and PMHS as hydride source. Such deoxygenations were successfully with aryl alkyl ketones and diaryl ketones, as exemplified by the reductive deoxygenation of acetophenone and benzopheneone, respectively. The corresponding benzylic alcohols and secondary alcohol analogues could also be converted into their respective methylene hydrocarbons by the PdCl 2 /PMHS system.
Journal of Organometallic Chemistry, 1985
The palladium-mediated reaction of oxidative carbonylation of arylmercury compounds to form the derivatives (particularly anhydrides or esters) of the corresponding carboxylic acids has been fully re-investigated in order to establish its synthetic utility. The reaction, which can be accomplished either starting from the preformed mercury compounds or via their preliminary synthesis in situ, is solvent-dependent. Yields can be increased by the carefully controlled addition of a co-catalyst such as a base (sodium acetate) and in the latter case also strong acids (HClO, or HBF,). The best yields are obtained in trifluoroacetic acid, which is an ideal solvent for carrying out the reaction; conditions are very mild (room temperature and under 1 atm of CO pressure). * For part 1X see ref. 11. ** Dedicated to Prof. J. Halpern on the occasion of his 60th birthday. 0022-328X/85/%03.30 0 1985 Elsevier Sequoia S.A.
Recent advances in the homogeneous palladium-catalyzed aerobic oxidation of alcohols
Journal of the Iranian Chemical Society, 2008
This review is dedicated to Professor Habib Firouzabadi on the occasion of his 65 th birthday and also his honerable retirement The use of palladium catalysts for the oxidation of alcohols to aldehydes and ketones in the presence of various types of reoxidants is well known. Recently, the advantages of using molecular oxygen as the oxidant in the Pd-catalyzed oxidation of alcohols have been explored. The aim of this review is to provide an overview on the most important homogeneous palladiumcatalyzed aerobic oxidation of alcohols without a co-catalyst during last decade until the end of 2007.