- Imidazolium-urea low transition temperature mixtures for the UHP-promoted oxidation of boron compounds
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Different carboxy-functionalized imidazolium salts have been considered as components of low transition temperature mixtures (LTTMs) in combination with urea. Among them, a novel LTTM based on 1-(methoxycarbonyl)methyl-3-methylimidazolium chloride and urea has been prepared and characterized by differential scanning calorimetry throughout its entire composition range. This LTTM has been employed for the oxidation of boron reagents using urea-hydrogen peroxide adduct (UHP) as the oxidizer, thus avoiding the use of aqueous H2O2, which is dangerous to handle. This metal-free protocol affords the corresponding alcohols in good to quantitative yields in up to 5 mmol scale without the need of further purification. The broad composition range of the LTTM allows for the reaction to be carried out up to three consecutive times with a single imidazolium salt loading offering remarkable sustainability with an E-factor of 7.9, which can be reduced to 3.2 by the threefold reuse of the system.
- Martos, Mario,Pastor, Isidro M.
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- Impact of oxygen vacancies in Ni supported mixed oxide catalysts on anisole hydrodeoxygenation
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The hydrodeoxygenation (HDO) activity of anisole has been investigated over Ni catalysts on mixed metal oxide supports containing Nb–Zr and Ti–Zr in 1:1 and 1:4 ratios. XRD patterns indicate the incorporation of Ti (or Nb) into the ZrO2 framewo
- Ali, Hadi,Kansal, Sushil Kumar,Lauwaert, Jeroen,Saravanamurugan, Shunmugavel,Thybaut, Joris W.,Vandevyvere, Tom
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- Catalytic Activation of Unstrained C(Aryl)-C(Alkyl) Bonds in 2,2′-Methylenediphenols
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Catalytic activation of unstrained and nonpolar C-C bonds remains a largely unmet challenge. Here, we describe our detailed efforts in developing a rhodium-catalyzed hydrogenolysis of unstrained C(aryl)-C(alkyl) bonds in 2,2′-methylenediphenols aided by removable directing groups. Good yields of the monophenol products are obtained with tolerating a wide range of functional groups. In addition, the reaction is scalable, and the catalyst loading can be reduced to as low as 0.5 mol %. Moreover, this method proves to be effective to cleave C(aryl)-C(alkyl) linkages in both models of phenolic resins and commercial novolacs resins. Finally, detailed experimental and computational mechanistic studies show that with C-H activation being a competitive but reversible off-cycle reaction, this transformation goes through a directed C(aryl)-C(alkyl) oxidative addition pathway.
- Dong, Guangbin,Ratchford, Benjamin L.,Xue, Yibin,Zhang, Rui,Zhu, Jun
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supporting information
p. 3242 - 3249
(2022/02/23)
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- A mild desilylation of phenolic tert-butyldimethylsilyl ethers using in situ generated tetraethylammonium superoxide
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Desilylation of phenolic tert-butyldimethylsilyl ethers has been achieved under the mild reaction conditions of in situ generated tetraethylammonium superoxide, at room temperature. (Figure presented.).
- Pandey, Surabhi,Shukla, Ajay K.,Raghuvanshi, Raghvendra S.
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p. 809 - 811
(2021/07/16)
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- Crystal Facet Engineering of Copper-Based Metal-Organic Frameworks with Inorganic Modulators
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Manipulating the exposed facets of metal-organic frameworks (MOFs) is of importance toward understanding their facet-dependent property in a variety of applications. Herein, we apply a novel inorganic competitive coordination strategy to control the growth orientation of copper-based MOFs (HKUST-1, MOF-14, and Cu-MOF-74) without sacrificing the pore accessibility and crystallinity. Through monitoring the reactant composition, we find that the competitive coordination induced by the added aluminium nitrate mainly affects the crystal growth stage rather than the nucleation stage. The kinetic study further reveals that Al3+ competes with Cu2+ to coordinate with ligands, restraining the growth rate of certain facets and resulting in the orientated growth of copper-based MOFs. Compared to the reduced pore accessibility of HKUST-1 crystals modulated by the organic modulation method, Al3+-modulated HKUST-1 displays a much larger surface area (>2200 m2/g) and more accessible Cu active sites. Hydroxylation of toluene was utilized as a model reaction to investigate the facet-catalytic activity for as-synthesized HKUST-1. The selectivity of the preferred product cresol increases with the morphology transformation of HKUST-1 from octahedron to cube.
- Wang, Zhanke,Ge, Lei,Feng, Desheng,Jiang, Zongrui,Wang, Hao,Li, Mengran,Lin, Rijia,Zhu, Zhonghua
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p. 926 - 934
(2021/01/26)
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- Visible light-induced photodeoxygenation of polycyclic selenophene Se-oxides
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Photodeoxygenation of dibenzothiophene S-oxide (DBTO) is believed to produce ground-state atomic oxygen [O(3P)] in solution. Compared with other reactive oxygen species (ROS), O(3P) is a unique oxidant as it is potent and selective. Derivatives of DBTO have been used as O(3P)-precursors to oxidize variety of molecules, including plasmid DNA, proteins, lipids, thiols, and other small organic molecules. Unfortunately, the photodeoxygenation of DBTO requires ultraviolet irradiation, which is not an ideal wavelength range for biological systems, and has a low quantum yield of approximately 0.003. In this work, benzo[b]naphtho[1,2-d]selenophene Se-oxide, benzo[b]naphtho[2,1-d]selenophene Se-oxide, dinaphtho[2,3-b:2’,3’-d]selenophene Se-oxide, and perylo[1,12-b,c,d]selenophene Se-oxide were synthesized, and their ability to utilize visible light for generating O(3P) was interrogated. Benzo[b]naphtho[1,2-d]selenophene Se-oxide produces O(3P) upon irradiation centered at 420 nm. Additionally, benzo[b]naphtho[1,2-d]selenophene Se-oxide, benzo[b]naphtho[2,1-d]selenophene Se-oxide, and dinaphtho[2,3-b:2’,3’-d]selenophene Se-oxide produce O(3P) when irradiated with UVA light and have quantum yields of photodeoxygenation ranging from 0.009 to 0.33. This work increases the utility of photodeoxygenation by extending the range of wavelengths that can be used to generate O(3P) in solution.
- Chintala, Satyanarayana M.,Throgmorton, John C.,Maness, Peter F.,McCulla, Ryan D.
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- Highly selective demethylation of anisole to phenol over H4Nb2O7modified MoS2catalyst
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Hydrogenolysis of lignin to obtain value-added phenolic chemicals is an important approach for its comprehensive utilization. Herein, H4Nb2O7modified MoS2catalyst with short slabs and narrow stacking degree was successfully synthesized by the one step hydrothermal method and used in the selective demethylation of anisole to phenol. The MoS2-H4Nb2O7-160 catalyst exhibited the best activity with 97.7% conversion of anisole and 98.0% selectivity of phenol under 3 MPa H2pressure at 270 °C for 4 h, which has been rarely reported on anisole transformation over heterogeneous catalysts so far. The characterizations results demonstrated that the H4Nb2O7modification reduced the slab length and stacking degree of MoS2during the hydrothermal process and enhanced the acidity property therefore improved the cleavage ability of CArO-CH3bond. This study provides a new scheme for the activity enhancement of MoS2in lignin demethylation, laying a foundation on the improvement of lignin utilization and the development of renewable energy strategy.
- Ji, Na,Wang, Zhenjiao,Diao, Xinyong,Jia, Zhichao,Li, Tingting,Zhao, Yujun,Liu, Qingling,Lu, Xuebin,Ma, Degang,Song, Chunfeng
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p. 800 - 809
(2021/02/26)
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- Rational design of oligomeric MoO3 in SnO2 lattices for selective hydrodeoxygenation of lignin derivatives into monophenols
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Novel Mo-Sn bimetallic oxide catalysts with highly dispersed oligomeric MoO3 in SnO2 lattices, which were synthesized by the co-precipitation method and pretreated by anhydrous ethanol, were first employed in the hydrodeoxygenation of various lignin derivatives to produce monophenols with high activity and selectivity. In comparison with the pure α-MoO3 and the previous reported catalysts, the α-2Mo1Sn exhibited superior activity in the hydrodeoxygenation of guaiacol, with full conversion and 92.5% phenol yield at 300 °C under 4 MPa initial H2 pressure in n-hexane for 4 h. According to comprehensive characterizations and catalytic measurements, the excellent performance of α-2Mo1Sn was ascribed to the formation of abundant Sn-O-Mo-OV interfacial sites, which possessed strong Mo-Sn interaction with enhanced surface area, electron-donating group binding ability, Lewis acidity, and redox ability. It was demonstrated that over the present α-2Mo1Sn catalyst system, the Sn-O-Mo-OV interfacial sites could greatly facilitate the adsorption and activation of Caromatic-OCH3 and Caromatic-CH3 bonds, and thus significantly promote the demethoxylation and demethylation reaction to produce phenol. This work figures out the rational design of MoO3-based catalyst and displays a clear potential for the selective hydrodeoxygenation of lignin derivatives into monophenols.
- Diao, Xinyong,Ji, Na,Jia, Zhichao,Jiang, Sinan,Li, Tingting,Liu, Caixia,Liu, Qingling,Lu, Xuebin,Song, Chunfeng,Wang, Zhenjiao
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p. 234 - 251
(2021/08/19)
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- Aromatic C?H Hydroxylation Reactions with Hydrogen Peroxide Catalyzed by Bulky Manganese Complexes
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The oxidation of aromatic substrates to phenols with H2O2 as a benign oxidant remains an ongoing challenge in synthetic chemistry. Herein, we successfully achieved to catalyze aromatic C?H bond oxidations using a series of biologically inspired manganese catalysts in fluorinated alcohol solvents. While introduction of bulky substituents into the ligand structure of the catalyst favors aromatic C?H oxidations in alkylbenzenes, oxidation occurs at the benzylic position with ligands bearing electron-rich substituents. Therefore, the nature of the ligand is key in controlling the chemoselectivity of these Mn-catalyzed C?H oxidations. We show that introduction of bulky groups into the ligand prevents catalyst inhibition through phenolate-binding, consequently providing higher catalytic turnover numbers for phenol formation. Furthermore, employing halogenated carboxylic acids in the presence of bulky catalysts provides enhanced catalytic activities, which can be attributed to their low pKa values that reduces catalyst inhibition by phenolate protonation as well as to their electron-withdrawing character that makes the manganese oxo species a more electrophilic oxidant. Moreover, to the best of our knowledge, the new system can accomplish the oxidation of alkylbenzenes with the highest yields so far reported for homogeneous arene hydroxylation catalysts. Overall our data provide a proof-of-concept of how Mn(II)/H2O2/RCO2H oxidation systems are easily tunable by means of the solvent, carboxylic acid additive, and steric demand of the ligand. The chemo- and site-selectivity patterns of the current system, a negligible KIE, the observation of an NIH-shift, and the effectiveness of using tBuOOH as oxidant overall suggest that hydroxylation of aromatic C?H bonds proceeds through a metal-based mechanism, with no significant involvement of hydroxyl radicals, and via an arene oxide intermediate. (Figure presented.).
- Masferrer-Rius, Eduard,Borrell, Margarida,Lutz, Martin,Costas, Miquel,Klein Gebbink, Robertus J. M.
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p. 3783 - 3795
(2021/03/09)
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- Catalytic oxidation of a model volatile organic compound (toluene) with tetranuclear Cu(II) complexes
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A tetranuclear Cu(II) cubane [Cu2(μ-1κONO’:2κOO’:3κO-HL)(μ-1κONO’:2κOO’-HL)]2?4dmf (1) derived form (2,3-dihydroxybenzylidene)-2-hydroxybenzohydrazide (H3L) was synthesized at room temperature and characterized by elemental analysis, IR spectroscopy, ESI-MS and single crystal X-ray diffraction. The known tetranuclear Cu(II) open-cubane [Cu(HL)]4?4EtOH (2) was synthesized from the same pro-ligand following a similar method or the reported one. The different tautomeric forms (keto and enol) of the organic ligands in 1 and 2 explain their different structural features. Both complexes were screened as catalysts for the peroxidative oxidation of toluene with tert-butyl hydroperoxide, achieving benzaldehyde and o-cresol as the main products. Complex 1 exhibits the highest activity (maximum product yield of 11%).
- Sutradhar, Manas,Alegria, Elisabete C.B.A.,Barman, Tannistha Roy,Lapa, Hugo M.,Guedes da Silva, M. Fátima C.,Pombeiro, Armando J.L.
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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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- 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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- Selective upgrading of biomass-derived benzylic ketones by (formic acid)–Pd/HPC–NH2 system with high efficiency under ambient conditions
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Upgrading biomass-derived phenolic compounds provides a valuable approach for the production of higher-value-added fuels and chemicals. However, most established catalytic systems display low hydrodeoxygenation (HDO) activities even under harsh reaction conditions. Here, we found that Pd supported on –NH2-modified hierarchically porous carbon (Pd/HPC–NH2) with formic acid (FA) as hydrogen source exhibits unprecedented performance for the selective HDO of benzylic ketones from crude lignin-derived oxygenates. Designed experiments and theoretical calculations reveal that the H+/H? species generated from FA decomposition accelerates nucleophilic attack on carbonyl carbon in benzylic ketones and the formate species formed via the esterification of intermediate alcohol with FA expedites the cleavage of C–O bonds, achieving a TOF of 152.5 h?1 at 30°C for vanillin upgrading, 15 times higher than that in traditional HDO processes (~10 h?1, 100°C–300°C). This work provides an intriguing green route to produce transportation fuels or valuable chemicals from only biomass under mild conditions.
- Chen, Yuzhuo,Chen, Zhirong,Gong, Yutong,Mao, Shanjun,Ning, Honghui,Wang, Yong,Wang, Zhenzhen
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p. 3069 - 3084
(2021/11/16)
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- Electrochemical-induced hydroxylation of aryl halides in the presence of Et3N in water
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A thorough study of mild and environmentally friendly electrochemical-induced hydroxylation of aryl halides without a catalyst is presented. The best protocol consists of hydroxylation of different aryl iodides and aryl bromides by water solution in the presence of Et3N under air, affording the target phenols in good isolated yields. Moreover, aryl chlorides were successfully employed as substrates. This methodology also provides a direct pathway for the formation of deoxyphomalone, which displayed a significant anti-proliferation effect.
- Ke, Fang,Lin, Chen,Lin, Mei,Long, Hua,Wu, Mei,Yang, Li,Zhuang, Qinglong
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supporting information
p. 6417 - 6421
(2021/08/03)
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- Selective hydroxylation of aryl iodides to produce phenols under mild conditions using a supported copper catalyst
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Owing to the high activity and low-cost, copper-based catalysts are promising candidates for transforming aromatic halides to yield phenols. In this work, we report the selective hydroxylation of aromatic iodides to produce phenols using an atomically dispersed copper catalyst (Cu-ZnO-ZrO2) under mild reaction conditions. The reactions were conducted without the use of additional organic ligands, and the protection of an inert atmosphere environment is not required. The catalyst can be easily prepared, scalable, and is very efficient for a wide range of substrates. The catalytic reactions can be carried out with only 1.24 mol% Cu loading, which shows great potential in mass production.
- Auni, Anika,Ding, Guodong,Hao, Leiduan,Li, Tao,Li, Xiaoyu,Xu, Haiping,Zhang, Qiang
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p. 25348 - 25353
(2021/08/03)
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- Method for synthesizing heteroatom- substituted aromatic compound from styrene compound
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The invention discloses a method for synthesizing a heteroatom-substituted aromatic compound from a styrene compound, which comprises the following steps of: mixing a styrene compound with a general formula (I) and a heteroatom-containing compound with a general formula (II), and reacting in the presence of an acid additive and an organic solvent to obtain a heteroatom-substituted compound with ageneral formula (III). According to the synthesis method disclosed by the invention, a large amount of styrene compounds are used as raw materials and react to generate aromatic amine or phenol compounds under the action of no metal catalysis; and compared with the traditional aromatic amine and phenol synthesis method, the method has the advantages of high yield, simple conditions, low waste discharge amount, no metal participation, simple reaction equipment, easiness in industrial production and the like.
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Paragraph 0338-0341
(2021/02/06)
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- Highly recyclable Ti0.97Ni0.03O1.97catalyst coated on cordierite monolith for efficient transformation of arylboronic acids to phenols and reduction of 4-nitrophenol
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A stable Ni2+substituted TiO2catalyst (Ti0.97Ni0.03O1.97) has been synthesized by a solution combustion method with an average crystallite size of 7.5 nm. Ti1?xNixO2?x(x= 0.01-0.06) crystallizes in the TiO2anatase structure with Ni2+substituted in Ti4+ion sites and Ni taking a nearly square planar geometry. This catalyst is found to be highly active in the transformation of diverse arylboronic acids to the corresponding phenols. The catalyst coated cordierite monolith can even be recycled for up to 20 cycles with a cumulative TOF of 1.8 × 105h?1. In scale-up reactions, various phenols are synthesized by employing a single cordierite monolith. It also shows high performance in the reduction of 4-nitrophenol.
- Hegde, M. S.,Prasanna,Usha, K. M.
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supporting information
p. 14223 - 14234
(2021/10/25)
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- Isotruxene-based porous polymers as efficient and recyclable photocatalysts for visible-light induced metal-free oxidative organic transformations
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Two new isotruxene-based porous polymers were prepared and demonstrated to be highly efficient, metal-free heterogeneous photocatalysts for oxidative transformations using air as the mild oxidant under visible-light irradiation. Both catalysts show excellent recyclability. In addition, the reactions can be performed in water, further indicating the greenness of this method. This journal is
- Zhang, Haowen,Zhang, Xiao,Zheng, Ying,Zhou, Cen
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supporting information
p. 8878 - 8885
(2021/11/27)
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- Catalyst-free rapid conversion of arylboronic acids to phenols under green condition
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A catalyst-free and solvent-free method for the oxidative hydroxylation of aryl boronic acids to corresponding phenols with hydrogen peroxide as the oxidizing agent was developed. The reactions could be performed under green condition at room temperature within very short reaction time. 99% yield of phenol could be achieved in only 1 min. A series of different arenes substituted aryl boronic acids were further carried out in the hydroxylation reaction with excellent yield. It was worth nothing that the reaction could completed within 1 min in all cases in the presence of ethanol as co-solvent.
- Dong, Zhenhua,Liu, Mengmeng,Pan, Hongguo
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- The graphite-catalyzed: ipso -functionalization of arylboronic acids in an aqueous medium: metal-free access to phenols, anilines, nitroarenes, and haloarenes
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An efficient, metal-free, and sustainable strategy has been described for the ipso-functionalization of phenylboronic acids using air as an oxidant in an aqueous medium. A range of carbon materials has been tested as carbocatalysts. To our surprise, graphite was found to be the best catalyst in terms of the turnover frequency. A broad range of valuable substituted aromatic compounds, i.e., phenols, anilines, nitroarenes, and haloarenes, has been prepared via the functionalization of the C-B bond into C-N, C-O, and many other C-X bonds. The vital role of the aromatic π-conjugation system of graphite in this protocol has been established and was observed via numerous analytic techniques. The heterogeneous nature of graphite facilitates the high recyclability of the carbocatalyst. This effective and easy system provides a multipurpose approach for the production of valuable substituted aromatic compounds without using any metals, ligands, bases, or harsh oxidants.
- Badgoti, Ranveer Singh,Dandia, Anshu,Parewa, Vijay,Rathore, Kuldeep S.,Saini, Pratibha,Sharma, Ruchi
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p. 18040 - 18049
(2021/05/29)
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- Blacklight-Induced Hydroxylation of Arylboronic Acids Leading to Hydroxyarenes Using Molecular Oxygen and Tetrabutylammonium Borohydride
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A new simple protocol for the conversion of arylboronic acids to hydroxyarenes was achieved using molecular oxygen in the presence of tetrabutylammonium borohydride under blacklight irradiation (360 nm). A radical chain mechanism in which a superoxide ion (O2?.) plays a key role is proposed.
- Kawamoto, Takuji,Ryu, Ilhyong
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- An efficient Ti0.95Cu0.05O1.95 catalyst for ipso – hydroxylation of arylboronic acid and reduction of 4-nitrophenol
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A stable, active and selective Ti0.95Cu0.05O1.95 catalyst, crystallized in anatase TiO2 structure with 5% Cu2+ ions substituted for Ti4+ ions with 5% oxide ion vacancy has been synthesized by solution combustion method. The catalyst was coated over a cordierite monolith (Mg2Al4Si5O18) by solution combustion method. By the first principle density functional theory (DFT) calculations, 48 atoms bulk structure has been optimized and density of states (DOS) has been calculated. Ti – O bond distribution in Ti0.95Cu0.05O1.95 has been compared with pure TiO2. Bond distribution analysis has shown longer Cu – O and Ti – O bonds compared to those in CuO and TiO2 creating Cu2+ and oxide ion vacancy as electrophilic and nucleophilic active sites, respectively. This catalyst was found to be very active for ipso – hydroxylation of arylboronic acid and 4-nitrophenol reduction reactions at room temperature. Catalyst coated cordierite monolith was used in the recycling process of the reaction for 20 cycles and cumulative turnover frequency was found to be 184,840 h?1. Ti0.95Cu0.05O1.95 catalyst coated on cordierite monolith enhanced the rate of the reaction compared to powder catalyst and made the handling and recycling of the catalyst very easy. Graphic abstract: [Figure not available: see fulltext.]
- Bhat, Shrikanth K,Dasappa, Jagadeesh Prasad,Hegde, M. S.,Prasanna
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- Tuning the redox potential of Ag?Ag2O/WO3 and Ag?Ag2S/WO3 photocatalysts toward diclofenac oxidation and nitrophenol reduction
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WO3 nanoplates modified with either Ag2O or Ag2S nano-architectures were synthesized by a deposition-hydrothermal route (180 °C for 5 h). They were characterized using X-ray powder diffraction, N2 sorptiometry, Transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, Photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. The photo-catalytic (λ > 420 nm, 160 W) degradation of Diclofenac (DCF; 60 mg/l), was achieved using H2O2 (1 × 10?4 M) with either Ag?Ag2O/WO3 (K = 32.0 × 10-3 min-1) or Ag?Ag2S/WO3 (K = 7.3 × 10-3 min-1) catalysts. In the case of DCF degradation using radical scavengers, [rad]O2? played a key role in the degradation process whilst [rad]OH and holes acted moderately minor roles. The possible DCF degradation paths and intermediates were assessed by LC–MS. Both Ag?Ag2O/WO3 and Ag?Ag2S/WO3 catalysts were used in the photo-reduction of 4-nitrophenol (4-NP; 1.8 × 10?4 M) to 4-aminophenol (4-AP) with rate constants equal 8.3 x 10?3 min-1 and 1.6 x 10?3 min?1, respectively.
- Ismail, Eman H.,Khalil, Mostafa M. H.,Mohamed, Mohamed Mokhtar,Torad, Eman
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- Separation of Anisole and Valuable Byproducts from Liquid Reaction Mixtures by Solvent Extraction and Multicomponent Distillation
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Anisole (methoxybenzene) is a widely used organic intermediate that can be synthesized via vapor-phase alkylation of phenol by methanol in the presence of a commercial NaX zeolite as a catalyst (SiO2:Al2O3 ratio of 2.6:3). The indigenously synthesized anisole is then separated from the multicomponent liquid reaction mixture, consisting of o-cresol, p-cresol and p-xylen, along with unreacted methanol and phenol. The separated anisole has substantial demand for applications in the chemical, pharmaceutical, plastics and pesticides industries. Separation of individual components from the reaction mixture requires identification of techniques that could be scaled up. Distillation is one of the most dependable techniques for the separation of multicomponent liquid mixtures. The novelty of the present study is the synthesis and separation of anisole along with individual components of methanol, phenol and o-cresol from its reaction mixture using a single distillation column under atmospheric and vacuum conditions, respectively. Through this process, the purity of the resulting methanol, anisole and phenol were found to be 99.99, 99.80 and 98.29% by simple distillation, whereas 91.0% pure o-cresol was separated by vacuum distillation due to its high boiling point. The experimental results were used to calculate the material, individual component and energy balances, whereas the PRO/II process simulation was performed to scale-up the process. On the other hand, anisole recovery from a synthetic multicomponent liquid mixture was also successfully conducted using solvent extraction. The overall observations found the integration of solvent extraction with distillation to be an effective, economical and dependable solution for the isolation of anisole and other important by-products.
- Vani, Bukke,Pabba, Manideep,Kalyani, Swayampakula,Sridhar, Sundergopal
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p. 160 - 177
(2021/01/29)
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- Optimizing the carburization conditions of supported rhenium carbide for guaiacol conversion
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The present work evaluates the effect of ethylene content of a carburization mixture on the formation of carburized rhenium supported on activated carbon. The resulting catalysts were characterized by N2 physisorption, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and temperature-programmed reduction, and the results show a strong effect on the final phase obtained. A high amount of ethylene inhibited the carburization process, resulting in carbon formation, while a lower amount (≤ 35 %) of ethylene was favorable to the formation of the carbide phase. The catalysts were evaluated for the hydrodeoxygenation (HDO) of guaiacol, a bio-oil model compound, and a high yield of benzene (50 %), a desirable aromatic compound, was obtained at complete conversion over the catalysts containing the carbide phase.
- Blanco, Elodie,Dongil, Ana Belén,Escalona, Néstor,García-Fierro, Jose Luis,Ghampson, I. Tyrone
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- Application of two morphologies of Mn2O3for efficient catalyticortho-methylation of 4-chlorophenol
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Vapor phaseortho-methylation of 4-chlorophenol with methanol was studied over Mn2O3catalyst with two kinds of morphologies. Here, Mn2O3was prepared by a precipitation and hydrothermal method, and showed the morphology of nanoparticles and nanowires, respectively. XRD characterization and BET results showed that, with the increase of calcination temperature, Mn2O3had a higher crystallinity and a smaller specific surface area. N2adsorption/desorption and TPD measurements indicated that Mn2O3nanowires possessed larger external surface areas and more abundant acid and base sites. Simultaneously, in the fixed bed reactor, methanol was used as the methylation reagent for theortho-methylation reaction of 4-chlorophenol. XRD, XPS, TG-MS and other characterizations made it clear that methanol reduced 4-chlorophenol and its methide, which were the main side-reactions. And Mn3+was reduced to Mn2+under the reaction conditions. Changing the carrier gas N2to a H2/Ar mixture further verified that the hydrogen generated by the decomposition of methanol was not the reason for dechlorination of 4-chlorophenol compounds. Here we summarized the progress of 4-chlorophenol methylation based on the methylation of phenol. Also, we proposed a mechanism of the 4-chlorophenol dechlorination effect which was similar to the Meerwein-Ponndorf-Verley-type (MPV) reaction. The crystal phase and carbon deposition were investigated in different reaction periods by XRD and TG-DTA. The reaction conditions for the two kinds of morphologies of the Mn2O3catalyst such as calcination temperature, reaction temperature, phenol-methanol ratio and reaction space velocity were optimized.
- Gui, Wenying,Liu, Xiaofei,Wang, Zhenlu,Zhang, Chunlei,Zhang, Hongqiang,Zhang, Li,Zhu, Wanchun
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p. 20836 - 20849
(2021/07/01)
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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 0029; 0089-0090; 0156-0159
(2021/04/30)
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- Reduced Amino Acid Schiff Base-Iron(III) Complexes Catalyzing Oxidation of Cyclohexane with Hydrogen Peroxide
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The reduced amino acid Schiff base ligands have been prepared and were coordinated with ferric chloride to generate the iron(III) complexes. The ligands and complexes have been characterized using FT-IR, UV-vis, elemental analysis, ICP-AES analysis, mass spectra etc. After the structural characterization, these complexes were applied for the oxidation of cyclohexane using hydrogen peroxide as the oxidant under mild conditions. The activity tests showed that the L-phenylalanine-derived reduced Schiff base iron(III) complex(Ph?FeCl) afforded the highest yield of cyclohexanol and cyclohexanone(total yield up to 23.2 %). Notably, the Ph?FeCl complex catalyzes the reaction via a heterogeneous approach, allowing the complex to be separated and recycled conveniently after the oxidation reaction. Besides, the Ph?FeCl catalyst can also be extended for the selective oxidation of other alkanes and aromatics into alcohols, ketones and phenols etc. Finally, the reaction mechanism of cyclohexane oxidation on the iron(III) complex was proposed as well by the free radical inhibitors and EPR study of active intermediates.
- Zheng, Anna,Zhou, Qingqing,Ding, Bingjie,Li, Difan,Zhang, Tong,Hou, Zhenshan
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p. 3385 - 3395
(2021/08/23)
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- Catalytic SNAr Hydroxylation and Alkoxylation of Aryl Fluorides
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Nucleophilic aromatic substitution (SNAr) is a powerful strategy for incorporating a heteroatom into an aromatic ring by displacement of a leaving group with a nucleophile, but this method is limited to electron-deficient arenes. We have now established a reliable method for accessing phenols and phenyl alkyl ethers via catalytic SNAr reactions. The method is applicable to a broad array of electron-rich and neutral aryl fluorides, which are inert under classical SNAr conditions. Although the mechanism of SNAr reactions involving metal arene complexes is hypothesized to involve a stepwise pathway (addition followed by elimination), experimental data that support this hypothesis is still under exploration. Mechanistic studies and DFT calculations suggest either a stepwise or stepwise-like energy profile. Notably, we isolated a rhodium η5-cyclohexadienyl complex intermediate with an sp3-hybridized carbon bearing both a nucleophile and a leaving group.
- Kang, Qi-Kai,Li, Ke,Li, Yuntong,Lin, Yunzhi,Shi, Hang,Xu, Lun
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supporting information
p. 20391 - 20399
(2021/08/13)
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- Reaction of hydroxyl radical with arenes in solution—On the importance of benzylic hydrogen abstraction
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The regioselectivity of hydroxyl radical reactions with alkylarenes was investigated using a nuclear magnetic resonance (NMR)-based methodology capable of trapping and quantifying addition and hydrogen abstraction products of the initial elementary step of the oxidation process. Abstraction products are relatively minor components of the product mixtures (15–30 mol%), depending on the magnitude of the overall rate coefficient and the number of available hydrogens. The relative reactivity of addition at a given position on the ring depends on its relation to the methyl substituents on the hydrocarbons under study. The reactivity enhancements for disubstituted and trisubstituted rings are approximately additive under the conditions of this study.
- Waggoner, Abygail R.,Abdulrahman, Yahya,Iverson, Alexis J.,Gibson, Ethan P.,Buckles, Mark A.,Poole, James S.
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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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- Single-step benzene hydroxylation by cobalt(ii) catalysts: Via a cobalt(iii)-hydroperoxo intermediate
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The cobalt(ii) complexes of 4N tetradentate ligands have been synthesized and characterized as the catalysts for phenol synthesis in a single step. The molecular structure of the complexes showed a geometry in between square pyramidal and trigonal bipyramidal (τ, 0.49-0.88) with Co-Namine and Co-NPy bond distances of 2.104-2.254 ? and 2.043-2.099 ?, respectively. The complexes exhibited a Co2+/Co3+ redox potential around 0.489-0.500 V vs. Ag/Ag+ in acetonitrile. The complexes catalyzed hydroxylation of benzene using H2O2 (30%) and afforded phenol selectively as the major product. A maximum yield of phenol up to 29% and turnover number (TON) of 286 at 60 °C, and a yield of 19% and TON of 191 at 25 °C are achieved. This is the highest catalytic performance reported using cobalt(ii) complexes as catalysts to date. This aromatic hydroxylation presumably proceeded via a cobalt(iii)-hydroperoxo species, which was characterized by ESI-MS, and vibrational and electronic spectral methods. The formation of key intermediate [(L)CoIII(OOH)]2+ was accompanied by the appearance of the characteristic O → Co(iii) ligand to metal charge transfer (LMCT) transition around 488-686 nm and vibration modes at 832 cm-1 (O-OH) and 564 cm-1 (Co-O). The geometry of one of the catalytically active intermediates was optimized by DFT and its spectral properties were calculated by TD-DFT calculations. These data are comparable to the experimental observations. The kinetic isotope effect (KIE) values (0.98-1.07) support the involvement of cobalt-bound oxygen species as a key intermediate. Isotope-labeling experiments using H218O2 showed an 89% incorporation of 18O, revealing that H2O2 is the main oxygen supplier for phenol formation from benzene. The catalytic efficiencies of cobalt complexes are tuned by ligand architectures via their geometrical configurations and steric properties.
- Anandababu, Karunanithi,Mayilmurugan, Ramasamy,Muthuramalingam, Sethuraman,Velusamy, Marappan
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p. 2540 - 2548
(2020/05/14)
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- Method for synthesizing phenol or derivative thereof in aqueous phase by photocatalytic one-pot method
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The invention discloses a method for synthesizing phenol or a derivative thereof in an aqueous phase by a photocatalytic one-pot method. The method comprises the following steps: by taking a compoundaryl halide shown in formula (I) as a raw material and water as a solvent, adding a catalyst and an auxiliary agent, and carrying out reacting under the conditions of alkali and visible light to obtain the phenol or the derivative (II) thereof. Compared with the prior art, the method is applicable to a large number of functional groups, high in yield, few in byproducts, simple and safe to operate,low in cost and environmentally friendly, wherein R is selected from substituted or non-substituted phenyl, pyridyl, quinolyl or pyrimidinyl; X is selected from halogen; the substituted phenyl is substituted by C1-C4 alkyl, C1-C4 alkoxy, hydroxyl, halogen, cyano, aldehyde group, nitro, amino, acetyl or carboxyl; and the substituted pyridyl, quinolyl or pyrimidinyl is pyridyl, quinolyl or pyrimidinyl substituted by C1-C4 alkyl.
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Paragraph 0032-0033; 0058-0059; 0085-0106
(2020/12/08)
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- Method for preparing alcohol and phenol through aerobic hydroxylation reaction of boric acid derivative in absence of photocatalyst
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The invention discloses a method for preparing alcohol and phenol through aerobic hydroxylation reaction of a boric acid derivative in the absence of a photocatalyst, wherein the boric acid derivativeis aryl boronic acid or alkyl boronic acid, and the corresponding target compounds are respectively a phenol-based compound and an alcohol-based compound. According to the method, by using a boric acid derivative as a reaction substrate, an additive is added under a solvent condition, and a hydroxylation reaction is performed under aerobic and illumination conditions to obtain a corresponding target compound. According to the invention, the new strategy is provided for the synthesis of phenols through aerobic hydroxylation of aryl boronic acid without a photocatalyst; the catalyst-free aerobic hydroxylation method for photocatalysis of aryl boronic acid or alkyl boronic acid by using triethylamine as an additive is firstly disclosed; and the new method has advantages of photocatalyst-freecondition, wide substrate range and good functional group compatibility.
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Paragraph 0025-0028; 0030-0032
(2020/01/25)
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- Cu(i) complexes obtained: Via spontaneous reduction of Cu(ii) complexes supported by designed bidentate ligands: Bioinspired Cu(i) based catalysts for aromatic hydroxylation
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Copper(i) complexes [Cu(L1-7)2](ClO4) (1-7) of bidentate ligands (L1-L7) have been synthesized via spontaneous reduction and characterized as catalysts for aromatic C-H activation using H2O2 as the oxidant. The single crystal X-ray structure of 1 exhibited a distorted tetrahedral geometry. All the copper(i) complexes catalyzed direct hydroxylation of benzene to form phenol with good selectivity up to 98%. The determined kinetic isotope effect (KIE) values, 1.69-1.71, support the involvement of a radical type mechanism. The isotope-labeling experiments using H218O2 showed 92% incorporation of 18O into phenol and confirm that H2O2 is the key oxygen supplier. Overall, the catalytic efficiencies of the complexes are strongly influenced by the electronic and steric factor of the ligand, which is fine-tuned by the ligand architecture. The benzene hydroxylation reaction possibly proceeded via a radical mechanism, which was confirmed by the addition of radical scavengers (TEMPO) to the catalytic reaction that showed a reduction in phenol formation. This journal is
- Kumari, Sheela,Muthuramalingam, Sethuraman,Dhara, Ashish Kumar,Singh,Mayilmurugan, Ramasamy,Ghosh, Kaushik
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p. 13829 - 13839
(2020/10/26)
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- VISIBLE LIGHT INDUCED PHOTOGENERATION OF GROUND STATE ATOMIC OXYGEN
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The present invention generally relates to various polycyclic aromatic selenoxide compounds, methods for preparing these compounds, and methods of us these and other compounds to generate ground state atomic oxygen.
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Paragraph 0088-0090
(2020/12/01)
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- Zinc-mediated reactions on salicylaldehyde for Botrytis cinerea control
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Botrytis cinerea is a necrotrophic fungus that affects various plant species. Chemical control is a necessity and as much as possible, eco-friendly conditions and bioresources to obtain these chemicals should be used. In this context, a series of products was obtained from salicylaldehyde using zinc as a powerful reagent and tested for antifungal activity against Botrytis cinerea
- Franche, Antoine,Imbs, Claire,Fayeulle, Antoine,Merlier, Franck,Billamboz, Muriel,Léonard, Estelle
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supporting information
p. 706 - 710
(2019/09/13)
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- The development of a Cu(I)/pyrazolylpyridineamine catalyst system for the hydroxylation of aryl halides
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A catalyst system comprising of pyrazolylpyridineamine/Cu(I)/CsOH is reported. for the hydroxylation of aryl iodides and bromides with moderate to outstanding yields, without the use of an inert atmosphere. A comprehensive parameter optimisation study established optimum component concentrations: [Cu(MeCN)4]BF4 and 2-(1H-pyrazol-1-yl)-N-(pyridine-2-ylmethyl)ethan-1-amine (L01) (2 mol %), substrate (1 mmol), CsOH (4 mmol) and DMSO:H2O (1:1, 3 mL). Monitoring substrate conversion as a function of time revealed an induction period of 90 min, which could be eliminated through the initial in situ formation of the proposed [(L01)Cu-OH] intermediate. Eliminating the induction period resulted in complete conversion within one hour, with turnover numbers exceeding that of the benchmark catalyst system operating at an optimal catalyst loading of 0.05 mol %.
- Marais, Lindie,Vosloo, Hermanus C.M.,Swarts, Andrew J.
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- Visible-light-promoted aerobic oxidative hydroxylation of arylboronic acids in water by hydrophilic organic semiconductor
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A green and sustainable catalytic system was developed based on perylenediimide (PDI) organic semiconductor for the aerobic oxidative hydroxylation of arylboronic acids in aqueous solution with visible light. By using PDI-SN, a hydrophilic organic semiconductor, which can activate oxygen to produce superoxide radicals in aqueous solution, this reaction proceeds under ambient conditions: water as the solvent and air as the oxidant, giving various phenols as products with high yields. In contrast to methods using organic solvents, this novel process has the potential of green industrial application.
- Yu, Kunyi,Zhang, Hanjie,Sheng, Yuqiang,Zhu, Yongfa
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supporting information
(2020/06/23)
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- Aerobic photooxidative hydroxylation of boronic acids catalyzed by anthraquinone-containing polymeric photosensitizer
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We report herein the synthesis of a polymeric photosensitizer and its application in aerobic photooxidative hydroxylation of boronic acids. The polymeric photosensitizer was synthesized by the condensation of anthraquinone-2-carbonyl chloride (AQ-2-COCl) with poly (2-hydroxyethyl methacrylate) (PHEMA). The photo-oxidative hydroxylation of boronic acids using anthraquinone-containing-poly (2-hydroxyethyl methacrylate) (AQ-PHEMA) was then explored and shown to exhibit high efficiency and broad scope. Moreover, AQ-PHEMA could be easily recovered and reused for more than 20 times without significant loss of the catalytic activity.
- Chen, Yang,Ding, Aishun,Hu, Jianhua
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p. 7927 - 7932
(2020/03/11)
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- Nickel-catalyzed oxidative hydroxylation of arylboronic acid: Ni(HBTC)BPY MOF as an efficient and ligand-free catalyst to access phenolic motifs
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A straightforward and mild oxidative ipso-hydroxylation of arylboronic acids has been achieved using a simple and non-noble metal, nickel-based reusable heterogeneous catalyst Ni(HBTC)BPY MOF (HBTC = benzene-1,3,5-tricarboxylate, BPY = 4,4′-bipyridine) in the presence of benign hydrogen peroxide as an oxidant under ambient reaction condition. The Ni(HBTC)BPY MOF exhibits excellent catalytic activity towards the formation of phenols from diverse arylboronic acids within short time and can be reused up to five times without any notable loss in its activity as well as shown high functional group tolerance even in the presence of sensitive functionalities and useful to achieve hydroxyl group in heterocycles.
- Latha, Ganesapandian,Devarajan, Nainamalai,Karthik, Murugan,Suresh, Palaniswamy
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- Trinuclear Mn2+/Zn2+based microporous coordination polymers as efficient catalysts foripso-hydroxylation of boronic acids
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Two microporous coordination polymers based on hourglass trinuclear building units, [Mn3(bpdc)3(bpy)]·2DMF and [Zn3(bpdc)3(bpy)]·2DMF·4H2O (bpdc = 4,4′-biphenyl dicarboxylic acid, bpy = 4,4′-bipyridine), have been synthesized under solvothermal conditions employing DMF as the solvent. Each structure consists of two crystallographically distinct M2+(M1 and M2) centers that are connectedviacarboxylate bridges from six bpdc ligands, generating a trinuclear metal cluster, [M3(bpdc)3(bpy)]. Cluster representation of the structure resulted in an interpenetrated net of rarehextopological type. Catalytic activities of the CPs have been assessed for the oxidative hydroxylation of phenylboronic acids (PBAs) using aqueous hydrogen peroxide (H2O2). Various substituted aryl/hetero-arylboronic acids RB(OH)2[R = phenyl, 2,4-difluorophenyl, 4-aminophenyl, 2-thiopheneetc.] underwentipso-hydroxylation smoothly at room temperature to generate the corresponding phenols in excellent yields. The main advantages of this protocol are the aqueous medium reaction, heterogeneous catalytic system, and short reaction time with excellent yield.
- Bora, Sanchay J.,Dutta, Anurag,Goswami, Shyam,Guha, Ankur K.,Paul, Rima,Thakur, Ashim J.
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p. 5454 - 5462
(2020/05/16)
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- A scalable and green one-minute synthesis of substituted phenols
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A mild, green and highly efficient protocol was developed for the synthesis of substituted phenols via ipso-hydroxylation of arylboronic acids in ethanol. The method utilizes the combination of aqueous hydrogen peroxide as the oxidant and H2O2/HBr as the reagent under unprecedentedly simple and convenient conditions. A wide range of arylboronic acids were smoothly transformed into substituted phenols in very good to excellent yields without chromatographic purification. The reaction is scalable up to at least 5 grams at room temperature with one-minute reaction time and can be combined in a one-pot sequence with bromination and Pd-catalyzed cross-coupling to generate more diverse, highly substituted phenols.
- Elumalai, Vijayaragavan,Hansen, J?rn H.
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p. 40582 - 40587
(2020/11/18)
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- Helical Carbenium Ion: A Versatile Organic Photoredox Catalyst for Red-Light-Mediated Reactions
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Red light has the advantages of low energy, less health risks, and high penetration depth through various media. Herein, a helical carbenium ion (N,N′-di-n-propyl-1,13-dimethoxyquinacridinium (nPr-DMQA+) tetrafluoroborate) has been used as an organic photoredox catalyst for photoreductions and photooxidations in the presence of red light (λmax = 640 nm). It has catalyzed red-light-mediated dual transition-metal/photo-redox-catalyzed C-H arylation and intermolecular atom-transfer radical addition through oxidative quenching. Moreover, its potential in photooxidation catalysis has also been demonstrated by successful applications in red-light-induced aerobic oxidative hydroxylation of arylboronic acids and benzylic C(sp3)-H oxygenation through reductive quenching. Thus, a versatile organic photoredox catalyst (helical carbenium ion) for red-light-mediated photoredox reactions has been developed.
- Mei, Liangyong,Veleta, José M.,Gianetti, Thomas L.
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supporting information
p. 12056 - 12061
(2020/08/07)
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- Improved performance of SiO2-supported Ni3Ga intermetallic compound for deoxygenation of phenolic compounds
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Ni/SiO2 and SiO2-supported Ni3Ga and Ni5Ga3 intermetallic compounds were prepared by the sol-gel method and evaluated for the hydrodeoxygenation of various phenolic compounds at 0.1 MPa. In the hydrodeoxygenation of anisole, Ni3Ga/SiO2 was more active for direct deoxygenation to benzene than the corresponding catalyst prepared by the impregnation method as well as Ni/SiO2. The anisole conversion and selectivity to benzene reached 95.1% and 92.5% on Ni3Ga/SiO2 at 300 °C and WHSV of 2 h?1, respectively. In the HDOs of cresols and guaiacol, Ni3Ga/SiO2 still more dominatingly facilitated the direct deoxygenation, while Ni/SiO2 significantly promoted the C-CH3 bond cleavage.
- Chen, Jixiang,Niu, Xiongxiong,Wang, Liwen
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- Nickel-catalyzed removal of alkene protecting group of phenols, alcohols via chain walking process
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An efficient nickel-catalyzed removal of alkene protection group under mild condition with high functional group tolerance through chain walking process has been established. Not only phenolic ethers, but also alcoholic ethers can be tolerated with the retention of stereocenter adjacent to hydroxyl group. The new reaction brings the homoallyl group into a start of new type of protecting group.
- Meng, Chenkai,Niu, Haolin,Ning, Juehan,Wu, Wengang,Yi, Jun
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- Benzylic C?H Functionalisation by [Et3SiH+KOtBu] leads to Radical Rearrangements in o-tolyl Aryl Ethers, Amines and Sulfides
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Reaction of Et3SiH+KOtBu with diaryl ethers, sulfides and amines that feature an ortho alkyl group leads to rearrangement products. The rearrangements arise from formation of benzyl radicals, likely formed through hydrogen atom abstraction by triethylsilyl radicals. The rearrangements involve cyclisation of the benzyl radical onto the partner arene, which, from computation, is the rate determining step. In the case of diaryl ethers, Truce-Smiles rearrangements arise from radical cyclisations to form 5-membered rings, but for diarylamines, cyclisations to form dihydroacridines are observed. (Figure presented.).
- Arokianathar, Jude N.,Kolodziejczak, Krystian,Bugden, Frances E.,Clark, Kenneth F.,Tuttle, Tell,Murphy, John A.
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p. 2260 - 2267
(2020/05/06)
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- Structural features and antioxidant activities of Chinese quince (Chaenomeles sinensis) fruits lignin during auto-catalyzed ethanol organosolv pretreatment
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Chinese quince fruits (Chaenomeles sinensis) have an abundance of lignins with antioxidant activities. To facilitate the utilization of Chinese quince fruits, lignin was isolated from it by auto-catalyzed ethanol organosolv pretreatment. The effects of three processing conditions (temperature, time, and ethanol concentration) on yield, structural features and antioxidant activities of the auto-catalyzed ethanol organosolv lignin samples were assessed individually. Results showed the pretreatment temperature was the most significant factor; it affected the molecular weight, S/G ratio, number of β-O-4′ linkages, thermal stability, and antioxidant activities of lignin samples. According to the GPC analyses, the molecular weight of lignin samples had a negative correlation with pretreatment temperature. 2D-HSQC NMR and Py-GC/MS results revealed that the S/G ratios of lignin samples increased with temperature, while total phenolic hydroxyl content of lignin samples decreased. The structural characterization clearly indicated that the various pretreatment conditions affected the structures of organosolv lignin, which further resulted in differences in the antioxidant activities of the lignin samples. These results can be helpful for controlling and optimizing delignification during auto-catalyzed ethanol organosolv pretreatment, and they provide theoretical support for the potential applications of Chinese quince fruits lignin as a natural antioxidant in the food industry.
- Cheng, Xi-Chuang,Guo, Xin-Ran,Liu, Hua-Min,Liu, Yu-Lan,Qin, Zhao,Wang, Xue-De
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p. 4348 - 4358
(2020/09/22)
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- Photodeoxygenation of phenanthro[4,5-bcd]thiophene S-oxide, triphenyleno[1,12-bcd]thiophene S-oxide and perylo[1,12-bcd]thiophene S-oxide
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Sulfoxides, upon irradiation with ultraviolet (UV) light undergo α-cleavage, hydrogen abstraction, photodeoxygenation, bimolecular photoreduction, and stereo-mutation. The UV irradiation of dibenzothiophene S-oxide (DBTO) yields dibenzothiophene (DBT) as a major product along with ground-state atomic oxygen [O(3P)]. This is a common method for generating O(3P) in solution. The low quantum yield of photodeoxygenation and the requirement of UVA light are drawbacks of using this method. The sulfoxides benzo[b]naphtho-[1,2,d]thiophene S-oxide, benzo[b]naphtho [2,1,d]thiophene S-oxide, benzo[b] phenanthro[9,10-d]thiophene S-oxide, dinaphtho- [2,1-b:1’,2’-d]thiophene S-oxide, and dinaphtho[1,2-b:2’,1’-d]thiophene S-oxide have shown to deoxygenate up to three times faster than DBTO upon UVA irradiation; however, the photodeoxygenation of these sulfoxides does not appear to be limited to the production of O(3P). In this work, phenanthro[4,5-bcd]thiophene S-oxide, triphenyleno[1,12-bcd]thiophene-S-oxide, and perylo[1,12-bcd]thiophene-S-oxide were synthesized and their photodeoxygenation was studied. Phenanthro[4,5-bcd]thiophene-S-oxide, triphenyleno[1,12-bcd]thiophene-S-oxide, and perylo[1,12-bcd]thiophene-S-oxide deoxygenated upon UVA irradiation. However, the common intermediate experiments did not conclusively identify the photodeoxygenation mechanism of these sulfoxides.
- Chintala, Satyanarayana M.,Petroff II, John T.,Barnes, Andrew,McCulla, Ryan D.
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p. 503 - 515
(2019/05/29)
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