Showing papers on "Cyclohexanone published in 1999"

Keggin-type polyoxotungstates as catalysts in the oxidation of cyclohexane by dilute aqueous hydrogen peroxide

Abstract: Oxidation of cyclohexane by hydrogen peroxide in the presence of catalytic amounts of the Keggin-type heteropolytungstates [PW 11 O 39 ] 7− and [PW 11 M(L)O 39 ] (7− m )− , M m + =first row transition metal cation, L=H 2 O or CH 3 CN, was found to produce cyclohexanol, cyclohexanone and, in certain cases, cyclohexyl hydroperoxide. The presence of the latter was demonstrated by negative chemical ionization GC-MS. The reactions were carried out in acetonitrile, using tetra n -butylammonium salts of the catalysts and aqueous 30% hydrogen peroxide as oxidant. The polyanions [PW 11 O 39 ] 7− and [PW 11 Fe(H 2 O)O 39 ] 4− showed higher catalytic activity and different selectivity for the oxidation of cyclohexane than did the corresponding Cu-, Co-, Mn- and Ni-substituted complexes.

Selective hydrogenation of phenol to cyclohexanone over palladium supported on calcined Mg/Al hydrotalcite

Abstract: Calcined Mg/Al hydrotalcites (CHTs) with various atomic ratios of Mg/Al were prepared and used as supports for palladium catalysts. Selective hydrogenation of phenol to cyclohexanone was investigated over Pd/CHT catalysts and compared with Pd/Al 2 O 3 , Pd/SiO 2 , Pd/CaO–Al 2 O 3 and Pd/MgO. The Pd/CHT(2–4) catalysts showed high reactivities and selectivities to cyclohexanone, reaching 95% selectivity with 40% conversion. For Pd/CHT(2–4) catalysts, the calcined hydrotalcites exhibit strong base sites that were more effective than acid sites to affect the selectivity of cyclohexanone. The 0.3%Pd/CHT(2) catalyst was a good candidate for one-step process of cyclohexanone formation. On it the reaction orders of rate were found to be 2 with respect to the hydrogen pressure and −1 with respect to the partial pressure of phenol.

Selective oxidations with hydrogen peroxide and titanium silicalite catalyst

Abstract: Titanium silicalite (TS-1) samples with increasing amount of titanium incorporated into the silicalite framework (from 1 to 3.45 wt.% TiO2) have been synthesized and characterized by UV-DRS spectroscopy. The samples have been tested on propylene epoxidation, cyclohexanone ammoximation and ammonia oxidation reactions. It has been found that the yield obtained with TS-1, expressed as turnover number, increases with the Ti content. The trend is common for all the reactions investigated.

Density, Refractive Index, Viscosity, and Speed of Sound in Binary Mixtures of Cyclohexanone with Benzene, Methylbenzene, 1,4-Dimethylbenzene, 1,3,5-Trimethylbenzene, and Methoxybenzene in the Temperature Interval (298.15 to 308.15) K

Abstract: Experimental results of density, refractive index, and viscosity at 298.15, 303.15, and 308.15 K and speed of sound at 298.15 K are presented for the binary mixtures of cyclohexanone with benzene, ...

Stability and selectivity of bimetallic Cu–Co/SiO2 catalysts for cyclohexanol dehydrogenation

Abstract: Bimetallic Cu–Co/SiO 2 catalysts with different metal loading (5:5, 15:15, 35:35 – Cu:Co) were prepared by deposition–precipitation method and evaluated by using the cyclohexanol dehydrogenation. XRD results show that only the 15%Cu–15%Co/SiO 2 oxide precursor exhibits mainly a phase containing Cu and Co with spinel-like structure, while other bimetallic precursors present CuO and Co 3 O 4 as distinct phases. The Rietveld method was used to quantify the different phases on the precursors and to determinate how much Cu there was in the spinel form and as CuO. After reduction and passivation, the 15%Cu–15%Co/SiO 2 catalyst showed a Cu–Co alloy formation and a different H 2 chemisorption capacity. The H 2 uptake was 2.5 greater than 35%Cu–35%Co/SiO 2 catalyst and the same order of magnitude for the monometallic 35%Co/SiO 2 . Catalytic results showed that the 15%Cu–15%Co/SiO 2 catalyst presented the highest stability and selectivity to cyclohexanone, with the lowest phenol production.

Stereoselective oxidation and reduction by immobilized Geotrichum candidum in an organic solvent

Abstract: Cells of the fungus, Geotrichum candidum, were immobilized on a water-absorbing polymer and used for stereoselective oxidation and reduction in an organic solvent using cyclohexanone, cyclopentanol or alkan-2-ols as additive. Enantiomerically pure (R)-1-arylethanols were obtained by the stereoselective oxidation of racemic 1-arylethanols, whereas enantiomerically pure (S)-1-arylethanols were obtained by the reduction of the corresponding ketones, in contrast to reduction in water by the free cells in which (R)- or (S)-1-arylethanols were produced in low ee.The reaction mechanism was investigated by measuring the partition of the substrates and products between the organic phase and aqueous phase in the polymer around which the cells were immobilized. Deuterated compounds were used to determine the role of the additives.

Aldol Condensation of Cycloalkanones with Aromatic Aldehydes Catalysed with TiCl3(SO3CF3)

Abstract: Efficient cross-aldol condensation of cyclopentanone, cyclohexanone and 1-indanone with various aromatic aldehydes is catalysed with TiCl3(SO3CF3) at room temperature in excellent yields.

Influence of alkali promotion on phenol hydrogenation activity of palladium/alumina catalysts

Abstract: A series of alkali metals (Li, Na, K and Cs) promoted alumina-supported palladium catalysts prepared by wet impregnation method were characterised by XRD and CO chemisorption measurements. The samples were evaluated for the gas phase hydrogenation of phenol to cyclohexanone in a fixed-bed micro reactor at 503 K under normal atmospheric pressure. The promoted palladium catalysts show a higher rate of phenol conversion and yield of cyclohexanone than unpromoted catalyst. Despite similar activity and selectivity for cyclohexanone between lithium- and sodium-promoted catalysts, the Na-promoted ones show a higher resistance for coke formation. The increase in the intrinsic activity of the palladium site on alkali promotion has been attributed to the increase in phenol activity of the promoted catalysts.

Samarium Ion-Promoted Cross-Aldol Reactions and Tandem Aldol/Evans-Tishchenko Reactions.

Abstract: Cross-aldol reactions of carbonyl compounds were achieved by the catalysis of SmI(2) or SmI(3), together with molecular sieves, at ambient temperature. 1,3-Dichloroacetone and 1-chloroacetone can be used as acceptor substrates in the cross-aldol reactions with donor substrates such as acetone, cyclopentanone, and cyclohexanone. The cross-aldol reactions with (R)-glyceraldehyde acetonide gave optically pure compounds 25-32, the stereochemistry of which was in agreement with a chairlike chelate transition state of dipolar mode. SmI(2)-molecular sieves or SmI(3)-molecular sieves also functioned as effective Lewis acids to catalyze tandem aldol/Evans-Tishchenko reactions. The aldol/Evans-Tishchenko reactions of methyl ketones with aldehydes occurred at 0 degrees C to give alpha,gamma-anti diol monoesters 53a-59a. When the reactions were conducted at room temperature, a certain degree of transesterification took place. The aldol/Evans-Tishchenko reactions of ethyl or benzyl ketones with aldehydes yielded alpha,beta-anti-alpha,gamma-anti diol monoesters 60a-65a. However, the aldol/Evans-Tishchenko reactions of cyclic ketones with benzaldehyde occurred with a different stereoselectivity to give alpha,beta-syn-alpha,gamma-anti diol monoesters 66a-76a. The structures of products were determined by chemical and spectroscopic methods including an X-ray diffraction analysis of 72a derived from the reaction of 4-tert-butylcyclohexanone and benzaldehyde. A reaction mechanism involving dissociation-recombination of aldols followed by intramolecular stereoselective hydride shift is proposed, based on some experimental evidence, to explain the dichotomous stereoselectivity using acyclic or cyclic ketones as the reaction substrates.

Effect of support modification by carbon coverage in the dehydrogenation activity of Cu/Al2O3 catalyst

Abstract: Gamma alumina and carbon covered gamma alumina supported Cu catalysts were prepared and characterized by adsorptive decomposition of N2O, NH3 chemisorption and temperature-programmed reduction. The decrease in interaction of copper species with alumina of carbon covered alumina has influence on the conversion and selectivity of the reaction of cyclohexanol to cyclohexanone.

The oxyfunctionalization of cyclohexane catalyzed by Mn(II) complexes included in zeolite Y

Abstract: The oxygen transfer from tert -butylhydroperoxide (TBHP) to cyclohexane and the formation of cyclohexanol and cyclohexanone is catalyzed by Cr(III), Mn(II), Fe(II), Co(II), Ni(II), and Cu(II) exchanged with zeolite Y. This oxidation was successfully achieved on complex Mn(II) with ligands of 2,2′-bipyridine, ethylenediamine, tetramethylethylenediamine, and tetramethyl 1,8-naphtalenediamine included in zeolite Y. The enhancement of the conversion percentage from 2.4% to 60% shows that the transition metal complex immobilized on zeolite Y represent a good cytochrome P -450 type oxidation system.

Asymmetric sulfoxidation of a β-carbonyl sulfide series by chloroperoxidase

Abstract: The chloroperoxidase (CPO)-catalyzed oxidation of a series of β-carbonyl sulfides to sulfoxides has been studied at room temperature in aqueous citrate buffer. For dialkyl β-carbonyl sulfides, the products with methyl and ethyl substituents are obtained in ca. 100% yield. However when the alkyl group is n- propyl or i -propyl the yield drops dramatically (25%). An aryl sulfide derivative afforded product in very low yield (4%), but when the phenyl group bears a carbonyl, and the sulfur substituents are methyl or ethyl, the oxidation occurs with high yields (91–95%). Steric control of the sulfoxidation reaction is also confirmed with cyclohexanone derivatives, where a low product yield is observed even at high enzyme concentrations. Noteworthy are the yields obtained with cyclopentanone sulfide (65%) and an unexpected quantitative yield obtained with the γ-butyrolactone sulfide.

Transformation of acetophenone over Pd HFAU catalysts—reaction scheme

Abstract: The transformation of acetophenone was carried out over a 0.5 wt.% Pd HFAU catalyst (Si/Al=17) under the following conditions: flow reactor, 250°C, pressure of ketone and hydrogen equal to 0.8 and 0.2 bar, respectively. The reaction products were identified either by comparison in GC with reference compounds: benzene (B), ethylbenzene (EB), styrene (EB=), cumene (IPB), isopropylbenzene (IPB=) and benzoic acid (BA) or through GC/MS coupling: 1,3-diphenylbutane (DPB), 1,3-diphenylbutenes (DPB=), 1,3-diphenylbutan-1-one (DPBO), 1,3-diphenylbut-2-ene-1-one (DPBO=) and 2,4-diphenyl-3-methylpentenes (DPMP=). These products are formed through three main reaction paths. DPBO= results from successive aldolisation of acetophenone and dehydration of the resulting alcohol over the protonic sites of the zeolite, DPBO from the hydrogenation of 1,3-diphenylbuten-1-one over the Pd sites (path 1). The formation of EB= involves hydrogenation of acetophenone followed by dehydration of the produced alcohol; EB results from EB= hydrogenation (path 2). DPB= can result from EB= dimerization (path 2) or from hydrogenation of DPBO followed by dehydration of the resulting alcohol (path 2). These reactions are similar to those observed during acetone and cyclohexanone transformation over bifunctional catalysts. In these reactions no alcohol intermediate is observed, which shows that alcohol dehydration is much faster than aldolisation and hydrogenation steps. The third reaction path which leads mainly to IPB, IPB= and BA, plays a significant role in acetophenone transformation whereas this path was very slow in acetone and cyclohexanone transformations. BA and IPB= result from acid cracking of DPBO=, IPB from hydrogenation of IPB=. IPB= undergoes also dimerization into DPMP= and IPB undergoes dealkylation into B over the protonic sites of the HFAU zeolite.

Evaluation of simple enzyme kinetics by response surface modelling

Abstract: The activity of a horse liver alcohol dehydrogenase catalysed reduction of cyclohexanone was investigated by using a central composite circumscribed design in which two parameters (pH and cyclohexanone concentration) were varied. By log transformation of the substrate concentration an adequate model could be obtained from which reliable kinetic constants and pH profiles were determined.

Solubility of 2-Hydroxybenzoic Acid in Select Organic Solvents at 298.15 K

Abstract: Experimental solubilities are reported for 2-hydroxybenzoic acid dissolved in 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, 1-octanol, dibutyl ether, 1,4-dioxane, tetrahydrofuran, ethyl acetate, butyl acetate, 2-propanone, 2-butanone, and cyclohexanone at 298.15 K. Results of these measurements reveal that the observed solubilities in the eight alcohol solvents fall within a fairly narrow mole fraction range of each other. 2-Hydroxybenzoic acid is more soluble in both 1,4-dioxane and tetrahydrofuran than in any of the other alcohol, ester, or ketone solvents studied.

Biomimetic Oxidation Studies. 11. Alkane Functionalization in Aqueous Solution Utilizing in Situ Formed [Fe(2)O(eta(1)-H(2)O)(eta(1)-OAc)(TPA)(2)](3+), as an MMO Model Precatalyst, Embedded in Surface-Derivatized Silica and Contained in Micelles.

Abstract: The biomimetic, methane monooxygenase enzyme (MMO) precatalyst, [Fe2O(η1-H2O)(η1-OAc)(TPA)2]3+ (TPA = tris[(2-pyridyl)methyl]amine), 1, formed in situ at pH 42 from [Fe2O(μ-OAc)(TPA)2]3+, 2, was embedded in an amorphous silicate surface modified by a combination of hydrophilic poly(ethylene oxide) and hydrophobic poly(propylene oxide) The resulting catalytic assembly was found to be a biomimetic model for the MMO active site within a hydrophobic macroenvironment, allowing alkane functionalization with tert-butyl hydroperoxide (TBHP)/O2 in an aqueous reaction medium (pH 42) For example, cyclohexane was oxidized to a mixture of cyclohexanone, cyclohexanol, and cyclohexyl-tert-butyl peroxide, in a ratio of ∼3:1:2 The balance between poly(ethylene oxide) and poly(propylene oxide), tethered on the silica surface, was crucial for maximizing the catalytic activity The silica-based catalytic assembly showed reactivity somewhat higher in comparison to an aqueous micelle system utilizing the surfactant, cetyl

Synthesis of 1,2,3,4‐tetrahydrocarbazole over zeolite catalysts

Abstract: 1,2,3,4‐tetrahydrocarbazole (CAR) has been synthesized over H‐ZSM‐12, H‐beta, H‐mordenite, H‐Y, H‐ZSM‐22, H‐EU‐1, H‐ZSM‐5 and acetic acid by Fisher's method using phenylhydrazine and cyclohexanone. H‐Y is more active than the other zeolites studied for the synthesis of CAR. The influence of different parameters such as the duration of the run, catalyst concentration, reaction temperature and molar ratios of the reactants in the synthesis of CAR are also studied. A number of arylhydrazines such as o-tolylhydrazine, p-tolylhydrazine and 1,1‐diphenylhydrazine and cyclic ketones such as cyclopentanone, cyclohexanone and 3‐methylcyclohexanone have also been taken to study the effect of substitution in phenylhydrazine and the size of the cyclic ketones in the reaction. The yields of indoles correlated with the degree of substitution of the reactants and products, and the limitations imposed on diffusion through zeolite pores.

The Meerwein–Ponndorf–Verley–Oppenauer reaction between 2-hexanol and cyclohexanone on magnesium phosphates

Abstract: Various magnesium phosphates were tested as catalysts for the vapour-phase Meerwein–Ponndorf–Verley–Oppenauer (MPVO) reaction between 2-hexanol and cyclohexanone. Some of the solids studied are as selective as MgO in this reaction. Others are also active in the dehydration of the alcohols. The activity and selectivity of the catalysts are related to their structure and surface chemical properties.

Synthesis and characterization of soluble polyimides from 2,2‐bis(4‐aminophenyl)cycloalkane derivatives

Abstract: A series of novel aromatic diamines (1−3) containing kinked cyclohexylidene moieties was synthesized by a reaction of excess aniline and corresponding methyl-substituted cyclohexanone derivatives. The structures of (1−3) were identifield by 1H NMR, 13C NMR, and FT-IR. The polymers were synthesized from the obtained diamines and various aromatic dianhydrides by the conventional polycondensation reaction followed by chemical imidization as well as high-temperature one-step polymerization. The inherent viscosities and weight-average molecular weights of the resulting polyimides were in the ranges of 0.55−1.58 dL/g and (7.4−15.2) × 104 g/mol, respectively. The prepared polyimides showed excellent thermal stabilities and good solubility. All polymers were readily soluble in common organic solvents such as tetrahydrofuran, chloroform, tetrachloroethane, etc., and the glass transition temperatures were observed at 290−372 °C.

Stereospecific Synthesis of (+)- and (−)-Cyclooctenone Derivatives Using a Ring Expansion Reaction with Me3SiSnBu3 and CsF

Abstract: Novel synthesis of an eight-membered compound by the ring expansion reaction of a two-carbon unit was developed using the stannyl anion generated from Me3SiSnBu3 and CsF in DMF. cis- and trans-cyclooctenone derivatives were synthesized from cyclohexanone derivatives having vinyl iodide in a tether by treatment with Me3SiSnBu3 and CsF in DMF in a stereospecific manner. The trans-cyclooctenone derivative was isomerized to the cis-isomer in the presence of Me3SiSnBu3 and CsF. It is known that the trans-eight-membered ring is an asymmetric compound. Using this procedure, (+)- and (−)-trans-cyclooctenone derivatives could be synthesized from the corresponding optically active cyclohexanone derivatives.

A formal total synthesis of (±)-α-pinguisene and (±)-pinguisenol

Abstract: Formal total synthesis of (±)-α-pinguisene and (±)-α-pinguisenol, containing a cis-1,2,6,7-tetramethylbicyclo[4.3.0]nonane skeleton incorporating two vicinal quaternary carbon atoms and four cis oriented methyl groups on four contiguous carbon atoms, isolated from liverworts is described. Thus, an orthoester Claisen rearrangement of the allyl alcohol 14, obtained from the Hagemann’s ester 15, afforded the ene ester 18. Hydrolysis of the ketal and ester moieties transformed the ene ester 18 into keto acid 23. Intramolecular cyclopropanation of the diazo ketone 24 derived from the keto acid 23 afforded a 3∶2 mixture of chromatographically separable tricyclic diones 25 and 26. Simultaneous regioselective reductive cyclopropane-ring cleavage and reduction of the cyclohexanone carbonyl in the dione 25 with lithium in liquid ammonia furnished the keto alcohol 27, which on Wolff–Kishner reduction followed by oxidation of the alcohol afforded the bicyclic ketone 11, Schinzer’s precusor of pinguisenol 9 and α-pinguisene 10.

Environmentally friendly liquid phase oxidation : enhanced selectivity in the aerial oxidation of alkyl aromatics, epoxidations and the Baeyer-Villiger oxidation using novel silica supported transition metal ions

Abstract: Active transition metal species (Co, Cu, Cr, Ni or Mn) supported on a chemically modified silica gel are used as heterogeneous catalysts in a range of liquid phase oxidation reactions: alkyl aromatic side chain oxidations, epoxidations of alkenes and Baeyer–Villiger oxidations of linear ketones to esters and cyclic ketones to lactones. The catalyst employs metal centres bound to the silica surface via a hydrophobic spacer chain and is thus chemically robust and has a relatively high loading for a supported reagent (c 0.4 mmol g−1). The Cr version of the catalyst promotes the oxidation of ethylbenzene to acetophenone in a solvent-free system at a rate of 5.5% h−1 (>370 turnover h−1). It is also active for the oxidation of p-chlorotoluene and p-xylene to p-chlorobenzoic acid and p-toluic acid respectively. Cyclohexene is converted to its oxide at room temperature at a rate of c 28% h−1 (c 12 turnover h−1) using either the Ni or Cu versions of the catalyst. The room temperature Baeyer–Villiger oxidation of cyclohexanone is achieved at a rate of 44% h−1 (49 turnover h−1) using the Ni-containing catalyst. The same material also promotes the Baeyer–Villiger oxidation of linear aliphatic ketones and aromatic side chains. All the above systems use either air or molecular oxygen as the oxidant rather than peroxides or peracids. © 1999 Society of Chemical Industry