- Increasing the steric hindrance around the catalytic core of a self-assembled imine-based non-heme iron catalyst for C-H oxidation
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Sterically hindered imine-based non-heme complexes4and5rapidly self-assemble in acetonitrile at 25 °C, when the corresponding building blocks are added in solution in the proper ratios. Such complexes are investigated as catalysts for the H2O2oxidation of a series of substrates in order to ascertain the role and the importance of the ligand steric hindrance on the action of the catalytic core1, previously shown to be an efficient catalyst for aliphatic and aromatic C-H bond oxidation. The study reveals a modest dependence of the output of the oxidation reactions on the presence of bulky substituents in the backbone of the catalyst, both in terms of activity and selectivity. This result supports a previously hypothesized catalytic mechanism, which is based on the hemi-lability of the metal complex. In the active form of the catalyst, one of the pyridine arms temporarily leaves the iron centre, freeing up a lot of room for the access of the substrate.
- Frateloreto, Federico,Capocasa, Giorgio,Olivo, Giorgio,Abdel Hady, Karim,Sappino, Carla,Di Berto Mancini, Marika,Levi Mortera, Stefano,Lanzalunga, Osvaldo,Di Stefano, Stefano
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p. 537 - 542
(2021/02/09)
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- Insight into the chemoselective aromatic: Vs. side-chain hydroxylation of alkylaromatics with H2O2catalyzed by a non-heme imine-based iron complex
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The oxidation of a series of alkylaromatic compounds with H2O2 catalyzed by an imine-based non-heme iron complex prepared in situ by reaction of 2-picolylaldehyde, 2-picolylamine, and Fe(OTf)2 in a 2?:?2?:?1 ratio leads to a marked chemoselectivity for aromatic ring hydroxylation over side-chain oxidation. This selectivity is herein investigated in detail. Side-chain/ring oxygenated product ratio was found to increase upon decreasing the bond dissociation energy (BDE) of the benzylic C-H bond in line with expectation. Evidence for competitive reactions leading either to aromatic hydroxylation via electrophilic aromatic substitution or side-chain oxidation via benzylic hydrogen atom abstraction, promoted by a metal-based oxidant, has been provided by kinetic isotope effect analysis. This journal is
- Ticconi, Barbara,Capocasa, Giorgio,Cerrato, Andrea,Di Stefano, Stefano,Lapi, Andrea,Marincioni, Beatrice,Olivo, Giorgio,Lanzalunga, Osvaldo
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p. 171 - 178
(2021/01/28)
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- CATALYTIC FUNNELING OF PHENOLICS
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In general, present invention concerns an integrated wood-to-xylochemicals biorefinery, enabling production of renewable phenol, phenolic oligomers, propylene, and carbohydrate pulp from lignocellulosic biomass.
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Paragraph 0035; 0089-0090; 0169
(2021/04/30)
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- Nickel Hydride Catalyzed Cleavage of Allyl Ethers Induced by Isomerization
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This report discloses the deallylation of O - and N -allyl functional groups by using a combination of a Ni-H precatalyst and excess Bronsted acid. Key steps are the isomerization of the O - or N -allyl group through Ni-catalyzed double-bond migration followed by Bronsted acid induced O/N-C bond hydrolysis. A variety of functional groups are tolerated in this protocol, highlighting its synthetic value.
- Kathe, Prasad M.,Berkefeld, Andreas,Fleischer, Ivana
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supporting information
p. 1629 - 1632
(2021/02/09)
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- Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
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Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
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supporting information
p. 9029 - 9039
(2021/06/28)
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- Guaiacol demethoxylation catalyzed by Re2O7 in ethanol
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Re2O7 is used to convert guaiacol in alcohols at 280–320 °C. In ethanol, guaiacol is deoxygenated and alkylated, and the major products are phenol and alkylphenols (including ethylphenol, diethylphenol, diisopropylphenol, di-tert-butylphenol and 2,6-di-tert-butyl-4-ethylphenol), accounting for 97 mol% of all products after 6 hour reaction at 320 °C. Both catechol and phenol are the intermediates of guaiacol demethoxylation. Among the substituents, ethyl is directly provided by ethanol while isopropyl and tert-butyl are formed by the addition of methyl to ethyl step by step. In addition, Re2O7 has negligible activity for the saturation of benzene ring so it does not cause considerable over-consumption of reductant. The actual catalyst for guaiacol demethoxylation is likely a ReIV?VI species.
- Yan, Fei,Sang, Yushuai,Bai, Yunfei,Wu, Kai,Cui, Kai,Wen, Zhe,Mai, Fuhang,Ma, Zewei,Yu, Linhao,Chen, Hong,Li, Yongdan
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p. 231 - 237
(2019/08/12)
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- Synthesis of Highly Substituted Phenols and Benzenes with Complete Regiochemical Control
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Substituted phenols are requisite molecules for human health, agriculture, and diverse synthetic materials. We report a chemical synthesis of phenols, including penta-substituted phenols, that accommodates programmable substitution at any position. This method uses a one-step conversion of readily available hydroxypyrone and nitroalkene starting materials to give phenols with complete regiochemical control and in high chemical yield. Additionally, the phenols can be converted into highly and even fully substituted benzenes.
- Zhang, Xiaojie,Beaudry, Christopher M.
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supporting information
p. 6086 - 6090
(2020/08/12)
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- Metal-organic frameworks containing nitrogen-donor ligands for efficient catalytic organic transformations
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Metal-organic framework (MOFs) compositions based on nitrogen donor-based organic bridging ligands, including ligands based on 1,3-diketimine (NacNac), bipyridines and salicylaldimine, were synthesized and then post-synthetically metalated with metal precursors, such as complexes of first row transition metals. Metal complexes of the organic bridging ligands could also be directly incorporated into the MOFs. The MOFs provide a versatile family of recyclable and reusable single-site solid catalysts for catalyzing a variety of asymmetric organic transformations. The solid catalysts can also be integrated into a flow reactor or a supercritical fluid reactor.
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Page/Page column 36-37
(2020/06/03)
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- Selective hydrodeoxygenation of hydroxyacetophenones to ethyl-substituted phenol derivatives using a FeRu?SILP catalyst
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The selective hydrodeoxygenation of hydroxyacetophenone derivatives is achieved opening a versatile pathway for the production of valuable substituted ethylphenols from readily available substrates. Bimetallic iron ruthenium nanoparticles immobilized on an imidazolium-based supported ionic liquid phase (Fe25Ru75?SILP) show high activity and stability for a broad range of substrates without acidic co-catalysts. This journal is
- Bordet, Alexis,Goclik, Lisa,Leitner, Walter,Offner-Marko, Lisa
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supporting information
p. 9509 - 9512
(2020/09/02)
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- Ionic liquid-stabilized vanadium oxo-clusters catalyzing alkane oxidation by regulating oligovanadates
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Alkane oxidation under mild conditions occupies an important position in the chemical industry. Herein, we have designed a novel class of ionic liquid ([TBA][Pic])-stabilized vanadium oxo-clusters (TBA = tetrabutylammonium; Pic = picolinate ions), in which the molar ratio of the IL to V atoms can be tuned facilely to obtain V-OC?IL-0.5, V-OC?IL-1 and V-OC?IL-2, respectively. The as-synthesized vanadium oxo-clusters have been characterized by elemental analysis, FT-IR, UV-vis, XRD, TGA, EPR, NMR and MS. These vanadium oxo-clusters were catalytically active for catalyzing the oxidation of cyclohexane with H2O2 as an oxidant. In particular, the oxo-cluster V-OC?IL-1 (where IL/V is 1.0) can provide an approximately 30% total yield of KA oil (cyclohexanol and cyclohexanone) without adding any co-catalyst at 50 °C within 1.0 h. Moreover, the present vanadium oxo-cluster was recyclable owing to the modification of the IL and it can also be extended to the oxidation of the sp2 hybrid aromatic ring. The further characterization results demonstrated that the oligovanadate anions were strongly dependent on the molar ratio of the IL to V atoms. The vanadium oxo-clusters with the appropriate molar ratio of IL/V could exist in the form of a trimer and a dimer due to the presence of the TBA cation and the coordination of picolinate. Notably, the oligovanadate anions are highly active species for the C-H oxidation but the mononuclear vanadate afforded a very poor activity according to the activity assessment and the identification of vanadium species from the 51V NMR spectra and MS spectra. The annihilation reaction of free radicals and EPR characterization suggested that the vanadium oxo-clusters operated via a mechanism of the HO radical in the oxidation reaction.
- Ding, Bingjie,Gong, Xueqing,Hou, Zhenshan,Li, Difan,Yao, Yefeng,Zhang, Ran,Zheng, Anna,Zhou, Qingqing
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p. 7601 - 7612
(2020/11/27)
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- Photoarylation of Pyridines Using Aryldiazonium Salts and Visible Light: An EDA Approach
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A metal-free methodology for the photoarylation of pyridines, in water, is described giving 2 and 4-arylated-pyridines in yields up to 96percent. The scope of the aryldiazonium salts is presented showing important results depending on the nature and position of the substituent group in the diazonium salt, that is, electron-donating or electron-withdrawing in the ortho, meta, or para positions. Further heteroaromatics were also successfully photoarylated. Mechanistic studies and comparison between our methodology and similar metal-catalyzed procedures are presented, suggesting the occurrence of a visible-light EDA complex which generates the aryl radical with no need for an additional photocatalyst.
- Bartolomeu, Aloisio De A.,Brocksom, Timothy J.,De Oliveira, Kleber T.,No?l, Timothy,Silva, Rodrigo C.
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- Method for preparing hydrocarbyl phenol by catalytic conversion of phenolic compound in presence of molybdenum-based catalyst
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The invention discloses a method for preparing hydrocarbyl phenol by catalytic conversion of a phenolic compound in the presence of a molybdenum-based catalyst. The method comprises mixing a phenoliccompound, a molybdenum-based catalyst and a reaction solvent, adding the mixture into a sealed reactor, feeding gas into the reactor, heating the mixture to 150-350 DEG C, carrying out stirring for areaction for 0.5-2h, then filtering to remove a solid catalyst and carrying out rotary evaporateion to obtain a liquid product. The phenolic compound has a wide source, a cost is low, product alkyl phenol selectivity is high, an added value is high, alcohol or an alcohol-water mixture is used as a reaction solvent, environmental friendliness is realized, pollution is avoided, any inorganic acids and alkalis are avoided in the reaction process, the common environmental pollution problems in the biomass processing technology are solved, the reaction conditions are mild, the process can be carried out at a low temperature, high-efficiency conversion of the reactants can be realized without consuming hydrogen gas and the method is suitable for large-scale industrial trial production.
- -
-
Paragraph 0046; 0070
(2018/04/02)
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- Highly Selective and Efficient Ring Hydroxylation of Alkylbenzenes with Hydrogen Peroxide and an Osmium(VI) Nitrido Catalyst
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The OsVI nitrido complex, OsVI(N)(quin)2(OTs) (1, quin=2-quinaldinate, OTs=tosylate), is a highly selective and efficient catalyst for the ring hydroxylation of alkylbenzenes with H2O2 at room temperature. Oxidation of various alkylbenzenes occurs with ring/chain oxidation ratios ranging from 96.7/3.3 to 99.9/0.1, and total product yields from 93 % to 98 %. Moreover, turnover numbers up to 6360, 5670, and 3880 can be achieved for the oxidation of p-xylene, ethylbenzene, and mesitylene, respectively. Density functional theory calculations suggest that the active intermediate is an OsVIII nitrido oxo species.
- Kwong, Hoi-Ki,Lo, Po-Kam,Yiu, Shek-Man,Hirao, Hajime,Lau, Kai-Chung,Lau, Tai-Chu
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supporting information
p. 12260 - 12263
(2017/09/06)
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- METHOD FOR PREPARING P-HYDROXYMANDELIC COMPOUNDS IN STIRRED REACTORS
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The process allows the preparation of a p-hydroxymandelic compound, comprising at least one step of condensation of at least one aromatic compound bearing at least one hydroxyl group and whose para position is free, with glyoxylic acid, the condensation reaction being performed in at least one reactor equipped with at least one mixing means, the specific mixing power being between 0.1 kW/m3 and 15 kW/m3. In addition, the invention also relates to a process for preparing a 4-hydroxyaromatic aldehyde by oxidation of this p-hydroxymandelic compound.
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- Silica supported palladium phosphine as a robust and recyclable catalyst for semi-hydrogenation of alkynes using syngas
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This work reports a chemo-selective semi-hydrogenation of alkynes to alkenes using silica supported palladium phosphine catalyst with syngas (CO/H2). This developed methodology is an alternative to classical Lindlar catalyst for chemo-selective semi-hydrogenation of alkynes to alkenes. Various alkynes were smoothly convert to alkenes in 60-97% conversion with 85-98% selectivity. The prepared catalyst was well characterized by Field Emmission Gun Scanning Electron Microscopy (FEG-SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), Inductively Coupled Plasma- Atomic Emmission Spectroscopy (ICP-AES) analysis techniques. In addition, catalyst was effectively recycled up to four consecutive run without significant loss in its catalytic activity and selectivity.
- Jagtap, Samadhan A.,Sasaki, Takehiko,Bhanage, Bhalchandra M.
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- Direct Hydroxylation of Benzene to Phenol Using Hydrogen Peroxide Catalyzed by Nickel Complexes Supported by Pyridylalkylamine Ligands
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Selective hydroxylation of benzene to phenol has been achieved using H2O2 in the presence of a catalytic amount of the nickel complex [NiII(tepa)]2+ (2) (tepa = tris[2-(pyridin-2-yl)ethyl]amine) at 60°C. The maximum yield of phenol was 21% based on benzene without the formation of quinone or diphenol. In an endurance test of the catalyst, complex 2 showed a turnover number (TON) of 749, which is the highest value reported to date for molecular catalysts in benzene hydroxylation with H2O2. When toluene was employed as a substrate instead of benzene, cresol was obtained as the major product with 90% selectivity. When H218O2 was utilized as the oxidant, 18O-labeled phenol was predominantly obtained. The reaction rate for fully deuterated benzene was nearly identical to that of benzene (kinetic isotope effect = 1.0). On the basis of these results, the reaction mechanism is discussed.
- Morimoto, Yuma,Bunno, Shuji,Fujieda, Nobutaka,Sugimoto, Hideki,Itoh, Shinobu
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supporting information
p. 5867 - 5870
(2015/05/27)
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- Syntheses and in Vitro Antiplasmodial Activity of Aminoalkylated Chalcones and Analogues
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(Chemical Equqation Presented). A series of readily synthesized and inexpensive aminoalkylated chalcones and diarylpropane analogues (1-55) were synthesized and tested against chloroquinone-sensitive (D10 and NF54) and -resistant (Dd2 and K1) strains of Plasmodium falciparum. Hydrogenation of the enone to a diarylpropane moiety increased antiplasmodial bioactivity significantly. The influence of the structure of the amine moiety, A-ring substituents, propyl vs ethyl linker, and chloride salt formation on further enhancing antiplasmodial activity was investigated. Several compounds have IC50 values similar to or better than chloroquine (CQ). The most active compound (26) had an IC50 value of 0.01 μM. No signs of resistance were detected, as can be expected from compounds with structures unrelated to CQ and other currently used antimalarial drugs. Toxicity tests (in vitro CHO cell assay) gave high SI indices.
- Wilhelm, Anke,Kendrekar, Pravin,Noreljaleel, Anwar E. M.,Abay, Efrem T.,Bonnet, Susan L.,Wiesner, Lubbe,De Kock, Carmen,Swart, Kenneth J.,Van Der Westhuizen, Jan Hendrik
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p. 1848 - 1858
(2015/09/08)
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- Selective synthesis of p-ethylphenol by gas-phase alkylation of phenol with ethanol
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The selective synthesis of p-ethylphenol from gas-phase alkylation of phenol with ethanol was studied on zeolites HZSM5 and HMCM22 at 523 K. Phenol reacted directly with ethanol to form ethylphenylether by O-alkylation, and p- and o-ethylphenol isomers by C-alkylation; secondary products were m-ethylphenol and dialkylated compounds. Both zeolites presented similar activity and formed low amounts of ethylphenylether and dialkylated products, but exhibited different ethylphenol isomers distribution. In fact, for a contact time of 99.3gh/mol the selectivity to p-ethylphenol was 51.4% on HMCM22 and only 14.2% on HZSM5. The superior performance of zeolite HMCM22 for selectively producing p-ethylphenol was due to its narrower pore channels that suppressed the formation of dialkylated products and hampered by diffusional constraints the formation of o-ethylphenol. The maximum p-ethylphenol yield obtained on HMCM22 was 41% at a contact time of 250gh/mol; for higher contact times, p-ethylphenol was increasingly converted to m-ethylphenol. All the samples deactivated on stream because of coke formation. The carbon amount built on HMCM22 diminished when contact time was increased thereby indicating that coke was mainly formed from the reactants. Additional catalytic runs showed that phenol was the main responsible of catalyst deactivation, probably because of its strong adsorption on surface active sites.
- Sad,Duarte,Padró,Apesteguía
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- One step C-N bond formation from alkylbenzene and ammonia over Cu-modified TS-1 zeolite catalyst
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A Cu doped TS-1 zeolite sample was applied to catalyze the formation of C-N bonds on both the ring and the side chain of toluene, as well as other alkylbenzenes. A yield of 3.4% of toluidine was obtained for the amination of toluene, with a 1.0% yield of nitrobenzene. Cyanobenzene was also obtained as the C-N bond product on the side chain with a yield of 1.0%. The selectivity for C-N bond formation was 52.4%. The catalyst promoted the formation of a hydroxylamine intermediate from ammonia and hydrogen peroxide, and then the instantaneously generated amino cation reacted with the substrate to form C-N bonds on both the ring and side chain. Cyanobenzene was produced from the dehydration of benzylamine, formed via the reaction of ammonia and toluene. The formation of C-N bonds on the ring had an ortho-orientation advantage for mono-substituted-benzenes. With the increase in the number of methyl substituents, the yield of the ring products decreased, which might be caused by steric hindrance. the Partner Organisations 2014.
- Xia, Sheng,Yu, Tianhua,Liu, Huihui,Li, Guiying,Hu, Changwei
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p. 3108 - 3119
(2014/08/18)
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- Synthesis of tsetse fly attractants from a cashew nut shell extract by isomerising metathesis
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Starting from a purified cashew nut shell extract containing mostly anacardic acid derivatives, the tsetse fly attractants 3-ethyl- and 3-propylphenol were selectively synthesised. The mixture was first converted into 3-(non-8-enyl)phenol in 98% purity via ethenolysis and distillation with concomitant decarboxylation. The olefinic side chain was then shortened by isomerising cross-metathesis with short-chain olefins in the presence of a [Pd(μ-Br)(tBu3P)]2 isomerisation catalyst and a second-generation Hoveyda-Grubbs catalyst, and the synthesis was completed by a hydrogenation step.
- Baader,Podsiadly,Cole-Hamilton,Goossen
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supporting information
p. 4885 - 4890
(2015/01/08)
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- Postsynthetic metalation of bipyridyl-containing metal-organic frameworks for highly efficient catalytic organic transformations
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We have designed highly stable and recyclable single-site solid catalysts via postsynthetic metalation of the 2,2-bipyridyl-derived metal-organic framework (MOF) of the UiO structure (bpy-UiO). The Ir-functionalized MOF (bpy-UiO-Ir) is a highly active catalyst for both borylation of aromatic C-H bonds using B2(pin)2 (pin = pinacolate) and ortho-silylation of benzylicsilyl ethers; the ortho-silylation activity of the bpy-UiO-Ir is at least 3 orders of magnitude higher than that of the homogeneous control. The Pd-functionalized MOF (bpy-UiO-Pd) catalyzes the dehydrogenation of substituted cyclohexenones to afford phenol derivatives with oxygen as the oxidant. Most impressively, the bpy-UiO-Ir was recycled and reused 20 times for the borylation reaction without loss of catalytic activity or MOF crystallinity. This work highlights the opportunity in designing highly stable and active catalysts based on MOFs containing nitrogen donor ligands for important organic transformations.
- Manna, Kuntal,Zhang, Teng,Lin, Wenbin
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p. 6566 - 6569
(2014/05/20)
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- The use of ultrasmall iron(0) nanoparticles as catalysts for the selective hydrogenation of unsaturated C-C bonds
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The performance of well-defined ultrasmall iron(0) nanoparticles (NPs) as catalysts for the selective hydrogenation of unsaturated C-C and CX bonds is reported. Monodisperse iron nanoparticles of about 2 nm size are synthesized by the decomposition of {Fe(N[Si(CH3)3]2) 2}2 under dihydrogen. They are found to be active for the hydrogenation of various alkenes and alkynes under mild conditions and weakly active for CO bond hydrogenation.
- Kelsen, Vinciane,Wendt, Bianca,Werkmeister, Svenja,Junge, Kathrin,Beller, Matthias,Chaudret, Bruno
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p. 3416 - 3418
(2013/05/22)
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- Correlating lignin structural features to phase partitioning behavior in a novel aqueous fractionation of softwood Kraft black liquor
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In this work, a set of softwood lignins were recovered from a Kraft black liquor using a novel pH-based fractionation process involving sequential CO 2 acidification and separation of the solvated aqueous lignin fraction. These recovered lignin fractions were characterized with respect to properties that may be responsible for their phase partitioning behavior as well as properties that may render the lignins more suitable for materials applications. Lignin fractions were recovered between a pH range of 12.8 and 9.5 with the bulk of the lignin (90%) recovered between a pH of 11.1 and 10.0. While all the fractions were found to consist primarily of lignin as validated by sample methoxyl content, the first fractions to phase separated were found to be especially enriched in aliphatic extractives and polysaccharides. From the bulk of the lignin that was recovered between a pH of 11.1 and 10.0 a number of noteworthy trends were discernible from the data. Specifically, the phenolic hydroxyl content was found to exhibit a strong negative correlation to the fractionation pH and exhibited a nearly 50% increase with recovery at decreasing pH, while the GPC-estimated molecular weights and 13C NMR-estimated β-O-4 content showed strong positive correlations to the pH at recovery. The aliphatic hydroxyl content exhibited minimal differences between recovery conditions. Overall, these results suggest that this fractionation approach can generate lignin fractions enriched in select physical or structural properties that may be important for their application as feedstocks for renewable chemicals or materials.
- Stoklosa, Ryan J.,Velez, Julian,Kelkar, Shantanu,Saffron, Christopher M.,Thies, Mark C.,Hodge, David B.
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supporting information
p. 2904 - 2912
(2013/10/08)
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- Chemo- and regioselective direct hydroxylation of arenes with hydrogen peroxide catalyzed by a divanadium-substituted phosphotungstate
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Peroxide in, phenol out: The catalyst [-PW10O38V 2(μ-OH)2]3- showed high activity in the hydroxylation of various aromatic compounds with aqueous H2O 2. The system was regioselective, producing para-phenols from monosubstituted benzene derivatives. Furthermore, alkylarenes with reactive side-chain Ca spa 3-H bonds could be chemoselectively hydroxylated without significant formation of side-chain oxygenated products. Copyright
- Kamata, Keigo,Yamaura, Taiyo,Mizuno, Noritaka
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supporting information; experimental part
p. 7275 - 7278
(2012/08/28)
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- Facile regio- and stereoselective hydrometalation of alkynes with a combination of carboxylic acids and group 10 transition metal complexes: Selective hydrogenation of alkynes with formic acid
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A facile, highly stereo- and regioselective hydrometalation of alkynes generating alkenylmetal complex is disclosed for the first time from a reaction of alkyne, carboxylic acid, and a zerovalent group 10 transition metal complex M(PEt3)4 (M = Ni, Pd, Pt). A mechanistic study showed that the hydrometalation does not proceed via the reaction of alkyne with a hydridometal generated by the protonation of a carboxylic acid with Pt(PEt 3)4, but proceeds via a reaction of an alkyne coordinate metal complex with the acid. This finding clarifies the long proposed reaction mechanism that operates via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Bronsted acid and Pd(0) complex. This finding also leads to the disclosure of an unprecedented reduction of alkynes with formic acid that can selectively produce cis-, trans-alkenes and alkanes by slightly tuning the conditions.
- Shen, Ruwei,Chen, Tieqiao,Zhao, Yalei,Qiu, Renhua,Zhou, Yongbo,Yin, Shuangfeng,Wang, Xiangbo,Goto, Midori,Han, Li-Biao
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supporting information; experimental part
p. 17037 - 17044
(2011/12/04)
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- Selective activation of C-H bonds on the ring of ethylbenzene catalyzed by several diperoxovanadate complexes
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The competitive oxidation of the C-H bonds on the aromatic ring and side-chain of ethylbenzene (EB) with hydrogen peroxide is investigated over four diperoxovanadate catalysts, that is, K3[VO(O2) 2(ox)] (bpV(ox)), K2
- Liu, Qiuyuan,Zhu, Liangfang,Li, Li,Guo, Bin,Hu, Xiaoke,Hu, Changwei
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experimental part
p. 71 - 77
(2011/01/08)
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- Aromatic Hydroxylation at a Non-Heme Iron Center: Observed Intermediates and Insights into the Nature of the Active Species
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Mechanism of substrate oxidations with hydrogen peroxide in the presence of a highly reactive, biomimetic, iron aminopyridine complex, [Fe II(bpmen)(CH3CN)2][ClO4] 2 (1; bpmen=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2- diamine), is elucidated. Complex 1 has been shown to be an excellent catalyst for epoxidation and functional-group-directed aromatic hydroxylation using H2O2, although its mechanism of action remains largely unknown.1, 2 Efficient intermolecular hydroxylation of unfunctionalized benzene and substituted benzenes with H2O2 in the presence of 1 is found in the present work. Detailed mechanistic studies of the formation of iron(III)-phenolate products are reported. We have identified, generated in high yield, and experimentally characterized the key FeIII(OOH) intermediate (Imax=560 nm, rhombic EPR signal with g=2.21, 2.14, 1.96) formed by 1 and H2O2. Stopped-flow kinetic studies showed that FeIII(OOH) does not directly hydroxylate the aromatic rings, but undergoes rate-limiting self-decomposition producing transient reactive oxidant. The formation of the reactive species is facilitated by acid-assisted cleavage of the O-O bond in the iron-hydroperoxide intermediate. Acid-assisted benzene hydroxylation with 1 and a mechanistic probe, 2-Methyl-1-phenyl-2-propyl hydroperoxide (MPPH), correlates with O-O bond heterolysis. Independently generated FeIV=O species, which may originate from O-O bond homolysis in FeIII(OOH), proved to be inactive toward aromatic substrates. The reactive oxidant derived from 1 exchanges its oxygen atom with water and electrophilically attacks the aromatic ring (giving rise to an inverse H/D kinetic isotope effect of 0.8). These results have revealed a detailed experimental mechanistic picture of the oxidation reactions catalyzed by 1, based on direct characterization of the intermediates and products, and kinetic analysis of the individual reaction steps. Our detailed understanding of the mechanism of this reaction revealed both similarities and differences between synthetic and enzymatic aromatic hydroxylation reactions.
- Makhlynets, Olga V.,Rybak-Akimova, Elena V.
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supporting information; experimental part
p. 13995 - 14006
(2011/04/12)
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- ALKYLATION OF HYDROXYARENES WITH OLEFINS, ALCOHOLS AND ETHERS IN IONIC LIQUIDS
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Hydroxyarenes are alkylated using an ionic liquid catalyst system with olefins, alcohols, or ethers as alkylating agents. The ionic liquid catalyst system comprises chloroindate (III) anions. The reactions may be conducted at moderate temperatures and pressures to yield commercially relevant alkylated hydroxyarene compounds.
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Page/Page column 22
(2008/06/13)
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- Monooxygenation of aromatic compounds by dioxygen with bioinspired systems using non-heme iron catalysts and tetrahydropterins: Comparison with other reducing agents and interesting regioselectivity favouring meta-hydroxylation
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Monooxygenation of aromatic compounds by dioxygen in the presence of catalytic amounts of an iron(II) salt and tetrahydropterins as reducing agents occurs with a regioselectivity favouring meta-hydroxylation of arenes bearing an electron-donating substituent, such as anisole, phenetole, toluene, and ethylbenzene. Comparison of similar systems using various reducing agents showed that only tetrahydropterins and ascorbate led to such a major meta-hydroxylation. The tetrahydropterin- and ascorbate-dependent systems should be useful for the preparation of meta-hydroxylated metabolites of aromatic drugs, as shown here in the case of diclofenac.
- Mathieu, Delphine,Bartoli, Jean Fran?ois,Battioni, Pierrette,Mansuy, Daniel
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p. 3855 - 3862
(2007/10/03)
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- Process for functionalising a phenolic compound carrying an electron-donating group
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The invention concerns a method for functionalizing a phenolic compound bearing an electron-donor group, in said group para position, inter alia a method for the amidoalkylation of a phenolic compound bearing an electron-donor group, and more particularly, a phenolic compound bearing an electron-donor group preferably, in the hydroxyl group ortho position. The method for functionalizing in para position with respect to an electron-donor group carried by a phenolic compound is characterised in that the phenolic compound bearing an electron-donor group is subjected to the following steps: a first step which consists of protecting the hydroxyl group in the form of a sulphonic ester function; a second step which consists in reacting the protected phenolic compound with an electrophilic reagent; optionally, a third step deprotecting the hydroxyl group.
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- Catalytic ethylation of phenols
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Alkylation of phenol and cresols with ethanol in the presence of iron-aluminum catalyst was studied.
- Agaev,Shakhtakhtinskaya,Eminov,Guliev
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p. 651 - 653
(2007/10/03)
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- O-alkylation of phenolic compounds via rare earth orthophosphate catalysts
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Carbocyclic/aliphatic ethers, for example anisole, quaicol, guaethol, p-methoxyphenol and ethylene dioxybenzene, are selectively prepared, in good yield, by reacting a phenolic compound, for example a phenol, hydroquinone, pyrocatechin, naphthol, or the like, with an alcohol, for example methanol, ethanol, isopropanol, ethylene glycol, etc., in gaseous phase, in the presence of a catalytically effective amount of a trivalent rare earth metal orthophosphate, for example a lanthanum, cerium or samarium orthophosphate, optionally doped with an alkali or alkaline earth metal, preferably cesium.
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- Kinetics of oxidation of phenoxyacetic acids by pyridinium hydrobromide perbromide
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The oxidation of several monosubstituted phenoxyacetic acids by pyridinium hydrobromide perbromide (PHPB) was studied in aqueous acetic acid. The reaction is first order with respect to PHPB. Michaelis-Menten-type kinetics are observed with respect to phenoxyacetic acids. The oxidation of [2,2-2H2]phenoxyacetic acid exhibits a substantial kinetic isotopic effect. The effect of solvent composition indicates that the transition state is more polar than the reactants. The formation constants of the intermediate phenoxyacetic acid-PHPB complexes and the rates of their decomposition were determined at different temperatures. The rates of oxidation of para- and meta-substituted phenoxyacetic acids were correlated with Hammett's substituent constants. The ρ value is -2.59 at 35 °C. The rates of oxidation of ortho-substituted compounds are correlated with Charton's triparametric equation. A mechanism involving transfer of a hydride ion from the substrate to the oxidant is proposed.
- Karunakaran,Elango
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p. 105 - 110
(2007/10/03)
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- Preparation of diphenolics
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A process for the production of diphenolic compounds having a divalent bridge. A first disubstituted phenol is reacted with an aldehyde in the presence of a secondary amine and excess alcohol to form an ether intermediate. The ether intermediate is reacted with a phenol having an open ortho or para position to form a diphenolic.
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- Process for the selective production of dihydroxybenzenes
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The known nuclear hydroxylation of phenol or substituted phenols or phenol ethers with organic solutions of hydrogen peroxide in the presence of a catalyst is carried out in improved manner by employing both (1) a special, practically water free solution of hydrogen peroxide in an organic solvent which forms an azeotrope with water, which azeotrope boils below the boiling point of hydrogen peroxide, and (2) selenium dioxide as a catalyst. Through this, the nuclear hydroxylation is substantially simpler than previously. Besides, for the first time, it is possible to control the ortho to para ratio or the two ortho ratios to each other.
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- REACTION OF PHENOL WITH ALKYLBENZENES ON A ZEOLITE-CONTAINING CATALYST.
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The purpose of this investigation is a study of transfer of ethyl and isopropyl groups from the aromatic hydrocarbon molecule to phenol with a zeolite-containing catalyts. From the data given it is evident that ethyltoluene reacts with phenol significantly more energetically than ethylbenzene. In addition, the reaction proceeded well at 350 degree C with 15% conversion of phenol. Under these conditions, the main transalkylation product was a mixture of ethylphenol isomers. Increasing the temperature increased the conversion both of phenol and of the hydrocarbon. However, this led to a decrease of the yield of ethylphenols and simultaneously to an increase of the amount of cresols in the reaction products.
- Sibarov,Dokuchaeva,Mukhin
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p. 2479 - 2481
(2007/10/02)
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- Process for preparing m-alkylhydroxybenzene
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An improved process for preparing m-alkylhydroxybenzene which comprises heating alkylbenzene or an isomeric mixture of alkylbenzenesulfonic acid in the presence of sulfuric acid and an inorganic salt at a temperature of from 150° to 210° C. to form an isomeric mixture of alkylbenzenesulfonic acid which is rich in the m-isomer, selectively hydrolyzing the isomers of alkylbenzenesulfonic acid other than the m-isomer, and caustically fusing the unhydrolyzed alkylbenzenesulfonic acid.
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- DIRECT HYDROXYLATION OF COMPOUNDS IN AN RF PLASMA
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The hydoxylation of aromatic compounds was carried out in the plasma generated by a radiofrequency discharge.Benzene and naphthalene yielded phenol and naphthols, respectively, as single volatile products.With respect to alkylbenzenes, the oxidation of the side-chains competed with the aromatic hydroxylation.
- Tezuka, Meguru,Yajima, Tatsuhiko,Tsuchiya, Atsuhiko
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p. 1437 - 1438
(2007/10/02)
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