- Oxidation of Substituted Benzyl Alcohols by Pyridinium Fluorochromate: A Kinetic Study
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The kinetics of the oxidation of 30 monosubstituted benzyl alcohols to the corresponding benzaldehydes by pyridinium fluorochromate (PFC) have been studied.The reaction is first order with respect to PFC.A Michaelis-Menten type kinetics was observed with respect to the substrate, indicating the formation of a PFC-alcohol complex in the preequilibrium.The formation constants and the rates of disproportionation of the complexes were determined.The oxidation of benzyl alcohol indicated the presence of a substantial primary kinetic isotope effect.The ratesof the decomposition of the complexes of the meta-and para-substituted alcohols were analyzed in terms of Taft's and Swain's dual substituent parameter equations.The meta compounds showed an excellent correlation with Taft's ?I and ?R0 values while the para-substituted compounds correlate with ?1 and ?RBA constants.The rates of the ortho-substituted alcohols correlate with Charton's equation of inductive, resonance, and steric paramaters.The reaction was studied in 19 solvents.The correlation analysis of the solvent effect indicated the greater importance of the cation-solvating power of the solvent.The reaction involves a hydride ion transfer in the rate-determining step.
- Banerji, Kalyan K.
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- Kinetic Study of the Oxidation of Substituted Benzyl Alcohols by Ethyl Chlorocarbamate
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The kinetics of the oxidation of twenty-four monosubstituted benzyl alcohols by ethyl chlorocarbamate (ECC) have been studied in aqueous acetic acid solution, in the presence of perchloric acid.The main product of the oxidation is the corresponding benzaldehyde.The reaction is first order with respect to the alcohol, ECC, and hydrogen ion.The oxidation of 2>benzyl alcohol indicated a primary kinetic isotope effect, kH/kD=5.40 at 298 K.The value of solvent isotope effect, k(H2O)/k(D2O), is 1.85 at 298 K.Addition of ethyl carbamate does not affect the reaction rate. + has been postulated as the reactive oxidizing species.The rates of oxidation of para- and meta-substituted benzyl alcohols show excellent correlation in Taft's dual substituent parameter equation, with negative reaction constants.The rates of the ortho-substituted compounds correlate well in Charton's equation of inductive, resonance and steric substituent parameters.A mechanism involving simultaneous transfer of a hydride ion from the C-H bond and of a proton from O-H bond to the oxidant is proposed.
- Jain, Suman,Banerji, Kalyan K.
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- An aerobic oxidation of alcohols into carbonyl synthons using bipyridyl-cinchona based palladium catalyst
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We have reported an aerobic oxidation of primary and secondary alcohols to respective aldehydes and ketones using a bipyridyl-cinchona alkaloid based palladium catalytic system (PdAc-5) using oxygen at moderate pressure. ThePdAc-5catalyst was analysed using SEM, EDAX, and XPS analysis. The above catalytic system is used in experiments for different oxidation systems which include different solvents, additives, and bases which are cheap, robust, non-toxic, and commercially available on the industrial bench. The obtained products are quite appreciable in both yield and selectivity (70-85%). In addition, numerous important studies, such as comparisons with various commercial catalysts, solvent systems, mixture of solvents, and catalyst mole%, were conducted usingPdAc-5. The synthetic strategy of oxidation of alcohol into carbonyl compounds was well established and all the products were analysed using1H NMR,13CNMR and GC-mass analyses.
- Cheedarala, Ravi Kumar,Chidambaram, Ramasamy R.,Siva, Ayyanar,Song, Jung Il
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p. 32942 - 32954
(2021/12/02)
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- Method for catalyzing one-pot hydrogenation and amidation of nitroaromatic hydrocarbon and carboxylic acid by visible light
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The invention discloses a method for catalyzing one-pot hydrogenation and amidation reaction of nitroaromatic hydrocarbon and carboxylic acid by visible light. The method comprises the following steps: preparing Pt nanoparticles uniformly dispersed on an N-doped titanium dioxide/titanium carbide (MXene) heterojunction as a photocatalyst (3% Pt/N-TiO2/Ti3C2), and applying the catalyst to a cascade reaction of an aromatic nitro compound and carboxylic acid to prepare an amide product. The 3% Pt/N-TiO2/Ti3C2 has excellent tandem hydrogenation and amidation activity and chemical selectivity of an aromatic nitro compound and carboxylic acid under the irradiation of visible light. The excellent catalytic performance of 3% Pt/N-TiO2/Ti3C2 is attributed to the close contact of TiO2 and conductive Ti3C2, and the separation efficiency of photo-induced electrons and holes is improved through charge short-range directional transmission. The preparation method of the catalyst is simple and easy to operate, the catalyst can be used for photocatalytic efficient one-pot hydrogenation and amidation reactions, the reaction conditions are mild, and the catalyst is easy to recycle.
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Paragraph 0030
(2021/06/09)
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- Chlorination Reaction of Aromatic Compounds and Unsaturated Carbon-Carbon Bonds with Chlorine on Demand
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Chlorination with chlorine is straightforward, highly reactive, and versatile, but it has significant limitations. In this Letter, we introduce a protocol that could combine the efficiency of electrochemical transformation and the high reactivity of chlorine. By utilizing Cl3CCN as the chloride source, donating up to all three chloride atom, the reaction could generate and consume the chlorine in situ on demand to achieve the chlorination of aromatic compounds and electrodeficient alkenes.
- Liu, Feng,Wu, Na,Cheng, Xu
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supporting information
p. 3015 - 3020
(2021/05/05)
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- Cu(OTf)2-Mediated Cross-Coupling of Nitriles and N-Heterocycles with Arylboronic Acids to Generate Nitrilium and Pyridinium Products**
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Metal-catalyzed C–N cross-coupling generally forms C?N bonds by reductive elimination from metal complexes bearing covalent C- and N-ligands. We have identified a Cu-mediated C–N cross-coupling that uses a dative N-ligand in the bond-forming event, which, in contrast to conventional methods, generates reactive cationic products. Mechanistic studies suggest the process operates via transmetalation of an aryl organoboron to a CuII complex bearing neutral N-ligands, such as nitriles or N-heterocycles. Subsequent generation of a putative CuIII complex enables the oxidative C–N coupling to take place, delivering nitrilium intermediates and pyridinium products. The reaction is general for a range of N(sp) and N(sp2) precursors and can be applied to drug synthesis and late-stage N-arylation, and the limitations in the methodology are mechanistically evidenced.
- Bell, Nicola L.,Xu, Chao,Fyfe, James W. B.,Vantourout, Julien C.,Brals, Jeremy,Chabbra, Sonia,Bode, Bela E.,Cordes, David B.,Slawin, Alexandra M. Z.,McGuire, Thomas M.,Watson, Allan J. B.
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supporting information
p. 7935 - 7940
(2021/03/03)
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- Visible-light induced one-pot hydrogenation and amidation of nitroaromatics with carboxylic acids over 2D MXene-derived Pt/N-TiO2/Ti3C2
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Pt nanoparticles supported on N doped titanium dioxide/titanium carbide (MXene) heterojunctions were employed as photocatalysts for the tandem reactions between aromatic nitro compounds and carboxylic acids to produce amide products. The 3%Pt/N-TiO2/Ti3C2 heterojunction was prepared by in situ grew TiO2 on Ti3C2 nanosheets and then N doped TiO2 with melamine, Pt nanoparticles with 3.3 nm mean diameter well dispersed on N-TiO2/Ti3C2. 3%Pt/N-TiO2/Ti3C2 had excellent amidation activity and chemoselectivity under visible-light irradiation. The elevated catalytic performance of 3%Pt/N-TiO2/Ti3C2 was owing to the improvement in photogenerated electron and hole separation efficiency through charge short-range directional transmission caused by the intimate contact between the TiO2 and the conductive Ti3C2. This direct hydrogenation along with amidation between nitroaromatics and carboxylic acids own actual merits in the amides produce with no harmful byproducts. In situ DRIFTS spectra verified that the amidation activation with visible light irradiation at 25 °C was much faster than heating.
- Jiang, Heyan,Hu, Zujie,Gan, Chuan,Sun, Bin,Kong, Shuzhen,Bian, Fengxia
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- Sequential Connection of Mutually Exclusive Catalytic Reactions by a Method Controlling the Presence of an MOF Catalyst: One-Pot Oxidation of Alcohols to Carboxylic Acids
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A functionalized metal-organic framework (MOF) catalyst applied to the sequential one-pot oxidation of alcohols to carboxylic acids controls the presence of a heterogeneous catalyst. The conversion of alcohols to aldehydes was acquired through aerobic oxidation using a well-known amino-oxy radical-functionalized MOF. In the same flask, a simple filtration of the radical MOF with mild heating of the solution completely altered the reaction media, providing radical scavenger-free conditions suitable for the autoxidation of the aldehydes formed in the first step to carboxylic acids. The mutually exclusive radical-catalyzed aerobic oxidation (the first step with MOF) and radical-inhibited autoxidation (the second step without MOF) are sequentially achieved in a one-pot manner. Overall, we demonstrate a powerful and efficient method for the sequential oxidation of alcohols to carboxylic acids by employing a readily functionalizable heterogeneous MOF. In addition, our MOF in-and-out method can be utilized in an environmentally friendly way for the oxidation of alcohols to carboxylic acids of industrial and economic value with broad functional group tolerance, including 2,5-furandicarboxylic acid and 1,4-benzenedicarboxylic acid, with good yield and reusability. Furthermore, MOF-TEMPO, as an antioxidative stabilizer, prevents the undesired oxidation of aldehydes, and the perfect "recoverability"of such a reactive MOF requires a re-evaluation of the advantages of MOFs from heterogeneity in catalytic and related applications.
- Kim, Seongwoo,Lee, Ha-Eun,Suh, Jong-Min,Lim, Mi Hee,Kim, Min
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supporting information
p. 17573 - 17582
(2020/12/22)
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- 1,1,1,3,3,3-Hexafluoroisopropanol as an efficient medium for the room temperature oxidation of styrenes to benzaldehydes
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A room temperature N-hydroxyphthalimide-catalyzed oxidation of styrene derivatives to the corresponding aldehydes has been developed. The use of 1,1,1,3,3,3-hexafluoroisopropanol as the solvent was determined as being key for efficient oxidation. The incorporated oxygen atom originates from molecular dioxygen.
- Zhang, Zhuyong,Chen, Weidong,Luo, Junfei
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supporting information
(2020/10/23)
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- Selective hydrogenation of nitroarenes under mild conditions by the optimization of active sites in a well defined Co?NC catalyst
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The catalytic hydrogenation of aromatic nitro compounds containing multiple functional groups into amino compounds with high conversion rates, selectivity, and stability under mild conditions is a great challenge. Herein, a well defined catalyst (Co?NC) is prepared through the pyrolysis of the Co-centered metal-organic framework (MOF) at the optimized temperature. The as-synthesized catalyst exhibits a high conversion rate and selectivity for the hydrogenation of 12 aromatic nitro compounds with different competing groups into desired amino compounds with hydrazine hydrate under mild conditions (80 °C, 30 min, and 1 atm). The catalyst also shows excellent stability and can be reused over 20 times without considerably losing its activity. It is found that the Co-Nx site is the main active site for catalytic hydrogenation, and the Mott-Schottky effect between the surface Co NPs and N-doped carbon can further promote the hydrogenation reaction. EXAFS, TEM, XPS, and Raman analyses confirm that cobalt nanoparticles (NPs) are properly encapsulated by the N-doped carbon matrix at the optimized temperature, and the Co species maintain a high spin state after the catalysis, which may be responsible for the high performance of Co?NC. This work demonstrates not only a highly efficient catalyst for hydrogenation under mild conditions, but also provides insight into the active sites in Co-based catalysts for hydrogenation.
- Chen, Shuo,Jiang, Hong,Jiang, Shun-Feng,Ling, Li-Li
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supporting information
p. 5730 - 5741
(2020/09/21)
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- Decarboxylative formylation of aryl halides with glyoxylic acid by palladium catalysis under oxygen
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A new free radical/palladium cooperative catalyzed formylation of aryl halides with glyoxylic acid as the formyl source under oxygen conditions has been developed. Various aromatic and heteroaromatic aldehydes were produced in medium to good yields.
- Cao, Hualiang,Pu, Weiwen,Zhang, Jie,Yan, Peijun,Zhang, Jun,Xu, Sheng
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supporting information
p. 1287 - 1290
(2020/08/21)
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- Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas
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The reductive carbonylation of aryl iodides to aryl aldehydes possesses broad application prospects. We present an efficient and facile Rh-based catalytic system composed of the commercially available Rh salt RhCl3·3H2O, PPh3 as phosphine ligand, and Et3N as the base, for the synthesis of arylaldehydes via the reductive carbonylation of aryl iodides with CO and H2 under relatively mild conditions with a broad substrate range affording the products in good to excellent yields. Systematic investigations were carried out to study the experimental parameters. We explored the optimal ratio of Rh salt and PPh3 ligand, substrate scope, carbonyl source and hydrogen source, and the reaction mechanism. Particularly, a scaled-up experiment indicated that the catalytic method could find valuable applications in industrial productions. The low gas pressure, cheap ligand and low metal dosage could significantly improve the practicability in both chemical researches and industrial applications.
- Chen, Suqing,Liu, Zhenghui,Mu, Tiancheng,Wang, Peng,Yan, Zhenzhong,Yu, Dongkun,Zhao, Xinhui
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p. 645 - 656
(2020/05/14)
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- A Simple, Mild and General Oxidation of Alcohols to Aldehydes or Ketones by SO2F2/K2CO3 Using DMSO as Solvent and Oxidant
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A practical, general and mild oxidation of primary and secondary alcohols to carbonyl compounds proceeds in yields of up to 99% using SO2F2 as electrophile in DMSO as both the oxidant and the solvent at ambient temperature. No moisture- and oxygen-free conditions are required. Stoichiometric amount of inexpensive K2CO3, which generates easy to separate by-products, is used as the base. Thus, 5-gram scale runs proceeded in nearly quantitative yields by a simple filtration as the work-up. The use of a polar solvent such as DMSO, which usually promotes competing Pummerer rearrangement, is also noteworthy. This protocol is compatible with a variety of common N-, O-, and S-functional groups on (hetero)arene, alkene and alkyne substrates (68 examples). The protocol was applied (99% yield) to a formal synthesis of the important cholesterol-lowering drug Rosuvastatin. (Figure presented.).
- Zha, Gao-Feng,Fang, Wan-Yin,Leng, Jing,Qin, Hua-Li
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supporting information
p. 2262 - 2267
(2019/04/17)
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- Palladium-Catalyzed Amidation and Amination of (Hetero)aryl Chlorides under Homogeneous Conditions Enabled by a Soluble DBU/NaTFA Dual-Base System
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The palladium-catalyzed coupling of aryl and heteroaryl chlorides with primary amides under mild homogeneous reaction conditions is reported. Successful C-N coupling is enabled by the use of a unique "dual-base" system consisting of DBU and NaTFA, which serve as proton acceptor and halide scavenger, respectively, using low catalyst loadings (0.5 mol %) with readily available, air-stable palladium precatalysts. The DBU/NaTFA system also enables the room-temperature coupling of primary aryl amines with aryl chlorides and is tolerant of a variety of base-sensitive functional groups.
- Beutner, Gregory L.,Coombs, John R.,Green, Rebecca A.,Inankur, Bahar,Lin, Dong,Qiu, Jun,Roberts, Frederick,Simmons, Eric M.,Wisniewski, Steven R.
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supporting information
p. 1529 - 1537
(2019/09/04)
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by benzimidazolium dichromate - A kinetic and mechanistic aspects
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The oxidation of a number of para- and meta-substituted benzyl alcohols by benzimidazolium dichromate (BIDC), in dimethyl sulphoxide, leads to the formation of the corresponding benzaldehydes. The reaction is first order with respect to each BIDC and alcohol. The reaction is catalyzed by hydrogen ions and the dependence has the form kobs = a + b[H+]. The oxidation of [1,1-2H2]benzyl alcohol exhibited the presence of a substantial kinetic isotope effect. The rates of the oxidation of meta-substituted benzyl alcohols correlated best with Taft's σ1 and σR0 constants. The para-substituted compounds exhibited excellent correlation with σ1 and σRBA values. The polar reaction constants are negative. The rate of oxidation of benzyl alcohol was determined in nineteen organic solvents. An analysis of the solvent effect by multiparametric equations indicated the greater importance of the cation-solvating power of the solvents. Suitable mechanisms have been discussed.
- Kumar, Pravesh,Panday, Dinesh,Kothari, Seema
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p. 1207 - 1215
(2020/06/27)
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- Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage-Independent Activation of Strong C-O Bonds
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Despite the prevalence of alcohols and carboxylic acids as functional groups in organic molecules and the potential to serve as radical precursors, C-O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen-centered nucleophile. We show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H atom trapping to afford the deoxygenated products. Using the same method, we demonstrate access to synthetically versatile acyl radicals, which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge C-O, C-N, and C-C bonds in a single step.
- Stache, Erin E.,Ertel, Alyssa B.,Rovis, Tomislav,Doyle, Abigail G.
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p. 11134 - 11139
(2018/11/21)
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- Rhodium-Catalyzed Formylation of Aryl Halides with CO2 and H2
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The reductive formylation of aryl iodides/bromides to aryl aldehydes using CO2/H2 is presented for the first time. It was realized over a catalytic system composed of RhI3 or RhI3/Pd(dppp)Cl2 (dppp = 1,3-bis(diphenyphosphino)propane) and PPh3 in the presence of Ac2O/Et3N at 100 °C, affording aromatic aldehydes in good to excellent yields, together with good functional-group tolerance and broad substrate scope. The reaction proceeds through three cascade steps, involving HCOOH formation, CO release, and formylation of aryl halides.
- Liu, Zhenghui,Yang, Zhenzhen,Yu, Bo,Yu, Xiaoxiao,Zhang, Hongye,Zhao, Yanfei,Yang, Peng,Liu, Zhimin
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supporting information
p. 5130 - 5134
(2018/09/13)
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- Imidazolium chloride: An efficient catalyst for transamidation of primary amines
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A highly efficient and convenient protocol of imidazolium chloride (30 mol %) catalyzed amidation of amines with moderate to excellent yields was reported. The protocol shows broad substrate scope for aromatic, aliphatic, and heterocyclic primary amines.
- Tian, Qingqiang,Gan, Zongjie,Wang, Xuetong,Li, Dan,Luo, Wen,Wang, Huajun,Dai, Zeshu,Yuan, Jianyong
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supporting information
(2018/09/10)
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- Aerobic oxidation of benzyl alcohols to benzaldehydes using monoclinic bismuth vanadate nanoparticles under visible light irradiation: Photocatalysis selectivity and inhibition
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Monoclinic bismuth vanadate nanoparticles (nan-BiVO4) have been used for the selective photo-oxidation of benzyl alcohols (13 examples) to benzaldehydes under visible light irradiation using dioxygen as oxidant. Illumination with a blue LED (λmax = 470 nm) gave yields more than 30 times greater than bulk BiVO4 with >99% selectivity for several cases. Photo-oxidation of PhCH2OH/PhCD2OH isotopomers gave a kinetic isotope effect of 1.3 indicating that C–H bond activation is not the rate determining step in contrast to other reported photocatalysts including TiO2 and carbon nitride. Collectively, structural characterisation, spectroscopic, and reactivity data are correlated with the greater surface area of nan-BiVO4 compared to bulk BiVO4. Furthermore, conversion is shown to be limited as reaction progresses. Control experiments indicate that photo-oxidation is retarded by product aldehyde and that trace amounts (1%) of the corresponding benzoic acid, from over-oxidation, result in significant reduction in conversion.
- Unsworth, Christopher A.,Coulson, Ben,Chechik, Victor,Douthwaite, Richard E.
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p. 152 - 159
(2017/09/13)
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- Halogen–metal exchange on bromoheterocyclics with substituents containing an acidic proton via formation of a magnesium intermediate
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A selective and practical bromine–metal exchange on bromoheterocyclics bearing substituents with an acidic proton under non-cryogenic conditions was developed by a simple modification of an existing protocol. Our protocol of using a combination of i-PrMgCl and n-BuLi has not only solved the problem of intermolecular quenching that often occurred when using alkyl lithium alone as the reagent for halogen–lithium exchange, but also offered a highly selective method for performing bromo–metal exchange on dibrominated arene compounds through chelation effect.
- Tian, Qingqiang,Shang, Suqin,Wang, Huajun,Shi, Guoqiang,Li, Zhiyao,Yuan, Jianyong
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supporting information
(2017/12/05)
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- Synthesis of Aldehydes by Organocatalytic Formylation Reactions of Boronic Acids with Glyoxylic Acid
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Reported herein is a conceptually novel organocatalytic strategy for the formylation of boronic acids. New reactivity is engineered into the α-amino-acid-forming Petasis reaction occurring between aryl boronic acids, amines, and glyoxylic acids to prepare aldehydes. The operational simplicity of the process and its ability to generate structurally diverse and valued aryl, heteroaryl, and α,β-unsaturated aldehydes containing a wide array of functional groups, demonstrates the practical utility of the new synthetic strategy.
- Huang, He,Yu, Chenguang,Li, Xiangmin,Zhang, Yongqiang,Zhang, Yueteng,Chen, Xiaobei,Mariano, Patrick S.,Xie, Hexin,Wang, Wei
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supporting information
p. 8201 - 8205
(2017/06/30)
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- Selective Aerobic Oxidation of Methylarenes to Benzaldehydes Catalyzed by N-Hydroxyphthalimide and Cobalt(II) Acetate in Hexafluoropropan-2-ol
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Efficient and highly selective catalytic conditions for the aerobic autoxidation of methylarenes to benzaldehydes, based on N-hydroxyphthalimide (NHPI) and cobalt(II) acetate in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP), were developed. The sustainable conditions enable a multigram scale preparation of benzaldehyde derivatives in high efficiency and with excellent chemoselectivity (up to 99 % conversion and 98 % selectivity).
- Gaster, Eden,Kozuch, Sebastian,Pappo, Doron
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supporting information
p. 5912 - 5915
(2017/05/12)
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- Visible-Light-Promoted Nickel- and Organic-Dye-Cocatalyzed Formylation Reaction of Aryl Halides and Triflates and Vinyl Bromides with Diethoxyacetic Acid as a Formyl Equivalent
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A simple formylation reaction of aryl halides, aryl triflates, and vinyl bromides under synergistic nickel- and organic-dye-mediated photoredox catalysis is reported. Distinct from widely used palladium-catalyzed formylation processes, this reaction proceeds by a two-step mechanistic sequence involving initial in situ generation of the diethoxymethyl radical from diethoxyacetic acid by a 4CzIPN-mediated photoredox reaction. The formyl-radical equivalent then undergoes nickel-catalyzed substitution reactions with aryl halides and triflates and vinyl bromides to form the corresponding aldehyde products. Significantly, besides aryl bromides, less reactive aryl chlorides and triflates and vinyl halides serve as effective substrates for this process. Since the mild conditions involved in this reaction tolerate a plethora of functional groups, the process can be applied to the efficient preparation of diverse aromatic aldehydes.
- Huang, He,Li, Xiangmin,Yu, Chenguang,Zhang, Yueteng,Mariano, Patrick S.,Wang, Wei
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supporting information
p. 1500 - 1505
(2017/02/05)
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- A highly efficient heterogeneous aerobic alcohol oxidation catalyzed by immobilization of bipyridine copper(I) complex in MCM-41
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A heterogeneous copper(I)-catalyzed aerobic oxidation of primary benzylic and allylic alcohols to aldehydes was achieved under air in EtOH at 50°C in the presence of 5 mol % of MCM-41-immobilized bipyridine copper(I) complex [MCM-41-bpy-CuI] and 5 mol % of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) using aqueous ammonia as base, yielding a variety of aromatic and α,β-unsaturated aldehydes in good to excellent yields. This heterogeneous copper catalyst can be easily recovered by a simple filtration of reaction solution and reused for at least 10 consecutive trials without any decreases in activity. The use of recyclable heterogeneous copper catalyst and green reagents, such as air as oxidant and ethanol as solvent, made the system attractive for environmentally sustainable processes.
- Zhao, Hong,Chen, Qiurong,Wei, Li,Jiang, Yuanyuan,Cai, Mingzhong
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p. 8725 - 8731
(2015/10/20)
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- Fluorous bispidine: A bifunctional reagent for copper-catalyzed oxidation and knoevenagel condensation reactions in water
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Fluorous bispidine-type ligands have been developed to facilitate its recovery and reusability and to demonstrate its bifunctional property as a ligand and base in copper-catalyzed aerobic oxidation, the Knoevenagel condensation and tandem oxidation/Knoevenagel condensation in water under mild conditions. Application of the fluorous ligand was also extended to the surfactant-free copper-catalyzed allylic and benzylic sp3 C-H oxidation reaction in water. The fluorous ligands could be recovered using F-SPE with recovery ranging from 91-97% and could be reused five times with little loss of activity.
- Ang, Wei Jie,Chng, Yong Sheng,Lam, Yulin
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p. 81415 - 81428
(2015/10/06)
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- Palladium-catalyzed synthesis of aldehydes from aryl halides and tert-butyl isocyanide using formate salts as hydride donors
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An efficient one-pot palladium-catalyzed hydroformylation of aryl halides to produce aromatic aldehydes has been achieved, employing tert-butyl isocyanide as a C1 resource and formate salt as a hydride donor without any additional bases. Characterized by its mild reaction conditions, easy operation and lower toxicity, this reaction can tolerate a wide array of functional groups with moderate to excellent yields.
- Zhang, Ying,Jiang, Xiao,Wang, Jin-Mei,Chen, Jing-Lei,Zhu, Yong-Ming
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p. 17060 - 17063
(2015/03/30)
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- Exploring the synthetic applicability of a new carboxylic acid reductase from Segniliparus rotundus DSM 44985
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A new carboxylic acid reductase (CAR) gene from Segniliparus rotundus DSM 44985 was overexpressed in Escherichia coli. The recombinant enzyme exhibited high activity toward a variety of aromatic and aliphatic carboxylic acids. Especially, it effectively reduced 4-hydroxybenzoic acid (8a) and 4-nitrobenzoic acid (19a), toward which the known Nocardia CAR exhibited no or little activity. The recombinant E. coli cells co-expressing the Segniliparus CAR and Nocardia PPTase genes catalyzed the reductions of vanillic acid (20a) and 3,4-dihydroxyphenylacetic acid (25a) to give vanillyl alcohol (20c) and 3-hydroxytyrosol (25c) with high yield, respectively. The endogenous aldehyde reductases of E. coli should be responsible for the further reduction of the produced aldehydes. These results demonstrated that Segniliparus CAR was a useful addition to the biocatalyst tool-box for the reduction of carboxylic acids and might find applications in the synthesis of valuable bio-based chemicals from renewable resources.
- Duan, Yitao,Yao, Peiyuan,Chen, Xi,Liu, Xiangtao,Zhang, Rui,Feng, Jinhui,Wu, Qiaqing,Zhu, Dunming
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- ZnAl2O4@SiO2 nanocomposite catalyst for the acetylation of alcohols, phenols and amines with acetic anhydride under solvent-free conditions
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A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process, and characterized by X-ray diffraction, Fourier transform infrared, transmission electron microscopy, and N2 adsorption-desorption measurements. The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols, phenols, and amines under solvent-free conditions. Under optimized conditions, efficient acetylation of these substrates with acetic anhydride over the ZnAl2O4@SiO2 nanocomposite was obtained. Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature, while the reaction time was longer for the acetylation of alcohols and phenols, showing that an amine NH2 group can be selectively acetylated in the presence of alcoholic or phenolic OH groups. The catalyst can be reused without obvious loss of catalytic activity. The catalytic activity of the ZnAl2O4@SiO2 nanocomposite was higher than that of pure ZnAl2O4. The method gives high yields, and is clean, cost effective, compatible with substrates having other functional groups and it is suitable for practical organic synthesis.
- Farhadi, Saeed,Jahanara, Kosar
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p. 368 - 375
(2014/04/03)
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- RuCl 3-DCHA catalyst system: A selective aerobic oxidation of primary benzylic alcohols under mild conditions
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The aerobic oxidation of benzylic alcohols to their corresponding aldehydes was performed in a RuCl3 · 3H2O-dicyclohexylamine (DCHA) catalyst system under ambient atmosphere at room temperature. It is noteworthy that the RuCl3 · 3H2O-DCHA system displayed a preference for the primary versus secondary benzylic alcohols in both intermolecular and intramolecular competition experiments.
- Yu, Kaihui,Ye, Dongnai,Shu, Lei,Zhang, Shiyong,Hu, Qiaosheng,Liu, Liangxian
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experimental part
p. 2318 - 2326
(2012/06/18)
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- Aminophenylnitronylnitroxides: Highly networked hydrogen-bond assembly in organic radical materials
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2-(Meta-aminophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide- 1-oxyl (mAPN) and 2-(para-aminophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H- imidazole-3-oxide-1-oxyl (pAPN) were synthesized and subjected to magnetostructural analysis. Both form extended hydrogen bonding networks involving both amino NH bonds to radical spin-density bearing nitronylnitroxide NO groups. Their crystallographic assembly motifs and magnetic exchange properties are compared to those of tert-butoxylcarbonyl (BOC) and amide derivatives having only one NH bond. The conversion of pAPN to acid salt derivatives gives a solid that is essentially diamagnetic, although dissolution of the solid shows the radical spin units to be preserved.
- Aboaku, Safo,Paduan-Filho, Armando,Bindilatti, Valdir,Oliveira, Nei Fernandes,Schlueter, John A.,Lahti, Paul M.
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scheme or table
p. 4844 - 4856
(2012/05/20)
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- Spinel-type zinc aluminate (ZnAl2O4) nanoparticles prepared by the co-precipitation method: A novel, green and recyclable heterogeneous catalyst for the acetylation of amines, alcohols and phenols under solvent-free conditions
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Zinc aluminate (ZnAl2O4) nanoparticles with an average particle size of about 8 nm were easily prepared by the co-precipitation method using aqueous ammonia solution as the precipitating agent. This nanosized spinel-type oxide was characterized by TGA, XRD, FT-IR, TEM, and surface area measurement and used as the heterogeneous catalyst for the acetylation reaction. Efficient acetylation of various amines, alcohols and phenols was carried out over ZnAl2O4 nanoparticles using acetic anhydride and/or acetyl chloride as the acetylating agents at room temperature without the use of a solvent. The method is highly selective, allowing the alcoholic hydroxyl group to be protected while the phenolic hydroxyl group remains intact, and the amine group can be acetylated in the presence of the hydroxyl group. This method is fast and has a high yield. It is also clean, safe, cost effective, compatible with substrates that have other functional groups and very suitable for practical organic synthesis. In addition, the catalyst can be reused without significant loss of activity. Indeed, the catalytic activity of the ZnAl2O4 nanoparticles is higher than that of bulk ZnAl2O4.
- Farhadi, Saeid,Panahandehjoo, Somayeh
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scheme or table
p. 293 - 302
(2010/09/04)
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- Low-pressure hydrogenation of arenecarboxylic acids to aryl aldehydes
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A highly effective palladium catalyst has been developed that allows the selective hydrogenation of arenecarboxylic acids to the aryl aldehydes in the presence of pivalic anhydride already at 5 bar hydrogen pressure. With the new catalyst, diversely functionalized aromatic and heteroaromatic aldehydes are conveniently accessible from the corresponding carboxylic acids in a single reaction step without any overreduction to the alcohols.
- Goossen, Lukas J.,Khan, Bilal Ahmad,Fett, Thomas,Treu, Matthias
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supporting information; experimental part
p. 2166 - 2170
(2010/11/04)
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- Study of 4-acetylaminotoluene ozonation in acetic acid
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The reaction of 4-aminotoluene with ozone in acetic acid was studied. It was found that the reaction proceeds at a high rate, giving predominantly tars. The product composition changes after acylation of the amino group: aliphatic peroxides prevailed among the oxidation products and 4-acetylaminobenzoic acid was identified (16%) as well. It was shown that the presence of a catalyst (cobalt(II) acetate) had no substantial effect on the oxidation selectivity for the methyl group (32%) and only the addition of potassium bromide increased the activity of the catalyst; the yield of 4-acetylaminobenzoic acid reached 70%. The mechanism of oxidation in the presence of a cobalt-bromide catalyst explaining the obtained results was discussed.
- Galstyan,Bushuev,Shumilova
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scheme or table
p. 397 - 400
(2010/06/19)
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by morpholinium chlorochromate
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Oxidation of benzyl alcohol and some ortho-, meta- andparo-monosubstitutcd derivatives by morpholinium chlorochromate in dimethyl stilphoxide leads to the formation of corresponding benzaldehydcs. The reaction is first order each in both morpholinium chlorochromate and the alcohol. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form kob8 = a + b [H+]. Oxidation of α,α-dideuteriobenzyl alcohol exhibits a substantial primary kinetic isotope effect (kH/kD = 5.86 at 298 K). The reaction has been studied in nineteen organic solvents and the effect of solvent analysed using Taft's and Swain's multi-parametric equations. The rates of oxidation of para- and meta-substituted benzyl alcohols have been correlated in terms of Charton's tripararnetric LDR equation whereas the oxidation of ortho-substituted benzyl alcohols with tetraperametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the derealization effect than that of ortho- and meta- substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism is also proposed.
- Soni, Neelam,Tiwari, Vandana,Sharma, Vinita
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scheme or table
p. 669 - 676
(2009/02/08)
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by 2,2′-bipyridinium chlorochromate
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Oxidation of benzyl alcohol and some ortho-, meta- and para-monosubstituted ones by 2.2′-bipyridinium chlorochromate (BPCC) in DMSO leads to the formation of corresponding benzaldehydes. The reaction is first order in both BPCC and the alcohol. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form : kobs = a + b [H+]. Oxidation of α,α-dideuteriobenzyl alcohol (PhCD2OH) has exhibited a substantial primary kinetic isotope effect (kH/k D = 5.60 at 298 K). The reaction has been studied in nineteen organic solvents and the effect of solvent analysed using Taft's and Swain's multi-parametric equations. The rates of oxidation of para- and meta-substituted benzyl alcohols have been correlated in terms of Charton's triparametric LDR equation whereas the oxidation of ortho-substituted benzyl alcohols with tetraparametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than that of ortho- and meta-substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism has been proposed.
- Yajurvedi, Deeksha,Baghmar, Manju,Sharma, Pradeep K.
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body text
p. 496 - 501
(2009/07/18)
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- Oxidation of 4-aminotoluene with ozone in acetic acid solution
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The possibility of preparing 4-aminobenzoic acid by oxidation of 4-aminotoluene with ozone in acetic acid in the presence of cobalt(II) acetate and potassium bromide was examined. The optimal oxidation conditions were found.
- Galstyan,Bushuev,Solomyannyi
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p. 1198 - 1201
(2008/12/23)
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- Photosensitizing properties of actarit, an antirheumatic drug
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The photobiological properties of 4-acetylaminophenylacetic acid (Actarit, ACT, MS-932, CAS 18699-02-0) were studied using in vitro phototoxicity assays: photohemolysis, photoperoxidation of linoleic acid and Candida sp phototoxicity test. ACT reduced nitro blue tetrazolium (NBT) when irradiated with λ ≥ 300 nm in deoxygenated aqueous buffer solution (pH 7.4). The photohemolysis rate and photoperoxidation of linoleic acid were inhibited significantly by reduced glutathione. ACT was phototoxic to Candida sp. The isolation and identification of the photodegradation products of ACT in phosphate buffered saline solution (pH 7.4) and methanol were studied under aerobic conditions. Four compounds were identified and two of them isolated and characterized by spectroscopic methods. A photodecarboxylation with the participation of oxygen via a type I mechanism was proposed for the photodegradation of ACT which undergoes direct electron transfer from the excited state of ACT carboxylate and homolytic rupture of the α-carbon bond. A photodynamic mechanism involving radicals and electron transfer reactions was suggested for the observed in vitro phototoxicity. ECV - Editio Cantor Verlag.
- Canudas, Nieves,Figueroa, Lillian,Zamora, Delimar,Villamizar, Jose E.,Guedez, Arlen,Fuentes, Juan M.,Castelli, Cristina,Taddei, Antonieta
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p. 182 - 187
(2008/09/21)
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- Reductive carbonylation - An efficient and practical catalytic route for the conversion of aryl halides to aldehydes
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Alternative routes for the introduction of aldehyde functionality are particularly desirable for fine chemical and pharmaceutical intermediates because of the wide range of further transformations that are possible. Catalytic processes are of particular interest for minimising waste, and therefore the reductive carbonylation of aryl halides has been explored. We have shown that high yields of aldehydes may be obtained for a wide selection of aryl iodides and bromides using mild conditions (3 bar of CO, temperatures 60-120°C) and silanes as hydride source. A choice of conditions (catalyst, base, solvent) is required to cover the range of aryl substituents varying in electron donation and steric influence. This is related to the competing needs of the several steps of this reaction, including oxidative addition, CO substitution, CO insertion, hydride transfer, and reductive elimination.
- Ashfield, Laura,Barnard, Christopher F. J.
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by quinolinium bromochromate
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Oxidation of benzyl alcohol and some ortho- meta- and para-monosubstituted ones by quinolinium, bromochromate (QBC) in dimethyl sulphoxide (DMSO) leads to the formation of corresponding benzaldehydes. The reaction is first order each in both QBC and the alcohol. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form kobs = a + b [H+]. Oxidation of α,α-dideuteriobenzyl alcohol (PhCD2OH) has exhibited a substantial primary kinetic isotope effect (kH/k D = 5.60 at 298 K). The reaction has been studied in nineteen organic solvents and the effect of solvent analysed using Taft's and Swain's multi-parametric equations. The rates of oxidation of para- and meta-substituted benzyl alcohols have been correlated in terms of Charton's triparametric LDR equation whereas the oxidation of ortho-substituted benzyl alcohols with tetraparametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than that of ortho- and meta-substituted compounds which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism has been proposed.
- Prakash, Om,Sharma, Pradeep K.
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p. 467 - 473
(2007/10/03)
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- Kinetics and mechanism of the oxidation of substituted benzyl alcohols by [bis(trifluoroacetoxy)iodo]benzene
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The oxidation of substituted benzyl alcohols by bis(trifluoroacetoxy)iodo] benzene in aqueous acetic acid solution results in the formation of the corresponding benzaldehydes. The reaction is first order with respect to each of the alcohol, TFAIB and hydrogen ions. The oxidation of [1,1-2H 2]benzyl alcohol exhibited the presence of a substantial primary kinetic isotope effect, indicating the cleavage of the α-C-H bond in the rate-determining step. Increase in the amount of water, in the solvent mixture of acetic acid and water, results in a decrease of the reaction rate. The analysis of the substituent effect in terms of Charton's LDR equation yielded an excellent correlation with negative reaction constants. A mechanism involving a hydride-ion transfer in the rate-determining step has been proposed.
- Kansara, Alpna,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 581 - 584
(2007/10/03)
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- The Dual Roles of Oxodiperoxovanadate Both as a Nucleophile and an Oxidant in the Green Oxidation of Benzyl Alcohols or Benzyl Halides to Aldehydes and Ketones
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One catalyst, two roles: VO(O2)2- reacts as a nucleophilic oxidant under acidic conditions towards benzyl alcohols. Altogether 15 alcohols have been oxidized, in the absence of organic solvent, in excellent yields. Benzyl halides are also oxidized by H2O 2 in water catalyzed by oxodiperoxovanadate and a phase transfer catalyst into aromatic aldehydes and ketones (see scheme). This reaction is the first green oxidation of benzyl halides.
- Li, Chunbao,Zheng, Pengwu,Li, Jie,Zhang, Hang,Cui, Yi,Shao, Qiyun,Ji, Xiujie,Zhang, Jian,Zhao, Pengying,Xu, Yanli
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p. 5063 - 5066
(2007/10/03)
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by quinolinium fluorochromate
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Oxidation of benzyl alcohol and some ortho-, meta- and para-monosubstituted ones by quinolinium fluorochromate (QFC) in dimethyl sulphoxide (DMSO) leads to the formation of corresponding banzaldehydes. The reaction is first order each in both QFC and the alcohol. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form kobs= a + b [H+]. Oxidation of α,α-dideuteriobenzyl alcohol (PhCD2OH) has exhibited a substantial primary kinetic isotope effect. The reaction has been studied in nineteen organic solvents and the effect of solvent analysed using Taft's and Swain's multi-parametric equations. The rates of oxidation of para- and meta-substituted benzyl alcohols have been correlated in terms of Charton's triparametric LDR equation, whereas the oxidation of ortho-substituted benzyl alcohols with tetraparametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than that of ortho- and meta-substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism has been proposed.
- Dave, Itishri,Sharma, Vinita,Banerji, Kalyan K.
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p. 493 - 499
(2007/10/03)
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- Correlation analysis of reactivity in oxidation of substituted benzyl alcohols by tetrabutylammonium tribromide
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Oxidation of benzyl alcohol and some ortho-, meta- and para-monosubstituted benzyl alcohols by tetrabutylammonium tribromide (TBATB) in aqueous acetic acid leads to the formation of corresponding benzaldehydes. The reaction is first order each in TBATB and the alcohol. The oxidation of [1,1-2H2]benzyl alcohol (PhCD2OH) exhibited a substantial kinetic isotope effect. Addition of tetrabutylammonium chloride or potassium bromide did not affect the rate. Tribromide ion has been postulated as the reactive oxidizing species. The reaction rate increases with increase in the polarity of the solvent. The rates of oxidation of meta- and para-substituted benzyl alcohols showed excellent correlation in terms of Charton's triparametric LDR, equation whereas the oxidation of ortho-substituted benzyl alcohols correlated best with the LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than is the oxidation of ortho- and meta-substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subject to steric acceleration by the ortho-substituents. A suitable mechanism is proposed. Copyright
- Kumar, Ashok,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 721 - 727
(2007/10/03)
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- Novel non-steroidal/non-anilide type androgen antagonists with an isoxazolone moiety
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3-Substituted (Z)-4-(4-N,N-dialkylaminophenylmethylene)-5(4H)-isoxazolones and related compounds were designed and prepared as candidates for structurally novel androgen antagonists. Several compounds showed potent anti-androgenic activity as assessed by nuclear androgen receptor binding assay and growth inhibition assay using androgen-dependent Shionogi carcinoma cells SC-3. They were approximately 10-220 times more potent than flutamide in these assay systems. They also showed anti-androgenic activity toward prostate tumor cell line LNCaP, which has an aberrant nuclear androgen receptor.
- Ishioka, Toshiyasu,Kubo, Asako,Koiso, Yukiko,Nagasawa, Kazuo,Itai, Akiko,Hashimoto, Yuichi
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p. 1555 - 1566
(2007/10/03)
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- New Pd-catalyzed selective reduction of carboxylic acids to aldehydes.
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A catalyst generated in situ from palladium acetate and tricyclohexylphosphine efficiently catalyzes the reduction of carboxylic acids with sodium hypophosphite in the presence of pivalic anhydride to give aldehydes with high selectivity. The low cost and convenient handling of the reagents makes this process a valuable alternative to hydrogenations and metal hydride reductions.
- Goossen, Lukas J,Ghosh, Keya
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p. 836 - 837
(2007/10/03)
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- Kinetics and Mechanism of the Oxidation of Substituted Benzyl Alcohol by Oxo(salen)manganese(V) Complexes
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The oxidation of monosubstituted benzyl alcohols by substituted oxo(salen)manganese(V) complexes, in acetonitrile, leads to the formation of the corresponding benzaldehydes. The reaction is first order with respect to both the alcohol and the Mn(V) complex. The oxidation of [1,1-2H2]benzyl alcohol exhibited the presence of a substantial kinetic isotope effect. The rate of oxidation of alcohols by four Mn(V) complexes have been determined. The rates of the oxidation of meta-substituted benzyl alcohols correlated best with Taft's ?1 and ?R0 constants. The para-substituted compounds exhibited excellent correlation with ?1 and ?R+ values. The ortho-substituted alcohols correlated well in terms of Charton's triparametric equation. The polar reaction constants are negative. The ortho- compounds showed a steric acceleration of the reaction. The rate of reduction of the substituted Mn(V) complexes showed an excellent correlation in terms of Hammett equation with positive reaction constants. The reactivity-selectivity principle (RSP) is obeyed in this reaction. The validity of RSP has been verified by Exner's mathematical procedure. Suitable mechanism have been discussed.
- Kumbhat, Vinita,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 562 - 585
(2007/10/03)
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- Isoquinoline compound melanocortin receptor ligands and methods of using same
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The invention relates to melanocortin receptor ligands and methods of using the ligands to alter or regulate the activity of a melanocortin receptor. The invention further relates to tetrahydroisoquinoline aromatic amines that function as melanocortin receptor ligands and as agents for controlling cytokine-regulated physiologic processes and pathologies, and combinatorial libraries thereof.
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- Correlation analysis of reactivity in oxidation of substituted benzyl alcohols by benzyltrimethylammonium chlorobromate
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Oxidation of benzyl alcohol and some ortho-, meta- and para-monosubstituted benzyl alcohols by benzyltrimethylammonium chlorobromate (BTMACB) in aqueous acetic acid leads to the formation of corresponding benzaldehydes. The reaction is first order each in BTMACB and the alcohol. The oxidation of α,α-dideuteriated benzyl alcohol (PhCD2OH) exhibits a substantial kinetic isotope effect. Addition of benzyltrimethylammonium chloride or potassium bromide ions does not affect the rate. Chlorobromate ion has been postulated as the reactive oxidizing species. The effect of solvent composition indicates that the reaction rate increases with an increase in the polarity of the solvent. The rates of oxidation of meta- and para-substituted benzyl alcohols have been correlated in terms of Charton's triparametric LDR equation whereas the oxidation of ortho-substituted benzyl alcohols has been correlated with tetraparametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than is the oxidation of ortho- and meta-substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism has been proposed.
- Sita Rama Raju,Sharma,Banerji
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p. 1258 - 1263
(2007/10/03)
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- Correlation Analysis of Reactivity in the Oxidation of Substituted Benzyl Alcohols by Benzyltrimethylammonium Tribromide
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Oxidation of benzyl alcohol and some ortho-, meta- and para- monosubstituted benzyl alcohols by benzyltrimethylammonium tribromide (BTMAB) in aqueous acetic acid leads to the formation of corresponding benzaldehydes. The reaction is first order with respect to both BTMAB and the alcohol. The oxidation of deuteriated benzyl alcohol exhibited a substantial kinetic isotope effect. Addition of benzyltrimethylammonium or bromide ions did not affect the rate. Tribromide ion has been postulated as the reactive oxidizing species. The rates of the oxidation of para- and meta-substituted benzyl alcohols were correlated with Taft's and Swain's field and resonance substituent constants. The oxidation of para-substituted benzyl alcohols showed excellent correlation with Taft's ?1 and ?RBA values; the meta-compounds correlated best with ?1 and ?R0 values. Rates of the ortho-substituted compounds showed a significant correlation with Charton's triparametric equation. Suitable mechanism has been proposed.
- Anjana,Kothari, Seema,Banerji, Kalyan K.
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p. 2118 - 2135
(2007/10/03)
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- Stereoselectivity in the Wittig reaction of phenyl 3-pyridyl ketones: Amide substituent effect on the preferential (E)-olefin formation
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A Wittig reaction of amide substituted phenyl 3-pyridyl ketones with 'nonstabilized' phosphorus ylides which contain a carboxyl terminus preferentially forms (E)-olefin. The preference for this stereoselectivity stems from either hydrogen bonding or salt-bridge formation between the amide group and the carboxyl terminus during the oxaphosphetane intermediate formation.
- Takeuchi, Kumiko,Kohn, Todd J.
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p. 5689 - 5692
(2007/10/03)
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