- Probing Ensemble Effects in Surface Reactions. 1. Site-Size Requirements for the Dehydrogenation of Cyclic Hydrocarbons on Pt(111) Revealed by Bismuth Site Blocking
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Catalytic reactions on bimetallic surfaces are often thought to be controlled by ensemble effects, whereby a side reaction requiring a large ensemble of active sites can be selectively suppressed by diluting the active metal with a second, inert metal.Unfortunately, the lack of knowledge of surface structure and the complications due to coexisting electronic effects have, until now, precluded accurate determinations of ensemble requirements for surface reactions.We analyze here applications of a new method for determining ensemble sizes that partially overcomes these obstacles and allows for semiquantitative assessment of ensemble effects.The method involves the controlled blocking of sites on a well-defined transition-metal surface with a dispersed overlayer of inert bismuth adatoms.The interactions of five cyclic hydrocarbones (cyclopentane, cyclohexane, cyclopentene, cyclohexene, and benzene) with Pt(111) have been studied in this way in an accompanying series of papers.In particular, the influence of Bi upon the competing dehydrogenation and desorption kinetics of these adsorbed molecules has been qualitatively measured.This present paper correlates the results for those five molecules and fits them with a simple kinetic model to extract the absolute ensemble requirements for the surface dehydrogenation reactions.The method and model may have applicability to a broad range of surface reactions.In addition, an effective ensemble requirement is defined, whose value is useful in predicting ensemble effects in catalysis.Trends in the value of kinetic parameters and the ensemble requirements with hydrocarbon character are discussed. The absolute ensemble requirements for the dehydrogenation of these adsorbed hydrocarbons are surprisingly large and indicate in some cases that at least six additional free Pt atoms are necessary for dehydrogenation (beyond those required for adsorption).Mechanistic implications of these results are discussed.
- Campbell, C. T.,Campbell, J. M.,Dalton, P. J.,Henn, F. C.,Rodriguez, J. A.,Seimanides, S. G.
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- Structural distortions and dynamic behavior of the elusive "L"-shaped cis-bicyclo[3.3.0]octenyllithium: X-ray crystallographic and NMR studies
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(Chemical Equation Presented) Substituted cis-bicyclo[3.3.0]octenyllithium prepared by addition of t-BuLi to 3-methylene-1,4-cyclooctadiene in the presence of TMEDA crystallizes as a dimer with one unsolvated Li+ sandwiched between the external faces of two allyl anions in a triple ion, and external to it the second Li+ is bidentately complexed to TMEDA, 8. Within each allyl unit, the allyl bonds have different lengths, and all four rings deviate from coplanarity which relieves strain in the rings despite introducing partial localization of the allyl anions. A similar structure prevails in solution as shown by 7Li NMR and the results of 7Li{1H} HOESY and 1H, 1H NOESY experiments. Carbon-13 NMR line shape changes indicate that the system undergoes a fast allyl bond shift concerted with conformation shifts of the out of plane carbons, ca. ΔG? = 9 kcal·mol-1. Cyclopentyllithium prepared by CH3Li cleavage of the trimethylstannyl derivative slowly undergoes an allowed ring opening to pentadienyllithium as well as deprotonating the solvent. The different behavior of dienylic lithium species is attributed to the relative separation of their termini.
- Fraenkel, Gideon,Chen, Xiao,Gallucci, Judith,Lu, Yan
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- Ring opening and hydrogen atom transfer trapping of the bicyclo[2.1.0]pent-2-yl radical
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Relative rate constants (kr/kH) for ring opening of the bicyclo[2.1.0]pent-2-yl radical (1) to the cyclopent-3-enyl radical and trapping of radical 1 with t-BuSH, PhSH, and PhSeH in solvent THF were measured at temperatures between -78 and 50 °C. The hydrogen atom donors reacted more rapidly with radical 1 than with the cyclopropylcarbinyl radical (6). Rate constants for ring opening of 1 (kr) could be obtained by estimating the values of kH via Marcus theory. From initial kH values for reactions with radical 6, new kH values were calculated for increasingly exergonic reactions until the derived kr values from the three trapping agents agreed with one another and an extrapolated value of kr from Tempo trapping of 1. The results suggest that hydrogen atom transfer reactions with 1 were about 3 kcal/mol more exergonic than reactions with 6. Arrhenius functions for ring opening of 1 averaged log (ks/s-1) = 13.0 - 5.2/2.3RT; the value of kr at 25 °C is 1.5 × 109 s-1. Trapping studies of 1 and 6 with 2,6-dimethylthiophenol indicated that no special steric effects were present in hydrogen atom transfers to 1. However, highly stereoselective trapping of 1 was observed in reactions with ArSD with endo-bicyclo[2.1.0]pentane-2-d predominating, and the rate constant for decarboxylation of the endo-bicyclo[2.1.0]pentane-2-carboxy radical (endo-3) at -78 °C apparently was greater than that for decarboxylation of exo-3. The stereochemical results are ascribed to a stereoelectronic effect between the C1-C4 bond and endo-C2-X bonds of bicyclo[2.1.0]pentanes that weakens endo-C2-X bonds.
- Newcomb, Martin,Manek, M. Beata,Glenn, Anne G.
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- Transition-metal-promoted chemoselective photoreactions at the cucurbituril rim
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When included in a supramolecular barrel with transition-metal ions as lids, bicyclic azoalkanes undergo phase-selective photolysis to afford new photoproducts and photoproduct distributions. In the presence of the macrocycle cucurbit[7]uril and Ag+ ions, 2,3-diazabicyclo[2.2.1]hept-2-ene forms a ternary host-guest inclusion complex in which the cations are coordinated to the carbonyl rims of the host. Direct photolysis of this ternary complex provides cyclopentene as a new photoproduct.
- Koner, Apurba L.,Marquez, Cesar,Dickman, Michael H.,Nau, Werner M.
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- Kinetics of the Gas-phase Addition Reactions of Trichlorosilyl Radicals. Part 3.-Additions to 2-Olefins
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The following Arrhenius parameters for the forward and reverse steps of trichlorosilyl radical additions to trans-but-2-ene, cis-but-2-ene, cis-pent-2-ene, 2-methyl-but-2-ene and cyclopentene have been obtained by a competitive method.The relevant elementary reactions are .SiCl3 + CH3COCH3 --> (CH3)2C.OSiCl3 (3) .SiCl3 + >C=C >C.-C-SiCl3 (5,-5) and >C.-C-SiCl3 + HSiCl3 --> HC-C-SiCl3 + .SiCl3 (6). The rate parameters of reaction (5) are expressed per reaction site; an asterisk indicates the site of addition in an unsymmetrical olefin.Evaluted values of A-5 and A5 imply a fairly 'loose' transition state in reaction (5).The Si-C bond energy has been estimated. .SiCl3 radicals have been revealed to be electrophilic and susceptible to steric hindrance.
- Dohmaru, Takaaki,Nagata, Yoshio
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- Benzophenone-sensitized two-photon chemistry of azoalkanes in the "laser/ liquid jet": Evidence for photoinduced hydrogen 1,2-shift in 1,3-cyclopentadiyl triplet diradicals
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While the triplet-sensitized photolysis of the bicyclicazoalkanes 1 led on denitrogenation to the corresponding bicycloalkanes 2, the laser/liquid jet photochemistry gave additionally also the cyclopentenes 3 by hydrogen 1,2-shift; the amount of the latter increased with increasing lifetime of the intermediary cyclopentadiyl triplet diradicals 4, which suggests that two-photon chemistry may operate.
- Adam, Waldemar,Finzel, Ralf,Kita, Fumio
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- SELECTIVE HYDROGENATION OF CYCLOPENTADIENE TO CYCLOPENTENE USING COLLOIDAL PALLADIUM SUPPORTED ON CHELATE RESIN.
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Cyclopentadiene was hydrogenated to cyclopentene selectively by using colloidal palladium supported on chelate resin with iminodiacetic acid moieties as a catalyst. The hydrogenation rate was correlated to the polarity parameter, E//T(30) values, of the solvents used in the reaction, except in the case of dimethyl sulfoxide. The equilibrium constant for complex formation between cyclopentadiene and the catalyst, K//D, was estimated to be over 400 times larger than that between cyclopentene and the catalyst, K//E. A mechanism, including the coordination of olefins to the catalyst and the subsequent hydrogenation of the coordinated complexes, was proposed.
- Hirai,Komatsuzaki,Toshima
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- Infrared Multiphoton Photochemistry of Vinylcyclopropane. Variation of Yield and Branching Ratio with Experimental Parameters
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The infrared photochemistry of vinylcyclopropane has been comprehensively investigated.Irradiation of vinylcyclopropane at relatively low pressures with the partially focused output of a CO2 laser leads to a mixture of the C5 products cyclopentene, cyclopentadiene, 1,4-pentadiene, and cis- and trans-1,3-pentadiene.The composition of the product mixture as well as the total product yields are a sensitive function of experimental parameters.The effects of bath gas pressure, laser power, laser intensity, laser frequency, and number of pulses have been systematically examined.A simple physical picture of the multiphoton activation and resulting decomposition is developed.RRKM theory is employed to calculate energy-dependent unimolecular reaction rates.The model is quite successful in rationalizing these data, providing good evidence for the qualitative validity of a rate equation description of infrared multiphoton dissociation.
- Farneth, William E.,Thomsen, Marcus W.,Schultz, Nancy L.,Davies, Mark A.
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- Crystal Structure and Photochemistry of Four α-Cycloalkyl-p-chloroacetophenones
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The photochemical fragmentation or cyclization reactions of α-cycloalkylacetophenones have been studied by crystal-structure analyses of four chloro derivatives with varying cycloalkyl-ring sizes, and by correlation of crystal- and molecular-structure par
- Evans, Stephen V.,Trotter, James
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- Characterization and reactivity of γ-Al2O3 supported Pd-Ni bimetallic nanocatalysts for selective hydrogenation of cyclopentadiene
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Abstract Several γ-Al2O3 supported Pd-Ni bimetallic nanocatalysts (Pd-Ni (x:y)/Al2O3; where x and y represent the mass ratio of Pd and Ni, respectively) were prepared by the impregnation method and used for selective hydrogenation of cyclopentadiene to cyclopentene. The Pd-Ni/Al2O3 samples were confirmed to generate Pd-Ni bimetallic nanoparticles by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The catalytic activity was assessed in view of the effects of different mass ratios of Pd and Ni, temperature, pressure, etc. Among all the samples, the Pd-Ni (1:1)/Al2O3 (PN-1:1) catalyst showed extremely high catalytic ability. The conversion of cyclopentadiene and selectivity for cyclopentene can be simultaneously more than 90%.
- Feng, Yi-Si,Hao, Jian,Liu, Wei-Wei,Yao, Yun-Jin,Cheng, Yue,Xu, Hua-Jian
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- Mechanism of Formation of Grignard Reagents. Rate of Reaction of Cyclopentyl Bromide with a Rotating Disk of Magnesium
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Careful studies of the dependence of the rate of reaction (k) of cyclopentyl bromide in diethyl ether with the surface of rotating disk as a function of the angular lelocity (ω) of the disk confirm the relation k * ω1/2 expected for a mass-transfer limited reaction.More limited studies also indicate that the variations in this rate with other parameters are compatible with those expected for a mass-transfer limited reaction: k * (η)-5/6(ρ)1/6 (η is the shear viscosity of the solution and ρ is its density); k * D2/3 (D is the diffusion coefficient of the alkyl halide).
- Root, Karen S.,Deutch, John,Whitesides, George M.
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- Diastereotopically Distinct. Secondary Deuterium Kinetic Isotope Effects on the Thermal Isomerization of Vinylcyclopropane to Cyclopentene
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The (2'-deuterioethenyl)cyclopropanes isomerize to 3-deuteriocyclopentene at 341 deg C with kH/kD = 1.08 and 1.15 for the Z and E isomers, respectively.These normal effects are consistent with 2Z-penten-1,5-diyl diradical transition structures for the isomerization.
- Baldwin, John E.,Villarica, Karla A.
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- Mechanism of Formation of Grignard Reagents. The Rate of Reaction of Cyclopentyl Bromide with Magnesium Is Transport Limited in Diethyl Ether
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Three observations indicate that the rate of reaction of cyclopentyl bromide with metallic magnesium in several ethereal solvents is limited by the rate of its encounter with the metal.First, the rate of disappearance of cyclopentyl bromide is dependent on the first power of the organic halide concentration, the magnesium surface area, and rate at which the solution is stirred, and is inversely dependent on the solution viscosity (-d/dt infinite 1, A1, ω1, η-1).Second, the activation energy for the reaction in diethyl ether (Ea ca. 2.3 kcal/mol) is consistent with mixing and diffusion as rate limiting.Third, a number of representative alkyl halides react with magnesium in diethyl ether at very similar rates; no organic halides examined react faster than this rate.The dependence of the rate of reaction of neopentyl bromide on solution dielectric constant illustrates transition from transport-limited to non-transport-limited rates, and suggests appreciable charge separation in the chemical step which breaks the carbo-bromine bond.
- Rogers, Harold R.,Deutch, John,Whitesides, George M.
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- Polymer supported 2,2'-dipyridylmethane: catalytic activity of transition metal complexes in hydrogenations and oligomerizations
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The palladium(II) acetate complex of the chelating ligand 2,2'-dipyridylmethane supported on polystyrene-2percent divinylbenzene is an efficient catalyst for hydrogenation of alkenes and alkynes.Cyclopentadiene can be reduced with high selectivity to cyclopentene, but no selectivity is observed for the non-conjugated diene 1,5-cyclooctadiene.In the hydrogenation of 3-methylcyclohex-2-en-1-ol only small amounts of ketone are formed as a by-product, in contrast to the reaction catalysed by palladium on charcoal.Nickel(II) complexes of the same ligand catalyze the trimerization of butadiene to 1,5,9-cyclododecatrienes.
- Moberg, Christina,Rakos, Laszlo
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- Substituent Effects on Hydrogen Abstraction by Phenyl Ketone Triplets
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Triplet lifetimes in deaerated cyclopentane have been measured for a variety of ring-substituted benzophenones, acetophenones, and α-α-α-trifluoroacetophenones.The ketones undergo photoreduction under these conditions to mixtures of products formed from cyclopentyl and hemipinacol radicals.That triplet lifetimes are determined by rates of hydrogen abstraction from solvent is indicated by lifetimes being three times in cyclohexane-d12 than in cyclohexane-h12.For the benzophenones, reciprocal lifetimes correlate comparably well with Hammett ? or ?+ constants, with ρ values of 0.55 and 0.43, respectively.The effect of two substituentsis best fitted to the sum of both ? values.These weak inductive effects are in accord with expectations for a reactive n,?* triplet.Rates for the acetophenones show the same substituent effects as previously observed for valerophenones; conjugating and electron-donating substituents stabilize the ?,?* triplet and sharply reduce reactivity.Substituent effects are largest for the trifluoroacetophenones, consistent with their all having ?,?* lowest triplets and reacting from weakly populated but highly reactive (k>107 M-1 s-1) n,?* states.Fluorine substitution, both on the ring and at the α-carbon, produces large rate enhancements, decafluorobenzophenone triplet being too short-lived to measure.
- Wagner, Peter J.,Truman, Royal J.,Scaiano, J. C.
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- The thermal rearrangement of 6-methyl-6-vinylbicyclo[3.2.0]heptane
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Gas-phase pyrolysis of theendo-vinyl epimer (1A) of the title compound at 275°C affords predominantly 3-(2-methyl-2-butenyl)cyclopentene (presumably the Z isomer), a direct [1,5]-hydrogen shift product, whereas the exo-vinyl epimer (IB) favors the fragmentation products, cyclopentene and isoprene.
- Glass, Timothy E.,Leber, Phyllis A.
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- Production Of Cyclopentadiene From Furfural
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The application relates to processes and systems that use a furfural compound for producing five-membered carbocyclic rings that are unsaturated, such as cyclopentene and cyclopentadiene. Examples methods for conversion of furfural compounds may include converting a furfural compound to at least a five-membered, saturated carbocyclic ring, and converting the five-membered, saturated carbocyclic ring in a presence of a catalyst to at least a five-membered, unsaturated carbocyclic ring.
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Paragraph 0040; 0081-0085
(2021/06/26)
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- SELECTIVE HYDROGENATION OF CYCLIC DIENE TO CORRESPONDING CYCLIC MONO OLEFIN USING SONICATED RANEY NICKEL
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The present invention provides an improved and economical process for selective hydrogenation of cyclic di-olefins to their corresponding cyclic mono-olefins, essentially in presence of sonicated S1-modified Raney-Nickel as a highly active hydrogenation catalyst.
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Page/Page column 14-17
(2020/02/14)
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- GROUP 1 METAL ION CONTENT OF MICROPOROUS MOLECULAR SIEVE CATALYSTS
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A catalyst comprising a microporous crystalline aluminosilicate having a Constraint Index less than or equal to 12, a Group 1 alkali metal or a compound thereof and/or a Group 2 alkaline earth metal or a compound thereof, a Group 10 metal or a compound thereof, and optionally a Group 11 metal or a compound thereof; wherein the total amount of Group 1 and/or Group 2 metal is present at a ratio that is optimized for the desirable chemical conversion process.
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Paragraph 0046-0047
(2020/05/28)
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- Preparation of Highly Active Monometallic Rhenium Catalysts for Selective Synthesis of 1,4-Butanediol from 1,4-Anhydroerythritol
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1,4-Butanediol can be produced from 1,4-anhydroerythritol through the co-catalysis of monometallic mixed catalysts (ReOx/CeO2+ReOx/C) in the one-pot reduction with H2. The highest yield of 1,4-butanediol was over 80 %, which is similar to the value obtained over ReOx–Au/CeO2+ReOx/C catalysts. Mixed catalysts of CeO2+ReOx/C showed almost the same performance, giving 89 % yield of 1,4-butanediol. The reactivity trends of possible intermediates suggest that the reaction mechanism over ReOx/CeO2+ReOx/C is similar to that over ReOx–Au/CeO2+ReOx/C: deoxydehydration (DODH) of 1,4-anhydroerythritol to 2,5-dihydrofuran over ReOx species on the CeO2 support with the promotion of H2 activation by ReOx/C, isomerization of 2,5-dihydrofuran to 2,3-dihydrofuran catalyzed by ReOx on the C support, hydration of 2,3-dihydrofuran catalyzed by C, and hydrogenation to 1,4-butanediol catalyzed by ReOx/C. The reaction order of conversion of 1,4-anhydroerythritol with respect to H2 pressure is almost zero and this indicates that the rate-determining step is the formation of 2,5-dihydrofuran from the coordinated substrate with reduced Re in the DODH step. The activity of ReOx/CeO2+ReOx/C is higher than that of ReOx–Au/CeO2+ReOx/C, which is probably related to the reducibility of ReOx/C and the mobility of the Re species between the supports. High-valent Re species such as Re7+ on the CeO2 and C supports are mobile in the solvent; however, low-valent Re species, including metallic Re species, have much lower mobility. Metallic Re and cationic low-valent Re species with high reducibility and low mobility can be present on the carbon support as a trigger for H2 activation and promoter of the reduction of Re species on CeO2. The presence of noble metals such as Au can enhance the reducibility through the activation of H2 molecules on the noble metal and the formation of spilt-over hydrogen over noble metal/CeO2, as indicated by H2 temperature-programmed reduction. The higher reducibility of ReOx–Au/CeO2 lowers the DODH activity of ReOx–Au/CeO2+ReOx/C in comparison with ReOx/CeO2+ReOx/C by restricting the movement of Re species from C to CeO2.
- Wang, Tianmiao,Tamura, Masazumi,Nakagawa, Yoshinao,Tomishige, Keiichi
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p. 3615 - 3626
(2019/07/15)
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- Dinuclear Pathways for the Activation of Strained Three-Membered Rings
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Dinuclear, strain-induced ring-opening reactions of vinylaziridines and vinylcyclopropanes are described. The previously reported [NDI]Ni2(C6H6) complex (NDI = naphthyridine-diimine) reacts with N-tosyl-2-vinylaziridine via C-N oxidative addition to generate a dinickel metallacyclic product. On the basis of this stoichiometric reactivity, the [NDI]Ni2(C6H6) complex is shown to be a highly active catalyst for the rearrangement of vinylcyclopropane to cyclopentene. Notably, 2-phenyl-1-vinylcyclopropane undergoes regioselective activation at the less hindered C-C bond in contrast to the noncatalytic thermal rearrangement. DFT calculations provide insight into the ability of the Ni-Ni bond to stabilize key intermediates and transition states along the catalytic pathway.
- Rounds, Heather R.,Zeller, Matthias,Uyeda, Christopher
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p. 545 - 550
(2018/03/08)
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- Metal-Free Catalytic Reductive Cleavage of Enol Ethers
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In contrast to the well-known reductive cleavage of the alkyl-O bond, the cleavage of the alkenyl-O bond is much more challenging especially using metal-free approaches. Unexpectedly, alkenyl-O bonds were reductively cleaved when enol ethers were reacted with Et3SiH and a catalytic amount of B(C6F5)3. Supposedly, this reaction is the result of a B(C6F5)3-catalyzed tandem hydrosilylation reaction and a silicon-assisted β-elimination. A mechanism for this cleavage reaction is proposed based on experiments and density functional theory (DFT) calculations.
- Chulsky, Karina,Dobrovetsky, Roman
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supporting information
p. 6804 - 6807
(2018/11/02)
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- Metathesis in water conducted by tailor-made encapsulated Grubbs' catalyst
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Metathesis in water represents a current challenge in green chemistry, since hydrophobic catalysts are non-soluble in this medium. Although this issue has been addressed by modification of the hydrophobic ligand structure, alternative methods for conducting metathesis in water are of interest, such as catalyst encapsulation. In this contribution we report successful encapsulation of the Grubbs' second-generation catalyst in alginate hydrogels, representing a renewable resource, to perform ring-closing metathesis (RCM) in water. We initially investigated the influence of different solvents on the reaction rate and confirmed that water is a preferred solvent. A comparison of non-encapsulated and encapsulated catalyst in calcium alginate revealed that the reaction rate for non-encapsulated catalyst was notably higher, which can be explained by "on water" conditions in this case. Inside the beads the encapsulated catalyst remained heterogeneous, thus allowing to switch the catalysis mode between "in/on water" through encapsulation. To overcome diffusion limitation and enhance reaction rate, we prepared a tailor-made bead material by introducing hydrophobic octyl-grafted alginate amide. Using such a hydrogel, diffusion limitation was positively influenced by hydrophobisation of the matrix, resulting in up to quadrupled reaction rates compared to calcium alginate as a standard encapsulation material. In terms of recycling, this encapsulated catalyst revealed promising performance, retaining 80% of its activity after ten runs. This is the first reported application of hydrophobised alginate derivatives in catalysed organic synthesis, achieving excellent encapsulation efficiency, no measurable leaching and yields of up to 87%.
- Pauly, Jan,Gr?ger, Harald,Patel, Anant V.
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supporting information
p. 5179 - 5187
(2018/11/24)
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- Atomic layer deposition of aluminium on anatase: A solid acid catalyst with remarkable performances for alcohol dehydration
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Here we reported the synthesis of Al sites with ultra-high dispersion on anatase by an atomic layer deposition (ALD) method (ALD-Al/TiO2), which exhibits Br?nsted acidity and satisfactory activity in the dehydration of alcohols, a key step in the deoxygenation of biomass. More importantly, the ALD-Al/TiO2 catalyst has good stability, which is sintering-resistant and gives constant catalytic performances after treatments at high temperature.
- Song, Yingji,Xu, Shaodan,Ling, Fei,Tian, Panpan,Ye, Tao,Yu, Deqing,Chu, Xuefeng,Lin, Yingzi,Yang, Xiaotian,Tang, Junhong
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- Hemilability of the 1,2-Bis(dimethylphosphino)ethane (dmpe) Ligand in Cp?Mo(NO)(κ2-dmpe)
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Reaction of Cp?Mo(NO)Cl2 with 1 equiv of 1,2-bis(dimethylphosphino)ethane (dmpe) in THF at ambient temperature forms [Cp?Mo(NO)(Cl)(κ2-dmpe)]Cl (1), which is isolable as an analytically pure yellow powder in 65% yield. Further addition of 2 equiv of Cp2Co to 1 in CH2Cl2 affords dark red Cp?Mo(NO)(κ2-dmpe) (2), which was isolated in 36% yield by recrystallization from Et2O at -30 °C. Reaction of a benzene solution of 2 with an equimolar amount of elemental sulfur results in the immediate production of dark blue (μ-S)[Cp?Mo(NO)(κ1-dmpeS)]2 (3), which is a rare example of a bimetallic transition-metal complex bridged by only a single sulfur atom and involving Mo=S=Mo bonding. In contrast, reaction of 2 with an excess of sulfur in benzene results in the formation of Cp?Mo(NO)(η2-S2)(κ1-dmpeS) (4). Complex 4 can also be formed by the addition of elemental sulfur to 3, thereby indicating that 3 is a precursor to 4. Cp?Mo(NO)(κ2-dmpe) (2) also undergoes interesting transformations when treated with organic bromides. For instance, reaction of 2 with 5 equiv benzyl bromide in THF produces the bimetallic complex (μ-dmpe)[ Cp?Mo(NO)Br2]2 (5) and bibenzyl after 4 d at 70 °C probably via radical intermediates. In contrast to its reaction with benzyl bromide, complex 2 forms [Mo(NO)Br2(κ2-dmpe)]2 (6), olefin, alkane, and Cp?H when treated with 5 equiv of 1-bromopropane or 1-bromooctane in THF at 70 °C for 72 h. Interestingly, complex 2 does not display any reactivity with bromobenzene or 1-bromoadamantane even after being heated for several days at 70 °C. All new complexes were characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of most of them were established by single-crystal X-ray crystallographic analyses.
- Holmes, Aaron S.,Patrick, Brian O.,Levesque, Taleah M.,Legzdins, Peter
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p. 11299 - 11309
(2017/09/25)
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- Synthetic method for medical intermediate cyclopentene of ketamine
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The invention discloses a synthetic method for a medical intermediate cyclopentene of ketamine. The synthetic method includes the following steps that 1.56 mol of nickel oxide, 1.3 mol of cyclopentylamine, 1.6-1.9 mol of a 1-nitrotoluene solution and 300 ml of oxalic acid are added into a tubular reaction container, the reaction temperature is increased to 270-280 DEG C, and a reaction is carried out for 90-120 min; then the temperature is increased to 300-310 DEG C, and the reaction continues to be carried out for 50-70 min; after a thermal cracking reaction is carried out, the temperature of a reactor is reduced to 20-25 DEG C, steam condensation is carried out, a water layer is separated, an oil layer is washed with a salt solution, washed with xylene, dehydrated through a dehydrating agent and recrystallized in acetamide, and the crystal of cyclopentene is obtained.
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Paragraph 0015-0016
(2017/03/08)
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- Hydrophobic aluminosilicate zeolites as highly efficient catalysts for the dehydration of alcohols
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Efficient dehydration of alcohols to olefins, acting as a control step in the upgrading of phenolic biofuel into alkane fuels, is an important topic in biomass conversion. Here, we report the design and synthesis of hydrophobic aluminosilicate ZSM-5 zeolites by an organosilane-modification approach (ZSM-5-OS). Water-droplet contact angle tests confirm the formation of hydrophobic surface after the modification. Interestingly, the obtained ZSM-5-OS catalysts exhibit excellent catalytic properties in dehydration of various alcohols into the corresponding olefins in water solvent. The approach reported in this work would be potentially important for developing more efficient catalysts for biomass conversion in the future.
- Xu, Shaodan,Sheng, Huadong,Ye, Tao,Hu, Dan,Liao, Shangfu
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- Convergent Synthesis of a Metal-Organic Framework Supported Olefin Metathesis Catalyst
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Synthesis of a metal-organic framework (MOF)-supported olefin metathesis catalyst has been accomplished for the first time following a new, convergent approach where an aldehyde-functionalized derivative of Hoveyda's recently reported ruthenium catecholate olefin metathesis catalyst is condensed with an amine-functionalized IRMOF-74-III. The resulting material, denoted MOF-Ru, has well-defined, catalytically active ruthenium centers confined within channels having a ca. 20 ? diameter. MOF-Ru is a recyclable, single-site catalyst for self-cross-metathesis and ring-closing metathesis of terminal olefins. Comparison of this heterogeneous catalyst with a homogeneous analogue shows different responses to substrate size and shape suggestive of confinement effects. The MOF-Ru catalyst also displays greater resistance to double-bond migration that can be attributed to greater catalyst stability. For the preparation of well-defined, single-site heterogeneous catalysts where catalyst purity is essential, the convergent approach employed here, where the catalytic center is prepared ex situ and covalently linked to an intact MOF, offers an attractive alternative to in situ catalyst preparation as currently practiced in MOF chemistry.
- Yuan, Jian,Fracaroli, Alejandro M.,Klemperer, Walter G.
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p. 2149 - 2155
(2016/07/07)
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- Tetrahydroxydiboron-Mediated Palladium-Catalyzed Transfer Hydrogenation and Deuteriation of Alkenes and Alkynes Using Water as the Stoichiometric H or D Atom Donor
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There are few examples of catalytic transfer hydrogenations of simple alkenes and alkynes that use water as a stoichiometric H or D atom donor. We have found that diboron reagents efficiently mediate the transfer of H or D atoms from water directly onto unsaturated C-C bonds using a palladium catalyst. This reaction is conducted on a broad variety of alkenes and alkynes at ambient temperature, and boric acid is the sole byproduct. Mechanistic experiments suggest that this reaction is made possible by a hydrogen atom transfer from water that generates a Pd-hydride intermediate. Importantly, complete deuterium incorporation from stoichiometric D2O has also been achieved.
- Cummings, Steven P.,Le, Thanh-Ngoc,Fernandez, Gilberto E.,Quiambao, Lorenzo G.,Stokes, Benjamin J.
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supporting information
p. 6107 - 6110
(2016/06/09)
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- Dehydrogenation of cycloalkanes at rhodium complexes bearing fluorinated cyclopentadienyl ligands
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The fluorinated cyclopentadienyl complexes [Rh(η5-C5H4CH2CH2C6F13)(CO)2] (2), [Rh(η5-C5H4CH2CH2C8F17)(CO)2] (3), [Rh(η5-C5H4CH2CH2C10F21)(CO)2] (4), [Rh(η5-C5H4CH2CH2CnF2n+1)(CO)(PEt3)] (7: n = 6; 8: n = 8; 9: n = 10) and [Rh(η5-C5H4CH2CH2CnF2n+1)(CO){P(CH2CH2C6F13)3}] (10: n = 8; 11: n = 10) were synthesized and their reactivity was investigated. Compound 3 converts at room temperature into the trinuclear complex [Rh2(η5-C5H4CH2CH2C8F17)2(μ-CO)2Rh(η5-C5H4CH2CH2C8F17)(CO)] (6). The complexes 9 and 11 were employed in dehydrogenation reactions of cycloalkanes in C6F14/hydrocarbon mixtures. Photocatalytic conversions were observed and a turnover number of 16 for the dehydrogenation of cyclooctane with complex 11 was obtained.
- Liebau, Frank,Braun, Thomas,Braun, Beatrice
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p. 192 - 200
(2015/10/28)
-
- Why are organotin hydride reductions of organic halides so frequently retarded? kinetic studies, analyses, and a few remedies
-
Kinetic data for reduction of organic halides (RX) by tri-n-butylstannane (SnH) reveal a serious flaw in the current view of the kinetic radical chain: the tacit but unproven assumption that the speed of reaction is determined by the slowest propagation step. Our results show this is rarely true for reductive chains and that the observed rate is in fact controlled by unseen side-reactions of propagating R? and Sn? radicals with the solvent (notably, benzene!) or solvent impurities (e.g., trace benzophenone dryness indicator in THF) or, crucially, with allylic-CH and conjugated unsaturated groups in substrates and products. Most R? and/or Sn? radicals are therefore converted into relatively inert delocalized species A? and/or B? that inhibit the chain. Retardation in the degraded chain is given by a simple sum of terms, each being the ratio of the chain-transfer rate divided by the rate of chain-return. The model kinetic equation is linear and easy to ratify, interpret, and apply: to calculate retarding rate constants, optimize reaction conditions, and identify additives or "remedies" that repair the chain and accelerate reaction. The present work is thus expected to have a helpful impact on the practice and design of SnH radical chain based (and related) syntheses.
- Ingold,Bowry, Vincent W.
-
p. 1321 - 1331
(2015/02/19)
-
- Palladium nanoparticles encapsulated in a dendrimer networks as catalysts for the hydrogenation of unsaturated hydrocarbons
-
A novel method has been proposed for encapsulating palladium nanoparticles up to 5 nm in the matrix of polymeric support networks based on polyamidoamine dendrimers. The shape of the particle size distribution and the catalytic activity of the materials obtained during the hydrogenation of unsaturated compounds depend strongly on the support structure. High activity (TOF up to 86,000 h-1) has been observed during the hydrogenation of styrene.
- Karakhanov, Edward A.,Maksimov, Anton L.,Zakharian, Elena M.,Kardasheva, Yulia S.,Savilov, Sergey V.,Truhmanova, Nadezhda I.,Ivanov, Andrey O.,Vinokurov, Vladimir A.
-
-
- Catalytic conversion of cellulose into hydrocarbon fuel components
-
The results of catalytic processing of cellulose to hydrocarbon fuel component are presented. Nanoscale Mo,Fe(III) catalytic systems have been formed from organic solutions of mono and bimetallic complex compounds on the surface of the substrate. Tetralin, an analogue of naphthenoaromatic compounds of crude oil and its refining products, has been used as a hydrogen donor. The effect of the precursor nature and catalyst activation method on the parameter of the process has been investigated. It has been shown that the cellulose conversion reaches 97-98% under optimal conditions, yielding up to 90% of liquid hydrocar- bons with the exhaustive deoxygenation. It has been found that the most efficient method of preliminary activation of both active components and cellulose is ultrasonic treatment leading to an increase of the rate of cellulose conversion into hydrocarbons. Pleiades Publishing, Ltd., 2013.
- Tsodikov,Chudakova,Chistyakov,Maksimov
-
p. 367 - 373
(2014/02/14)
-
- Oxygen/sulfur scrambling during the copolymerization of cyclopentene oxide and carbon disulfide: Selectivity for copolymer vs cyclic [Thio]carbonates
-
The catalytic coupling of cyclopentene oxide with carbon disulfide has been investigated utilizing (salen)CrCl in the presence of added onium salts. Both polymeric and cyclic materials were produced, with oxygen/sulfur atom scrambling observed in both instances. This atom redistribution process was found to require (salen)CrCl and excess epoxide, though an increase in the rate of atom scrambling was noted upon the addition of the onium salt. Cyclopentene sulfide was observed as a side product of the coupling reaction and was found to be unreactive toward both CS2 and CO2, instead undergoing desulfurization to cyclopentene under the conditions of the reaction. Of the 12 cyclic cyclopentene [thio]carbonates possibly produced by this coupling reaction, eight were observed, and the crystal structure of trans-cyclopentene trithiocarbonate is reported herein. Computational studies reveal that the cis- cyclic materials are more stable than their trans-counterparts by >5 kcal/mol of enthalpy, and there is a 10-25 kcal/mol preference for the formation of a C=O vs C=S double bond. When trans-cyclohexene trithiocarbonate was exposed to the catalyst system in the presence of excess cyclopentene oxide, mixed-species scrambling was observed, whereby cyclic [thio]carbonate compounds displaying both cyclopentyl and cyclohexyl backbones were produced. A proposed mechanistic pathway for atom scrambling involves nucleophilic alkoxide attack at a [thio]carbonyl center to induce oxygen/sulfur atom exchange.
- Darensbourg, Donald J.,Wilson, Stephanie J.,Yeung, Andrew D.
-
p. 8102 - 8110
(2013/11/06)
-
- Metal-free catalytic olefin hydrogenation: Low-temperature H2 activation by frustrated lewis pairs
-
Weak nucleophiles for strong activation: The reversible activation of dihydrogen by an electron-deficient phosphine, (C6F 5)PPh2, in combination with the Lewis acid B(C 6F5)3 at -80 °C was accomplished. The catalytic hydrogenation of olefins proceeds through protonation and subsequent hydride attack. Electron-deficient phosphines and diarlyamines were demonstrated to be viable Lewis bases for the reaction, thus allowing catalyst loadings of 10 to 5 mol %. Copyright
- Greb, Lutz,Paradies, Jan,Ona-Burgos, Pascual,Schirmer, Birgitta,Grimme, Stefan,Stephan, Douglas W.
-
supporting information
p. 10164 - 10168,5
(2020/09/09)
-
- Toward a simulation approach for alkene ring-closing metathesis: Scope and limitations of a model for RCM
-
A published model for revealing solvent effects on the ring-closing metathesis (RCM) reaction of diethyl diallylmalonate 7 has been evaluated over a wider range of conditions, to assess its suitability for new applications. Unfortunately, the model is too flexible and the published rate constants do not agree with experimental studies in the literature. However, by fixing the values of important rate constants and restricting the concentration ranges studied, useful conclusions can be drawn about the relative rates of RCM of different substrates, precatalyst concentration can be simulated accurately and the effect of precatalyst loading can be anticipated. Progress has also been made toward applying the model to precatalyst evaluation, but further modifications to the model are necessary to achieve much broader aims.
- Nelson, David J.,Carboni, Davide,Ashworth, Ian W.,Percy, Jonathan M.
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supporting information; experimental part
p. 8386 - 8393
(2012/01/02)
-
- Why is RCM favoured over dimerisation? Predicting and estimating thermodynamic effective molarities by solution experiments and electronic structure calculations
-
The thermodynamic effective molarities of a series of simple cycloalkenes, synthesised from α,ω-dienes by reaction with Grubbs' second generation precatalyst, have been evaluated. Effective molarities were measured from a series of small scale metathesis reactions and agreed well with empirical predictions derived from the number of rotors and the product ring strain. The use of electronic structure calculations (at the M06-L/6-311G* level of theory) was explored for predicting thermodynamic effective molarities in ring-closing metathesis. However, it was found that it was necessary to apply a correction to DFT-derived free energies to account for the entropic effects of solvation. Complete control: Can classical theory, developed for ring-closing metathesis (RCM) reactions that involve σ-bond formation, describe the thermodynamics of RCM reactions forming π bonds? Empirical theory and modern electronic structure calculations have been employed to predict the outcome of RCM reactions of simple α,ω-dienes with Grubbs' second generation pre-catalysts, resulting in mixtures of cycloalkenes and oligomers (see scheme). Copyright
- Nelson, David J.,Ashworth, Ian W.,Hillier, Ian H.,Kyne, Sara H.,Pandian, Shanthi,Parkinson, John A.,Percy, Jonathan M.,Rinaudo, Giuseppe,Vincent, Mark A.
-
supporting information; experimental part
p. 13087 - 13094
(2012/01/02)
-
- On the relationship between structure and reaction rate in olefin ring-closing metathesis
-
In the RCM reactions of a series of simple α,ω-dienes, the relative order of reactivity has been unambiguously determined showing that cyclohexene forms faster than cyclopentene or cycloheptene. 1,5-Hexadiene inhibits the RCM of 1,7-octadiene; 1,5-hexadiene cannot progress to the RCM product (cyclobutene) but forms an unexpectedly stable cyclic η2-complex.
- Ashworth, Ian W.,Carboni, Davide,Hillier, Ian H.,Nelson, David J.,Percy, Jonathan M.,Rinaudo, Giuseppe,Vincent, Mark A.
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supporting information; experimental part
p. 7145 - 7147
(2010/11/16)
-
- PROCESS FOR PRODUCING ETHYLIDENE NORBORNENE
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Process for producing ethylidenorbornene (ENB) comprising a stage of thermal cracking of DCPD to CPD carried out in an inert fluid to which it is fed a stream of DCPD comprising virgin DCPD from cracking containing up to 10% wt of tetrahydroindene (THI) and recycled DCPD containing THI coming from the subsequent stage of formation of vinylnorbornene. The contact time of DCPD with the heat transfer fluid is of few seconds and it is sufficient to achieve a conversion of said DCPD ≥ 95%, with little formation of oligomers. THI is then separated from the heat transfer fluid substantially free from DCPD and enriched in THI to a fractionation column.
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Page/Page column 6
(2010/04/03)
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- Homogeneous catalytic transfer dehydrogenation of alkanes with a group 10 metal center
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Unambiguous catalytic homogeneous alkane transfer dehydrogenation was observed with a group 10 metal complex catalyst, LPtII(cyclo-C 6H10)H, supported by a lipophilic dimethyl-di(4-tert- butyl-2-pyridyl)borate anionic ligand and tert-butylethene as the sacrificial hydrogen acceptor.
- Khaskin, Eugene,Lew, Daniel L.,Pal, Shrinwantu,Vedernikov, Andrei N.
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supporting information; experimental part
p. 6270 - 6272
(2010/02/16)
-
- An efficient didehydroxylation method for the biomass-derived polyols glycerol and erythritol. Mechanistic studies of a formic acid-mediated deoxygenation
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An efficient 1,2-deoxygenation method, involving an unexpected mechanism, was found for simple diols and for biomass-derived polyols (glycerol and erythritol) that results in the conversion of the 1,2-dihydroxy group to a carbon-carbon double bond.
- Arceo, Elena,Marsden, Peter,Bergman, Robert G.,Ellman, Jonathan A.
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supporting information; experimental part
p. 3357 - 3359
(2009/12/26)
-
- A systematic approach to the generation of long-lived metal alkane complexes: Combined IR and NMR study of (Tp)Re(CO)2(cyclopentane)
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Short wavelength photolysis of (Tp)Re(CO)3 (Tp = tris(pyrazol-1-yl)borate) at low-temperature in cyclopentane yielded (Tp)Re(CO)2(cyclopentane), an alkane complex with three nitrogen ligands that was characterised by NMR spectroscopy
- Duckett, Simon B.,George, Michael W.,Jina, Omar S.,Matthews, Steven L.,Perutz, Robin N.,Sun, Xue-Zhong,Vuong, Khuong Q.
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supporting information; experimental part
p. 1401 - 1403
(2009/07/10)
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- Novel photoinduced reduction of conjugate dienes by the combination of benzenethiol and diphenyl diselenide
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By using a binary system that consisted of benzenethiol and diphenyl diselenide under photoirradiation through a Pyrex vessel with a xenon lamp (λ > 300 nm), a variety of conjugate dienes could be reduced to the corresponding internal alkenes under mild conditions.
- Mitamura, Takenori,Imanishi, Yoshiaki,Nomoto, Akihiro,Sonoda, Motohiro,Ogawa, Akiya
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experimental part
p. 2443 - 2445
(2009/09/30)
-
- Moving bed process for producing propylene, recycling a fraction of used catalyst
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The invention concerns a process for producing propylene from a steam cracking and/or catalytic cracking light olefinic cut, said process comprising a moving bed catalytic cracking step with a catalyst regeneration loop. The process recycles a portion of the used catalyst to the inlet of the moving bed reactor. The conversion is high using the process of the invention, with a good yield and good propylene selectivity.
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Page/Page column 5-6
(2008/06/13)
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- Conformational product control in the low-temperature photochemistry of cyclopropylcarbenes
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Different conformers of two fused-ring cyclopropylchlorocarbenes are shown to undergo distinct, wavelength-selectable, photochemistry in low-temperature matrixes. Conformers with H and Cl syn give ring expansion predominantly, whereas those with H and Cl anti mainly fragment.
- Zuev, Peter S.,Sheridan, Robert S.,Sauers, Ronald R.,Moss, Robert A.,Chu, Gaosheng
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p. 4963 - 4966
(2007/10/03)
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- Activation energies for the 1,2-carbon migration of ring-fused cyclopropylchlorocarbenes
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Fused-ring cyclopropylchlorocarbenes 2 and 3 ring expand to fused-ring chlorocyclobutenes 10 and 11, respectively, with activation energies of 3-4 kcal/mol and activation entropies of ～-20 e.u. Carbon tunneling appears to be unimportant at low temperatures.
- Chu, Gaosheng,Moss, Robert A.,Sauers, Ronald R.,Sheridan, Robert S.,Zuev, Peter S.
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p. 4137 - 4141
(2007/10/03)
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- Facile alkane functionalization in copper-[2.1.1]-(2,6)-pyridinophane- PhINTs systems
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Mild catalytic dehydrogenation of cycloalkanes (cyclo-C5H 10, cyclo-C6H12, cyclo-C8H 16) and aziridination of resulting olefins is reported with PhINTs and copper-[2.1.1]-(2,6)-pyridinophane (L) complexes LCuXn (n = 1, 2; X = Cl, OTf) "activated" with NaBArF4 in dichloromethane solution.
- Vedernikov, Andrei N.,Caulton, Kenneth G.
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p. 162 - 163
(2007/10/03)
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- POLYMERIZATION PROCESSES FOR OLEFINS
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Certain olefins such as ethylene, alpha -olefins and cyclopentene can be polymerized by using catalyst system containing a nickel or palladium alpha -diimine complex, a metal containing hydrocarbylation compound, and a selected Lewis acid, or a catalyst system containing certain nickel[II] or palladium[II] compounds, an alpha -diimine, a metal containing hydrocarbylation compound, and optionally a selected Lewis acid. The process advantageously produces polyolefins useful for molding resins, films, elastomers and other uses.
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- NOVEL FLUOROPOLYMER, RESIST COMPOSITIONS CONTAINING THE SAME, AND NOVEL FLUOROMONOMERS
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There is provided a fluorine-containing copolymer having an aliphatic monocyclic structure in the polymer trunk chain which has a number average molecular weight of from 500 to 1,000,000 and is represented by the formula (Ma):- (M1) - (M2a) - (N) - in which the structural unit M1 is a structural unit derived from an ethylenic monomer having 2 or 3 carbon atoms and at least one fluorine atom, the structural unit M2a is at least one structural unit which introduces an aliphatic monocyclic structure in the polymer trunk chain and is represented by the formula (a): wherein R1 is at least one hydrocarbon group selected from the group consisting of a divalent hydrocarbon group having 1 to 8 carbon atoms and constituting a ring which may be further substituted with a hydrocarbon group or a fluorine-containing alkyl group and a divalent hydrocarbon group having ether bond which has the sum of carbon atoms and oxygen atoms of 2 to 8, constitutes a ring and may be further substituted with a hydrocarbon group or a fluorine-containing alkyl group; R2 is an alkylene group which has 1 to 3 carbon atoms and constitutes a ring; R3 and R4 are the same or different and each is a divalent alkylene group which has 1 or 2 carbon atoms and constitutes a ring; n1, n2 and n3 are the same or different and each is 0 or 1, the structural unit N is a structural unit derived from a monomer copolymerizable with the monomers to introduce the structural units M1 and M2a, and the structural units M1, M2a and N are contained in amounts of from 1 to 99 % by mole, from 1 to 99 % by mole and from 0 to 98 % by mole, respectively. The fluorine-containing polymer possesses excellent dry etching resistance and transparency in a vacuum ultraviolet region.
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- Polymerization of olefins
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Selected olefins such as ethylene and α-olefins are polymerized by nickel [II] complexes of certain monoanionic ligands. The polyolefins are useful in many applications such as molding resins, film, fibers and others. Also described are many novel nickel compounds and their precursors, as well a novel ligands.
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- Alpha- haloenamine reagents
-
The present invention describes immobilized haloenamine reagents, immobilized tertiary amides, methods for their preparation, and methods of use.
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- Rate constants for the reaction of HO2 radicals with cyclopentane and propane between 673 and 783 K
-
Studies have been made of the separate addition of cyclopentane (c-C5H10) and propane (C3H8) to mixtures of O2 and tetramethylbutane (TMB) between 673 and 783 K in aged boric-acid-coated vessels to ob
- Handford-Styring,Walker
-
p. 620 - 627
(2007/10/03)
-
- Cycloalkenyl substituted compounds
-
Novel pyridyl or pyrimidinyl substituted cycloalkenyl compounds and compositions for use in therapy.
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-
- Preparation of preparing substituted indanones
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a process for the preparation of indanones of the formula II from, indanones of the formula I or of indanones of the formula IIa from indanones of the formula Ia comprises reacting an indanone of the formula I or Ia with a coupling component.
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-
- Flash vacuum pyrolysis over magnesium. Part 1 - Pyrolysis of benzylic, other aryl/alkyl and aliphatic halides
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Flash vacuum pyrolysis over a bed of freshly sublimed magnesium on glass wool results in efficient coupling of benzyl halides to give the corresponding bibenzyls. Where an ortho halogen substituent is present further dehalogenation gives some dihydroanthracene and anthracene. Efficient coupling is also observed for halomethylnaphthalenes and halodiphenylmethanes while chlorotriphenylmethane gives 4,4′-bis(diphenylmethyl)biphenyl. By using α,α′-dihalo-o-xylenes, benzocyclobutenes are obtained in good yield, while the isomeric α,α′-dihalo-p-xylenes give a range of high thermal stability polymers by polymerisation of the initially formed p-xylylenes. Other haloalkylbenzenes undergo largely dehydrohalogenation where this is possible, in some cases resulting in cyclisation. Deoxygenation is also observed with haloalkyl phenyl ketones to give phenylalkynes as well as other products. With simple alkyl halides there is efficient elimination of HCl or HBr to give alkenes. For aliphatic dihalides this also occurs to give dienes but there is also cyclisation to give cycloalkanes and dehalogenation with hydrogen atom transfer to give alkenes in some cases. For 5-bromopent-1-ene the products are those expected from a radical pathway but for 6-bromohex-1-ene they are clearly not. For 2,2-dichloropropane and 1,1-dichloropropane elimination of HCl occurs but for 1,1-dichlorobutane, -pentane and -hexane partial hydrolysis followed by elimination of HCl gives E, E-, E,Z- and Z,Z- isomers of the dialk-1-enyl ethers and fully assigned 13C NMR data are presented for these. With 6-chlorohex-1-yne and 7-chlorohept-1-yne there is cyclisation to give methylenecycloalkanes and -cycloalkynes. The behaviour of 1,2-dibromocyclohexane and 1,2-dichlorocyclooctane under these conditions is also examined. Various pieces of evidence are presented that suggest that these processes do not involve generation of free gas-phase radicals but rather surface-adsorbed organometallic species.
- Aitken, R. Alan,Hodgson, Philip K.G.,Morrison, John J.,Oyewale, Adebayo O.
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p. 402 - 415
(2007/10/03)
-
- Reactivity of bismuth(III) halides towards alcohols. A tentative to mechanistic investigation
-
The reactivity of bismuth(III) halides (BiX3; X=Cl, Br and I) towards a series of alcohols has been investigated. Three different reactions have been studied, namely: halogenation, dehydration and etherification. The behaviour of these bismuth derivatives was found to depend on the nature of the halide bonded to the bismuth atom. Their reactivities can be interpreted on the basis of the Hard and Soft Acids and Bases (HSAB) principle. A mechanism is proposed which involves the formation of a complex of the alcohol with Bi(III).
- Keramane, El Mehdi,Boyer, Bernard,Roque, Jean-Pierre
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p. 1909 - 1916
(2007/10/03)
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- 1,1,2,2-Tetrafluoroethyl-N,N-dimethylamine: A new selective fluorinating agent
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The title compound has been prepared in 96-98% yield by the reaction of tetrafluoroethylene and dimethylamine. 1,1,2,2-Tetrafluoroethyl-N,N-dimethylamine (1) is found to be an effective reagent for the conversion of alcohols into alkyl fluorides. Reaction of 1 and primary alcohols proceeds with high yield formation of the corresponding alkyl fluorides at elevated temperature. However, the reaction of secondary and tertiary alcohols rapidly takes place at 0-10°C, producing corresponding alkyl fluorides as major product along with some olefins.
- Petrov,Swearingen,Hong,Chris Petersen
-
-
- Vanadium-catalyzed synthesis of magnesium dicyclopentadienide
-
Formal-kinetic regularities of vanadium-catalyzed formation of magnesium dicyclopentadienide, cyclopentene, and hydrogen on magnesium oxidation with cyclopentadiene in THF were established. A number of intermediate reaction products were identified. A scheme of the formation of magnesium dicyclopentadienide was proposed. Thermodynamic parameters of adsorption of vanadium(III) chloride on the metal surface were determined.
- Ignat'ev,Maslennikov,Piskunov,Spirina,Lineva
-
p. 1472 - 1475
(2007/10/03)
-
- Parasiticidal pyrazoles
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Compounds of formula (I) or pharmaceutically, veterinarily or agriculturally acceptable salts thereof, or pharmaceutically, veterinarily or agriculturally acceptable solvates of either entity, wherein R1 is 2,4,6-trisubstituted phenyl or 3,5-disubstituted pyridin-2-yl; R3 is C1 -C4 alkyl optionally substituted with hydroxy or with one or more halo; cyano, C1 to C5 alkanoyl or phenyl; R5 is hydrogen, C1 to C4 alkyl, amino or halo; R2 and R4 are each independently selected from hydrogen, C1 to C4 alkyl, fluoro, chloro and bromo or, together with the carbon atom to which they are attached, form a C3 to C6 cycloalkyl group; R6 and R8 are each independently selected from hydrogen, C1 to C4 alkyl, fluoro, chloro and bromo; or, when R2 and R4 do not form part of a cycloalkyl group, R2 and R6, together with the carbon atoms to which they are attached, may form a C5 to C7 cycloalkyl group; and R7 is hydrogen, C1 to C4 alkyl optionally substituted with one or more halo, or C1 to C4 alkoxy; are parasiticidal agents.
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- Epoxide deoxygenation mediated by Salen complexes
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N,N'-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminocobalt(II) (1) catalyzes the reductive deoxygenation of epoxides by Na(Hg) in THE with 5-10 catalytic turnovers. The simpler N,N'- bis(salicylidene)ethylenediaminocobalt(II) [Co(Salen)2] (16) failed to catalyze deoxygenations in THF but did in DMF.
- Isobe, Hiroshi,Branchaud, Bruce P.
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p. 8747 - 8749
(2007/10/03)
-
- Processes for making α-olefins
-
Disclosed herein are processes for polymerizing ethylene, acyclic olefins, and/or selected cyclic olefins, and optionally selected olefinic esters or carboxylic acids, and other monomers. The polymerizations are catalyzed by selected transition metal compounds, and sometimes other co-catalysts. Since some of the polymerizations exhibit some characteristics of living polymerizations, block copolymers can be readily made. Many of the polymers produced are often novel, particularly in regard to their microstructure, which gives some of them unusual properties. Numerous novel catalysts are disclosed, as well as some novel processes for making them. The polymers made are useful as elastomers, molding resins, in adhesives, etc. Also described herein is the synthesis of linear α-olefins by the oligomerization of ethylene using as a catalyst system a combination a nickel compound having a selected α-diimine ligand and a selected Lewis or Bronsted acid, or by contacting selected α-diimine nickel complexes with ethylene.
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