- Tsuji-Wacker-Type Oxidation beyond Methyl Ketones: Reacting Unprotected Carbohydrate-Based Terminal Olefins through the "uemura System" to Hemiketals and α,β-Unsaturated Diketones
-
Aerobic Pd(AcO)2/pyridine-catalyzed oxidation of unprotected carbohydrate-based terminal alkenes was studied. In accordance with previous reports, the initial reaction step gave methyl ketones. However, our substrates partially gave subsequent α,β-water elimination and alcohol oxidation to α,β-unsaturated 2,5-diketones. Upon increasing the pressure of O2, the reaction was shifted toward formation of α,β-epoxy-2-ketones. The reactions were stereoselective and gave up to quantitative conversions. However, isolated yields were substantially lower because of the complexity of the product mixtures.
- Runeberg, Patrik A.,Eklund, Patrik C.
-
supporting information
p. 8145 - 8148
(2019/10/11)
-
- Β - hydroxy ketone compounds
-
The invention provides a synthesis method for a beta-hydroxy-ketone compound shown in a formula (III). The method comprises the steps that substitute vinyl acetate shown in a formula (I), a substitute alcohol compound shown in a formula (II) and an oxidizing agent are mixed to obtain reaction liquid, and the reaction liquid reacts for 2-12 hours at the temperature of 20 DEG C-120 DEG C, and then is treated to obtain the beta-hydroxy-ketone compound. The method is safe and environmentally friendly, and is a new path for synthesizing the beta-hydroxy-ketone compound containing various substituents, the substrate adaptability is good, and the reaction operation is easy.
- -
-
Paragraph 0061-0063
(2017/08/25)
-
- Base-Free Transfer Hydrogenation of Ketones Using Cp?Ir(pyridinesulfonamide)Cl Precatalysts
-
N-(2-(Pyridin-2-yl)ethyl)benzenesulfonamide derivatives and 1,1,1-trifluoro-N-(2-(pyridin-2-yl)ethyl)methanesulfonamide (1-4), along with three-legged piano stool Cp?IrIIICl complexes (5-11) (Cp? = pentamethylcyclopentadienyl) bearing pyridinesulfonamide ligands with varying electronic parameters, were synthesized. These ligands and air-stable complexes were characterized by 1H and 13C{1H} NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Precatalysts, 5-11, were assessed for transfer hydrogenation of aryl, diaryl, dialkyl, linear, cycloaliphatic, and α,β-unsaturated ketones, diones, β-ketoesters, and a biomass-derived substrate with 2-propanol, using 1 mol % precatalyst. Catalysis was also efficient using a 0.1 mol % loading. Remarkably, all catalysis experiments can be conducted in air without dried and degassed substrates, and basic additives and halide abstractors are not required for high activity in transfer hydrogenation. Control experiments and a mercury poisoning experiment support a homogeneous catalyzed pathway. Overall, the fastest reactions are observed using electron-poor substrates and precatalysts bearing electron-rich ligands.
- Ruff, Andrew,Kirby, Christopher,Chan, Benny C.,O'Connor, Abby R.
-
p. 327 - 335
(2016/02/19)
-
- Water-Soluble Gold-N-Heterocyclic Carbene Complexes for the Catalytic Homogeneous Acid- and Silver-Free Hydration of Hydrophilic Alkynes
-
Water-soluble gold(III/I) N-heterocylic carbene complexes behave as efficient catalysts for the hydration of terminal alkynes in neat water. The transformation proceeds in the absence of Bronsted acids or halide scavengers and is suitable for sensitive substrates. Kinetic profiles and DFT studies provide a clear picture of intermediates present during catalysis.
- Ibrahim, Houssein,Defrmont, Pierre,Braunstein, Pierre,Thry, Vincent,Nauton, Lionel,Cisnetti, Federico,Gautier, Arnaud
-
p. 3893 - 3900
(2016/01/25)
-
- Mechanistic insights into ring-opening and decarboxylation of 2-pyrones in liquid water and tetrahydrofuran
-
2-Pyrones, such as triacetic acid lactone, are a promising class of biorenewable platform chemicals that provide access to an array of chemical products and intermediates. We illustrate through the combination of results from experimental studies and first-principle density functional theory calculations that key structural features dictate the mechanisms underlying ring-opening and decarboxylation of 2-pyrones, including the degree of ring saturation, the presence of C=C bonds at the C4=C5 or C5=C6 positions within the ring, as well as the presence of a β-keto group at the C4 position. Our results demonstrate that 2-pyrones undergo a range of reactions unique to their structure, such as retro-Diels-Alder reactions and nucleophilic addition of water. In addition, the reactivity of 2-pyrones and the final products formed is shown to depend on the solvent used and the acidity of the reaction environment. The mechanistic insights obtained here provide guidance for the selective conversion of 2-pyrones to targeted chemicals.
- Chia, Mei,Haider, M. Ali,Pollock, Gerald,Kraus, George A.,Neurock, Matthew,Dumesic, James A.
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p. 5699 - 5708
(2013/05/21)
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- Silica-dendrimer core-shell microspheres with encapsulated ultrasmall palladium nanoparticles: Efficient and easily recyclable heterogeneous nanocatalysts
-
We report the synthesis, characterization, and catalytic properties of novel monodisperse SiO2@Pd-PAMAM core-shell microspheres containing SiO2 microsphere cores and PAMAM dendrimer-encapsulated Pd nanoparticle (Pd-PAMAM) shells. First, SiO2 microspheres, which were prepared by the Stoeber method, were functionalized with vinyl groups by grafting their surfaces with vinyltriethoxysilane (VTS). The vinyl groups were then converted into epoxides by using m-chloroperoxybenzoic acid. Upon treatment with amine-terminated G4 poly(amidoamine) (PAMAM) dendrimers, the SiO 2-supported epoxides underwent ring-opening and gave SiO 2@PAMAM core-shell microspheres. Pd nanoparticles within the cores of the SiO2-supported PAMAM dendrimers were synthesized by letting Pd(II) ions complex with the amine groups in the cores of the dendrimers and then reducing them into Pd(0) with NaBH4. This produced the SiO 2@Pd-PAMAM core-shell microspheres. The presence of the different functional groups on the materials was monitored by following the changes in FTIR spectra, elemental analyses, and weight losses on thermogravimetric traces. Transmission electron microscopy (TEM) images showed the presence of Pd nanoparticles with average size of 1.56 ± 0.67 nm on the surface of the monodisperse SiO2@Pd-PAMAM core-shell microspheres. The SiO 2@Pd-PAMAM core-shell microspheres were successfully used as an easily recyclable catalyst for hydrogenation of various olefins, alkynes, keto, and nitro groups, giving ~100% conversion and high turnover numbers (TONs) under 10 bar H2 pressure, at room temperature and in times ranging from 10 min to 3 h. In addition, the SiO2@Pd-PAMAM core-shell microspheres were proven to be recyclable catalysts up to five times with barely any leaching of palladium into the reaction mixture.
- Biradar, Ankush V.,Biradar, Archana A.,Asefa, Tewodros
-
experimental part
p. 14408 - 14418
(2012/03/26)
-
- Chemoselective aerobic diol oxidation by palladium(II)-pyridine catalysis
-
Neutral and cationic palladium complexes that bear pyridine ligands [i.e., pyridine (Py), 4-ethylpyridine (4-EtPy) and 2,4,6-trimethylpyridine (2,4,6-Me3Py)] have been isolated and characterized in solution by 1H and 13C{1H} NMR spectroscopy, cyclic voltammetry (CV) and in the solid state by elemental analysis and single-crystal structure analysis. All palladium compounds have been scrutinized as a precursor to catalyze the aerobic oxidation of diols either in the presence or in the absence of an external base (i.e., K2CO3). As a result, the chemoselective production of the corresponding hydroxy ketones has been achieved. The bis-cationic palladium complex of the formula [Pd(4-EtPy)4](OTs)2 (OTs = p-toluenesulfonate) [5b(OTs)2] emerged as the most promising precursor; it outperformed the neutral precursor that consisted of trans-[Pd(OAc)2(4-EtPy) 2] (OAc = acetate) and 4-EtPy [3b/2(4-EtPy)] (2 mol-equiv.). An operando high-pressure (HPNMR) spectroscopic study with the precursor 5b(OTs)2 combined with the results obtained from catalytic reactions has provided insight into the catalytic mechanism that is operative in 5b(OTs)2-catalyzed aerobic diol oxidation reactions. Neutral and cationic palladium(II) complexes with pyridine ligands were synthesized and employed as catalyst precursors for the aerobic K2CO 3-assisted oxidation of unprotected diols to chemoselectivelygive hydroxy ketones. Within the series of catalyst precursors studied, the bis-cationic compound [Pd(4-EtPy)4](OTs)2 (Py = pyridine, OTs = p-toluenesulfonate) emerged as the most promising.
- Bettucci, Lorenzo,Bianchini, Claudio,Filippi, Jonathan,Lavacchi, Alessandro,Oberhauser, Werner
-
experimental part
p. 1797 - 1805
(2011/06/25)
-
- Heterogenized Ru(II) phenanthroline complex for chemoselective hydrogenation of diketones under biphasic aqueous medium
-
The chemoselective hydrogenation of acetylacetone to 4-hydroxypentan-2-one over immobilized ruthenium phenanthroline metal complexes in amino functionalized MCM-41 in biphasic aqueous reaction medium was investigated. The catalyst was characterized by XRD, TEM, surface analysis, FT-IR and UV-vis to understand the morphology, complex geometry, and XPS such that the oxidation state of the metal complex inside the MCM-41 framework could be understood. The use of water as a solvent, not only gives high activity and selectivity for hydrogenation of acetylacetone, but also gives a path for an environmentally safer process. The optimizations of ligand, metal to ligand ratio, the choice of solvent and other reaction parameters were studied in detail. The heterogeneous catalytic system gave a higher degree of chemoselectivity (99%) towards 4-hydroxypentan-2-one as compared to homogeneous catalyst when hydrogenation was carried out using water as a solvent. The immobilized ruthenium-phenanthroline complex was easily separated and reused.
- Deshmukh, Amit,Kinage, Anil,Kumar, Rajiv,Meijboom, Reinout
-
scheme or table
p. 114 - 120
(2011/02/23)
-
- Chemoselective aerobic oxidation of unprotected diols catalyzed by Pd-(NHC) (NHC = N-heterocyclic carbene) complexes
-
Neutral Pd(X)(η3-allyl) (X = Cl, OAc (acetate)) complexes bearing mono-coordinating NHC ligands have been synthesized, characterized and employed to catalyze the aerobic oxidation of unprotected 1,2- and 1,3-diols selectively to hydroxy ketones. A comparison of the catalytic performance of these precursors with a reference system has shown that the precursor with the ligands N,N′-bis(adamantyl)imidazol-2-ylidene and chloride is the most efficient for the chemoselective oxidation of 1,2-diols is concerned. High-pressure 1H NMR (HPNMR) experiments in combination with catalytic batch reactions have provided valuable information on the activation of the precursor as well as on the stability of the catalysts.
- Bettucci, Lorenzo,Bianchini, Claudio,Oberhauser, Werner,Hsiao, Tsun-Hung,Lee, Hon Man
-
experimental part
p. 63 - 72
(2010/07/08)
-
- Isolable gold(I) complexes having one low-coordinating ligand as catalysts for the selective hydration of substituted alkynes at room temperature without acidic promoters
-
Hydration of a wide range of alkynes to the corresponding ketones has been afforded in high yields at room temperature by using gold(I)-phosphine complexes as catalyst, with no acidic cocatalysts required. Suitable substrates covering alkyl and aryl terminal alkynes, enynes, internal alkynes, and propargylic alcohols, including enantiopure forms, are cleanly transformed to the corresponding ketones in nearly quantitative yields. Acid-labile groups present in the substrates are preserved. The catalytic activity strongly depends on both the nature of the phosphine coordinated to the gold (I) center and the softness of the counteranion, the complex AuSPhOsNTf2 showing the better activity. A plausible mechanism for the hydration of alkynes through ketal intermediates is proposed on the basis of kinetic studies. The described catalytic system should provide an efficient alternative to mercury-based methodologies and be useful in synthetic programs.
- Leyva, Antonio,Corma, Avelino
-
scheme or table
p. 2067 - 2074
(2009/08/07)
-
- Catalytic enantioselective peroxidation of α,β-unsaturated ketones
-
Despite the potential of chiral peroxides as biologically interesting or even clinically important compounds, no catalytic enantioselective peroxidation has been reported. With a chiral catalyst not only to induce enantioselectivity but also to convert a well established epoxidation pathway into a peroxidation pathway, the first efficient catalytic peroxidation has been successfully developed. Employing readily available α,β-unsaturated ketones and hydroperoxides and an easily accessible cinchona alkaloid catalyst, this novel reaction will open new possibilities in the asymmetric synthesis of chiral peroxides. Under different conditions a highly enantioselective epoxidation with the same starting materials, reagents, and catalyst has was also established. Copyright
- Lu, Xiaojie,Liu, Yan,Sun, Bingfeng,Cindric, Brittany,Deng, Li
-
supporting information; body text
p. 8134 - 8135
(2009/02/02)
-
- TiCl4/tert-butyl hydroperoxide: Chemioselective oxidation of secondary alcohols and suppression of sharpless epoxidation
-
Replacing Ti(Oi-Pr)4 with TiCl4 under the normal Sharpless epoxiation conditions resulted in a shut down of the epoxidation reaction. Instead, a chemioselective oxidation of secondary alcohols in the presence of primary alcohols occurred. Georg Thieme Verlag Stuttgart.
- Shei, Chun-Tin,Chien, Hao-Lun,Sung, Kuangsen
-
experimental part
p. 1021 - 1026
(2009/04/04)
-
- Reduction of carbonyl compounds to the corresponding alcohols with isopropanol on dehydrated alumina under microwave irradiation
-
The reduction of different types of aldehydes and ketones were performed in the presence of isopropylalcohol (as solvent and hydride source) under microwave irradiation. It is proved that dehydrated Woelm chromatographic alumina supported KOH catalyses these transformations. Regioselectivity was observed in the reduction of cinnamaldehyde and chemoselectivity was observed in the reduction of carbonyl in the presence of nitro group.
- Kazemi,Kiasat
-
p. 2255 - 2260
(2007/10/03)
-
- n-Alkyl glycosides and p-hydroxybenzoyloxy glucose from fruits of Crescentia cujete
-
The fruits of Crescentia cujete afforded eight new compounds, along with four known compounds, acanthoside D, β-D-glucopyransoyl benzoate, (R)-1-O-β-D-glucopyranosyl-1,3-octanediol, and β-D-fructofuranosyl 6-O-(p-hydroxybenzoyl)-α-D-glucopyranoside. The structures of the new glycosides were established as three glycosides of (2R,4S)-2,4-pentanediol, two glycosides of (R)-4-hydroxy-2-pentanone, two glycosides of (R)-1,3-octanediol and 6-O-(p-hydroybenzoyl)-D-glucose, by spectroscopic and chemical methods.
- Kaneko, Tetsuo,Ohtani, Kazuhiro,Kasai, Ryoji,Yamasaki, Kazuo,Nguyen Minh, Duc
-
p. 259 - 263
(2007/10/03)
-
- Stereoselective synthesis of 5-alkyliden-6-aminotetrahydro-2-pyranones through an unexpected isomerization of the hydroxytetrahydro-2-pyridinones obtained by the selective reduction of acylated enaminones
-
A convenient methodology for the stem selective preparation of 5- alkyliden-6-aminotetrahydro-2-pyranone 4 is reported. The synthesis of 2- pyranone 4 occurs through an unknown isomerization mechanism of the hydroxytetrahydro-2-pyridinone 3 an accessible starting material obtained by mild and selective reduction of the 5-acyltetrahydro-2-pyridinone 2. The isomerization mechanism and the stereoselectivity in the synthesis of 2- pyranone 4 was investigated and rationalized.
- Cimarelli, Cristina,Palmieri, Gianni
-
p. 915 - 926
(2007/10/03)
-
- Oxidation of Diols and Ethers by NaBrO3/NaHSO3 Reagent
-
NaBrO3 combined with NaHSO3 was found to be an excellent oxidizing reagent of alcohols, diols, and ethers under mild conditions. A variety of aliphatic and cyclic diols were selectively oxidized with satisfactory yields to the corresponding hydroxy ketones and/or diketones, which are difficult to selectively prepare due to a concomitant formation of cleaved products. For example, 2-hydroxycyclohexanone and 1,2-cyclohexanedione were selectively formed by allowing 1,2-cyclohexanediol to react with NaBrO3/NaHSO3 reagent in a selected solvent. On the other hand, an alkyl ether, such as dioctyl ether, reacted with NaBrO3/NaHSO3, in water at room temperature to give octyl octanoate in 82% yield. The same oxidation at higher temperature (60°C) produced the α-brominated ester, octyl 2-bromooctanoate, which is considered to be formed through an alkenyl alkyl ether as the intermediate. The treatment of 1-ethoxy-l-heptene with NaBrO3/NaHSO3 afforded ethyl 2-bromoheptanoate and 2-bromoheptanoic acid as the major products.
- Sakaguchi, Satoshi,Kikuchi, Daisuke,Ishii, Yasutaka
-
p. 2561 - 2566
(2007/10/03)
-
- Degradation of vinyl alcohol oligomers by Geotrichum sp. WF9101
-
Geotrichum sp. WF9101 isolated from a poly(vinyl alcohol)-degrading mixed culture could utilized vinyl alcohol oligomers, but not the polymers. This strain is proposed to have utilized degradation products of poly(vinyl alcohol) in the mixed culture. Biodegradation of vinyl alcohol oligomers by this strain was discussed using 2,4-pentanediol as a model substrate.
- Mori, Tatsuma,Sakimoto, Michio,Kagi, Takashi,Sakai, Takuo
-
p. 1188 - 1190
(2007/10/03)
-
- Efficient desymmetrization of 1,2 and 1,3 diols by dimethyldioxirane
-
Dimethyldioxirane was used to monooxide 1,2 and 1,3 sec,sec-diols to the corresponding ketoalcohols, exploiting the inhibiting effect of the formed carbonyl group on the course of the process.
- Bovicelli, Paolo
-
p. 3031 - 3034
(2007/10/02)
-
- Ruthenium(II) Complexes with the Atropisomeric Diphosphine 2,2'-Bis(diphenylphosphino)-6,6'-dimethylbiphenyl in the Enantioselective Hydrogenation of Pentane-2,4-dione
-
The five-co-ordinate complex > reacts with pentane-2,4-dione (Hacac) in the presence of NEt3 to give >, which has been isolated in the solid state.The reaction of the chlorohydride > with Hacac gives > and eventually >, which were identified spectroscopically.The relevance of the formation of these new species to the enantioselective hydrogenation of 2,4-diketones to the corresponding diols has been studied by testing > and some of its derivatives as catalyst precursors, also in connection with the use of modifiers such as anhydrous HCl, PPh3, chloride ions, NEt3 and HBF4.The hydrogenation reaction has also been followed under ambient conditions by means of 31P and 1H NMR spectroscopy.The activity and selectivity data confirm that for optimum efficiency two chloride ligands must be present in the catalyst precursor.These data are discussed in view of the assessment of a possible reaction pathway for the catalytic reaction.
- Mezzetti, Antonio,Tschumper, Andreas,Consiglio, Giambattista
-
-
- ASYMMETRISCHE KATALYSEN, 68. ENANTIOSELEKTIVE HYDRIERUNG VON ACETYLACETON MIT NaBr/L-(+)-WEINSAEURE MODIFIZIERTEN UEBERGANGSMETALLEN
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Enantioselective hydrogenation of acetylacetone AcacH to 4-hydroxy-2-pentanone HP and 2,4-pentanediol PD on various types of transition metal complexes modified with NaBr/L-(+)-tartaric acid was carried out.Finely divided catalysts prepared by cocondensation of the transition metals Cr, Mn, Fe, Co, Ni, the alloys Ni/Al, Ni/Zn, Ni/Cu, which were activated by NaOH treatment, and nickel powders with different surface areas were used.Transition metals and alloys obtained by condensation showed satisfactory enantioselectivity but had low hydrogenation activity.Modified nickel powders achieved high enantioselectivities and activities.The enantioselectivity could be correlated to the surface area of the nickel catalysts with a maximum between 5-7.5 m2/g.
- Brunner, H.,Amberger, K.,Wiehl, J.
-
p. 571 - 584
(2007/10/02)
-
- Meerwein-Ponndorf-Verley-Type Reduction of Dicarbonyl Compounds to Hydroxy Carbonyl Compounds and α,β-Unsaturated Carbonyl Compounds to Allylic Alcohols Catalyzed by Zirconocene and Hafnocene Complexes
-
Group IVA metallocene complexes such as bis(η5-cyclopentadienyl)zirconium dihydrides, Cp2ZrH2 (1), and hafnium dihydrides, Cp2HfH2 (8), catalyze the chemoselective reduction of polycarbonyl compounds to hydroxy carbonyl compounds.For instance, the reduction of keto aldehydes 3-ketobutanal (2g) and 2-phenyl-2-ketoethanal (2h) proceeded selectively at aldehyde group to provide the corresponding hydroxy ketones 3g and 3h in 91percent and 93percent yields, respectively.Under similar conditions, however, cyclohexanediones were easily aromatized to benzenediols.On the other hand, 1 and 8 also catalyze the selective 1,2-reduction of various types of α,β-unsaturated carbonyl compounds, giving the corresponding allylic alcohols in good to excellent yields.Thus, steroidal dicarbonyl compounds, having an enone framework in their molecules Δ4-androstene-3,17-dione (11a) and Δ4-progestene-3,20-dione (11b) were reduced by 1 to 17-hydroxy-Δ4-androsten-3-one (12a) and 20-hydroxy-Δ4-progest-3-one (12b), which are essential human hormones, in 80percent and 67percent yields, respectively.
- Nakano, Tatsuya,Umano, Shigetoshi,Kino, Yoshio,Ishii, Yasutaka,Ogawa, Masaya
-
p. 3752 - 3757
(2007/10/02)
-
- The Mechanism of Thermal Eliminations. Part 22. Rate Data for Pyrolysis of Primary, Secondary, and Tertiary β-Hydroxy Alkenes, β-Hydroxy Esters, and β-Hydroxy Ketones. The Dependence of Transition-state Structure for Six-centre Eliminations upon Compound Type
-
Rates of pyrolysis of but-3-en-1-ol, pent-4-en-2-ol, and 2-methylpent-4-en-2-ol, the corresponding methyl hydroxy esters viz. methyl 3-hydroxypropanoate, methyl 3-hydroxybutanoate, and methyl 3-hydroxy-3-methylbutanoate, and the corresponding methyl hydroxy ketones viz. 4-hydroxybutan-2-one, 4-hydroxypentan-2-one, and 4-hydroxy-4-methylpentan-2-one have been measured between 556.4 and 713.7 K.The relative 1 deg:2 deg:3 deg rates at 600 K are 1:2.0:3.47 for alkenes, (1):9.3:44.6 for the esters, and (1):7.0:21.6 for the ketones (the rates for the primary compounds in the latter two series being less accurate because of significant concurrent dehydration).The order of reactivity is ketones>>esters>alkenes, the relative reactivities at 600 K being 338:2.21:1 for 4-hydroxy-4-methylpentan-2-one, methyl 3-hydroxy-3-methylbutanoate, and 2-methylpent-4-enol, respectively.The reactivity of the ketones compared with the alkenes contrasts with the results for the structurally analogous acetates and vinyl ethers which eliminate with near identical rates and for which methyl substitution on the double bond produces substantially less rate modification.At 600 K 3-methylbut-3-en-1-ol is 8.4 times as reactive as but-3-en-1-ol, and phenyl 3-hydroxypropanoate is much less reactive than methyl 3-hydroxypropanoate.The results provide further evidence that within the spectrum of Ei transition states for six-centre eliminations there are two broad mechanistic categories.For reactions with more E1-like transition states, breaking of the Cα-X bond is the most important step, whereas for other reactions including those described here, nucleophilic attack of the double bond upon the β-C-H bond becomes the most important step.The higher nucleophilicity of the C=O bond vs. the C=CH2 bond accounts for the difference in reactivity of ketones and alkenes, while the inductive effect of the methoxy group upon the nucleophilicity of the double bond appears to account for the lower reactivity of the esters compared to the ketones.
- August, Ryan,McEwen, Ian,Taylor, Roger
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p. 1683 - 1690
(2007/10/02)
-
- Degradation Mechanism of Poly(vinyl alcohol) by Successive Reactions of Secondary Alcohol Oxidase and β-Diketone Hydrolase from Pseudomonas sp.
-
The secondary alcohol oxidase from Pseudomonas sp. catalyzed the oxidation of various vinyl alcohol oligomers with the molecular weight of 220 to 1500 and of β-ketols such as 5-hydroxy-3-heptanone, 4-hydroxy-2-nonanone, 3-hydroxy-5-nonanone, 6-hydroxy-4-nonanone, 7-hydroxy-5-dodecanone, and 8-hydroxy-6-tridecanone. β-Diketone hydrolase from the same strain catalyzed the hydrolysis of various aliphatic β-diketones such as 1-phenyl-1,3-butanedione and 1-phenyl-2,4-pentanedione. 4,6-Nonanediol, used as a low molecular weight model of poly(vinyl alcohol) (PVA), was oxidized to 4,6-nonanedione by way of 6-hydroxy-44nonanone by secondary alcohol oxidase. 4,6-Nonanedione was hydrolyzed to 2-pentanone and n-butyric acid by β-diketone hydrolase.These reactions were stoichiometric.The presence of the β-diketone structure in PVA oxidized by secondary alcohol oxidase was confirmed by spectral experiments.The ratio of the amount of carboxyl groups in the degraded PVA to that of carbonyl groups in the oxidized PVA became more than 0.5.A pathway for the enzymatic degradation of PVA was proposed.
- Sakai, Kiyofumi,Hamada, Nobutake,Watanabe, Yasuto
-
p. 989 - 996
(2007/10/02)
-
- Stereochemical Studies of the Hydrogenation with an Asymmetrically Modified Raney Nickel Catalyst. The Hydrogenation of Acetylacetone
-
The hydrogenation of acetylacetone (I) over asymmetrically modified Raney nickel (MRNi) proceeded, step by step, as follows: Step 1 Step 2 acetylacetone (I) ------> 4-hydroxy-2-pentanone (III) ------> 2,4-pentanediol (II).It was demonstrated that the optical yield of Step 1 and the diastereomer excess of Step 2 are governed by the ratio of the stereo-differentiating reaction site to the non-stereo-differentiating reaction site on the catalyst.The stereochemistry of each step was also discussed based on the mode of the intermolecular hydrogen bondings between the substrate and tartaric acid adsorbed on the catalyst.RNi modified with a mixture of tartaric acid and NaBr (TA-NaBr-MRNi) gave the best result with respect to both Step 1 and Step 2.
- Tai, Akira,Ito, Kazuhisa,Harada, Tadao
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p. 223 - 227
(2007/10/02)
-
- The retroaldol reaction of 3-penten-2-one: equilibrium constant for hydration and rate constant for the hydration and retroaldol reactions in base
-
In aqueous sodium hydroxide solutions at 25 degC, 3-penten-2-one undergoes retroaldol cleavage to acetone and acetaldehyde.The kinetics can be followed spectrophotometrically, and show two exponential phases with rather different rate constats.By a new analysis of the mathematical solution to this system we have been able to derive an improved method for calculating the microscopic rate constants.These rate constants are khyd=2.89*1E-3 M-1s-1, kdehyd=4.04*1E-4 M-1s-1, and kretro=3.36*1E-4 M-1s-1.The equlibrium constant for hydration of 3-penten-2-one (standard state for water is the pure liquid) is 7.13.
- Guthrie, J. Peter
-
-
- Dehydrogenation of Cyclic and Bicyclic Secondary Alkyl Peroxides during Flash Vacuum Pyrolysis
-
Dehydrogenation to the corresponding diketone occurs to the extent of 16percent and 42percent respectively in the flash vacuum pyrolysis of 3,6-dimethyl-1,2-dioxacyclohexane and 2,3-dioxabicyclooctane, but is unimportant in similar pyrolyses of 3,5-dimethyl-1,2-dioxacyclopentane and 2,3-dioxabicycloheptane.
- Bloodworth, A. J.,Baker, David S.
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p. 547 - 549
(2007/10/02)
-