- Directing the Rate-Enhancement for Hydronium Ion Catalyzed Dehydration via Organization of Alkanols in Nanoscopic Confinements
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Alkanol dehydration rates catalyzed by hydronium ions are enhanced by the dimensions of steric confinements of zeolite pores as well as by intraporous intermolecular interactions with other alkanols. The higher rates with zeolite MFI having pores smaller than those of zeolite BEA for dehydration of secondary alkanols, 3-heptanol and 2-methyl-3-hexanol, is caused by the lower activation enthalpy in the tighter confinements of MFI that offsets a less positive activation entropy. The higher activity in BEA than in MFI for dehydration of a tertiary alkanol, 2-methyl-2-hexanol, is primarily attributed to the reduction of the activation enthalpy by stabilizing intraporous interactions of the Cβ-H transition state with surrounding alcohol molecules. Overall, we show that the positive impact of zeolite confinements results from the stabilization of transition state provided by the confinement and intermolecular interaction of alkanols with the transition state, which is impacted by both the size of confinements and the structure of alkanols in the E1 pathway of dehydration.
- Shetty, Manish,Wang, Huamin,Chen, Feng,Jaegers, Nicholas,Liu, Yue,Camaioni, Donald M.,Gutiérrez, Oliver Y.,Lercher, Johannes A.
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supporting information
p. 2304 - 2311
(2020/12/01)
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- Upgrading 1-butanol to unsaturated, carbonyl and aromatic compounds: A new synthesis approach to produce important organic building blocks
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Unsaturated, carbonyl and aromatic products were obtained by reacting 1-butanol or a 1-butanol:methanol mixture with a copper mixed metal oxide catalyst in a fixed bed reactor. The selectivities observed, mostly for the unsaturated and carbonyl products, can represent a new alternative and greener pathway for the production of fine-chemicals and organic building blocks.
- Boscolo, Mauricio,Metzker, Gustavo,Mora Vargas, Jorge,Orduna Ortega, Julieth,Tofaneli Morelato, Luiz Henrique
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supporting information
p. 2365 - 2369
(2020/05/13)
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- Olefin Dimerization and Isomerization Catalyzed by Pyridylidene Amide Palladium Complexes
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A series of cationic palladium complexes [Pd(N^N′)Me(NCMe)]+ was synthesized, comprising three different N^N′-bidentate coordinating pyridyl-pyridylidene amide (PYA) ligands with different electronic and structural properties depending on the PYA position (o-, m-, and p-PYA). Structural investigation in solution revealed cis/trans isomeric ratios that correlate with the donor properties of the PYA ligand, with the highest cis ratios for the complex having the most donating o-PYA ligand and lowest ratios for that with the weakest donor p-PYA system. The catalytic activity of the cationic complexes [Pd(N^N′)Me(NCMe)]+ in alkene insertion and dimerization showed a strong correlation with the ligand setting. While complexes bearing more electron donating m- and o-PYA ligands produced butenes within 60 and 30 min, respectively, the p-PYA complex was much slower and only reached 50% conversion of ethylene within 2 h. Likewise, insertion of methyl acrylate as a polar monomer was more efficient with stronger donor PYA units, reaching a 32% ratio of methyl acrylate vs ethylene insertion. Mechanistic investigations about the ethylene insertion allowed detection, for the first time, by NMR spectroscopy both cis- and trans-Pd-ethyl intermediates and, furthermore, revealed a trans to cis isomerization of the Pd-ethyl resting state as the rate-limiting step for inducing ethylene conversion. These PYA palladium complexes induce rapid double-bond isomerization of terminal to internal alkenes through a chain-walking process, which prevents both polymerization and also the conversion of higher olefins, leading selectively to ethylene dimerization.
- Navarro, Miquel,Rosar, Vera,Montini, Tiziano,Milani, Barbara,Albrecht, Martin
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p. 3619 - 3630
(2018/10/05)
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- CATALYSTS AND CATALYTIC PROCESSES
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A process for migrating C=C double bonds within an unsaturated organic compound is described. The process involves contacting an unsaturated organic compound starting material with a heteropoly acid catalyst in the presence of light having a wavelength of less than or equal to 700 nm. Also described is a process for the preparation of novel heteropoly acids having markedly increased surface area.
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Page/Page column 19
(2017/05/28)
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- Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations
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Ketones are efficiently deoxygenated in the presence of silane using highly electrophilic phosphonium cation (EPC) salts as catalysts, thus affording the corresponding alkane and siloxane. The influence of distinct substitution patterns on the catalytic effectiveness of several EPCs was evaluated. The deoxygenation mechanism was probed by DFT methods.
- Mehta, Meera,Holthausen, Michael H.,Mallov, Ian,Pérez, Manuel,Qu, Zheng-Wang,Grimme, Stefan,Stephan, Douglas W.
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p. 8250 - 8254
(2015/07/07)
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- Conversion of biomass-derived butanal into gasoline-range branched hydrocarbon over Pd-supported catalysts
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For production of gasoline-range branched hydrocarbon from butanal, Pd catalysts supported on different metal oxides were applied. Among the prepared catalysts, Pd/ZrO2 showed the complete butanal conversion with the formation of C7-to-C9 branched hydrocarbon (75% yield). Additionally, the ratios of O/C and straight-chain to branched hydrocarbon (n-C/br-C) were found to be 0.005 and 0.17, respectively. This indicates that an adequate combination of Pd dispersion and amphoteric ZrO2 character promoted hydrodeoxygenation, C-C coupling and isomerization reactions. Consequently, both Pd dispersion and acid-base properties of supports are suggested to play a pivotal role in producing gasoline-range hydrocarbon at a high yield.
- Kim, Sung Min,Lee, Mi Eun,Choi, Jae-Wook,Suh, Dong Jin,Suh, Young-Woong
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scheme or table
p. 108 - 113
(2012/03/10)
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- Z-selective olefin metathesis processes catalyzed by a molybdenum hexaisopropylterphenoxide monopyrrolide complex
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(Figure Presented) The molybdenum-based monoaryloxide monopyrrolide (MAP) species, Mo(NAd)(CHCMe2Ph) (C4H4N)(HIPTO) (2a), which contains "small" imido (Ad = 1-adamantyl) and "large" aryloxide (HIPTO = O-2,6(2,4,6-i-Pr3C6H 2)C6H3) ligands, catalyzes Z-selective metathesis reactions as a consequence of intermediate metallacyclobutane species not being able to have an (anti) substituent pointing toward the HIPTO group. Ring-opening metathesis polymerization (ROMP) of dicarbomethoxynorbornadiene (DCMNBD) with 2percent 2a in toluene leads to >99percent cis and >99percent syndiotactic poly(DCMNBD), while ROMP of cyclooctene and 1,5-cyclooctadiene (300 equiv) with initiator 2a leads to poly(cyclooctene) and poly(cyclooctadiene) that have cis contents of >99percent; all arepreviously unknown microstructures. Z-Selectivity is also observed in t he metathesis of cis-4-octene and cis-3-hexene by initiator 2a to give cis-3-heptene.
- Flook, Margaret M.,Jiang, Annie J.,Schrock, Richard R.,Mueller, Peter,Hoveyda, Amir H.
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supporting information; body text
p. 7962 - 7963
(2009/12/02)
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- Transfer semihydrogenation of alkynes catalyzed by a zero-valent palladium N-heterocyclic carbene complex
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(Chemical Equation Presented) Beyond Lindlar and without hydrogen: Transfer hydrogenation of internal alkynes catalyzed by a palladium(0) catalyst containing an N-heterocyclic carbene ligand gives Z alkenes without over-reduction to alkanes (see scheme). Contrary to most transfer hydrogenations, ketones are not reduced. As such, this is the first catalyst that shows excellent stereo- and chemo-selectivity for the semihydrogenation of alkynes without the need for hydrogen gas.
- Hauwert, Peter,Maestri, Giovanni,Sprengers, Jeroen W.,Catellani, Marta,Elsevier, Cornelis J.
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p. 3223 - 3226
(2008/12/23)
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- Polylithiumorganic compounds. Part 28. The reaction of allene and alkyl substituted allenes with lithium metal
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The reaction of allene (3a) and alkyl substituted allenes 1,2-hexadiene (3b), cyclopropylallene (3c), and vinylidene cyclopropane (3d) with lithium metal was investigated in order to access 2,3-dilithioalkenes 4a-d. These dilithioalkenes 4a-d are very reactive in polar solvents like THF and act as strong bases, either metalation of the starting allene 3a-d, the solvent, or sufficiently acidic intermediates like 8 a-d is observed. The metalation products 5-7 show follow-up reactions like 1,3-H shift to the corresponding 1-lithio-1-alkynes 8 and subsequent metalation to the dilithioalkynes 9. Additionally, lithium hydride elimination and ring-chain rearrangement (for 5c) are observed. 1,2-Hexadiene (3b) can be brought to reaction with lithium metal in the apolar solvent pentane, here the follow-up reactions are much slower due to the insolubility of 4b. In all cases the elucidation of the reaction pathways is hampered by the formation of complex mixtures of, amongst others, regio- and stereoisomeric products upon quenching with simple electrophiles.
- Maercker, Adalbert,Tatai, Andrea,Grebe, Burkhard,Girreser, Ulrich
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- Transformations of butyraldehyde in the presence of catalysts based on large-pore molecular sieves VPI-5 and AlPO4-8
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It was found that zeolite-like ctystalline aluminophosphates VPI-5, Si-VPI-5, and Mn-VPI-5 as well as those derived from them, AlPO4-8, SAPO4-8, and MnAPO4-8, are capable of catalyzing aldol condensation and crotonization of butyraldehyde (BA).Pd/AlPO4-8 is catalytically active in hydrocondensation of BA with H2 at atmospheric pressure.The activities in BA conversion to 2-ethylhexane-3-ol-1-al increase in following order: Mn-VPI-5 +NaX (CsNaX), but they are much more stable.Pd/AlPO4-8 catalyzes BA conversion to 2-ethylhexanal even in the absence of H2 feed to the reaction zone.The influence of catalyst pretreatments and experimental conditions on the catalyst structures and catalytic activities is discussed. - Key words: butyraldehyde; condendation; crystalline aluminophosphates; molecular sieves; VPI-5; AlPO4-8; catalysis.
- Isakov, Ya. I.,Minachev, Kh. M.,Tome, R.,Tissler, A.,Oehlmann, G.,et al.
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p. 2004 - 2010
(2007/10/02)
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- Dehalogenation of Vicinal Dibromides by Electrogenerated Polysulfide Ions in Dimethylacetamide
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Dehalogenation reactions of vic-dibromides by electrogenerated S62- (S3 anion radical), S42- or S32- polysulfide ions have been investigated in dimethylacetamide by use of spectroelectrochemistry on a series of dibromides: methyl erythro-2,3-dibromo-3-phenylpropanoate (1), diethyl meso-2,3-dibromosuccinate (2), meso-1,2-dibromo-1,2-diphenylethane (3), DL-1,2-dibromo-1,2-diphenylethane (4), 1,2-dibromobutane (5), 1,2-dibromophenylethane (6), DL-2,3-dibromobutane (7), erythro-3,4-dibromoheptane (8), threo-3,4-dibromoheptane (9), meso-5,6-dibromodecane (10), trans-1,2-dibromocyclohexane (11).Substitution and elimination are competing mechanism with 5-7 while the quantitative formation of alkenes is observed with the other substituted dibromides.In dilute solutions, indirect electrochemical reductions of vic-dibromides have been performed in the presence of small amounts of sulfur as catalyst at potentials leading to S(-1/3) ions with 1-3, or at more cathodic potentials (formation of S42-/S32- ions) for 8-11.On a preparative scale, stereospecific anti debrominations afford only E alkenes from chemical reaction with 3 or mediated electrolysis of 1,2 or 10.Kinetic studies of the reactions between S(-1/3) ions and compounds 4, 8-10 imply that the dianions S62- are the eliminating agents rather than S3 anion radical ions for the concerted anti dehalogenations.
- Bosser, Gerard,Paris, Jacky
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p. 2057 - 2063
(2007/10/02)
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- Protium-deuterium exchange of cyclic and acyclic alkanens in dilute acid medium at elevated temperatures
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A modification of the high temperature - dilute acid (HTDA) method for deuterium labelling of aromatic compounds has been applied to the H-D exchange of a number of cyclic and acyclic alkenes.Cyclopentene, cyclohexene, cyclododecene, and tetramethylethylene have been completely exchanged in excellent yield. 1-Methylcyclopentene and 1-methylcyclohexene have also been perdeuterated and cycloheptene and cyclooctene partially labelled but require spinning band distillation or preparative glpc for separation from rearrangement products.A variety of C5-C8 acyclic alkeneshave also been treated under HTDA conditions.
- Werstiuk, Nick Henry,Timmins, George
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p. 530 - 533
(2007/10/02)
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- One-pot Conversions of Amines into Olefins via Non-isolated Pyridinium Intermediates
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Secondary alkyl primary amines are converted by the pyrylium salt (1) directly at 20 deg C into olefins via the corresponding secondary carbenium ions.Isomeric olefin mixtures are elucidated and result from carbenium ion rearrangements.
- Katritzky, Alan R.,Lloyd, Jeremy M.
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p. 2347 - 2352
(2007/10/02)
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- Synthesis of Olefins from α-Chlorocarbonyl Compounds
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Olefins or diolefins with the double bonds in predetermined positions are obtained in moderate to good yields by treatment of α-chlorocarbonyl compounds with Grignard reagents and lithium in a single process.
- Barluenga, Jose,Yus, Miguel,Concellon, Jose M.,Bernad, Pablo
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p. 677 - 692
(2007/10/02)
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- HOMOGENEOUS CATALYTIC HYDROGENATION OF DIOLEFINS AND ALKYNES IN THE PRESENCE OF PALLADIUM(II) COMPLEXES
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Palladium(II)chloride in dimethylformamide catalyzes the hydrogenation of conjugated diolefins and alkynes in homogeneous solution.Monoolefins are formed selectively.
- Sisak, A.,Jablonkai, I.,Ungvary, F.
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- PREPARATION OF HIGHER ADAMANTANE HOMOLOGUES BY REACTION OF ADAMANTAN-1-OL WITH HEPTENES IN SULFURIC ACID
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Reaction of adamantan-1-ol with heptenes in conc. sulfuric acid affords a complicated mixture of hydrocarbons, containing heptyladamantanes, diheptyladamantanes, tetradecyladamantanes, diadamantylheptanes and adamantyl-heptyladamantylheptanes.The reaction mixture can be separated into narrower fractions containing hydrocarbons of approximately equal molecular weight.The method can be utilized for the preparation of technical mixtures of high-boiling alkyladamantanes.
- Vodicka, Ludek,Burkhard, Jiri,Janku, Josef
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p. 835 - 842
(2007/10/02)
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