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All total 1108 Articles be foundApplication of the Savage-Wood Treatment to the Quantitative Analysis of Kinetic Solvent Effects in Highly Aqueous Binary Solutions
Blokzijl, Wilfried,Jager, Jan,Engberts, Jan B. F. N.,Blandamer, Michael J.
, p. 6411 - 6413 (1986)
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A new stilbene glucoside from a Chinese crude drug 'Heshouwu', (root of Polygonum multiflorum Thunb) (Japanese)
Hata,Kozawa,Baba
, p. 211 - 213 (1975)
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Facile electrochemical transformation of diazonium salts into carboxylic acids
Otero, M. Dolores,Batanero, Belen,Barba, Fructuoso
, p. 8215 - 8216 (2006)
The electrolyses of aryldiazonium tetrafluoroborates in dry DMF and Bu4NHSO4 as solvent-supporting electrolyte system, in the presence of CO2 led to the corresponding arylcarboxylic acids in very good yields.
A simple, one-pot oxidative esterification of aryl aldehydes through dialkyl acetal using hydrogen peroxide
Devarajan,Vijayakumar,Ramalingam,Vijayaraghavan
, p. 5849 - 5858 (2016)
A simple and an efficient one-pot procedure has been developed to synthesize various aryl carboxylic esters directly from aryl aldehydes using hydrogen peroxide without any catalyst. The reaction proceeds smoothly at room temperature. A preliminary investigation suggests the formation of dialkyl acetal as an intermediate during the reaction sequence.
Bromate exchange resin as an oxidizing agent in organic synthesis
Chetri, Ajay B.,Kalita, Biswajit,Das, Pranab J.
, p. 3317 - 3319 (2000)
Bromate exchange resin has been prepared by a simple elution technique and used for the oxidation of aromatic aldehydes to the carboxylic acids. Oxidation is carded out under biphasic condition. Work up is simple. Resin immobilized bromate ions have been used for the first time as an oxidizing agent in organic synthesis.
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Frimer et al.
, p. 4631,4632, 4634 (1977)
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Green and simple synthesis of p-anisic acid and other analogs from methyl paraben
Periyasamy, Senthil,Subbiah, Selvaraj
, p. 85 - 88 (2018)
Synthesis of p-anisic acid from commercially available methyl paraben was obtained in good yield and performed the each steps in shorter duration is reported. The E-factor was evaluated for each step was 3.0 and 2.30 respectively without transition metals content in the waste disposal. The solvents used in each steps were completely recovered and recycled in the consecutive batches. This methodology was applied to the synthesis of p-ethoxy benzoic acid and p-propyloxy benzoic acid and the other derivatives from methyl paraben obtained in good yield.
Dithioester-enabled chemodivergent synthesis of acids, amides and isothiazoles via C[sbnd]C bond cleavage and C[sbnd]O/C[sbnd]N/C[sbnd]S bond formations under metal- and catalyst-free conditions
Soni, Sonam,Koley, Suvajit,Singh, Maya Shankar
, p. 2512 - 2516 (2017)
An operationally simple and user-friendly process to access privileged scaffolds such as acids, amides and isothiazoles has been devised employing β-ketodithioesters for the first time. Remarkably, the new protocol involves combination of C[sbnd]C bond cl
Aquachlororuthenium(III) catalysis in the oxidation of substituted 4-oxo-4-arylbutanoic acids by bromate in acid medium: A kinetic and mechanistic study and validity of linear free-energy relationships
Manjari, Padma Sunitha,Reddy, Cherkupally Sanjeeva
, p. 707 - 719 (2011)
Ru(III) acts an efficient catalyst in the oxidation of substituted 4-oxo-4-arylbutanoic acids (4-oxo acids) by bromate in sulfuric acid medium, giving the corresponding benzoic acids in quantitative yields. The reaction shows first-order dependence in both [bromate] and [H2SO 4], and a non-linear dependence on both [oxo acid] and [catalyst]. Changing solvent from H2O to D2O increases the rate. The rate is not affected by ionic strength but decreases with increase in dielectric constant of the medium. Electron-releasing substituents in the phenyl ring of the substrate greatly accelerate the rate, whereas the retardation by electron-withdrawing substituents, though perceptible, is small. The linear free-energy relationship is characterized by smooth curves in Hammett plots of log k versus σ; however, linear plots are obtained with excellent correlation coefficients at all the studied temperatures, when Brown's σ+ values are used. The reaction constant is negative and decreases with increase in temperature. From the intersection of the lines in the Hammett and Arrhenius plots, the isokinetic relationship is evaluated. A mechanism involving a cyclic oxidant-substrate-catalyst ternary complex is proposed, in which both C-C bond-breaking and C-O bond formation are involved, and the oxidation state of Ru(III) remains unchanged. A rate law explaining all the kinetic results has been derived and verified. The reaction is an example of neighboring group participation in intramolecular catalysis and is potentially useful for the synthesis of substituted benzoic acids.
Palladium catalyzed carbonylation of iodoarenes in aqueous solubilized systems
Cheprakov, Andrei V.,Ponomareva, Natalia V.,Beletskaya, Irina P.
, p. 297 - 300 (1995)
Iodobenzene and substituted iodobenzenes can be easily carbonylated into benzoic acids under mild conditions, with simple palladium salts as catalysts and normal pressure of CO, by using aqueous microemulsions of the oil-in water kind as the reaction media.Surfactants of all three kinds, anionic, nonionic, and cationic, and simple aliphatic alcohols can be used to form the microemulsion media for carbonylation.The use of nonionic surfactants, the derivatives of polyethyleneglycol, is the most advantageous method as the surfactant is highly efficient in small amountswithout a cosurfactant because of its strong solubilizing ability.Keywords: Palladium; Carbon monoxide; Carbonylation; Water
Combining Oxoammonium Cation Mediated Oxidation and Photoredox Catalysis for the Conversion of Aldehydes into Nitriles
Nandi, Jyoti,Witko, Mason L.,Leadbeater, Nicholas E.
, p. 2185 - 2190 (2018)
A method to oxidize aromatic aldehydes to nitriles has been developed. It involves a dual catalytic system of 4-acetamido-TEMPO and visible-light photoredox catalysis. The reaction is performed using ammonium persulfate as both the terminal oxidant and nitrogen source.
Hydrothermal synthesis of platinum-group-metal nanoparticles by using HEPES as a reductant and stabilizer
So, Man-Ho,Ho, Chi-Ming,Chen, Rong,Che, Chi-Ming
, p. 1322 - 1331 (2010)
Platinum-group-metal (Ru, Os, Rh, Ir, Pd and Pt) nanoparticles are synthesized in an aqueous buffer solution of 4-(2-hydroxyethyl)-1-piper- azineethanesulfonic acid (HEPES) (200 mM, pH 7.4) under hydrothermal conditions (180 °C). Monodispersed (monodisper
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Cahours
, (1845)
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Rapid chemoselective deprotection of benzyl esters by nickel boride
Khurana, Jitender M.,Arora, Reema
, p. 1127 - 1130 (2009)
Benzyl esters of a variety of acids can be chemoselectively cleaved on treatment with nickel boride in methanol at ambient temperature to give the parent carboxylic acids in high yields. Other protecting functionalities such as methyl, ethyl, tert-butyl, and trityl esters as well as benzyl ethers, tert-butyl ethers, and Nbenzylamides are unaffected under these conditions. Georg Thieme Verlag Stuttgart.
Copper catalyzed oxidation of benzylic alcohols in water with H 2O2
Ahmad, Jahir Uddin,R?is?nen, Minna T.,Leskel?, Markku,Repo, Timo
, p. 180 - 187 (2012)
A straightforward, efficient and sustainable copper catalyzed method was developed for oxidation of benzylic alcohols with 30% H2O2 in water. The reaction proceeded with CuSO4 catalyst (1 mol%) at 100 °C without additional base or ligand. Primary benzylic alcohols were converted almost quantitatively to aldehydes with 70-90% selectivity, corresponding acids being the major side products. Also secondary benzylic alcohols afforded the corresponding ketones in high conversion with selectivities greater than 90%. It was demonstrated that the CuSO4 catalyst can be recycled and reused at least for three runs, even though with some loss of catalytic activity. Selectivity of the CuSO4 based catalyst system could be further increased by using 2-N-(p-fluorophenyl)- pyrrolecarbaldimine (1) as a ligand in combination with TEMPO in K 2CO3 solution. The catalyst system was individually optimized (1 mol% CuSO4, 2 mol% 1, 0.1 M K2CO3 and 5 mol% TEMPO) for a wide range of benzylic and allylic alcohols, which were quantitatively and selectively converted into the corresponding aldehydes with 3 eq. of H2O2 in 1 h.
A Woven Supramolecular Metal-Organic Framework Comprising a Ruthenium Bis(terpyridine) Complex and Cucurbit[8]uril: Enhanced Catalytic Activity toward Alcohol Oxidation
Li, Zhan-Ting,Liu, Yi,Wang, Hui,Wang, Ze-Kun,Xu, Zi-Yue,Zhang, Dan-Wei,Zhang, Yun-Chang
, p. 1498 - 1503 (2020)
The self-assembly of a diamondoid woven supramolecular metal–organic framework wSMOF-1 has been achieved from intertwined [Ru(tpy)2]2+ (tpy=2,2′,6′,2′′-terpyridine) complex M1 and cucurbit[8]uril (CB[8]) in water, where the intermolecular dimers formed by the appended aromatic arms of M1 are encapsulated in CB[8]. wSMOF-1 exhibits ordered pore periodicity in both water and the solid state, as confirmed by a combination of 1H NMR spectroscopy, UV-vis absorption, isothermal titration calorimetry, dynamic light scattering, small angle X-ray scattering and selected area electron diffraction experiments. The woven framework has a pore aperture of 2.1 nm, which allows for the free access of both secondary and primary alcohols and tert-butyl hydroperoxide (TBHP). Compared with the control molecule [Ru(tpy)2]Cl2, the [Ru(tpy)2]2+ unit of wSMOF-1 exhibits a remarkably higher heterogeneous catalysis activity for the oxidation of alcohols by TBHP in n-hexane. For the oxidation of 1-phenylethan-1-ol, the yield of acetophenone was increased from 10 percent to 95 percent.
Photo-tunable oxidation of toluene and its derivatives catalyzed by TBATB
Mardani, Atefeh,Kazemi, Foad,Kaboudin, Babak
, (2021)
In this report, tetrabutylammonium tribromide (TBATB) was introduced as an efficient visible light active catalyst to carry out the aerobic oxidation of toluene, its derivatives, and some of methyl arenes to benzaldehydes, benzoic acids and ketones in good to high yields. All the oxidation reactions were performed under mild conditions using oxygen as a green oxidant, a catalytic amount of TBATB under blue (460 nm), royal blue (430 nm), and violet LED (400 nm) irradiation. It was found that the reactions selectivity was significantly affected by changing the solvent (from CH3CN to EtOAc) and LED wavelength (from blue to violet). In the following, our mechanistic studies revealed that the visible light oxidation of toluenes and methyl arenes over TBATB could be following a benzyl peroxy radical intermediate.
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Kharasch,Fuchs
, p. 292,294 (1945)
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Carbon nitride-catalyzed oxidative cleavage of carbon-carbon bond of α-hydroxy ketones with visible light and thermal radiation
Zhan, Haiying,Liu, Wenjie,Fu, Minling,Cen, Jinghe,Lin, Jingxin,Cao, Hua
, p. 184 - 189 (2013)
Mesoporous carbon nitride (mpg-C3N4) as a photocatalyst showed higher photocatalytic activities in organic synthesis. Herein we reported a mpg-C3N4-catalyzed oxidation of α-hydroxy ketones to synthesize benzoic acids with visible light. This reaction represented a green and facile route to synthesize benzoic acids for which catalytic approaches were scarce.
Cobalt(II)-Catalyzed Reaction of Aldehydes with Acetic Anhydride under an Oxygen Atmosphere: Scope and Mechanism
Bhatia, Beena,Punniyamurthy, T.,Iqbal, Javed
, p. 5518 - 5523 (1993)
The reaction of aldehydes with acetic anhydride in the presence of catalytic cobalt(II) chloride under an oxygen atmosphere at ambient temperature is dependent upon the reaction medium.Aliphatic aldehydes react in acetonitrile to give 1,2-diones whereas the aromatic aldehydes are acylated to yield the corresponding acylals.On the other hand, carboxylic acids are obtained from aliphatic and aromatic aldehydes by conducting the reaction in dichloroethane or benzene.Cobalt(II) chloride in acetonitrile catalyzes the conversion of aliphatic aldehydes to the correspondinganhydrides in the absence of acetic anhydride whereas aromatic aldehydes remain largely unaffected under these conditions.A preliminary mechanistic study in three different solvents (i.e. acetonitrile, dichloroethane, and DMF) has revealed that in acetonitrile and in the presence of acetic anhydride, aliphatic aldehydes behave differently than aromatic aldehydes.Some trapping experiments using methyl acrylate and stilbene have been conducted to demonstrate the occurence of an acyl cobalt and peroxyacyl cobalt intermediate during these reactions.
A new, highly selective synthesis of aromatic aldehydes by aerobic free-radical oxidation of benzylic alcohols, catalysed by n-hydroxyphthalimide under mild conditions. Polar and enthalpic effects
Minisci, Francesco,Punta, Carlo,Recupero, Francesco,Fontana, Francesca,Pedulli, Gian Franco
, p. 688 - 689 (2002)
A new selective synthesis of aromatic aldehydes is described, based on catalytic oxidation of benzyl alcohols with molecular oxygen at rt and atmospheric pressure.
Transition-Metal-Free carboxylation of organozinc reagents using CO 2 in DMF solvent
Kobayashi, Koji,Kondo, Yoshinori
, p. 2035 - 2037 (2009)
An efficient process for the carboxylation of functionalized organozinc reagents with CO2 under transition-metal-free conditions was developed by employing DMF solvent in the presence of LICl.
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Hauser,Swamer,Ringler
, p. 4023,4025 (1948)
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Metal-Organic Framework Based on Heptanuclear Cu-O Clusters and Its Application as a Recyclable Photocatalyst for Stepwise Selective Catalysis
Zhou, Jie,Huang-Fu, Xu,Huang, Yang-Ying,Cao, Chu-Ning,Han, Jie,Zhao, Xiao-Li,Chen, Xu-Dong
, p. 254 - 263 (2020)
Visible-light driven photoreactions using metal-organic frameworks (MOFs) as catalysts are promising with regard to their environmental friendly features such as the use of renewable and sustainable energy of visible light and potential catalyst recyclability. To develop potential heterogeneous photocatalysts, a family of three copper(II) coordination polymers bearing different Cu-O assemblies have been synthesized with the ligand 4,4-disulfo-[1,1-biphenyl]-2,2-dicarboxylate acid (H4DSDC), namely, {[Cu7(DSDC)2(OH)6(H2O)10]·xH2O}n (1), {[Cu4(DSDC)(4,4-bpy)2(OH)4]·2H2O}n (2), and {Cu2(DSDC)(phen)2(H2O)2}n (3) (4,4-bpy = 4,4-bipyridine and phen = 1,10-phenanthroline). Complex 1 represents a metal-organic framework featuring a NbO type topology constructed from the infinite linkage of heptanuclear [Cu7(μ3-OH)6(H2O)10]8+ clusters by deprotonated DSDC4- ligands, comprising one-dimensional hexagonal channels of a diameter around 11 ? that are filled with water molecules. The infinite waving {[Cu2(OH)2]2+}n ladderlike chains in complex 2 are bridged by DSDC4- and 4,4-bpy ligands into a three-dimensional framework. A two-dimensional layered structure is formed in complex 3 due to the existence of terminal phenanthroline ligands. All of the coordination polymers 1-3 are able to catalyze the visible-light driven oxidation of alcohols at mild conditions using hydrogen peroxide as an oxidant, in which complex 1 demonstrates satisfactory efficiency. Significantly for this photoreaction catalyzed by 1, the extent of oxidation over aryl primary alcohols is fully controllable with time-resolved product selectivity, giving either corresponding aldehydes or carboxylate acids in good yields. It is also remarkable that the photocatalyst could be recovered almost quantitatively on completion of the catalytic cycle without any structure change, and could be recycled for catalytic use for at least five cycles with constant efficiency. This photocatalyst with time-resolved selectivity for different products may provide new insight into the design and development of novel catalytic systems.
Oxidation of Primary Alcohols and Aldehydes to Carboxylic Acids via Hydrogen Atom Transfer
Tan, Wen-Yun,Lu, Yi,Zhao, Jing-Feng,Chen, Wen,Zhang, Hongbin
, p. 6648 - 6653 (2021)
The oxidation of primary alcohols and aldehydes to the corresponding carboxylic acids is a fundamental reaction in organic synthesis. In this paper, we report a new chemoselective process for the oxidation of primary alcohols and aldehydes. This metal-free reaction features a new oxidant, an easy to handle procedure, high isolated yields, and good to excellent functional group tolerance even in the presence of vulnerable secondary alcohols and tert-butanesulfinamides.
A Mild Heteroatom (O -, N -, and S -) Methylation Protocol Using Trimethyl Phosphate (TMP)-Ca(OH) 2Combination
Tang, Yu,Yu, Biao
, (2022/03/27)
A mild heteroatom methylation protocol using trimethyl phosphate (TMP)-Ca(OH)2combination has been developed, which proceeds in DMF, or water, or under neat conditions, at 80 °C or at room temperature. A series of O-, N-, and S-nucleophiles, including phenols, sulfonamides, N-heterocycles, such as 9H-carbazole, indole derivatives, and 1,8-naphthalimide, and aryl/alkyl thiols, are suitable substrates for this protocol. The high efficiency, operational simplicity, scalability, cost-efficiency, and environmentally friendly nature of this protocol make it an attractive alternative to the conventional base-promoted heteroatom methylation procedures.
Mechanochemical Grignard Reactions with Gaseous CO2 and Sodium Methyl Carbonate**
Pfennig, Victoria S.,Villella, Romina C.,Nikodemus, Julia,Bolm, Carsten
supporting information, (2022/01/22)
A one-pot, three-step protocol for the preparation of Grignard reagents from organobromides in a ball mill and their subsequent reactions with gaseous carbon dioxide (CO2) or sodium methyl carbonate providing aryl and alkyl carboxylic acids in up to 82 % yield is reported. Noteworthy are the short reaction times and the significantly reduced solvent amounts [2.0 equiv. for liquid assisted grinding (LAG) conditions]. Unexpectedly, aryl bromides with methoxy substituents lead to symmetric ketones as major products.
Urchin-like Nb2O5 hollow microspheres enabling efficient and selective photocatalytic C–C bond cleavage in lignin models under ambient conditions
Chen, Huan,Hong, Donghui,Long, Donghui,Niu, Bo,Wan, Kun,Wang, Junjie,Zhang, Yayun
supporting information, (2022/03/27)
Selective cleavage of robust C?C bonds to harvest value-added aromatic oxygenates is an intriguing but challenging task in lignin depolymerization. Photocatalysis is a promising technology with the advantages of mild reaction conditions and strong sustainability. Herein, we show a novel urchin-like Nb2O5 hollow microsphere (U-Nb2O5 HM), prepared by one-pot hydrothermal method, are highly active and selective for Cα?Cβ bond cleavage of lignin β-O-4 model compounds under mild conditions, achieving 94% substrate conversion and 96% C?C bond cleavage selectivity. Systematic experimental studies and density functional theory (DFT) calculations revealed that the superior performance of U-Nb2O5 HMs arises from more exposed active sites, more efficient free charge separation and the active (001) facet, which facilitates the activation of Cβ?H bond of lignin models and generate key Cβ radical intermediates by photogenerated holes, further inducing the Cα?Cβ bond cleavage to produce aromatic oxygenates. This work could provide some suggestions for the fabrication of hierarchical photocatalysts in the lignin depolymerization system.
