- Mechanism of the Liquid-Phase Catalytic Hydrogenolysis on Palladium/Carbon of Cyclohexene Epoxides
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Heterogeneous catalytic hydrogenolysis of cyclohexene epoxides on 10percent Pd/C was studied in different solvents. The principal products were found to be alcohols, formed by cleavage of one epoxide C-O bond. In addition, simultaneous cleavage of both C-O bonds gave hydrocarbons, and isomerization on the catalyst gave ketones as byproducts. The deuterolysis of cis- and trans-tert-butylcyclohexene epoxides and kinetic studies with cyclohexene epoxides carrying an axial methyl group in position 3 or 5 showed that hydrogenolysis gives preferentially axial alcohols and trans hydrogen addition, after a "roll over" on the catalyst. If one epoxide carbon carries a methyl group, conformational and steric factors come into play. C-O bond cleavage at the more substituted carbon, leading to equatorial alcohols, becomes competitive with preferential formation of axial alcohols, and steric hindrance to molecular reorientation on the catalyst causes cis as well as trans hydrogen addition.
- Accrombessi, Georges C.,Geneste, Patrick,Olive, Jean-Louis,Pavia, Andre A.
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- Stereoselective hydrogenation of tert-butylphenols over charcoal-supported rhodium catalyst in supercritical carbon dioxide solvent
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Hydrogenation of 2-, 3-, and 4-tert-butylphenols was studied over a charcoal-supported rhodium catalyst in supercritical carbon dioxide (scCO2) solvent, and the results were compared with those in organic solvents. In the hydrogenation of 4-ter
- Hiyoshi, Norihito,Rode, Chandrashekhar V.,Sato, Osamu,Tetsuka, Hiroyuki,Shirai, Masayuki
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- The functionalization of saturated hydrocarbons. Part 24. The use of tert-butyl hydroperoxide: GoAggIV and GoAggV
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The use of tert-butyl hydroperoxide as an oxidant in Gif-type systems (GoAggIV and GoAgfV) catalyzed by various Fe(III) species is examined. Regioselectivity studids of these systems have revealed several characteristics similar to those observed for other prdviously reported Gif-type reactions. A common rdaction pathway for the GoAggIV and GoAggV oxidation systems and other Gif-type reactions (from alkane via alkyl hydroperoxide to ketone or alcohol) is seen.
- Barton, Derek H. R.,Chavasiri, Warinthorn
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- Trans-Selective and Switchable Arene Hydrogenation of Phenol Derivatives
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A trans-selective arene hydrogenation of abundant phenol derivatives catalyzed by a commercially available heterogeneous palladium catalyst is reported. The described method tolerates a variety of functional groups and provides access to a broad scope of trans-configurated cyclohexanols as potential building blocks for life sciences and beyond in a one-step procedure. The transformation is strategically important because arene hydrogenation preferentially delivers the opposite cis-isomers. The diastereoselectivity of the phenol hydrogenation can be switched to the cis-isomers by employing rhodium-based catalysts. Moreover, a protocol for the chemoselective hydrogenation of phenols to cyclohexanones was developed.
- Bergander, Klaus,Glorius, Frank,Heusler, Arne,Wollenburg, Marco
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p. 11365 - 11370
(2020/11/24)
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- Cobalt-Nanoparticles Catalyzed Efficient and Selective Hydrogenation of Aromatic Hydrocarbons
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The development of inexpensive and practical catalysts for arene hydrogenations is key for future valorizations of this general feedstock. Here, we report the development of cobalt nanoparticles supported on silica as selective and general catalysts for such reactions. The specific nanoparticles were prepared by assembling cobalt-pyromellitic acid-piperazine coordination polymer on commercial silica and subsequent pyrolysis. Applying the optimal nanocatalyst, industrial bulk, substituted, and functionalized arenes as well as polycyclic aromatic hydrocarbons are selectively hydrogenated to obtain cyclohexane-based compounds under industrially viable and scalable conditions. The applicability of this hydrogenation methodology is presented for the storage of H2 in liquid organic hydrogen carriers.
- Murugesan, Kathiravan,Senthamarai, Thirusangumurugan,Alshammari, Ahmad S.,Altamimi, Rashid M.,Kreyenschulte, Carsten,Pohl, Marga-Martina,Lund, Henrik,Jagadeesh, Rajenahally V.,Beller, Matthias
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p. 8581 - 8591
(2019/09/12)
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- γ-Silicon Stabilization of Carbonium Ions in Solvolysis. 4. Solvolysis of cis- and trans-3-(Trimethylsilyl)cyclohexyl and -3-tert-Butylcyclohexyl p-Bromobenzenesulfonates
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The solvolyses of cis- and trans-3-(trimethylsilyl)cyclohexyl and -3-tert-butylcyclohexyl p-bromobenzenesulfonates (1-4) have been examined in several ethanol- and trifluoroethanol-water solvent mixtures.The α- and β-deuterium kinetic isotope effects have
- Shiner, V.J.,Ensinger, Mark W.,Kriz, George S.,Halley, Karen A.
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p. 653 - 661
(2007/10/02)
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- Stereochemical Aspects of Oxirane Ring Opening. Heterogeneous Catalytic Deuterolysis of cis and trans-1,2-Epoxy-4-t-butylcyclohexanes
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2H NMR analysis of deuterolyzed products from cis- and trans-1,2-epoxy-4-t-butylcyclohexane indicated that the cleavage of the oxirane C-O bond proceeds with inversion of configuration over noble metal catalysts except for Ru, while with retention over Co
- Ishiyama, Jun-ichi,Yashima, Hiroaki,Matsuo, Hironobu,Senda, Yasuhisa,Imaizumi, Shin,et al.
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p. 989 - 992
(2007/10/02)
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- Reactions of Cyclohexenyl Halides with Tributylstannane. Stereoelectronic Effects on SH2 Reactions at Halogen
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Allylic halogenation of t-butylcyclohexene (2a) with t-butyl hypochlorite or N-bromosuccinimide affords mixtures containing mainly trans-5-t-butyl-3-chlorocyclohexene (2b) and the corresponding trans bromo compound (2c) respectively.The copper-catalysed r
- Beckwith, Athelstan L. J.,Westwood, Steven W.
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p. 2123 - 2132
(2007/10/02)
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