- 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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- Aryl phenol compound as well as synthesis method and application thereof
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The invention discloses a synthesis method of an aryl phenol compound shown as a formula (3). All systems are carried out in an air or nitrogen atmosphere, and visible light is utilized to excite a photosensitizer for catalyzation. In a reaction solvent, ArNR1R2 as shown in a formula (1) and water as shown in a formula (2) are used as reaction raw materials and react under the auxiliary action of acid to obtain the aryl phenol compound as shown in a formula (3). The ArNR1R2 in the formula (1) can be primary amine and tertiary amine, can also be steroid and amino acid derivatives, and can also be drugs or derivatives of propofol, paracetamol, ibuprofen, oxaprozin, indomethacin and the like. The synthesis method has the advantages of cheap and easily available raw materials, simple reaction operation, mild reaction conditions, high reaction yield and good compatibility of substrate functional groups. The fluid reaction not only can realize amplification of basic chemicals, but also can realize amplification of fine chemicals, such as synthesis of drugs propofol and paracetamol. The invention has wide application prospect and use value.
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Paragraph 0050-0053
(2021/05/12)
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- Benzene Hydroxylation by Bioinspired Copper(II) Complexes: Coordination Geometry versus Reactivity
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A series of bioinspired copper(II) complexes of N4-tripodal and sterically crowded diazepane-based ligands have been investigated as catalysts for functionalization of the aromatic C-H bond. The tripodal-ligand-based complexes exhibited distorted trigonal-bipyramidal (TBP) geometry (τ, 0.70) around the copper(II) center; however, diazepane-ligand-based complexes adopted square-pyramidal (SP) geometry (τ, 0.037). The Cu-NPy bonds (2.003-2.096 ?) are almost identical and shorter than Cu-Namine bonds (2.01-2.148 ?). Also, their Cu-O (Cu-Owater, 1.988 ? Cu-Otriflate, 2.33 ?) bond distances are slightly varied. All of the complexes exhibited Cu2+ → Cu+ redox couples in acetonitrile, where the redox potentials of TBP-based complexes (-0.251 to -0.383 V) are higher than those of SP-based complexes (-0.450 to -0.527 V). The d-d bands around 582-757 nm and axial patterns of electron paramagnetic resonance spectra [g∥, 2.200-2.251; A∥, (146-166) × 10-4 cm-1] of the complexes suggest the existence of five-coordination geometry. The bonding parameters showed K∥ > K∥ for all complexes, corresponding to out-of-plane πbonding. The complexes catalyzed direct hydroxylation of benzene using 30% H2O2 and afforded phenol exclusively. The complexes with TBP geometry exhibited the highest amount of phenol formation (37%) with selectivity (98%) superior to that of diazepane-based complexes (29%), which preferred to adopt SP-based geometry. Hydroxylation of benzene likely proceeded via a CuII-OOH key intermediate, and its formation has been established by electrospray ionization mass spectrometry, vibrational, and electronic spectra. Their formation constants have been calculated as (2.54-11.85) × 10-2 s-1 from the appearance of an O (π?σ) → Cu ligand-to-metal charge-transfer transition around 370-390 nm. The kinetic isotope effect (KIE) experiments showed values of 0.97-1.12 for all complexes, which further supports the crucial role of Cu-OOH in catalysis. The 18O-labeling studies using H218O2 showed a 92% incorporation of 18O into phenol, which confirms H2O2 as the key oxygen supplier. Overall, the coordination geometry of the complexes strongly influenced the catalytic efficiencies. The geometry of one of the CuII-OOH intermediates has been optimized by the density functional theory method, and its calculated electronic and vibrational spectra are almost similar to the experimentally observed values.
- Anandababu, Karunanithi,Mayilmurugan, Ramasamy,Muthuramalingam, Sethuraman,Velusamy, Marappan
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p. 5918 - 5928
(2020/04/20)
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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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- Direct hydroxylation of benzene and aromatics with H2O2 catalyzed by a self-assembled iron complex: Evidence for a metal-based mechanism
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An iminopyridine Fe(ii) complex, easily prepared in situ by self-assembly of cheap and commercially available starting materials (2-picolylaldehyde, 2-picolylamine, and Fe(OTf)2 in a 2 : 2 : 1 ratio), is shown to be an effective catalyst for the direct hydroxylation of aromatic rings with H2O2 under mild conditions. This catalyst shows a marked preference for aromatic ring hydroxylation over lateral chain oxidation, both in intramolecular and intermolecular competitions, as long as the arene is not too electron poor. The selectivity pattern of the reaction closely matches that of electrophilic aromatic substitutions, with phenol yields and positions dictated by the nature of the ring substituent (electron-donating or electron-withdrawing, ortho-para or meta-orienting). The oxidation mechanism has been investigated in detail, and the sum of the accumulated pieces of evidence, ranging from KIE to the use of radical scavengers, from substituent effects on intermolecular and intramolecular selectivity to rearrangement experiments, points to the predominance of a metal-based SEAr pathway, without a significant involvement of free diffusing radical pathways.
- Capocasa, Giorgio,Olivo, Giorgio,Barbieri, Alessia,Lanzalunga, Osvaldo,Di Stefano, Stefano
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p. 5677 - 5686
(2017/12/07)
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- Hydrolysis of diazonium salts using a two-phase system (CPME and water)
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A new method for the hydrolysis of diazonium salts, without the formation of tar, was developed. A two-phase system consisting of cyclopentyl methyl ether (CPME) and water is very effective for the hydrolysis of diazonium salts. Using this solvent system, the diazonium salt prepared from 3-(4-nitrophenoxy)aniline gave 3-(4-nitrophenoxy)phenol in high yield (96%) within 20 min. The synthesized phenol is an industrially important raw material in polymer syntheses. Furthermore, the use of the present two-phase system of CPME and water successfully brought about the efficient conversions of several m-substituted anilines into the corresponding m-substituted phenols. This is the first example of hydrolysis of diazonium salts using the two-phase system (CPME and water).
- Taniguchi, Toshihide,Imoto, Mitsutaka,Takeda, Motonori,Nakai, Takeo,Mihara, Masatoshi,Iwai, Toshiyuki,Ito, Takatoshi,Mizuno, Takumi,Nomoto, Akihiro,Ogawa, Akiya
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p. 411 - 416
(2018/01/18)
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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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- Catalytic performance of Al-MCM-48 molecular sieves for isopropylation of phenol with isopropyl acetate
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Al-MCM-48 molecular sieves (Si/Al molar ratios = 25, 50, 75, and 100) were synthesized hydrothermally using cetyltrimethylammonium bromide as the structure directing template. The orderly arrangement of mesopores was evident from the low angle X-ray diffr
- Venkatachalam, Kandan,Visuvamithiran, Pitchai,Sundaravel, Balachandran,Palanichamy, Muthiapillai,Murugesan, Velayutham
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experimental part
p. 478 - 486
(2012/07/17)
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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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- Low Triphenylphosphate, High Phosphorous Content Isopropyl Phenyl Phosphates With High Ortho Alkylation
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The present invention relates to low triphenyl phosphate, high phosphorous content aryl phosphates with high ortho alkylation that are suitable for use as flame retardant compositions, processes for their preparation, and their use as flame retardants.
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Page/Page column 9
(2012/01/14)
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- Nickel-catalyzed Negishi cross-coupling reactions of secondary alkylzinc halides and aryl iodides
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A general Ni-catalyzed process for the cross-coupling of secondary alkylzinc halides and aryl/heteroaryl iodides has been developed. This is the first process to overcome the isomerization and β-hydride elimination problems that are associated with the use of secondary nucleophiles, and that have limited the analogous Pd-catalyzed systems. The impact of salt additives was also investigated. It was found that the presence of LiBF4 dramatically improves both isomeric retention and yield for challenging substrates.(Figure Presented)
- Joshi-Pangu, Amruta,Ganesh, Madhu,Biscoe, Mark R.
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supporting information; experimental part
p. 1218 - 1221
(2011/04/27)
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- Reaction of menthol and phenol in the presence of aluminium alkoxides
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Phenol was alkylated with menthol in the presence of organoaluminium catalysts such as aluminium phenoxide and aluminium isopropoxide. Reaction products were isolated and characterized. Certain features of the process were determined.
- Chukicheva,Fedorova,Koroleva,Kuchin
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experimental part
p. 450 - 454
(2009/04/11)
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- Preparation of Hydroperoxides by N-Hydroxyphthalimide-Catalyzed Aerobic Oxidation of Alkylbenzenes and Hydroaromatic Compounds and Its Application
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An efficient approach to phenols and aldehydes through the formation of hydroperoxides from alkylbenzenes was successfully achieved by aerobic oxidation using N-hydroxyphthalimide (NHPI) as a catalyst. The oxidation of various alkylbenzenes with dioxygen by NHPI followed by treatment with a Lewis acid or triphenylphosphine led to phenols or aldehydes, respectively, in good yields. For example, the aerobic oxidation of cumene in the presence of a catalytic amount of NHPI at 75°C and subsequent treatment with H2SO4 gave phenol in 77% yield. 1,4-Dihydroxybenzene (61%) and 4-isopropylphenol (33%) were obtained from 1,4-diisopropylbenzene. On the other hand, dibenzyl ether was converted into phenol or benzaldehyde upon treatment of the resulting hydroperoxide with InCl3 or PPh3, respectively.
- Fukuda, Osamu,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 809 - 813
(2007/10/03)
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- Mechanism of Arene Hydroxylation by Vanadium Picolinato Peroxo Complexes
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The mechanism of the reaction of VO(O2)PIC(H2O)2 (PIC = picolinic acid anion) with benzene and substituted benzenes in CH3CN, affording the corresponding phenols together with dioxygen, has been further investigated.The reaction is a radical chain process whose initiation produces the actual oxidant which may be described as a radical anion derived from the peroxovanadium complex, possessing, however, a marked electrophilic character.In the propagation steps such species react either with the original peroxo complex yielding dioxygen or with the aromatic substrates affording phenols via the formation of an intermediate.
- Bonchio, Marcella,Conte, Valeria,Di Furia, Fulvio,Modena, Giorgio,Moro, Stefano
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p. 6262 - 6267
(2007/10/02)
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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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- 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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- Alumina-Catalyzed Reactions of Hydroxyarenes and Hydroaromatic Ketones. 10. Reaction of Phenol with 2-Propanol
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At 300-350 deg C in the presence of alumina, phenol (1) reacts with excess 2-propanol (37) to give mixed monopropyl-, dipropyl-, and 2,4,6-triisopropyl- (42) phenols. At 300 deg C the principal components of the product mixture are 2-isopropylphenol (26-30 mol percent yield) and 2,6-diisopropylphenol (44-52percent); at 350-400 deg C , they are the isomeric monoisopropylphenols (50-60percent). With 3-isopropylphenol as substrate (instead of 1), 2,5-diisopropylphenol is obtained (79percent), while 4-isopropylphenol gives 2,4-diisopropylphenol and 42 (70percent combined yield). In various runs, 0-20percent of the propyl groups introduced are n-propyl ones. It is proposed that the principal products result from an SN2-type reaction mechanism which involves nucleophilic attack (variously by C-2, C-4, and C-6) of an adsorbed ambident phenoxide ion onto C-2 of an adsorbed isopropoxide group. n-Propylation is ascribed to a side reaction of SN1 type.
- Klemm, LeRoy H.,Taylor, Dennis R.
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p. 4326 - 4329
(2007/10/02)
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- Thermolysis of alkylated 2-cyclohexenones and related monoterpenoid ketones
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2-Cyclohexenone and three methylated cyclohexenones were thermolyzed at 400 deg C for 20 hours to give conversions to products in the range 11 to 45 percent.When three monoterpenes containing the cyclohexenone moiety were thermolyzed under the same conditions the conversions were over 75 percent.The major products formed were alkylated benzenes, alkylated phenols, and double bond isomers of the starting enones.Mechanisms are proposed to account for these products.
- Lange, Gordon L.,Pereira, Vincent A.,Weedle, Michael
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p. 1639 - 1644
(2007/10/02)
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