- New perspectives on polyoxometalate catalysts: Alcohol oxidation with Zn/Sb-polyoxotungstates
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Catalytic belts are the crucial feature of Zn/Sb-polyoxometalates as efficient and selective catalysts for alcohol oxidation. Comprehensive theoretical, analytical, and catalytic studies identify the active role of the Sb atom in the polyoxometalate metal belt. This sheds new light on low-cost catalyst tuning strategies for crucial oxidative transformations.
- Ni, Lubin,Patzke, Greta R.,Patscheider, Joerg,Baldridge, Kim K.
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p. 13293 - 13298,6
(2012)
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Read Online
- Sandwich-type zinc-containing polyoxometalates with a hexaprismane core [{Zn2W(O)O3}2]4+ synthesized by thermally induced isomerization of a metastable polyoxometalate
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Two novel sandwich-type silicotungstates, TBA8[{Zn 2W(O)O3}2H4{α-SiW 9O33}2]·5H2O (α-Zn4; TBA = tetra-n-butylammonium) and TBA8[{Zn2W(O)O 3}2H4{β-SiW9O 33}2]·7H2O (β-Zn4), were synthesized by the solid-state thermally induced isomerization of metastable TBA8[{Zn(OH2)(μ3-OH)}2{Zn(OH 2)2}2{γ-HSiW10O 36}2]·9H2O (γ-Zn4). Compounds α-Zn4 and β-Zn4 consisted of two [SiW9O33] 8- subunits sandwiching the unprecedented distorted hexaprismane core [{Zn2W(O)O3}2]4+.
- Kikukawa, Yuji,Yamaguchi, Kazuya,Mizuno, Noritaka
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Read Online
- Chromium-Catalyzed Production of Diols From Olefins
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Processes for converting an olefin reactant into a diol compound are disclosed, and these processes include the steps of contacting the olefin reactant and a supported chromium catalyst comprising chromium in a hexavalent oxidation state to reduce at least a portion of the supported chromium catalyst to form a reduced chromium catalyst, and hydrolyzing the reduced chromium catalyst to form a reaction product comprising the diol compound. While being contacted, the olefin reactant and the supported chromium catalyst can be irradiated with a light beam at a wavelength in the UV-visible spectrum. Optionally, these processes can further comprise a step of calcining at least a portion of the reduced chromium catalyst to regenerate the supported chromium catalyst.
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Paragraph 0111
(2021/03/19)
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- Enantioselective addition of selenosulfonates to α,β-unsaturated ketones
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An organo-catalyzed enantioselective addition of selenosulfonates to α,β-unsaturated ketones was developed for the first time. With a chiral squaramide as an efficient catalyst, the desired α-selenylated ketones were obtained in a good yields with high enantioselectivity up to 89% ee, and good results could be obtained on a gram scale. The products could also be efficiently transformed into useful building blocks with a propenylic stereocenter; the strategy presented in this study may find further applications in organic synthesis.
- Luo, Shilong,Zhang, Nan,Wang, Zhen,Yan, Hailong
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supporting information
p. 2893 - 2901
(2018/05/03)
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- Selective catalytic oxidation of alkenes employing homobinuclear manganese(II) catalysts with TBHP
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The two novel homobinuclear compounds [Mn2(II,II) (μ1,1-4-CH3-C6H4COO)2(phen)4](ClO4)2 (1) and [Mn2(II,II) (μ1,3-4-CH3-C6H4COO)2(bipy)4](ClO4)2 (2), where bipy = 2,2-bipyridine and phen = 1,10-phenanthroline, have been synthesized and characterized by elemental analyses and spectral methods (UV–Vis, FTIR, and X-ray). A single-crystal X-ray diffraction structure analysis of the compounds revealed that the manganese atom is octahedrally coordinated. In compound 1, the binuclear(II) structure is monodentate, bridged with one oxygen atom of carboxylate ligand in μ1,1 mode, and each Mn(II) center is coordinated with two phen ligands. In compound 2, the binuclear(II) structure is syn–anti bidentate, bridged with two oxygen atoms of carboxylate ligand in μ1,3 mode, and each Mn(II) center is coordinated with two bipy ligands. The Mn–Mn separation is 3.441 (1) ? and 4.450 (1) ? for 1 and 2, respectively. The catalytic potentials of these compounds have been tested for the oxidation reaction of various olefins (i.e., styrene, cyclohexene, ethyl benzene, 1-hexene, 1-octene). The oxidation reactions were carried out in the presence of catalytic amounts of 1 and 2 with a peroxide oxygen donor (TBHP = tert-Butyl hydroperoxide) in acetonitrile at 70 °C. On comparing the catalytic activities of 1 and 2, both catalysts showed good activity (~100% conv. in 24 h) in the oxidation of studied alkenes, and excellent conversion was obtained for cyclohexene (~100% conv. in 3 h; TON = 265 and TON = 257, respectively, for 1 and 2).
- K?l??, Yal??n,Kani, ?brahim
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p. 352 - 359
(2018/01/10)
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- A carboxylate-bridged Mn(II) compound with 6-methylanthranilate/bipy: oxidation of alcohols/alkenes and catalase-like activity
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A novel manganese compound, [Mn2(μ1,3-6-CH3-2-NH2C6H4COO)2(bipy)4](ClO4)2 (bipy?=?2,2′-bipyridine), was synthesized and used as a catalyst precursor in the oxidation of alkenes and primary alcohols to corresponding aldehydes, ketones, and acids. The six-coordinate compound has a binuclear structure in which two Mn(II) ions adopt a syn-anti μ1,3-bridging mode with two carboxylate groups and two chelated bipy ligands. The compound exhibits good activity in the oxidation of cyclohexene to 2-cyclohexene-1-one as the major product (93% conv. in 3?h, 79.3% selectivity) and of cinnamyl alcohol to cinnamaldehyde as the major product with 46% selectivity (100% conv. in 1.5?h) with tert-butyl hydroperoxide (TBHP) in acetonitrile at 70?°C. Furthermore, the catalase-like activity of the compound was studied in different solvents (acetonitrile, methanol, Tris-HCl buffer; TOF?=?29,910?h?1 in Tris-HCl buffer).
- Kilic, Yalcin,Bolat, Serkan,Kani, Ibrahim
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p. 2293 - 2303
(2018/05/14)
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- Fe3O4 magnetic nanoparticles (MNPs) as an efficient catalyst for selective oxidation of benzylic and allylic C-H bonds to carbonyl compounds with tert-butyl hydroperoxide
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Fe3O4 magnetic nanoparticles (MNPs) were prepared by a co-precipitation method with oleic acid as a surfactant and characterized by FT-IR, TEM, DLS, XRD, VSM techniques. XRD, DLS and TEM analysis of this catalyst clearly showed the formation of cubic structure Fe3O4 MNPs, with a mean size of 16 nm. Moreover, a magnetization measurement revealed that the Fe3O4 MNPs had superparamagnetic behaviour and the saturation magnetization of the catalyst was 54.6 emu g-1. The Fe3O4 MNPs in combination with tert-butyl hydroperoxide catalyzed the oxidation of various benzylic and allylic C-H bonds to the corresponding carbonyl compounds in excellent yields. These oxidation reactions were effectively and economically performed under mild conditions, and therefore the dual challenge of cost effectiveness and benign nature of the processes was met.
- Zarghani, Monireh,Akhlaghinia, Batool
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p. 38592 - 38601
(2016/05/24)
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- Direct Synthesis of γ-Keto Sulfones from Allylic Alcohols: One-Pot Palladium(II)-Catalyzed Generation of Enones Followed by Water-Mediated 1,4-Addition of Organosulfinates
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Allylic alcohols were exploited as synthetic precursors of γ-keto sulfones. The reaction involved the one-pot generation of α,β-enones in situ from the allylic alcohols by using a PdII–dioxygen catalytic system and subsequent sulfa-Michael addition in the presence of water. Importantly, water was identified as a sustainable substitute for a toxic copper salt to promote organosulfonyl addition. Diverse examples of aromatic and aliphatic γ-keto sulfones were prepared. Specially, Ar–X (X = Br, Cl) bonds were tolerated, which indicated a chemoselective catalytic system for the preparation of halogen-bearing γ-keto sulfones. This one-pot method does not require an acid, a base, or isolation of any intermediate. Control experiments indicated that the active catalyst of the first step also promoted the subsequent C–S bond-formation reaction. Water was found to accelerate the reaction rate and to be involved in the protonolysis of the σ-alkylpalladium complex, as corroborated by deuterium incorporation.
- Vellakkaran, Mari,Andappan, Murugaiah M. S.,Nagaiah, Kommu,Nanubolu, Jagadeesh Babu
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supporting information
p. 3575 - 3583
(2016/07/28)
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- Design and synthesis of nanoporous perylene bis-imide linked metalloporphyrin frameworks and their catalytic activity
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Two nanoporous perylene bis-imide linked metalloporphyrin framework catalysts have been synthesized via condensation of 5,10,15,20-tetrakis-(4 ′ -aminophenyl) iron(III) porphyrin chloride or 5,10, 15,20-tetrakis-(4 ′ -aminophenyl) manganese(III) porphyrin chloride with perylene-3,4,9,10-tetracarboxylic dianhydride. Both the materials were crystalline in nature and were characterized by electron microscopy techniques, solid-state 1H- 13C CP/MS NMR, powder X-ray diffraction (PXRD), and magnetic susceptibility measurements. The nitrogen gas physisorption study has indicated that both materials are porous in nature and have BET surface area with 653 m2/g and 974 m2/g with uniform pore size of 2.8 nm. These materials were found to act as very good heterogeneous catalysts for selective oxidation of alkanes and alkenes with tert-butyl hydroperoxide and were not degraded even after multiple uses up to 10 cycles.
- Singh, Manoj Kumar,Bandyopadhyay, Debkumar
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- 1,4-Diazabicyclo[2.2.2]octane-Promoted Aminotrifluoromethylthiolation of α,β-Unsaturated Carbonyl Compounds: N-Trifluoromethylthio-4-nitrophthalimide Acts as Both the Nitrogen and SCF3 Sources
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A novel difunctionalization reaction is described. It uses N-trifluoromethylthio-4-nitrophthalimide as the reagent, which serves as both the nitrogen and SCF3 sources. In the presence of DABCO (1,4-diazabicyclo[2.2.2]octane), the nitrogen and SCF3 groups can be incorporated into α,β-unsaturated carbonyl compounds easily and give versatile β-amino ketones and esters in good yields. This difunctionalization reaction features mild reaction conditions, high atom-economy, and efficient access to α-SCF3 amino acids.
- Xiao, Qing,He, Qijie,Li, Juncheng,Wang, Jun
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supporting information
p. 6090 - 6093
(2016/01/09)
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- Simple access to β-trifluoromethyl-substituted ketones via copper-catalyzed ring-opening trifluoromethylation of substituted cyclopropanols
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Tertiary cyclopropanols react rapidly with Togni reagent in methanol at room temperature in the presence of catalytic amounts (3 mol%) of CuCl affording β-trifluoromethyl ketones in 65-73% isolated yields. Ring opening in 1,2-dialkylsubstituted cyclopropanols gives a mixture of isomeric β-trifluoromethyl ketones in about 50% combined yield.
- Kananovich, Dzmitry G.,Konik, Yulia A.,Zubrytski, Dzmitry M.,J?rving, Ivar,Lopp, Margus
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supporting information
p. 8349 - 8352
(2015/05/13)
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- Control of the selectivity in multi-functional group molecules using supported gold-palladium nanoparticles
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The oxidation of 2-hexen-1-ol and 1-hexen-3-ol with air has been studied using supported gold, palladium and gold-palladium catalysts. The main aim was to determine if either the alcohol or alkene functional group can be oxidised selectively. However, based on the reaction products observed (2-hexen-1-ol forms 2-hexene, hexanal, (E)-2-hexenal, (E)-3-hexen-1-ol, 4-hexen-1-ol and (E)-2-hexanoic acid. 1-Hexen-3-ol forms 1-hexene, 3-hexanone, 1-hexen-3-one and 3-hexenol), the main pathway in these reactions is isomerisation and, in addition, significant yields of the products are due to a disproportionation reaction. Controlling the selectivity in molecules with multiple function groups by manipulating the catalyst composition and reaction conditions can promote or hinder the various reaction pathways, thereby increasing the selectivity to the desired oxidation products.
- Alshammari, Hamed,Miedziak, Peter J.,Morgan, David J.,Knight, David W.,Hutchings, Graham J.
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p. 1244 - 1254
(2013/06/26)
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- Metal-free, hydroacylation of CC and NN bonds via aerobic C-H activation of aldehydes, and reaction of the products thereof
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In this report, a thorough evaluation of the use of aerobically initiated, metal-free hydroacylation of various CC and NN acceptor molecules with a wide range of aldehydes is presented. The aerobic-activation conditions that have been developed are in sharp contrast to previous conditions for hydroacylation, which tend to use transition metals, peroxides that require thermal or photochemical degradation, or N-heterocyclic carbenes. The mildness of the conditions enables a number of reactions involving sensitive reaction partners and, perhaps most significantly, allows for α-functionalised chiral aldehydes to undergo radical-based hydroacylation with complete retention of optical purity. We also demonstrate how the resulting hydroacylation products can be transformed into other useful intermediates, such as γ-keto- sulfonamides, sultams, sultones, cyclic N-sulfonyl imines and amides.
- Chudasama, Vijay,Akhbar, Ahmed R.,Bahou, Karim A.,Fitzmaurice, Richard J.,Caddick, Stephen
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p. 7301 - 7317
(2013/10/22)
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- Aerobic oxidation of α,β-unsaturated alcohols using sequentially-grown AuPd nanoparticles in water and tetraalkylphosphonium ionic liquids
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Metallic and bimetallic nanoparticles (NPs) (Au, Pd, and AuPd) were synthesized in water with poly(vinylpyrroldine) (PVP) as a polymer stabilizer, as well as in tetraalkylphosphonium chloride ionic liquids (ILs). A borohydride reduction technique was used for the preparation of the monometallic NPs, while a sequential reduction strategy was seen to generate the putative core-shell varieties. Pd and sequentially grown Au-Pd NPs were seen to serve as efficient catalysts for the oxidation of α,β-unsaturated alcohols, while the Au NPs themselves showed minimal activity. However, a system with both Au NPs and a Pd(II) salt (K2PdCl4) also efficiently catalyzed the oxidation reaction in water. A number of aliphatic and aromatic unsaturated alcohols were oxidized using oxygen as an oxidant with these as-prepared catalysts at 60 °C in the absence of base. TEM and EXAFS studies of the nanoparticle catalysts before and after the oxidation reaction revealed that the Pd(II) salt was reduced in situ during catalytic conditions, and that there was large changes in particle size and morphology after catalysis, which suggests Ostwald ripening and the presence of a redox mechanism. In the IL system, the ease of Pd reduction led to high activities for many α,β-unsaturated alcohols in the absence of the Au promoter.
- Maclennan, Aimee,Banerjee, Abhinandan,Scott, Robert W.J.
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p. 170 - 179
(2013/06/27)
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- The dual role of cis-[RuCl2(dmso)4] in the synthesis of new water-soluble Ru(II)-phosphane complexes and in the catalysis of redox isomerization of allylic alcohols in aqueous-organic biphasic systems
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New air-stable, water-soluble Ru(II)-phosphane complexes were synthesized in high purity by the reaction of cis-[RuCl2(dmso)4] with 2 equivalents of 1,3,5-triaza-7-phosphaadamantane (pta) and its N-methyl and N-benzyl derivatives (pta-Me and pta-Bn, respectively). All new complexes were characterized by elementary analysis and spectroscopic methods (NMR, ESI-MS) and the molecular structures of cis-cis-trans-[RuCl2(dmso) 2(pta)2], cis-cis-trans-[RuCl2(dmso) 2(pta-H)2]Cl2 (obtained in acidic solutions) and that of cis-cis-trans-[RuCl2(dmso)2(pta-Me) 2](CF3SO3)2 were determined by single crystal X-ray diffraction. Under mild conditions, cis-[RuCl 2(dmso)4] actively catalyzed the transformation of allylic alcohols into the corresponding ketones with 100% selectivity while in the same reaction the new Ru(II)-pta complexes showed moderate activity and selectivity.
- Udvardy, Antal,Bényei, Attila Csaba,Kathó, ágnes
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p. 116 - 122
(2012/11/06)
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- New perspectives on polyoxometalate catalysts: Alcohol oxidation with Zn/Sb-polyoxotungstates
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Catalytic belts are the crucial feature of Zn/Sb-polyoxometalates as efficient and selective catalysts for alcohol oxidation. Comprehensive theoretical, analytical, and catalytic studies identify the active role of the Sb atom in the polyoxometalate metal belt. This sheds new light on low-cost catalyst tuning strategies for crucial oxidative transformations.
- Ni, Lubin,Patscheider, Joerg,Baldridge, Kim K.,Patzke, Greta R.
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p. 13293 - 13298
(2013/01/15)
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- Gold- and silver-catalyzed reactions of propargylic alcohols in the presence of protic additives
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A wide range of primary, secondary and tertiary propargylic alcohols undergo a Meyer-Schuster rearrangement to give enones at room temperature in the presence of a gold(I) catalyst and small quantities of MeOH or 4-methoxyphenylboronic acid. The syntheses of the enone natural products isoegomaketone and daphenone were achieved using this reaction as the key step. The rearrangement of primary propargylic alcohols can readily be combined in a one-pot procedure with the addition of a nucleophile to the resulting terminal enone, to give β-aryl, β-alkoxy, β-amino or β-sulfido ketones. Propargylic alcohols bearing an adjacent electron-rich aryl group can also undergo silver-catalyzed substitution of the alcohol with oxygen, nitrogen and carbon nucleophiles. This latter reaction was initially observed with a batch of gold catalyst that was probably contaminated with small quantities of silver salt.
- Pennell, Matthew N.,Turner, Peter G.,Sheppard, Tom D.
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experimental part
p. 4748 - 4758
(2012/05/04)
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- Selective oxygenation of α-olefins by means of metalloporphyrin catalysts mimicking cytochrome P-450
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A significant problem associated with synthetic metalloporphyrin catalysts used to mimic oxygenation function of cytochrome P-450 is their deactivation due to the formation of inactive μ-oxo dimer. We prepared a series of porphyrin-based catalysts mimicking cytochrome P-450 potentially resistant to deactivation by varying the central metal ion, porphyrin ring substitution, and catalyst support. The influence of the nature of a solid support, the type of central cation and the chemical modification of the porphyrin ring on the catalytic efficiency was studied. The oxygenation ability of the synthesized catalysts was tested using 1-hexene as a substrate and tert-butyl hydroperoxide as an oxidant under various reaction conditions. Identification of the oxygenation products was performed with gas chromatography-mass spectrometry (GC-MS). Quantification of the products formed was based on GC with flame ionization detection (FID). It was found that the application of low GC injection temperature (150 °C) was necessary to detect primary products of the oxygenation, peroxo alkenes, from which secondary oxygenation products, mainly epoxides, alcohols, aldehydes and ketones, were formed slowly. The efficiency of the individual catalysts depended on their structure and varied significantly. The most active catalysts were Fe(II)- tetraphenylporphyrin (TPP) immobilized on aminopolystyrene (aminoPS) and Mn(II)-TPP immobilized on aminoPS.
- Zachar, Pavel,Petkova, Galina,Sykora, David,Kral, Vladimir
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experimental part
p. 1163 - 1175
(2012/01/04)
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- A general procedure for the synthesis of enones via gold-catalyzed Meyer-Schuster rearrangement of propargylic alcohols at room temperature
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Meyer-Schuster rearrangements of propargylic alcohols take place readily at room temperature in toluene with 1-2 mol % PPh3AuNTf2, in the presence of 0.2 equiv of 4-methoxyphenylboronic acid or 1 equiv of methanol. Good to excellent yields of enones can be obtained from secondary and tertiary alcohols, with high selectivity for the E-alkene in most cases. A one-pot procedure for the conversion of primary propargylic alcohols into β-arylketones was also developed, via Meyer-Schuster rearrangement followed by Pd-catalayzed addition of a boronic acid.(Figure Presented)
- Pennell, Matthew N.,Unthank, Matthew G.,Turner, Peter,Sheppard, Tom D.
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supporting information; experimental part
p. 1479 - 1482
(2011/04/26)
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- Zinc(II) containing γ-keggin sandwich-type silicotungstate: Synthesis in organic media and oxidation catalysis
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Zinc in: Polyoxometalate 1 reacts with Zn2+ ions in acetone to form a novel sandwichtype POM 2 in almost quantitative yield. The H2O2-based oxidation of secondary alcohols with 2 efficiently proceeds, with an activity and chemoselectivity that is very different from those of tungsten-based catalysts including 1 (see scheme; green Zn).
- Kikukawa, Yuji,Yamaguchi, Kazuya,Mizuno, Noritaka
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supporting information; experimental part
p. 6096 - 6100
(2010/11/05)
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- Dissociated nonsteroidal glucocorticoid receptor modulators; discovery of the agonist trigger in a tetrahydronaphthalene-benzoxazine series
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The tetrahydronaphthalene-benzoxazine glucocorticoid receptor (GR) partial agonist 4b was optimized to produce potent full agonists of GR. Aromatic ring substitution of the tetrahydronaphthalene leads to weak GR antagonists. Discovery of an "agonist trigger" substituent on the saturated ring of the tetrahydronaphthalene leads to increased potency and efficacious GR agonism. These compounds are efficacy selective in an NFkB GR agonist assay (representing transrepression effects) over an MMTV GR agonist assay (representing transactivation effects). 52 and 60 have NFkB pIC50 = 8.92 (105%) and 8.69 (92%) and MMTV pEC50 = 8.20 (47%) and 7.75 (39%), respectively. The impact of the trigger substituent on agonism is modeled within GR and discussed. 36, 52, and 60 have anti-inflammatory activity in a mouse model of inflammation after topical dosing with 52 and 60, having an effect similar to that of dexamethasone. The original lead was discovered by a manual agreement docking method, and automation of this method is also described.
- Barker, Mike,Clackers, Margaret,Copley, Royston,Demaine, Derek A.,Humphreys, Davina,Inglis, Graham G. A.,Johnston, Michael J.,Jones, Haydn T.,Haase, Michael V.,House, David,Loiseau, Richard,Nisbet, Lesley,Pacquet, Francois,Skone, Philip A.,Shanahan, Stephen E.,Tape, Dan,Vinader, Victoria M.,Washington, Melanie,Uings, Iain,Upton, Richard,McLay, Iain M.,Macdonald, Simon J. F.
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p. 4216 - 4231
(2007/10/03)
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- Catalytic performance of [Ti,Al]-beta in the alkene epoxidation controlled by the postsynthetic ion exchange
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The catalytic performance of [Ti,Al]-Beta in the alkene epoxidation controlled by the postsynthetic ion exchange was studied. When as-synthesized [Ti,Al]-Beta was treated with aqueous ammonium nitrate solution and successively calcined at low temperature, a dramatic enhancement of epoxide selectivity was attained in the liquid-phase epoxidation of cyclohexene using H2O2 as an oxidant in protic solvent methanol. Addition of H2O2 to the system of three non-titanosilicates (H-ZSM-5, silicalite-1, and deboronated B-Beta) produced no enhancement effect in the solvolysis of cyclohexene oxide. The optimum thermal treatment temperature to achieve the maximum epoxide yield was 473 K, where the postsynthetic [Ti,Al]-Beta exhibited a catalytic activity comparable to the sample directly calcined at 793 K; nevertheless, the epoxide selectivity was ≤ 63% for the former in contrast to 0% for the latter. [Ti,Al]-Beta ion-exchanged with quaternary ammonium acetate followed by mild calcination showed similarly high epoxide selectivity. Tetramethylammonium acetate was the best modifier, resulting in almost no loss of epoxidation activity. Regeneration of the ion-exchange treatments catalysts was achieved by the repeated calcination and ion-exchange treatments, making the catalyst reusable. The pH in the ion-exchange treatment strongly influenced the catalytic performance. The optimal pH of the treatments was ~ 10. High pH treatments caused the partial dissolution of [Ti,Al]-Beta frameworks to increase the activity but decreased the epoxide selectivity.
- Goa, Yasuhide,Wu, Peng,Tatsumi, Takashi
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p. 8401 - 8411
(2007/10/03)
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- Cascade rearrangement of spiroepoxymethyl radicals into 2-oxocycloalkyl radicals: Evaluation of a two-carbon cycloalkanone ring expansion
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Series of 2-bromomethyl- and 2-hydroxymethyl-1-oxaspiro[2.n]alkanes were prepared from cycloalkanones by initial Wadsworth-Horner-Emmons methodology to afford ester-substituted methylenecycloalkanes. The latter were selectively reduced to hydroxymethylmethylenecycloalkanes which were epoxidised with peroxyacetic acid. Homolytic reactions were studied by EPR spectroscopy which enabled transient 3-oxoalk-1-enyl radicals, and their cyclisation products, 2-oxocycloalkyl and 2-oxocycloalkylmethyl radicals, to be characterised. This evidence, together with end product analyses of organotin hydride reductions of the 2-bromomethyl-1-oxaspiro[2.n]alkanes, established that the initial spiroepoxymethyl radicals rearranged by a three-stage cascade of two consecutive β-scissions followed by a cyclisation. Cyclisations of the 3-oxoalk-1-enyl radicals took place mainly in the endo-mode to afford 2-oxocycloalkyl radicals, except for the 5-oxohept-6-enyl radical for which exo-cyclisation to generate the 2-oxocyclohexylmethyl radical was preferred. Kinetic data for the exo-and endo-cyclisations of the 4-oxohex-5-enyl radical were obtained from tributyltin hydride mediated reactions of 2-bromomethyl-1-oxaspiro[2.3]hexane.
- Afzal, Mohammad,Walton, John C.
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p. 937 - 945
(2007/10/03)
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- Stereochemistry of the biotransformation of 1-hexene and 2-methyl-1- hexene with rat liver microsomes and purified p450s of rats and humans
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The epoxidation of 1-hexene (1a) and 2-methyl-1-hexene (1b), two hydrocarbons present in the ambient air as pollutants, is catalyzed by some human and rat P450 enzymes. The enantioselectivities of these processes, when the reactions were carried out using rat and human liver microsomal preparations, were modest and dependent on both P450 composition and substrate concentrations. Various P450 isoforms (rat P450 2B1 and human P450 2C10 and 2A6) catalyzed the double bond oxidation of 1a and 1b with different product enantioselectivities. In the case of 1a, a moderately enantioselective hydroxylation at the allylic C(3) with the formation of 1- hexen-3-ol (4a) by microsomes from control or preinduced rats was also observed. The oxidation of this metabolite was, in turn, catalyzed by rat liver microsomes and mainly by rat P450 2C11, leading exclusively to the formation of 1-hexen-3-one, with no double bond epoxidation being observed. The stereochemical course of the microsomal epoxide hydrolase-catalyzed hydrolysis of the epoxy alcohols, threo-(±)- and erythro-(±)-1,2- epoxyhexan-3-ol, theoretically expected to be formed from 4a, has been investigated.
- Chiappe, Cinzia,De Rubertis, Antonietta,Amato, Giada,Gervasi, Pier Giovanni
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p. 1487 - 1493
(2007/10/03)
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- Synthetic peptide lung surfactants having covalently bonded antioxidants
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Synthetic pulmonary surfactants having antioxidant properties consisting of a complex of a polypeptide of 3-4 amino acid residues, with an antioxidant moiety, and a lipid consisting of one or more of the lipids associated with natural pulmonary surfactant were prepared. These surfactants are useful in the treatment of respiratory distress syndrome.
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- Synthetic lung surfactant having antioxidant properties
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Synthetic pulmonary surfactants having antioxidant properties consisting of a complex of a polypeptide, with an antioxidant moiety, having an alpha-helical structure and a lipid consisting of one or more of the lipids associated with natural pulmonary surfactant were prepared. These surfactants are useful in the treatment of respiratory distress syndrome.
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- Chromium pillared clay catalysed allylic oxidation and oxidative deprotection of allyl ethers and amines : A simple and convenient procedure
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An efficient method for allylic oxidation of cyclic and acyclic alkenes to the corresponding α,β-unsaturated carbonyl compounds in good yields was described using catalytic amounts of chromiapillared montmorillonite and equimolar quantities of tert-butyl hydroperoxide. This is also a convenient method for selective oxidative deprotection of allyl ethers and amines using same system. Incidentally this is the first heterogeneous system for the allylic oxidation as well as oxidative deprotection.
- Choudary, Boyapati M.,Prasad, Annavajhula Durga,Swapna, Vinukonda,Valli, Velaga L. K.,Bhuma, Vedantam
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p. 953 - 962
(2007/10/02)
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- The Addition of 1-Lithio-1-(phenylthio)alkanes to 2-(N-Methylanilino)acrylonitrile: An Easy Access to 3-(Phenylthio)ketones and 2-Enones
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A simple and versatile strategy for the synthesis of the title compounds is described.The key-step consists in the addition of 1-lithio-1-(phenylthio)alkanes to 2-(N-methylanilino)acrylonitrile, the nucleophilic phenylthioalkylation of an enol-cation equivalent.Alkylation of the adducts and hydrolysis give 3-(phenylthio)ketones, which can be isolated, or without further purification can be transformed into 2-enones via the well known oxidation-elimination procedure.These reactions are possible with allylic derivatives too, therefore the homologous vinylic compoundscan be prepared by the same way.Pyrolysis of the 1-lithioaminonitriles formed within the first step gives aminonitriles of cyclopropanones via cyclization.
- Ahlbrecht, Hubertus,Ibe, Marcellinus
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p. 210 - 214
(2007/10/02)
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- Selective Oxidation of Alcohol Function in Allylic Alcohols to α,β-Unsaturated Carbonyl Compounds Catalyzed by Zirconocene Complexes
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Bis(η5-cyclopentadienyl)zirconium(IV) complexes, Cp2ZrH2 (1) and Cp2Zr(O-i-Pr)2 (4), in the presence of an appropriate hydrogen acceptor such as benzaldehyde or cyclohexanone catalyze the Oppenauer-type oxidation of allylic alcohols to α,β-unsaturated carbonyl compounds.For instance, primary allylic terpenoid alcohols, geraniol and nerol, were oxidized to α- and β-citrals, which are essential compounds in the perfumery industry, in substantial yields without any treatment.Similarly, secondary allylic alcohols such as 3-hexen-2-ol and 2-cyclohexen-1-ol were alsooxidized with ease to give 3-hexen-2-one and 2-cyclohexen-1-one in 93percent and 89percent yields, respectively.But the present OPP-type oxidation by zirconocene complexes is ineffective for propargylic alcohols.
- Nakano, Tatsuya,Ishii, Yasutaka,Ogawa, Masaya
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p. 4855 - 4859
(2007/10/02)
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- TRANSFORMATION OF ORGANIC COMPOUNDS IN THE PRESENCE OF METAL COMPLEXES I. TRANSFORMATION OF UNSATURATED ALCOHOLS WITH METAL COMPLEX CATALYSTS
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The transformations of unsaturated alcohols (2-hexen-3-ol, 1-penten-4-ol, 1-penten-4-ol and 2-methylenecyclohexanol) were studied under identical experimental conditions in the presence of various Rh and Ru complexes (RhCl(PPh3)3, RhH(PPh3)4, RhCl3*3H2O, RhCl3*3H2O + PPh3, Rh(COD)Cl2, Rh(COD)Cl2 + PPh3, RhCl2(PPh3)3 and RuH2(PPh3)4).Several aspects of both the unsaturated alcohol and the complex exertconsiderable effects on the extent of the main reactions; isomerization to ketone and double-bond migration.
- Felfoeldi, K.,Bartok, M.
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p. C37 - C40
(2007/10/02)
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- MONOOXYGENASE-LIKE OXIDATIONS OF OLEFINS AND ALKANES CATALYZED BY MANGANESE PORPHYRINS : COMPARISON OF SYSTEMS INVOLVING EITHER O2 AND ASCORBATE OR IODOSYLBENZENE
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A biphasic system using a manganese porphyrin as a catalyst and sodium ascorbate as a reducing agent is able to activate dioxygen and to oxidize olefins selectively into epoxides and alkanes into alcohols and ketones.Its properties and specifities are shown to be different from those of the manganese porphyrin-iodosylbenzene system, suggesting that a manganese -oxo complex is not involved in these O2-dependent oxidations.
- Fontecave, Marc,Mansuy, Daniel
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p. 4297 - 4312
(2007/10/02)
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- REGIOSELECTIVITY OF OLEFIN OXIDATION BY IODOSOBENZENE CATALYZED BY METALLOPORPHYRINS: CONTROL BY THE CATALYST
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The regioselectivity of the oxidation of three monosubstituted olefins, 6-phenoxyhex-1-ene, hex-1-ene and styrene, by iodosobenzene in the presence of various Fe-, Mn- or Cr-tetraaryl-porphyrins, was studied.It was found that, besides epoxides, known products from such systems, allylic alcohols and aldehydes were formed, the latter not being derived from the corresponding epoxides.The relative importance of these reactions greatly depends upon both the metal and porphyrin constituents of the catalyst.More particularly, the competition between epoxidation and allylic hydroxylation can be efficiently controlled by non bonded interactions between the olefin and porphyrin substituents.No hydroxylation of the aromatic rings and no oxidative dealkylation of the ether function was detected.
- Mansuy, Daniel,Leclaire, Jacques,Fontecave, Marc,Dansette, Patrick
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p. 2847 - 2857
(2007/10/02)
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- PREPARATION DE CETONES ET D'ALCOOLS INSATURES A PARTIR DE LA METHYLVINYLCETONE. UNE SYNTHESE SIMPLE ET EFFICACE D'ALCOOLS ISOPRENIQUES
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The preparation of olefinic ketones and alcohols by means of a retro Diels-Alder reaction is described.This process has been applied to high yield syntheses of linalool 6e, nerolidol 6f and the sesquiterpene alcohol 10 recently isolated from the alga Laurencia nidifica.
- Bloch, R.
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p. 639 - 644
(2007/10/02)
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- Process for preparation of adjacently disubstituted ketones
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A novel 7-hydroxyprostaglandin E1, or a stereoisomer thereof, or a protected derivative thereof, having the following formula: STR1 wherein R8 represents H, CH3 or C2 H5, R9 represents H or CH3, R10 and R11 are identical or different, and each represents H, tetrahydropyranyl or t-butyldimethylsilyl. Also provided is a process for producing an adjacently disubstituted ketone including the above compounds, i.e. 7-oxoprostaglandin, etc. which comprises reacting an α,β-unsaturated carbonyl compound with a cuprous salt and an organolithium compound in an aprotic inert organic medium in the presence of trialkylphosphine, the amounts of said cuprous salt and said organolithium compound being substantially equimolar, and reacting the product with a protected acetal derivative of an organic carbonyl compound or an aldehyde in the presence of a Lewis acid, if necessary, followed by reacting the product with a proton donor.
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