- Hydrogen-free homogeneous catalytic reduction of olefins in aqueous solutions
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(Chemical Equation Presented) Herein we report a study involving the homogeneous catalytic reduction of unsaturated substrates in aqueous solutions or water-organic solvent mixtures. The reduction of olefins has been carried out in the presence of catalytic amounts of [Fe(CN)5NH3] 3- and excess of NH2OH, which under mild reaction conditions can be used to reduce carbon-carbon unsaturations without affecting carbonyl functionalities and aromatic rings. To explore the scope of the catalytic reduction, a wide variety of representative unsaturated substrates have been examined. The steric effects of the substituents on the carbon-carbon multiple bond as well as the regioselectivity and stereoselectivity of the catalyst have been studied. The deuterium kinetic isotope effect on the catalytic reduction of double bonds in olefins has been analyzed, and no significant kinetic isotope effect was found. Among the great advantages of this novel procedure for catalytic reduction are that hydrogen and high pressures are not needed, the catalyst is inexpensive and easily prepared, and water as well as water-organic solvent mixtures can be used as reaction media.
- Gaviglio, Carina,Doctorovich, Fabio
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p. 5379 - 5384
(2008/12/20)
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- An ionic liquid as catalyst medium for stereoselective hydrogenations of sorbic acid with ruthenium complexes
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The ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate (bmim PF6) (6) has been studied as catalyst medium for biphasic homogeneous hydrogenations of sorbic acid (1). As catalyst we used the Cp*-ruthenium-complex [Cp*Ru(η4-CH3-CH=CH-CH=CH-COOH) (CF3SO3)] which efficiently enables the stereoselective hydrogenation of sorbic acid leading to the formation of cis-3-hexenoic acid (3) in selectivities of up to 90% with turnover frequencies of up to 1100 h-1. Compared to other biphasic systems the hydrogenation in bmim PF6 proceeds with enhanced activity. The kinetics can be described with a Michaelis-Menten-equation, and the activation energy for the whole process was determined to be EA = 78 ± 5 kJ/mol. Wiley-VCH Verlag GmbH, 2000.
- Steines, Stephan,Wasserscheid, Peter,Driessen-Hoelscher, Birgit
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p. 348 - 354
(2007/10/03)
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- Palladium(II) catalyzed novel rearrangement of 1-allyloxy-1-siloxycyclopropanes
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Pd(II) salts catalyze the rearrangement of 1-allyloxy-1-siloxycyclopropanes to provide a mixture of Δ2-, Δ3- and Δ4-hexenonic acids. This rearrangement proceeds via a double bond isomerization followed by a ring opening of
- Yasui, Kengo,Fugami, Keigo,Tanaka, Shuji,Tamaru, Yoshinao,Ii, Atsuhiko,Yoshida, Zen-Ichi,Saidi, Mohamad R.
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p. 789 - 792
(2007/10/02)
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- Lithium/Ammonia Reductions of 2-Thiophenecarboxylic Acids
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Lithium/ammonia reductions of 2-thiophenecarboxylic acids (1) in the absence of a proton source afforded mixtures of products.In the presence of methanol acyclic mercapto carboxylic acids (4) were the major products.Ring closure of 4 to the corresponding thiolactones (12) showed the double bonds in 4 to be of cis geometry.Attempts were made to prepare Z olefinic compounds derived from these mercapto carboxylic acids.Lithium 2-thiophenecarboxylate salts (2) afforded good yields of the corresponding 2,5-dihydro-2-thiophenecarboxylic acids (3).The presence of substituents on the ring and the ratio of metal to acid were significant factors in determining the nature of this products.A mechanism is proposed to explain the products observed.
- Blenderman, Walter G.,Joullie, Madeleine M.,Preti, George
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p. 3206 - 3213
(2007/10/02)
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