- Palladium-catalyzed ortho-C-H hydroxylation of benzoic acids
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A simple Pd(OAc)2 catalyzed ortho-hydroxylation of benzoic acids using TBHP as the sole oxidant has been explored. This protocol features relatively broad substrate scope and operational simplicity. The compatibility of ortho-substituted substrates is an effective complement to the previous ortho-hydroxylation reaction.
- Luo, Feihua,He, Shuhua,Gou, Quan,Chen, Jinyang,Zhang, mingzhong
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- Catalytic oxidation of alcohols and alkyl benzenes to carbonyls using Fe3O4?SiO2?(TEMPO)-: Co -(Chlorophyll-CoIII) as a bi-functional, self-co-oxidant nanocatalyst
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Chlorophyll b was extracted from heliotropium europaeum plant, demetalated, allylated and grafted to acrylated TEMPO through a copolymerization protocol. Then, the chlorophyll monomers were coordinated to Co ions, immobilized on magnetic nanoparticles and the resulting hybrid was used as a powerful catalyst for a variety of oxidation reactions. By using the present method, oxidation of benzylic alcohols and alkyl benzenes to carbonyls was accomplished in water under aerobic conditions. Moreover, direct oxidation of alcohols to carboxylic acids was performed by adding NaOCl to the mixture. All entries were oxidized to the corresponding desired product with high to excellent yields and up to 97% selectivity. The catalyst was thoroughly characterized by CV, TGA, VSM, XRD, XPS, DLS, FE-SEM, TEM, UV-Vis, EDX, and BET analyses. The activity of the catalyst was investigated by applying various components of the catalyst to the oxidation model separately. The reasonable mechanisms are suggested based on the cooperation between the TEMPO groups and cobalt(iii) (or Co(iv)) sites on the catalyst. The catalyst could be recovered and reused for at least 7 consecutive recycles without any considerable reactivity loss. This journal is
- Hamah-Ameen, Baram Ahmed,Kazemnejadi, Milad,Mahmoudi, Boshra,Rostami, Amin
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p. 6600 - 6613
(2020/11/16)
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- Fe3O4@SiO2@Im[Cl]Mn(III)-complex as a highly efficient magnetically recoverable nanocatalyst for selective oxidation of alcohol to imine and oxime
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An efficient and environmentally friendly oxidation process for the one-pot preparation of oxime, imine and carbonyl compounds through alcohol oxidation in the presence of H2O2 and/or O2 have been developed by a melamine-Mn(III) Schiff base complex supported on Fe3O4@SiO2–Cl nanoparticles, named as Fe3O4@SiO2@Im[Cl]Mn(III)-complex nanocomposite, at room temperature. Direct oxidation of alcohol to carboxylic acid was performed using the catalyst in the presence of molecular O2 at room temperature in a different approach. The oxidation products were obtained with excellent yields and high TOFs. The properties of the catalyst were characterized by Fourier transform infrared spectroscopy (FTIR), elemental analysis (C, H, N), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), inductive coupled plasma (ICP), cyclic voltammetry (CV), nuclear magnetic resonance (1H & 13C NMR), vibration sample magnetometer (VSM), Brunauer– Emmett–Teller (BET) and differential pulse voltammetry (DPV) analyses. The mechanism of the oxidation processes was investigated for the both H2O2 and O2 oxidants. The role of the imidazolium moiety in the catalyst as a secondary functionality was investigated. Chemoselectivity behavior of the catalyst was studied by some combinations. The catalyst could be recycled from the reaction mixture by a simple external magnet and reused for several times without any considerable reactivity loss.
- Kazemnejadi, Milad,Alavi, Seyyedeh Ameneh,Rezazadeh, Zinat,Nasseri, Mohammad Ali,Allahresani, Ali,Esmaeilpour, Mohsen
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p. 230 - 249
(2019/03/28)
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- Sodium perborate/NaNO2/KHSO4-triggered synthesis and kinetics of nitration of aromatic compounds
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Sodium perborate (SPB) was used as efficient green catalyst for NaNO2/KHSO4-mediated nitration of aromatic compounds in aqueous acetonitrile medium. Synthesis of nitroaromatic compounds was achieved under both conventional and solvent-free microwave conditions. Reaction times were comparatively shorter in the microwave-assisted than conventional reaction. The reaction kinetics for nitration of phenols in aqueous bisulfate and acetonitrile medium indicated first-order dependence on [Phenol], [NaNO2], and [SPB]. Reaction rates accelerated with introduction of electron-donating groups but retarded with electron-withdrawing groups. Kinetic results did not fit well quantitatively with Hammett’s equation. Observed deviations from linearity were addressed in terms of exalted Hammett’s constants (σˉ or σeff), para resonance interaction energy (ΔΔGp) parameter, and Yukawa–Tsuno parameter (r). This term provides a measure of the extent of resonance stabilization for a reactive structure that builds up charge (positive) in its transition state. The observed negative entropy of activation (?ΔS#) suggests greater solvation and/or cyclic transition state before yielding products.
- Rajanna,Muppidi, Suresh,Pasnoori, Srinivas,Saiprakash
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p. 6023 - 6038
(2018/09/21)
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- Potassium Periodate/NaNO2/KHSO4-Mediated Nitration of Aromatic Compounds and Kinetic Study of Nitration of Phenols in Aqueous Acetonitrile
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Synthesis and kinetics of potassium periodate(KIO4)/NaNO2/KHSO4)-initiated nitration of aromatic compounds have been studied in aqueous acetonitrile medium. Synthesis of nitroaromatic compounds is achieved under conventional and solvent-free microwave conditions. Reaction times in microwave-assisted reaction are comparatively less than in conventional reaction. The reaction kinetics for the nitration of phenols in aqueous bisulfate and acetonitrile medium indicated first-order dependence on [phenol], [NaNO2], and [KIO4]. An increase in [KHSO4] accelerated the rate of nitration under otherwise similar conditions. The rate of nitration increased in the solvent of high dielectric media (solvents with high dielectric constant (D)). Observed results were in accordance with Amis and Kirkwood plots [log k′ vs. (1/D) and [(D ? 1)/(2D + 1)]. These observations probably indicate the participation of anionic species and molecular or (dipolar) species in the rate-determining step. In addition, the plots of (log k′) versus volume% of organic solvent were also linear, which probably indicate the importance of both electrostatic and nonelectrostatic forces, solvent–solute interactions during nitration of phenols. Reaction rates accelerated with the introduction of electron-donating groups and retarded with electron-withdrawing groups, but results could not be quantitatively correlated with Hammett's equation and depicted deviations from linearity. These deviations could probably be attributed to cumulative effects arising inductive, resonance, and steric effects. Leffler's plot (ΔH# vs. ΔS#) was found linear indicating the compensation (cumulative) effect of both enthalpy and entropy parameters in controlling the mechanism of nitration.
- Sriram, Y. Hemanth,Fatima, Touheeth,Rajanna,Kumar, M. Satish,Raju, R. Madhusudan
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supporting information
p. 622 - 632
(2017/06/30)
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- Methyl salicylate as a selective methylation agent for the esterification of carboxylic acids
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Methyl salicylate is a selective and inexpensive methylating agent for the esterification of carboxylic acids with a wide range of functional group tolerance. The intramolecular hydrogen bonds between the carboxylate and hydroxyl groups in methyl salicylate are essential for the transformation. Allyl, benzyl, methallyl, and propargyl salicylates can also be used as alkylating agents for the preparation of the corresponding alkyl carboxylates.
- Chen, Si,Jia, Lei,Li, Xiaonan,Luo, Meiming
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p. 263 - 268
(2014/03/21)
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- PD(II)-CATALYZED HYDROXYLATION OF ARENES WITH O2 OR AIR
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Pd (II) -catalyzed ortho-hydroxylat ion of variously substituted aromatic carboxylic acids under O2 or air is achieved under non-acidic conditions. Extensive labeling studies support a direct oxygenation of aryl C-H bonds with molecular oxygen.
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Page/Page column 14; 19-20
(2011/04/24)
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- Pd(II)-catalyzed hydroxylation of arenes with 1 atm of O2 or air
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(Chemical Equation Presented) Pd(II)-catalyzed ortho-hydroxylation of variously substituted benzoic acids under 1 atm of O2 or air is achieved under nonacidic conditions. Extensive labeling studies support a direct oxygenation of aryl C-H bonds with molecular oxygen.
- Zhang, Yang-Hui,Yu, Jin-Quan
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supporting information; experimental part
p. 14654 - 14655
(2010/01/06)
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- Iron-promoted ortho-And/or ipso-hydroxylation of benzoic acids with H 2O2
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Regioselective hydroxylation of aromatic acids with hydrogen peroxide proceeds readily in the presence of iron(II) complexes with tetradentate aminopyridine ligands [FeII(BPMEN)-(CH3CN) 2](ClO4)2 (1) and [FeII(TPA)- (CH3CN)2](OTf)2 (2), where BPMEN=N, N'-dimethyl-N, N'-bis(2-pyridylmethyl)-1,2-ethylenediamine, TPA=tris-(2- pyridylmethyl)amine. Two cis-sites, which are occupied by labile acetonitrile molecules in 1 and 2, are available for coordination of H2O 2 and substituted benzoic acids. The hydroxylation of the aromatic ring occurs exclusively in the vicinity of the anchoring carboxylate functional group: ortho-hydroxylation affords salicylates, whereas ipso-hydroxylation with concomitant decarboxylation yields phenolates. The outcome of the substituent directed hydroxylation depends on the electronic properties and the position of substituents in the molecules of substrates:3-substituted benzoic acids are preferentially ortho-hydroxylated, whereas 2-and, to a lesser extent, 4-substituted substrates tend to undergo ipso-hydroxylation/decarboxylation. These two pathways are not mutually exclusive and likely proceed via a common intermediate. Electron-withdrawing substituents on the aromatic ring of the carboxylic acids disfavor hydroxylation, indicating an electrophilic nature for the active oxidant. Complexes 1 and 2 exhibit similar reactivity patterns, but 1 generates a more powerful oxidant than 2. Spectroscopic and labeling studies exclude acylperoxoiron(III) and FeIV=O species as potential reaction intermediates, but strongly indicate the involvement of an FeIII-OOH intermediate that undergoes intramolecular acid-promoted heterolytic O-O bond cleavage, producing a transient iron(V) oxidant.
- Makhlynets, Olga V.,Das, Parthapratim,Taktak, Sonia,Flook, Margaret,Mas-Balleste, Ruben,Rybak-Akimova, Elena V.,Que Jr., Lawrence
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experimental part
p. 13171 - 13180
(2010/07/03)
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- Regio- and chemoselective enzymatic N-oxygenation in vivo, in vitro, and in flow
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(Chemical Equation Presented) Action by the para: Evaluation of the nitro-group-forming N-oxygenase AurF in vivo, in vitro, and immobilized as a fusion protein with simply H2O2 as oxidant (peroxide shunt) reveals para-regioselective oxygenation of aromatic amines (see scheme). This effect includes the selective oxygenation of diamino compounds.
- Winkler, Robert,Richter, Martin E. A.,Knuepfer, Uwe,Merten, Dirk,Hertweck, Christian
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p. 8016 - 8018
(2007/10/03)
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- AMIDE DERIVATIVES AND THEIR USE AS INHIBITORS OF 11-BETA-HYDROXYSTEROID DEHYDROGENASE TYPE 1
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Compounds of the formula (I) provide pharmacological agents which lower intracellular glucocorticoid concentrations in mammals, in particular, intracellular cortisol levels in humans. Therefore, the compounds of the instant invention improve insulin sensitivity in the muscle and the adipose tissue, and reduce lipolysis and free fatty acid production in the adipose tissue. The compounds of the invention lower hepatic glucocorticoid concentration in mammals, in particular, hepatic cortisol concentration in humans, resulting in inhibition of hepatic gluconeogenesis and lowering of plasma glucose levels. Thus, the compounds of the instant invention may be particularly useful in mammals as hypoglycemic agents for the treatment and prevention of conditions in which hyperglycemia and/or insulin resistance are implicated, such as type-2 diabetes. The compounds of the invention may also be used to treat other glucocorticoid associated disorders, such as Syndrome-X, dyslipidemia, hypertension and central obesity. The invention furthermore relates to the use of the compounds according to the invention for the preparation of medicaments, in particular of medicaments useful for the treatment and prevention of glucocorticoid associated disorders, by improving insulin sensitivity, reducing plasma glucose levels, reducing lipolysis and free fatty acid production, and by decreasing visceral adipose tissue formation.
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- Bridged bicyclic amine derivatives useful as CCR-3 receptor antagonists
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Compounds having the formula (I), Ar—(F)(E)-(CR3R4)—(CHR5)m-(T)-(Q)-Ar1, are useful as CCR-3 receptor antagonists, wherein T is a bridged heterocyclyl group having one N atom and a bridge of one to two bridgehead carbon atoms; Ar and Ar1 are aryl or heteroaryl; F is alkylene, alkenylene, or a bond; E is —C(═O)N(R10)—, —SO2N(R10)—, —N(R11)C(═O)N(R10O)—, —N(R11)SO2N(R10)—, —N(R11)C(═S)N(R10)—, —N(R11)C(═O)—, —N(R11)SO2—, —N(R12)C(═O)CH(R13)—, or CH(R13)C(═O)N(R12)—; Q is —C(═O)— or C1-2alkylene; and R3, R4, R5, R9, R10, R11, R12, and R13 are defined as set forth in the specification.
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Page/Page column 8; 9; 10
(2010/02/08)
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- Design and synthesis of novel CCR3 antagonists
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As part of our investigation into the development of potent CCR3 antagonists, a series of piperidine analogues was designed and prepared. Exploration of the piperidine core examined both the basicity and the location of a nitrogen, as well as conformational variants. The bicyclo-piperidine 24c was found to be the most potent inhibitor of CCR3 with an IC50 of 0.0082 μM in the binding assay and 0.0024 μM in the chemotaxis assay.
- Gong, Leyi,Hogg, J. Heather,Collier, James,Wilhelm, Robert S.,Soderberg, Carol
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p. 3597 - 3600
(2007/10/03)
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- Synthesis of salicylic acid derivatives in presence of ultrasonic irradiation using water as solvent
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An improved synthesis of salicylic acid using ultrasonic irradiation and water as solvent can be achieved with copper and pyridine as catalysts. A number of salicylic acids were prepared in good yield and in a short reaction time.
- Docampo Palacios, Maite L.,Pellon Comdom, Rolando F.
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p. 1783 - 1787
(2007/10/03)
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- Synthesis of salicylic acid derivatives from the corresponding 2-chlorobenzoic acid using water as solvent
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An improved synthesis of salicylic acid using water as solvent can be achieved using the Ullmann-Goldberg reaction conditions in presence of pyridine as cocatalyst. A number of salicylic acids were prepared in good yield.
- Pellon Comdom, Rolando F.,Docampo Palacios, Maite L.
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p. 2055 - 2059
(2007/10/03)
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- Synthesis and antitumor activity of fused quinoline derivatives. IV. Novel 11-aminoindolo[3,2-b]quinolines
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Indolo[3,2-b]quinoline derivatives (1) having various amine moieties were prepared and their antitumor activities against P388 leukemia in mice were evaluated, for the purpose of gaining an insight into the role of the amine moiety in the antitumor activity and searching for an effective amine moiety. Introduction of a methylene group between the phenyl group and amino or methanesulfonamido group resulted in decrease or loss of activity.
- Takeuchi, Yasuo,Oda, Toshiaki,Chang, Ming-Rong,Okamoto, Yoko,Ono, Junko,Oda, Yoko,Harada, Kyoko,Hashigaki, Kuniko,Yamato, Masatoshi
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p. 406 - 411
(2007/10/03)
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- A New Class of Phospholipase A2 Substrates: Kinetics of the Phospholipase A2 Catalyzed Hydrolysis of 3-(Acyloxy)-4-nitrobenzoic Acids
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3-(Acyloxy)-4-nitrobenzoic acids were synthesized with acyl groups ranging from butyryl to dodecanoyl.All these compounds yielded monomeric solutions in water with 1.6percent (v/v) acetonitrile in the neutral pH range, and they were hydrolyzed by catalytic amounts of phospholipases A2 from a variety of sources as shown by the spectral change at 425 nm due to the appearance of nitrophenolate ion.Most of the kinetic studies were performed using Agkistrodon piscivorus piscivorus phospholipase A2, but similar results were obtained with porcine pancreatic and Crotalus atrox phospholipase A2.The catalytic reaction requires the presence of Ca2+, but unlike the hydrolysis of lecithins, the hydrolysis of these substrates also occurs in the presence of Ba2+ and Sr2+, while Mg2+ and Zn2+ are not catalytically competent.Increasing the acyl chain length increases the enzymatic rate mainly by enhancing the hydrophobic interaction in the E-Ca2+-S complex.Among structural isomers of the octanoyl compound, 3-nitro-4-(octanoyloxy)benzoic acid shows the highest specificity toward the enzyme, suggesting that it is in this compound that the distance between the negatively charged carboxylate and the reactive ester approximates best that found in the lecithin-enzyme complex.All kinetic characteristics of the enzymatic hydrolysis indicate that the reaction occurs by the same mechanism as that of the hydrolysis of lecithins.The highest catalytic efficiency observed with this series of substrates occurs with 3-dodecanoyl-4-nitrobenzoic acid, and the second-order rate constant of this reaction (kcat/Km = 9.1 x 1E+4 M-1 s-1) is only 1 order of magnitude lower than that of the hydrolysis of egg phosphatidylcholine in unilamellar vesicles.The reactivity of all isomers, especially that of the p-carboxy ester, shows that Ca2+ does not act as a catalyst in the phospholipase A2 catalyzed hydrolysis but rather serves to bind and orient the substrate at the active site of the enzyme.The octanoyl compounds, 1 and 2, are ideally suited for a rapid and sensitive spectrophotometric assay of phospholipases A2, and the conditions for the assay are described.
- Cho, Wonhwa,Markowitz, Michael A.,Kezdy, Ferenc J.
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p. 5166 - 5171
(2007/10/02)
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