- The solvent determines the product in the hydrogenation of aromatic ketones using unligated RhCl3as catalyst precursor
-
Alkyl cyclohexanes were synthesized in high selectivity via a combined hydrogenation/hydrodeoxygenation of aromatic ketones using ligand-free RhCl3 as pre-catalyst in trifluoroethanol as solvent. The true catalyst consists of rhodium nanoparticles (Rh NPs), generated in situ during the reaction. A range of conjugated as well as non-conjugated aromatic ketones were directly hydrodeoxygenated to the corresponding saturated cyclohexane derivatives at relatively mild conditions. The solvent was found to be the determining factor to switch the selectivity of the ketone hydrogenation. Cyclohexyl alkyl-alcohols were the products using water as a solvent.
- Bartling, Stephan,Chakrabortty, Soumyadeep,De Vries, Johannes G.,Kamer, Paul C. J.,Lund, Henrik,Müller, Bernd H.,Rockstroh, Nils
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p. 7608 - 7616
(2021/12/13)
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- Selective Hydrogenation and Hydrodeoxygenation of Aromatic Ketones to Cyclohexane Derivatives Using a Rh&at;SILP Catalyst
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Rhodium nanoparticles immobilized on an acid-free triphenylphosphonium-based supported ionic liquid phase (Rh&at;SILP(Ph3-P-NTf2)) enabled the selective hydrogenation and hydrodeoxygenation of aromatic ketones. The flexible molecular approach used to assemble the individual catalyst components (SiO2, ionic liquid, nanoparticles) led to outstanding catalytic properties. In particular, intimate contact between the nanoparticles and the phosphonium ionic liquid is required for the deoxygenation reactivity. The Rh&at;SILP(Ph3-P-NTf2) catalyst was active for the hydrodeoxygenation of benzylic ketones under mild conditions, and the product distribution for non-benzylic ketones was controlled with high selectivity between the hydrogenated (alcohol) and hydrodeoxygenated (alkane) products by adjusting the reaction temperature. The versatile Rh&at;SILP(Ph3-P-NTf2) catalyst opens the way to the production of a wide range of high-value cyclohexane derivatives by the hydrogenation and/or hydrodeoxygenation of Friedel–Crafts acylation products and lignin-derived aromatic ketones.
- Bordet, Alexis,Emondts, Meike,Leitner, Walter,Moos, Gilles
-
supporting information
p. 11977 - 11983
(2020/06/02)
-
- Bimetallic Nanoparticles in Supported Ionic Liquid Phases as Multifunctional Catalysts for the Selective Hydrodeoxygenation of Aromatic Substrates
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Bimetallic iron–ruthenium nanoparticles embedded in an acidic supported ionic liquid phase (FeRu@SILP+IL-SO3H) act as multifunctional catalysts for the selective hydrodeoxygenation of carbonyl groups in aromatic substrates. The catalyst material is assembled systematically from molecular components to combine the acid and metal sites that allow hydrogenolysis of the C=O bonds without hydrogenation of the aromatic ring. The resulting materials possess high activity and stability for the catalytic hydrodeoxygenation of C=O groups to CH2 units in a variety of substituted aromatic ketones and, hence, provide an effective and benign alternative to traditional Clemmensen and Wolff–Kishner reductions, which require stoichiometric reagents. The molecular design of the FeRu@SILP+IL-SO3H materials opens a general approach to multifunctional catalytic systems (MM′@SILP+IL-func).
- Offner-Marko, Lisa,Bordet, Alexis,Moos, Gilles,Tricard, Simon,Rengshausen, Simon,Chaudret, Bruno,Luska, Kylie L.,Leitner, Walter
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supporting information
p. 12721 - 12726
(2018/09/12)
-
- Teaching an old carbocation new tricks: Intermolecular C-H insertion reactions of vinyl cations
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Vinyl carbocations have been the subject of extensive experimental and theoretical studies over the past five decades. Despite this long history in chemistry, the utility of vinyl cations in chemical synthesis has been limited, with most reactivity studies focusing on solvolysis reactions or intramolecular processes. Here we report synthetic and mechanistic studies of vinyl cations generated through silylium-weakly coordinating anion catalysis. We find that these reactive intermediates undergo mild intermolecular carbon-carbon bond-forming reactions, including carbon-hydrogen (C-H) insertion into unactivated sp3 C-H bonds and reductive Friedel-Crafts reactions with arenes. Moreover, we conducted computational studies of these alkane C-H functionalization reactions and discovered that they proceed through nonclassical, ambimodal transition structures. This reaction manifold provides a framework for the catalytic functionalization of hydrocarbons using simple ketone derivatives.
- Popov, Stasik,Shao, Brian,Bagdasarian, Alex L.,Benton, Tyler R.,Zou, Luyi,Yang, Zhongyue,Houk,Nelson, Hosea M.
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p. 381 - 387
(2018/08/07)
-
- Nanoheterogeneous ruthenium-containing catalysts based on dendrimers in the hydrogenation of aromatic compounds under two-phase conditions
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Nanoheterogeneous catalysts based on ruthenium nanoparticles dispersed in crosslinked dendrimer matrixes with a size of polymer particles of 100–500 nm show high activity in the hydrogenation of aromatic compounds under two-phase conditions. The addition of water to the reaction medium exerts a strong promoting effect on the activity of the catalysts: The turnover frequency increases by a factor of 3–90 depending on the substrate. When bimetallic (PdRu) nanoparticles are incorporated into the catalyst composition, the rate of benzene hydrogenation increases while the rate of transformation of substituted benzenes decreases.
- Karakhanov,Maximov,Zolotukhina,Terenina,Vutolkina
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p. 491 - 502
(2016/07/29)
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- Cyclooctane metathesis catalyzed by silica-supported tungsten pentamethyl [(ΞSiO)W(Me)5]: Distribution of macrocyclic alkanes
-
Metathesis of cyclic alkanes catalyzed by the new surface complex [(ΞSiO)W(Me)5] affords a wide distribution of cyclic and macrocyclic alkanes. The major products with the formula CnH2n are the result of either a ring contraction or ring expans
- Riache, Nassima,Callens, Emmanuel,Samantaray, Manoja K.,Kharbatia, Najeh M.,Atiqullah, Muhammad,Basset, Jean-Marie
-
supporting information
p. 15089 - 15094
(2015/02/19)
-
- High-performance ring-opening catalysts based on iridium-containing zeolite Beta in the hydroconversion of decalin
-
Decalin was converted in a flow-type reactor under a hydrogen pressure of 5.2 MPa on Ir/H,A-Beta zeolite catalysts, where A stands for an alkali metal cation. In one series of catalysts, the Ir content was 3 wt.%, and the nature of A was varied from lithi
- Santi, Dominic,Holl, Tobias,Calemma, Vincenzo,Weitkamp, Jens
-
-
- Ring opening of decalin and methylcyclohexane over bifunctional Ir/WO 3/Al2O3 catalysts
-
Ring-opening reactions of decalin and methylcyclohexane (MCH) over bifunctional catalysts (1.2Ir/WO3/Al2O3) were investigated. A series of catalysts containing up to 5.3 at. W/nm2 and 1.2 wt.% Ir was prepared. The acidity of the solids was monitored by low-temperature CO adsorption followed by infrared spectroscopy. Characterization of the Ir metal phase was performed by H2 chemisorption and X-ray diffraction. The activity and product selectivity patterns obtained for the decalin ring-opening reaction were compared with those observed for MCH. For both naphthenes, ring contraction precedes ring opening, suggesting a similar ring-opening mechanism. Kinetic modeling based on the proposed reaction network allowed the determination of the activation energies and initial rates. Based on the yields and products distribution obtained for the decalin reaction, the potential for improvement of the cetane number is discussed.
- Moraes, Rodrigo,Thomas, Karine,Thomas, Sebastien,Van Donk, Sander,Grasso, Giacomo,Gilson, Jean-Pierre,Houalla, Marwan
-
-
- Ring opening of decalin via hydrogenolysis on Ir/- and Pt/silica catalysts
-
The catalytic conversion of cis-decalin was studied at a hydrogen pressure of 5.2 MPa and temperatures of 250-410 °C on iridium and platinum supported on non-acidic silica. The absence of catalytically active Br?nsted acid sites was indicated by both FT-IR spectroscopy with pyridine as a probe and the selectivities in a catalytic test reaction, viz. the hydroconversion of n-octane. On iridium/silica, decalin hydroconversion starts at ca. 250-300 °C, and no skeletal isomerization occurs. The first step is rather hydrogenolytic opening of one six-membered ring to form the direct ring-opening products butylcyclohexane, 1-methyl-2-propylcyclohexane and 1,2- diethylcyclohexane. These show a consecutive hydrogenolysis, either of an endocyclic carboncarbon bond into open-chain decanes or of an exocyclic carboncarbon bond resulting primarily in methane and C9 naphthenes. The latter can undergo a further endocyclic hydrogenolysis leading to open-chain nonanes. All individual C10 and C9 hydrocarbons predicted by this direct ring-opening mechanism were identified in the products generated on the iridium/silica catalysts. The carbon-number distributions of the hydrocracked products C9- show a peculiar shape resembling a hammock and could be readily predicted by simulation of the direct ring-opening mechanism. Platinum on silica was found to require temperatures around 350-400 °C at which relatively large amounts of tetralin and naphthalene are formed. The most abundant primary products on Pt/silica are spiro[4.5]decane and butylcyclohexane which can be readily accounted for by the well known platinum-induced mechanisms described in the literature for smaller model hydrocarbons, namely the bond-shift isomerization mechanism and hydrogenolysis of a secondary-tertiary carboncarbon bond in decalin.
- Haas, Andreas,Rabl, Sandra,Ferrari, Marco,Calemma, Vincenzo,Weitkamp, Jens
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experimental part
p. 97 - 109
(2012/07/13)
-
- Ring opening of decalin and methylcyclohexane over alumina-based monofunctional WO3/Al2O3 and Ir/Al 2O3 catalysts
-
Ring-opening reactions of decalin and MCH were studied over monofunctional acid (WO3/Al2O3) and metal (Ir/Al 2O3) catalysts containing, respectively, up to 5.3 at. W/nm2 and 1.8 wt% Ir. The catalysts were characterized by X-ray diffraction, Raman spectroscopy, low-temperature CO adsorption followed by infrared spectroscopy, and H2 chemisorption. A reaction network was proposed for both molecules and used to determine the kinetic parameters. Kinetic modeling allowed relating characterization results and catalytic performance. For WO3/Al2O3 catalysts, ring contraction precedes ring opening of both molecules. The evolution of ring contraction activity was consistent with the development of relatively strong Bronsted acid sites. Ring opening occurs according to a classic acid mechanism. For Ir/Al2O3 catalysts, only direct ring opening was observed. Ring opening proceeds mostly via dicarbene mechanism. Analysis of products indicated that monofunctional metal catalysts are better suited than acid solids for upgrading LCO.
- Moraes, Rodrigo,Thomas, Karine,Thomas, Sebastien,Van Donk, Sander,Grasso, Giacomo,Gilson, Jean-Pierre,Houalla, Marwan
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scheme or table
p. 62 - 77
(2012/03/11)
-
- A structure-activity study of Ni-catalyzed alkyl-alkyl kumada coupling. Improved catalysts for coupling of secondary alkyl halides
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A structureactivity study was carried out for Ni catalyzed alkylalkyl Kumada-type cross coupling reactions. A series of new nickel(II) complexes including those with tridentate pincer bis(amino)amide ligands (RN2N) and those with bidentate mixed amino-amide ligands (RNN) were synthesized and structurally characterized. The coordination geometries of these complexes range from square planar, tetrahedral, to square pyramidal. The complexes had been examined as precatalysts for cross coupling of nonactivated alkyl halides, particularly secondary alkyl iodides, with alkyl Grignard reagents. Comparison was made to the results obtained with the previously reported Ni pincer complex [( MeN2N)NiCl]. A transmetalation site in the precatalysts is necessary for the catalysis. The coordination geometries and spin-states of the precatalysts have a small or no influence. The work led to the discovery of several well-defined Ni catalysts that are significantly more active and efficient than the pincer complex [(MeN2N)NiCl] for the coupling of secondary alkyl halides. The best two catalysts are [(HNN)Ni(PPh3)Cl] and [(HNN)Ni(2,4-lutidine)Cl]. The improved activity and efficiency was attributed to the fact that phosphine and lutidine ligands in these complexes can dissociate from the Ni center during catalysis. The activation of alkyl halides was shown to proceed via a radical mechanism.
- Ren, Peng,Vechorkin, Oleg,Von Allmen, Kim,Scopelliti, Rosario,Hu, Xile
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supporting information; experimental part
p. 7084 - 7095
(2011/06/26)
-
- Thiotolerant Ir/SiO2-Al2O3 bifunctional catalysts: Effect of metal-acid site balance on tetralin hydroconversion
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The hydroconversion of tetralin over iridium nanoparticles supported on amorphous silica-alumina (ASA) has been investigated in a continuous high-pressure gas-phase micro-reactor in the presence of H2S. In order to tune the Ir particle size, the bifunctional Ir/ASA catalysts have been submitted to sintering treatments. The samples have been characterized by HRTEM and XPS. From careful analysis of tetralin conversion products by comprehensive two-dimensional gas chromatography (GC×GC-MS) and NMR, compound families have been unambiguously distinguished. Hydrogenation, dehydrogenation, (saturated and aromatic) ring-contraction products, and (saturated and aromatic) one-ring-opening products are formed, without significant cracking. The catalysts exhibit stable activity in the presence of sulfur. As the mean particle size increases from 1.5 to 8 nm, the ring-opening/contraction selectivity increases dramatically. This effect is related to an increase of the acid/metal site ratio.
- Nassreddine, Salim,Massin, Laurence,Aouine, Mimoun,Geantet, Christophe,Piccolo, Laurent
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scheme or table
p. 253 - 265
(2011/04/22)
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- Nickel complexes of a pincer amidobis(amine) ligand: Synthesis, structure, and activity in stoichiometric and catalytic C-C bond-forming reactions of alkyl halides
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The synthesis, properties, and reactivity of nickel(II) complexes of a newly developed pincer amidobis(amine) ligand (McNN2) are described. Neutral or cationic complexes [(MeNN2)NiX] (X = OTf (6), OC(O)CH3 (7), CH3CN (8), OMe (9)) were prepared by salt metathesis or chloride abstraction from the previously reported [( MeNN2)NiCl] (1). The Lewis acidity of the {( McNN2)Ni) fragment was measured by the 1H NMR chemical shift of the coordinated CH3CN molecule in 8. Electrochemical measurements on 1 and 8 indicate that the electron-donating properties of NN2 are similar to those of the analogous amidobis(phosphine) (pnp) ligands. The solid-state structures of 6-8 were determined and compared to those of 1 and [(MeNN2)NiEt] (3). In all complexes, the MeNN2 ligand coordinates to the NiII ion in a mer fashion, and the square-planar coordination sphere of the metal is completed by an additional donor. The coordination chemistry of MeNN 2 thus resembles that of other three-dentate pincer ligands, for example, pnp and arylbis(amine) (ncn). Reactions of 2 with alkyl monohalides, dichlorides, and trichlorides were investigated. Selective C-C bond formation was observed in many cases. Based on these reactions, efficient Kumada-Corriu-Tamao coupling of unactivated alkyl halides and alkyl Grignard reagents with 1 as the precatalyst was developed. Good yields were obtained for the coupling of primary and secondary iodides and bromides. Double C-C coupling of CH2Cl2 with alkyl Grignard reagents by 1 was also realized. The scope and limitations of these transformations were studied. Evidence was found for a radical pathway in Ni-catalyzed C-C cross-coupling reactions, which involves NiIl alkyl intermediates.
- Vechorkin, Oleg,Csok, Zsolt,Scopelliti, Rosario,Hu, Xile
-
experimental part
p. 3889 - 3899
(2009/12/26)
-
- Avoiding olefin isomerization during decyanation of alkylcyano α,ω-dienes: A deuterium labeling and structural study of mechanism
-
(Chemical Equation Presented) A two-step synthetic pathway involving decyanation chemistry for the synthesis of pure alkyl α,ω-dienes in quantitative yields is presented. Prior methodologies for the preparation of such compounds required 6-9 steps, sometimes leading to product mixtures resulting from olefin isomerization chemistry. This isomerization chemistry has been eliminated. Deuteration labeling and structural mechanistic investigations were completed to decipher this chemistry. Deuterium labeling experiments reveal the precise nature of this radical decyanation chemistry, where an alcohol plays the role of hydrogen donor. The correct molecular design to avoid competing intramolecular cyclization, and the necessary reaction conditions to avoid olefin isomerization during the decyanation process are reported herein.
- Rojas, Giovanni,Wagener, Kenneth B.
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p. 4962 - 4970
(2008/12/20)
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- Iron-catalysed sp3-sp3 cross-coupling reactions of unactivated alkyl halides with alkyl grignard reagents
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Iron-catalysed sp3-sp3 Kumada coupling with primary and secondary alkyl halides (RX) and alkyl Grignard reagents has been achieved in low to good yields depending on the nature of the R group.
- Dongol, Krishna G.,Koh, Huishi,Sau, Manisankar,Chai, Christina L.L.
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p. 1015 - 1018
(2008/03/28)
-
- Subtle factors are important: Radical formation and transmetallation in reactions of butyl cuprates with cyclohexyl iodide
-
The reactions of Bu2CuLi·LiI and Bu2CuLi LiCN with cyclohexyl iodide are critically dependent upon subtle factors such as the surface properties of the reaction vessel, nature of the solvent still and lot of 'ultrapure' copper salt i
- Bertz, Steven H.,Human, Jason,Ogle, Craig A.,Seagle, Paul
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p. 392 - 394
(2007/10/03)
-
- Radical deoxygenation of tertiary alcohols via trifluoroacetates
-
Trifluoroacetates of tertiary alcohols undergo deoxygenation by Ph 2SiH2 in the presence of (tBuO)2 in excellent yields of the deoxy products without affecting the stereochemistry at β-carbon.
- Kim, Joong-Gon,Cho, Dae Hyan,Jang, Doo Ok
-
p. 3031 - 3033
(2007/10/03)
-
- Reduction of carbonyl groups to the corresponding methylenes with Ni-Al alloy in water
-
The reduction of carbonyl compounds 1a-h using Ni-Al alloy in water under reflux proceeded to give the corresponding methylene compounds 2a-h within 2 h in 89.0-99.8% relative yields.
- Ishimoto, Keiko,Mitoma, Yoshiharu,Nagashima, Satoko,Tashiro, Hideki,Prakash, G. K. Surya,Olah, George A.,Tashiro, Masashi
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p. 514 - 515
(2007/10/03)
-
- A highly selective arene hydrogenation catalyst that operates in ionic liquid
-
The synthesis and structural characterization of [Ru(η6-p-cymene)(η2-TRIPHOS)Cl][PF6] is described. The complex is a highly active, homogeneous arene hydrogenation catalyst that is selective toward the hydrogenation of aromatic rings in preference to alkenes, as demonstrated by the hydrogenation of allylbenzene to allylcyclohexane. The catalyst operates in both dichloromethane and ionic liquids and undergoes no decomposition in the latter solvent. Copyright
- Boxwell, Clive J.,Dyson, Paul J.,Ellis, David J.,Welton, Thomas
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p. 9334 - 9335
(2007/10/03)
-
- New copper chemistry, part 29: Re-evaluation of organocuprate reactivity: Logarithmic reactivity profiles for iodo- versus cyano-Gilman reagents in the reactions of organocuprates with 2-cyclohexenone and iodocyclohexane
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Iodo-Gilman reagents Me2-CuLi·LiI, Bu2CuLi·LiI, and BuThCu-Li·LiI and cyano-Gilman reagents (nee "higher order cyanocuprates" Me2Cu-Li·LiCN, Bu2CuLi·LiCN, and BuTh-CuLi·LiCN react with 2-cyclohexenone at various rates, which depend upon the R groups (Me, Bu, Th=thienyl), Li salt (LiI vs. LiCN), solvent (ether vs. THF), and amount of trimethylsilyl chloride (TMSCl) additive. The effect of the Li salt (CuI vs. CuCN precursor) is less than that of solvent or TMSCl. The butylcuprate-iodocyclohexane reaction has also been examined as a function of Li salt, solvent, and TMSCl additive, and similar effects are observed. The reactivity matrix R with elements ri,j is a convenient way to store and present a large amount of relative reactivity data. Entry ri,j is the ratio of the rate with reagent i to the rate with reagent j, which we approximate by using yields measured after a short time (4 s). The logarithmic reactivity profile (LRP) provides an efficient means for determining yields under conditions where such comparisons are valid. The results of a large number of 4-point LRPs and related reactions are tabulated and analyzed to provide a clearer picture of organocuprate reactivity.
- Bertz, Steven H.,Chopra, Anu,Eriksson, Magnus,Ogle, Craig A.,Seagle, Paul
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p. 2680 - 2691
(2007/10/03)
-
- Photolysis of Dialkylthallium Halides in Cyclohexane
-
Photolysis of dialkylthallium halides in cyclohexane was performed under UV irradiation. The reaction involves cleavage of the carbon-thallium bond to form radical particles reacting with cyclohexane and with each other.
- Gun'kin,Finaenova
-
-
- Reaction of Bu2CuLi·LiI with alkyl iodides: Evidence for free radicals and electron transfer
-
Treatment of iodocyclohexane with Bu2CuLi·LiI yields substantial amounts of butylcyclohexane, cyclohexane, cyclohexene, bicyclohexyl, and octane. Trapping experiments demonstrate that the bulk of these products derive from cyclohexyl radicals, indicating that an electron-transfer mechanism is operative. Some of the cyclohexane and bicyclohexyl is traced to transmetalation. Likewise, 1-methyl-1-cyclohexyl iodide and 2-heptyl iodide react via electron transfer, whereas cyclohexyl bromide, 1-heptyl iodide, and 1-heptyl bromide do not. These results are in harmony with House's hypothesis that electron transfer from organocuprates occurs when the reduction potentials of the substrates are more positive than -2.35 V.
- Bertz, Steven H.,Dabbagh,Mujsce
-
p. 631 - 636
(2007/10/02)
-
- AZO ANIONS IN SYNTHESIS. USE OF TRITYL- AND DIPHENYL-4-PYRIDYLMETHYLHYDRAZONES FOR REDUCTIVE C-C BOND FORMATION.
-
The lithium salts of trityl- and diphenyl-4-pyridylmethyl-hydrazones of both aldehydes and ketones react with electrophiles (alkyl halides, aldehydes, ketones, crotonates) at low temperature to form C-trapped azo compounds; these intermediates decompose homolytically with loss of nitrogen below room temperature and can be diverted in a synthetically useful way to alkanes, alkenes, alcohols or saturated esters.
- Baldwin, Jack E.,Adlington, Robert M.,Bottaro, Jeffrey C.,Kolhe, Jayant N.,Newington, Ian M.,Perry, Matthew W. D.
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p. 4235 - 4246
(2007/10/02)
-
- DEPLACEMENTS HOMOLYTIQUES INTRAMOLECULAIRES-I; ETUDE DE LA DECOMPOSITION DU PERPENTENE-4 OATE DE t-BUTYLE DANS LES CYCLANES. SYNTHESE DE CYCLOALKYL-5 PENTANOLIDES-4
-
The thermolysis of t-butyl-4-peroxypentenoate 1, in cyclohexane led to several compounds; the main product was 5-cyclohexyl-4-pentanolide (yield 35percent).Hypotheses are proposed to explain their formation.The lactone could be obtained by two different mechanisms: a concerted one and a two-step one (cyclohexyl radical addition to the double bond of the perester leading to a discrete radical followed by an intramolecular displacement of a t-butoxyl radical).The thermolysis of 1 has synthetic interest: several original 5-cycloalkyl-4-pentanolides have been obtained by this way.
- Maillard, B.,Kharrat, A.,Gardrat, C.
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p. 3531 - 3538
(2007/10/02)
-
- Substitution Reactions of Secondary Halides and Epoxides with Higher Order, Mixed Organocuprates, R2Cu(CN)Li2: Synthetic, Stereochemical, and Mechanistic Aspects
-
Higher order cuprates, represented by the general formula R2Cu(CN)Li2, are readily prepared from copper cyanide and 2 equiv of an organolithium.These novel reagents react readily and efficiently with secondary unactivated iodides and bromides affording products of substitution.Likewise, mono-, di-, and trisubstituted epoxides undergo ring opening leading to the corresponding alcohols in excellent yields.The effects of solvent, temperature, gegenion, and variations in ligands are discussed.Replacement of the second equivalent of RLi by CH3Li strongly encouragestransfer of R over CH3 in R(CH3)Cu(CN)Li2 with halides.Use of PhLi as RRLi in place of one RTLi (i.e.RT(Ph)Cu(CN)Li2) is suggested for oxirane cleavage.The stereochemical implications associated with both couplings are also addressed.
- Lipshutz, Bruce H.,Wilhelm, Robert S.,Kozlowski, Joseph A.,Parker, David
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p. 3928 - 3938
(2007/10/02)
-
- Azo Anions in Synthesis. Use of Trityl- and Diphenyl-4-pyridylmethyl-hydrazones for Reductive C-C Bond Formation from Aldehydes and Ketones
-
The lithium salts for trityl- and diphenyl-4-pyridylmethyl-hydrazones of both aldehydes and ketones react with electrophiles (alkyl halides, aldehydes, and ketones) at low temperature to form C-trapped azo compounds; these intermediates decompose homolytically with loss of nitrogen below room temperature and can be diverted in a synthetically useful way to alkanes, or alkenes, or alcohols.
- Baldwin, Jack E.,Bottaro, Jeffrey C.,Kolhe, Jayant N.,Adlington, Robert M.
-
-
- FORMATION OF SULPHUR COMPOUNDS IN THE HYDRODENITROGENATION OF 2-METHYLQUINOLINE, 2-METHYLPIPERIDINE, INDOLE, AND ISOQUINOLINE ON A NICKEL-TUNGSTEN CATALYST IN THE PRESENCE OF HYDROGEN SULPHIDE
-
2-Methylquinoline, 2-methylpiperidine, indole, and isoquinoline were subjected to hydrodenitrogenation (HDN) on a sulphidized nickel-tungsten catalyst in an autoclave at 300 and 350 deg C using pure hydrogen or a hydrogen-hydrogen sulphide mixture.The neutral fraction from the HDN of 2-methylquinoline and 2-methylpiperidine contained 40 and 90percent sulphur compounds, respectively.The presence of hydrogen sulphide in the HDN of isoquinoline resulted in an enhanced fraction of the neutral moiety.A reaction mechanism is suggested for the HDN of 2-methylquinoline and 2-methylpiperidine in the presence of hydrogen sulphide, in which the latter contributes to the higher degree of conversion due to the formation of corresponding sulphur compounds.
- Cerny, Mirko,Trka, Antonin
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p. 3413 - 3420
(2007/10/02)
-
- Catalytic Hydrogenation of Aromatic Hydrocarbons. Stereochemical Definition of the Catalytic Cycle for η3-C3H5Co(P(OCH3)3)3
-
The η3-C3H5Co(P(OCH3)3)3-catalyzed hydrogenations with D2of a series of unsaturated organic molecules, including cyclohexenes, cyclohexadienes, and arenes, have been investigated.Complete cis stereoselectivity was observed in the addition of deuterium to the unsaturated ring systems.When alkyl-substituted arenes were reduced with D2, the hydrogen atoms in the alkyl chains underwent H-D exchange as long as each successive carbon atom in the chain possessed at least one hydrogen atom.Hence, extensive H-D exchange occured in n-alkyl side chains while the tert-butyl side chain was deuterium free.When alkyl-substituted arenes were hydrogenated in the presence of olefins such as 1-hexene, a variety of isomeric alkylcyclohexenes and alkenylcyclohexanes were observed.The relative concentrations of these isomeric species provided information about the relative stabilities of the (olefin)cobalt species in the catalytic cycle.Further mechanistic information was obtained from other competitive reactions, i.e., hydrogenation reactions involving equimolar quantities of two different unsaturated molecules.The proposed initiation steps of the catalytic cycle have been revised on the basis of a study of η3-C8H13Co(P(OCH3)3)3 as a catalyst precursor.The cyclooctenyl-cobalt bond was cleaved by hydrogen early in the reaction, leaving the highly coordinately unsaturated hydride, HCo(P(OCH3)3)2, which is probably the true catalytic species.
- Bleeke, J. R.,Muetterties, E. L.
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p. 556 - 564
(2007/10/02)
-