- Aromatic compound hydrogenation and hydrodeoxygenation method and application thereof
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The invention belongs to the technical field of medicines, and discloses an aromatic compound hydrogenation and hydrodeoxygenation method under mild conditions and application of the method in hydrogenation and hydrodeoxygenation reactions of the aromatic compounds and related mixtures. Specifically, the method comprises the following steps: contacting the aromatic compound or a mixture containing the aromatic compound with a catalyst and hydrogen with proper pressure in a solvent under a proper temperature condition, and reacting the hydrogen, the solvent and the aromatic compound under the action of the catalyst to obtain a corresponding hydrogenation product or/and a hydrodeoxygenation product without an oxygen-containing substituent group. The invention also discloses specific implementation conditions of the method and an aromatic compound structure type applicable to the method. The hydrogenation and hydrodeoxygenation reaction method used in the invention has the advantages of mild reaction conditions, high hydrodeoxygenation efficiency, wide substrate applicability, convenient post-treatment, and good laboratory and industrial application prospects.
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Paragraph 0094-0095; 0106-0113
(2021/05/29)
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- Insights into the Substrate Promiscuity of Novel Hydroxysteroid Dehydrogenases
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Hydroxysteroid dehydrogenases (HSDHs) are valuable biocatalysts for the regio- and stereoselective modification of steroids, bile acids and other steroid derivatives. In this work, we investigated the substrate promiscuity of this highly selective class of enzymes. In order to reach this goal, a preliminary search of HSDH homologues in in-house or public available (meta)genomes was carried out. Eight novel NAD(H)-dependent HSDHs, showing either 7α-, 7β-, or 12α-HSDH activity, and including, for the first time, enzymes from extremophilic microorganisms, were identified, recombinantly produced, and characterized. Among the novel HSDHs, four highly active (up to 92 U mg?1) NAD(H)-dependent 7β-HSDHs showing negligible similarity towards previously described 7β-HSDHs, were discovered. These enzymes, along with previously characterized HSDHs, were tested as biocatalysts for the stereoselective reduction of a panel of substrates including two α-ketoesters of pharmaceutical interest and selected ketones that partially resemble the structural features of steroids. All the reactions were coupled with a suitable cofactor regeneration system. Regarding the α-ketoesters, nearly all of the tested HSDHs showed a good activity toward the selected substrates, yielding the reduced α-hydroxyester with up to 99% conversions and enantiomeric excesses. On the other hand, only the 7β-HSDHs from Collinsella aerofaciens and Clostridium absonum showed appreciable activity toward more complex ketones, i. e., (±)-trans-1-decalone, but with interesting as well as different selectivity. (Figure presented.).
- Bertuletti, Susanna,Ferrandi, Erica Elisa,Marzorati, Stefano,Vanoni, Marta,Riva, Sergio,Monti, Daniela
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p. 2474 - 2485
(2020/05/06)
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- Chemoselective Oxidation of Equatorial Alcohols with N-Ligated λ3-Iodanes
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The site-selective and chemoselective functionalization of alcohols in complex polyols remains a formidable synthetic challenge. Whereas significant advancements have been made in selective derivatization at the oxygen center, chemoselective oxidation to the corresponding carbonyls is less developed. In cyclic systems, whereas the selective oxidation of axial alcohols is well known, a complementary equatorial selective process has not yet been reported. Herein we report the utility of nitrogen-ligated (bis)cationic λ3-iodanes (N-HVIs) for alcohol oxidation and their unprecedented levels of selectivity for the oxidation of equatorial over axial alcohols. The conditions are mild, and the simple pyridine-ligated reagent (Py-HVI) is readily synthesized from commercial PhI(OAc)2 and can be either isolated or generated in situ. Conformational selectivity is demonstrated in both flexible 1,2-substituted cyclohexanols and rigid polyol scaffolds, providing chemists with a novel tool for chemoselective oxidation.
- Mikhael, Myriam,Adler, Sophia A.,Wengryniuk, Sarah E.
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supporting information
p. 5889 - 5893
(2019/08/26)
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- Microwave-assisted isomerizations of epoxides to allylic alcohols
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The present work reports a study on the isomerization reactions of several alkyl epoxides to the corresponding allylic alcohols or bicyclic alcohols under microwave irradiation. The reaction occurred in the presence of lithium diisopropylamide as a base and different experimental conditions in terms of solvent, amount of the base, times and temperatures. The traditional heating with an oil-bath and the use of alternative organometallic bases, as the Lochmann-Schlosser bases, have been furthermore compared with the microwave heating. The results obtained show that the use of microwave irradiations on promoting the isomerization of epoxides gives access to a series of synthetically useful products, among which allylic alcohols and bicyclic alcohols, depending on the starting substrate.
- Consiglio, Gabriella Barozzino,Mordini, Alessandro
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p. 447 - 454
(2018/05/22)
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- Regioselective and Chemoselective Reduction of Naphthols Using Hydrosilane in Methanol: Synthesis of the 5,6,7,8-Tetrahydronaphthol Core
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A regioselective and chemoselective method for catalytic synthesis of biologically interesting 5,6,7,8-tetrahydronaphthols by reduction of naphthols was described. The side aromatic hydrocarbons in naphthols were site-selectively reduced, using hydrosilanes in methanol, allowing for retaining functional phenol scaffolds intact. It presents a rare example of using low-cost and air-stable hydrosilane for catalytic reduction of unactivated aromatic hydrocarbons under mild conditions. This reaction is scalable and proceeds in high selectivity without the formation of 1,2,3,4-tetrahydronaphthol byproducts with toleration of sensitive functionalities such as bromide, chloride, fluoride, ketone, ester, and amide.
- He, Yuan,Tang, Jinghua,Luo, Meiming,Zeng, Xiaoming
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supporting information
p. 4159 - 4163
(2018/07/29)
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- A stable and practical nickel catalyst for the hydrogenolysis of C-O bonds
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The selective hydrogenolysis of C-O bonds constitutes a key step for the valorization of biomass including lignin fragments. Moreover, this defunctionalization process offers the possibility of producing interesting organic building blocks in a straightforward manner from oxygenated compounds. Herein, we demonstrate the reductive hydrogenolysis of a wide variety of ethers including diaryl, aryl-alkyl and aryl-benzyl derivatives catalyzed by a stable heterogeneous NiAlOx catalyst in the presence of a Lewis acid (LA). The special feature of this catalyst system is the formation of substituted cyclohexanols from the corresponding aryl ether.
- Cui, Xinjiang,Yuan, Hangkong,Junge, Kathrin,Topf, Christoph,Beller, Matthias,Shi, Feng
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p. 305 - 310
(2017/01/24)
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- Alkane oxidation catalysed by a self-folded multi-iron complex
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A preorganised ligand scaffold is capable of coordinating multiple Fe(II) centres to form an electrophilic CH oxidation catalyst. This catalyst oxidises unactivated hydrocarbons including simple, linear alkanes under mild conditions in good yields with selectivity for the oxidation of secondary CH bonds. Control complexes containing a single metal centre are incapable of oxidising unstrained linear hydrocarbons, indicating that participation of multiple centres aids the CH oxidation of challenging substrates.
- Mettry, Magi,Moehlig, Melissa Padilla,Gill, Adam D.,Hooley, Richard J.
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p. 120 - 128
(2016/11/09)
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- Selective Catalytic Hydrogenation of Arenols by a Well-Defined Complex of Ruthenium and Phosphorus-Nitrogen PN3-Pincer Ligand Containing a Phenanthroline Backbone
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Selective catalytic hydrogenation of aromatic compounds is extremely challenging using transition-metal catalysts. Hydrogenation of arenols to substituted tetrahydronaphthols or cyclohexanols has been reported only with heterogeneous catalysts. Herein, we demonstrate the selective hydrogenation of arenols to the corresponding tetrahydronaphthols or cyclohexanols catalyzed by a phenanthroline-based PN3-ruthenium pincer catalyst.
- Li, Huaifeng,Wang, Yuan,Lai, Zhiping,Huang, Kuo-Wei
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p. 4446 - 4450
(2017/07/24)
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- Upgrading of aromatic compounds in bio-oil over ultrathin graphene encapsulated Ru nanoparticles
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Fast pyrolysis of biomass for bio-oil production is a direct route to renewable liquid fuels, but raw bio-oil must be upgraded in order to remove easily polymerized compounds (such as phenols and furfurals). Herein, a synthesis strategy for graphene encapsulated Ru nanoparticles (NPs) on carbon sheets (denoted as Ru@G-CS) and their excellent performance for the upgrading of raw bio-oil were reported. Ru@G-CS composites were prepared via the direct pyrolysis of mixed glucose, melamine and RuCl3 at varied temperatures (500-800 °C). Characterization indicated that very fine Ru NPs (2.5 ± 1.0 nm) that were encapsulated within 1-2 layered N-doped graphene were fabricated on N-doped carbon sheets (CS) in Ru@G-CS-700 (pyrolysis at 700 °C). And the Ru@G-CS-700 composite was highly active and stable for hydrogenation of unstable components in bio-oil (31 samples including phenols, furfurals and aromatics) even in aqueous media under mild conditions. This work provides a new protocol to the utilization of biomass, especially for the upgrading of bio-oil.
- Shi, Juanjuan,Zhao, Mengsi,Wang, Yingyu,Fu, Jie,Lu, Xiuyang,Hou, Zhaoyin
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supporting information
p. 5842 - 5848
(2016/05/24)
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- The Stereoselective Reductions of Ketones to the Most Thermodynamically Stable Alcohols Using Lithium and Hydrated Salts of Common Transition Metals
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A simple method is presented for the highly stereoselective reductions of ketones to the most thermodynamically stable alcohols. In this procedure, the ketone is treated with lithium dispersion and either FeCl2·4H2O or CuCl2·2H2O in THF at room temperature. This protocol is applied to a large number and variety of ketones and is both more convenient and efficient than those commonly reported for the diastereoselective reduction of five- and six-membered cyclic ketones.
- Kennedy, Nicole,Cohen, Theodore
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p. 8134 - 8141
(2015/09/02)
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- Polyketide intermediate mimics as probes for revealing cryptic stereochemistry of ketoreductase domains
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Among natural product families, polyketides have shown the most promise for combinatorial biosynthesis of natural product-like libraries. Though recent research in the area has provided many mechanistic revelations, a basic-level understanding of kinetic and substrate tolerability is still needed before the full potential of combinatorial biosynthesis can be realized. We have developed a novel set of chemical probes for the study of ketoreductase domains of polyketide synthases. This chemical tool-based approach was validated using the ketoreductase of pikromycin module 2 (PikKR2) as a model system. Triketide substrate mimics 12 and 13 were designed to increase stability (incorporating a nonhydrolyzable thioether linkage) and minimize nonessential functionality (truncating the phosphopantetheinyl arm). PikKR2 reduction product identities as well as steady-state kinetic parameters were determined by a combination of LC-MS/MS analysis of synthetic standards and a NADPH consumption assay. The d-hydroxyl product is consistent with bioinformatic analysis and results from a complementary biochemical and molecular biological approach. When compared to widely employed substrates in previous studies, diketide 63 and trans-decalone 64, substrates 12 and 13 showed 2-10 fold lower KM values (2.4 ± 0.8 and 7.8 ± 2.7 mM, respectively), indicating molecular recognition of intermediate-like substrates. Due to an abundance of the nonreducable enol-tautomer, the kcat values were attenuated by as much as 15-336 fold relative to known substrates. This study reveals the high stereoselectivity of PikKR2 in the face of gross substrate permutation, highlighting the utility of a chemical probe-based approach in the study of polyketide ketoreductases.
- Li, Yang,Fiers, William D.,Bernard, Steffen M.,Smith, Janet L.,Aldrich, Courtney C.,Fecik, Robert A.
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p. 2914 - 2922
(2015/02/19)
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- Selective activation of secondary C-H bonds by an iron catalyst: Insights into possibilities created by the use of a carboxyl-containing bipyridine ligand
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In this work, we report the discovery of a carboxyl-containing iron catalyst 1 (FeII-DCBPY, DCBPY = 2,2′-bipyridine-4,4′- dicarboxylic acid), which could activate the C-H bonds of cycloalkanes with high secondary (2°) C-H bond selectivity. A turnover number (TN) of 11.8 and a 30% yield (based on the H2O2 oxidant) were achieved during the catalytic oxidation of cyclohexane by 1 under irradiation with visible light. For the transformation of cycloalkanes and bicyclic decalins with both 2° and tertiary (3°) C-H bonds, 1 always preferred to oxidise the 2° C-H bonds to the corresponding ketone and alcohol products; the 2°/3° ratio ranged between 78/22 and >99/1 across 7 examples. 18O isotope labelling experiments, ESR experiments, a PPh3 method and the catalase method were used to characterize the reaction process during the oxidation. The success of 1 showed that, in addition to using a bulky catalyst, high 2° C-H bond selectivity could also be achieved using a less bulky molecular iron complex as the catalyst.
- Cheng, Shi,Li, Jing,Yu, Xiaoxiao,Chen, Chuncheng,Ji, Hongwei,Ma, Wanhong,Zhao, Jincai
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p. 3267 - 3273
(2013/10/01)
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- Aliphatic C-H activation with aluminium trichloride-acetyl chloride: Expanding the scope of the Baddeley reaction for the functionalisation of saturated hydrocarbons
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The functionalisation of decalin by means of an "aliphatic Friedel-Crafts" reaction was reported over fifty years ago by Baddeley et al. This protocol is of current relevance in the context of C-H activation and here we demonstrate its applicability to a range of other saturated hydrocarbons. Structural elucidation of the products is described and a mechanistic rationale for their formation is presented. The "aliphatic Friedel-Crafts" procedure allows for production of novel oxygenated building blocks from abundant hydrocarbons and as such can be considered to add significant synthetic value in a single step.
- Lyall, Catherine L.,Uosis-Martin, Mario,Lowe, John P.,Mahon, Mary F.,Panto?, G. Dan,Lewis, Simon E.
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supporting information
p. 1468 - 1475
(2013/05/21)
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- An iron catalyst for oxidation of alkyl C-H bonds showing enhanced selectivity for methylenic sites
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Many are called but few are chosen: A nonheme iron complex catalyzes the oxidation of alkyl C-H bonds by using H2O2 as the oxidant, showing an enhanced selectivity for secondary over tertiary C-H bonds (see scheme). Copyright
- Prat, Irene,Gomez, Laura,Canta, Merce,Ribas, Xavi,Costas, Miquel
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supporting information
p. 1908 - 1913
(2013/03/14)
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- Efficient stereo- and regioselective hydroxylation of alkanes catalysed by a bulky polyoxometalate
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Direct functionalization of alkanes by oxidation of C-H bonds to form alcohols under mild conditions is a challenge for synthetic chemistry. Most alkanes contain a large number of C-H bonds that present difficulties for selectivity, and the oxidants employed often result in overoxidation. Here we describe a divanadium-substituted phosphotungstate that catalyses the stereo- and regioselective hydroxylation of alkanes with hydrogen peroxide as the sole oxidant. Both cyclic and acyclic alkanes were oxidized to form alcohols with greater than 96% selectivity. The bulky polyoxometalate framework of the catalyst results in an unusual selectivity that can lead to the oxidation of secondary rather than the weaker tertiary C-H bonds. The catalyst also avoids wasteful decomposition of the stoichiometric oxidant, which can result in the production of hydroxyl radicals and lead to non-selective oxidation and overoxidation of the desired products.
- Kamata, Keigo,Yonehara, Kazuhiro,Nakagawa, Yoshinao,Uehara, Kazuhiro,Mizuno, Noritaka
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scheme or table
p. 478 - 483
(2010/09/17)
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- Self-terminating radical cyclizations: How are thiyl radicals performing?
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The performance of thiyl radicals RS' in "self-terminating radical cyclisations" was explored. Using the medium-sized cyclodecyne (1) as model system, the reaction of PhS' generated by photolysis of (PhS)2 was used to study the intermolecular S-radical addition and subsequent intramolecular radical translocations. This reaction resulted in the formation of three stereoisomeric sulfides 17a in very good yield, which all possess the bicyclo[4.4.0]decane framework with either cis and trans ring fusion. The isomeric bicyclo[5.3,0]decane framework was not: formed. Product identification was performed using a combination of techniques, e.g. synthesis of authentic samples, X-ray analysis and computational studies of the potential energy surface, which also revealed valuable insight into the mechanism, of this radical cyclisation cascade. The (PhS)2/PhS' system provides an efficient source for in situ generated thiols, which mediate reduction of the α-thio radical, e.g., 13a→17a. The radical cascade initiated by the addition of BnS', tBuS' or AllylS', respectively, to cycloalkyne 1 was typically terminated also by reduction, even in the absence of an apparent H-donor, and resulted in formation of various bicyclic and monocyclic thioethers. The desired "selftermination", e.g., β-fragmentation of the S-R bond in radical intermediate 12/13 and release of a stabilized radical R', was only observed, as minor reaction, pathway in one particular instance where tBuS' was generated by autoxidation of tBuSH. Computional studies showed that the different stereochemical outcome of the radical cyclizations involving S-radicals, compared to O- or N-centred radicals, could be attributed to the reversibility of the initial intermolecular Sradical addition to the C≡C triple bond in cycloalkyne 1.
- Tan, Kristine J.,White, Jonathan M.,Wille, Uta
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supporting information; experimental part
p. 4902 - 4911
(2010/11/05)
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- Efficient and Practical Arene Hydrogenation by Heterogeneous Catalysts under Mild Conditions
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An efficient and practical arene hydrogenation procedure based on the use of heterogeneous platinum group catalysts has been developed. Rh/C is the most effective catalyst for the hydrogenation of the aromatic ring, which can be conducted in iPrOH under neutral conditions and at ordinary to medium H 2 pressures (10 atm). A variety of arenes such as alkylbenzenes, benzoic acids, pyridines, furans, are hydrogenated to the corresponding cyclohexyl and heterocyclic compounds in good to excellet yields. The use of Ru/C, less expensive than Rh/C, affords an effective and practical method for the hydrogenation of arenes including phenols. Both catalysts can be reused several times after simple filtration without any significant loss of catalytic activity.
- Maegawa, Tomohiro,Akashi, Akira,Yaguchi, Kiichiro,Iwasaki, Yohei,Shigetsura, Masahiro,Monguchi, Yasunari,Sajiki, Hironao
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experimental part
p. 6953 - 6963
(2010/02/28)
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- Hydrogen-transfer reduction of carbonyl compounds catalysed by nickel nanoparticles
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We report for the first time the hydrogen-transfer reduction of carbonyl compounds catalysed by well-defined nickel(0) nanoparticles. The nickel nanoparticles could be reutilised several times in a very simple reaction medium composed of the nickel nanoparticles, isopropanol and the substrate, without any added base.
- Alonso, Francisco,Riente, Paola,Yus, Miguel
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p. 1939 - 1942
(2008/09/19)
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- Selective Deprotection of tert-Butyldimethylsilyl Ethers Using Nafion-H/Sodium Iodide (or Bromodimethylsulfonium Bromide) in Methanol
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Catalytic amounts of bromodimethyl sulfonium bromide, or Nafion-H along with NaI (1 equiv.), in methanol cleave a variety of TBDMS ethers readily in high yields. Alkyl TBDMS ethers react more readily and selectively compared to phenolic TBDMS ethers, benzyl, and methyl ethers.
- Rani, Shikha,Babu, J. Lokesh,Vankar, Yashwant D.
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p. 4043 - 4052
(2007/10/03)
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- Mn (Br8TPPS) supported on Amberlite IRA-400 as a robust and efficient catalyst for alkene epoxidation and alkane hydroxylation
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Manganese (III) meso-tetrakis(p-sulfonatophenyl)-β-octabromoporphyrin (supported on Amberlite IRA-400 [Mn(Br8TPPS)-Ad-400] is a robust and efficient catalyst for epoxidation of alkenes and hydroxylation of alkanes with sodium periodate at room temperature.
- Tangestaninejad,Habibi,Mirkhani,Moghadam
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p. 264 - 270
(2007/10/03)
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- Does substituent's conformation influence the kinetics of reduction reactions on trans-4-X-decal-1-ones and to what extent?
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Stereochemistry and relative rates kax and keq of reduction reactions on title compounds have been measured under five different reaction conditions (NaBH4 in i-PrOH, LiBH4 and NaAlH4 in THF and LiAlH4 in THF and in Et2O). Experiments indicate that axial substituents behave as far less electronegative than their equatorial counterpart in reactions at the equatorial side of molecules.
- Di Maio, Giorgio,Gabriella Mascia, Maria,Vecchi, Elisabetta
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p. 3313 - 3318
(2007/10/03)
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- Functional-Group-Directed Diastereoselective Hydrogenation of Aromatic Compounds
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Diastereoselective liquid phase hydrogenation of a series of monosubstituted indane and tetralin substrates was studied on supported rhodium catalysts. Predominantly the cis-cis diastereomer, obtained by hydrogenation from the diastereoface opposite the substituent (at the stereogenic center), and the cis-trans diastereomer, obtained by hydrogenation from the diastereoface on the same side as the substituent, were formed. The diastereoselectivity between the two isomers was dependent on the steric repulsion or the electronic attraction of the substituent with the surface of the catalyst. The hydroxyl group did not exhibit a strong attraction (haptophilicity), and the cis-cis diastereomer was obtained as the major product. The amino group exhibited a very high haptophilicity, yielding primarily the cis-trans diastereomer. The diastereoselectivity obtained in the hydrogenation of all the substrates was influenced on addition of bases to the reaction mixture. In the case of alcoholic substrates, the selectivity to the cis-trans diastereomer could be substantially increased with alkaline hydroxide additives.
- Ranade, Vidyadhar S.,Consiglio, Giambattista,Prins, Roel
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p. 8862 - 8867
(2007/10/03)
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- The selective functionalization of saturated hydrocarbons. Part 46. An investigation of Udenfriend's system under Gif conditions
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Under Gif conditions using ascorbic acid as reductant and oxygen as oxidant in pyridine, the selectivity for secondary hydrogen functionalization is exceptional. EDTA (ethylenediamine-tetra-acetic acid) is not needed as a ligand for iron.
- Barton, Derek H.R.,Delanghe, Nathalie C.
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p. 4471 - 4476
(2007/10/03)
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- Oxidation with the "O2 - H2O2 - Vauauium complex - Pyrazine-2-carboxylic acid" reagent 9. Oxidation of cyclohexene and decalin
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The oxidation of cyclohexene with hydrogen peroxide catalyzed by a vanadium complex and pyrazine-2-carboxylic acid (PCA) in air results in the formation of cyclohex-2-enyl hydroperoxide as the main product and cyclohex-2-enol, cyclohex-2-enone, cyclohex-3-enyl hydroperoxide, cyclohex-3-enol, cyclohexanol, cyclohexane, and 1,2-epoxycyclohexane in lesser amounts. The composition of the products of oxidation of decalin isomers with the system in question is similar to those obtained in the photochemical oxidation with hydrogen peroxide in air and in the oxidation with air in the presence of anthraquinone. A proposed mechanism for the oxidation includes the initiation by hydroxyl radicals generated from hydrogen peroxide under the action of the V - PCA system.
- Schuchardt,Guerreiro,Shul'pin
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p. 247 - 252
(2007/11/27)
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- The role of hydrogen migration in the mechanism of alcohol elimination from MH+ ions of ethers upon chemical ionization
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An enhanced elimination of alcohol under isobutane CI conditions, resulting in highly abundant [MH - ROH]+ ions, has been observed in several primary and secondary ethers having a tertiary β-position (methine), as compared with those with β-methylene. This elimination exhibits a significant degree of stereospecificity in stereoisomeric 2-methyl-1-methoxycyclohexanes 4 and 1-methoxy-trans-decalins 7, affording more abundant [MH - ROH]+ ions in the cis isomers 4c and 7tc than in their trans counterparts 4t and 7tt. These findings suggest involvement of a 1,2-hydride migration from the β- to α-position in the course of the alcohol elimination from the MH+ ions of the above cis-ethers, resulting in tertiary carbocation structures. The proposed mechanism of alcohol elimination is supported by a considerable deuterium isotope effect detected in β-deuterium-labeled cis-2-methyl-1-methoxycyclohexane and by a CID study of the structures of [MH - ROH]+ ions obtained from cis- and trans-1,2-dialkoxycyclohexanes. Ring contraction by a Meerwein-type rearrangement has also been observed in the latter system.
- Morlender-Vais,Mandelbaum
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p. 1124 - 1132
(2007/10/03)
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- Carbonyl reductase activity exhibited by pig testicular 20β- hydroxysteroid dehydrogenase
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The carbonyl reductase activity exhibited by pig testicular 20β- hydroxysteroid dehydrogenase (20β-HSD) was examined using a recombinant enzyme. Kinetic parameters were obtained for 48 carbonyl group-containing substrates, including aromatic aldehydes, aromatic ketones, cycloketones, quinones, aliphatic aldehydes and aliphatic ketones. 20β-HSD showed a high affinity towards quinones, such as 9,10-phenanthrenequinone, α- naphthoquinone and menadione (K(m) values of 4, 2 and 5 μM, respectively), and the substrate utilization efficiency (V(max)/K(m)) of the enzyme against these quinones was very high. Cyclohexanone and 2-methylcyclohexanone were also reduced with a high V(max)/K(m) value, but not cyclopentanone or 2- methylcyclopentanone. Various aromatic aldehydes and ketones including benzaldehyde- and acetophenone-derivatives were reduced by 20β-HSD. Especially, 4-nitrobenzaldehyde and 4-nitroacetophenone were reduced with high V(max)/K(m) values in the related compounds. The enzyme also reduced the pyridine-derivatives, 2-, 3-, and 4-benzoylpyridine, with the V(max)/K(m) value for 2-benzoylpyridine being the highest. 20β-HSD reduced aliphatic aldehydes and aliphatic ketones, but was more effective on the former. The correlation between the structure of carbonyl compounds and their substrate V(max)/K(m) is discussed.
- Nakajin, Shizuo,Tamura, Fumihiro,Takase, Noriko,Toyoshima, Satoshi
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p. 1215 - 1218
(2007/10/03)
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- Stereo- and chemoselective transfer hydrogenation of carbonyl groups with RuCl2(PPh3)3 and BINAP-Ru as catalysts and et3NH+H2PO2-·1,5H 2O as a hydrogen donor
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Using Et3NH+H2PO2-.1.5 H2O as a hydrogen donor, the RuCl2(Ph3P)3, RuCl2(PPh3)3 / C and BINAP-Ru proved highly active catalysts for transfer hydrogenation of ketones under milder conditions than other hydrogen donors. 2-Methyl-, 2-chloro-, 2-(ethoxycarbonyl)cyclohexanones and -cyclopentanones were reduced to the less stable axial alcohols in excellent diastereoisomeric excess (de: 90-100%), and the carbonyl group of α,β-unsaturated ketones was selectively reduced, in contrast with other hydrogen donors the C=C bond was reduced. Copyright
- Khai, Bui The,Arcelli, Antonio
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p. 6599 - 6602
(2007/10/03)
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- Catalytic Alkane Activations in Reverse Microemulsions Containing Iron Salts and Hydrogen Peroxide
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A microemulsion system generated from two reverse microemulsions containing respectively an aqueous solution of iron salts and 30percent H2O2 dispersed in liquid alkanes catalyses the oxidation of C-H bonds.
- Briffaud, T.,Larpent, C.,Patin, H.
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p. 1193 - 1194
(2007/10/02)
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- Mechanism of the Transannular Cyclization of 5-Cyclodecynone
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Acid-catalyzed intramolecular cyclization of 5-cyclodecynone (1) under a variety of conditions gives bicyclo-1(6)-decen-2-one (8) as the only product.In earlier reports the reaction was formulated as involving triple-bond participation with a polarized carbonyl group to give a vinyl cation, followed by external attack by a nucleophile.Studies of the rearrangement using Lewis acids in aprotic solvents, taking care to exclude water and moist air during workup, have shown that the oxygen atom in the starting acetylenic ketone 1 is the same as that in the bicyclic product 8.When the reaction was carried out with HCl in a solvent of methanol-H2(18)O, oxygen-18 incorporation in the final product was not significantly above exchange levels observed when the bicyclic ketone itself was treated with methanol-H2(18)O under similar conditions.A mechanism that will account for these observations is presented.
- Harding, Charles E.,Stanford, G. Richard
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p. 3054 - 3056
(2007/10/02)
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- The Chemical and Electrochemical Reductions of 5-Bromodecalone and 4-Bromodecalone
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5-Bromodecalone (1) was prepared by the reaction of potassium bromide in acetonitrile on (4aα,5α,8aβ)-5-tosyloxyoctahydronaphthalen-1(2H)-one (15) with apparent retention of configuration.It was also prepared by hydrogen bromide cleavage of (3aRS,3bRS,7aRS)-octahydro-7H-cyclopentacyclopropabenzen-7-one (17).On reaction with sodium potassium alloy ketone (1) gives α-decalone (33) and ketone (17) as the principal products whereas reduction with tributylstannane gives only ketone (33).Electrochemical reduction of ketone (1) gives trans-cyclodec-5-en-1-one (3) as well as ketones (17) and (33). 4-Bromodecalone (2) was prepared from (4α,4aα,8aβ)-4-tosyloxyoctahydronaphthalen-1(2H)-one (29), by the reaction with potassium bromide in acetonitrile, with inversion of configuration.Electrochemical reduction of ketone (2) gives trans-1-acetyl-2-vinylcyclohexane (36), α-decalone (33), (E)-cyclodec-4-en-1-one (4) and (1aRS,1bSR,5aRS,6aRS)-octahydrocyclopropainden-6(6aH)-one (24).
- Hamon, David P. G.,Richards, Kenneth R.
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p. 2243 - 2259
(2007/10/02)
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- Catalyzed Rearrangements of Ten-Membered-Ring Allenes
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Cyclodeca-1,2,5,8-tetraene (1) is shown to rearrange in the presence of various catalysts in acetic acid to cis,syn-tricyclo2,4>deca-5,8-diene (5) which is accompanied in some cases by rearranged acetate products, principally cis,syn-bicyclodeca-4,8-dien-2-yl acetate (3).Cyclodeca-1,2,5-triene (6) rearranges in a similar way, except that acetate product was only observed for Ag(I) catalysts.A related allene, bicyclodeca-2,3-diene underwent normal oxymercuration without rearrangement.
- Thies, Richard W.,Boop, Janice L.,Schiedler, Michael,Zimmerman, David C.,LaPage, Theodore H.
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p. 2021 - 2024
(2007/10/02)
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- Enzymic Resolution of (+/-)-axial-Alcohols via Asymmetric Hydrolysis of Corresponding Chloroacetates by Microorganisms
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Asymmetric hydrolysis of chloroacetates of (+/-)-axial-alcohols (+/-)-neomenthol (2), (1RS,4aRS,8aSR)-decahydro-1-naphthol (6) by Trichoderma koningi gave (-)-(1S,3R,4R)-neomenthol (2) (54percent optical purity, o.p.) and (-)-(1R,4aR,8aS)-decahydro-1-naphthol (6) (66percent o.p.) with their enantiomeric chloroacetates.However, the chloroacetate of (2RS,4aRS,8aSR)-decahydro-2-naphthol (10) was hydrolyzed by T. koningi to give the (-)-alcohol (10) (12percent o.p.) with low enantioselectivity.
- Oritani, Takayuki,Ichimura, Michio,Hanyu, Yoshifumi,Yamashita, Kyohei
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p. 2613 - 2618
(2007/10/02)
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- Aliphatic Hydroxylation Catalyzed by Iron Porphyrin Complexes
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The hydroxylation of unactivated alkanes has been observed in a catalytic system containing iodosylbenzene and various iron porphyrins.The yields and distributions of products have been found to be sensitive to the peripheral substitution pattern of the porphyrin.The oxidation of cyclohexane with chloro(5,10,15,20-tetra-o-tolylporphyrinato)iron(III) gave a 31percent yield of cyclohexanol and 6percent cyclohexanone based on iodosylbenzene.Two samples of Fe(TTP)ClCl with differing atropisomeric composition gave different product ratios.The hydroxylation of cycloheptane under these conditions and in the presence of bromotrichloromethane gave 24percent cycloheptanol and 18percent bromocycloheptane.Steric selectivity was observed by comparing the hydroxylation of cis-decalin with Fe(TPP)Cl, Fe(TTP)Cl, Fe(TNP)Cl, and Fe(TMP)Cl.The hydrogen-isotope effect for cyclohexane hydroxylation by Fe(TTP)Cl was found to be 12.9+/- 1.A mechanism for hydroxylation is proposed on the basis of these results that involves initial oxidation of the iron porphyrin, hydrogen atom abstraction from the alkane, and rapid collapse of this radical to give the product alcohol and to regenerate the iron(III) catalyst.
- Groves, John T.,Nemo, Thomas E.
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p. 6243 - 6248
(2007/10/02)
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- VANADIUM(V) PEROXO COMPLEXES. NEW VERSATILE BIOMIMETIC REAGENTS FOR EXPOXIDATION OF OLEFINS AND HYDROXYLATION OF ALKANES AND AROMATIC HYDROCARBONS.
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Novel covalent vandium(V) oxo peroxo complexes of general formula VO(O//2)(O-N)LL prime and anionic complexes with the general formula left bracket VO(O//2)(Pic)//2 right bracket ** minus A** plus L were synthesized and characterized by physicochemical methods and X-ray crystallography. The crystal structure of VO(O//2)(Pic) multiplied by (times) 2H//2O (Ia) revealed a pentagonal-bipyramidal environment, with a significant hydrogen bonding between the peroxo moiety and the equatorial water molecule. Protonated type II complexes (A** plus equals H** plus ) are dissociated in an aqueous solution and have an acidic nature (pK//a equals 1. 8) but are undissociated in a nonprotic solution, with a presumably peracid-like oxohydroperoxo structure. It is shown that vanadium peroxo complexes are effective oxidants in nonprotic solvents under mild conditions. They transform olefins to epoxides and cleavage products in a nonsteoroselective fashion (cis-2-butene gave a mixture of cis and trans epoxides). More interestingly, they hydroxylate aromatic hydrocarbons to phenols and alkanes to alcohols and ketones.
- Mimoun,Saussine,Daire,Postel,Fischer,Weiss
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p. 3101 - 3110
(2007/12/18)
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- Model Systems for Cytochrome P450 Dependent Mono-oxygenases. Part 3. The Stereochemistry of Hydroxylation of cis- and trans-Decahydronaphthalene by Chemical Models for Cytochrome P450 Dependent Mono-oxygenases
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The stereochemistry of hydroxylation of the tertiary C-H bonds of cis- and trans-decahydronaphthalene by seven chemical models for cytochrome P450 dependent mono-oxygenases has been studied.Oxidations by three of the model systems (H2O2-Fe2+-CH3CN, O2-Fe2+-2-mercaptobenzoic acid, and diazofluorene-hν-O2) are non-stereospecific giving the same ratio of cis- to trans-decahydronaphthalen-9-ol from each substrate.However, hydroxylations with pyridine N-oxide-hν show a partial retention of configuration and with trifluoroperacetic acid or with iron(III) porphyrins and iodosylbenzene the oxidations are >97percent stereospecific.The mechanism of these hydroxylations and their usefulness as models for the cytochrome P450 dependent mono-oxygenases are discussed.
- Smith, John R. Lindsay,Sleath, Paul R.
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p. 1165 - 1170
(2007/10/02)
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- STEREOSELECTIVITE DE L'ADDITION DE REACTIFS NUCLEOPHILES SUR DES CETONES POLYCYCLIQUES A JONCTION TRANS
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The nucleophilic additions of hindered organometallic compounds to polycyclic ketones with trans ring junctions involve predominant axial attack when flattening of the ring containing the carbonyl group occurs.The influence of nucleophile structure (O-Por C-metalled character) on equatorial or axial attack is discussed.
- Calmes, D.,Gorrichon-Guigon, L.,Maroni, P.,Accary, A.,Barret, R.,Huet, J.
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p. 879 - 885
(2007/10/02)
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