- Palladium supported on functionalized mesoporous silica as an efficient catalyst for Suzuki-Miyaura coupling reaction
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Mesoporous SBA-15 was modified with organic functional groups by co-condensation method. The functionalized mesoporous silica can be loaded with palladium and the resulting material used as a catalyst for the Suzuki-Miyaura coupling reactions. Highly dispersed and uniform palladium nanoparticles could be detected using transmission electron microscopy. The Pd-SBA-15 nanocomposite with controlled molar ratio of amino groups to palladium exhibits an excellent catalytic activity and low Pd leaching for the Suzuki-Miyaura coupling reaction. The catalyst can also be reused at least six recycles in air with only a minor loss of activity. Graphical Abstract: Mesoporous SBA-15 was modified with organic functional groups by co-condensation method. The functionalized mesoporous silica can be loaded with palladium and the resulting material used as a catalyst for the Suzuki-Miyaura coupling reactions. Highly dispersed and uniform palladium nanoparticles could be detected using transmission electron microscopy. The Pd-SBA-15 nanocomposite with controlled molar ratio of amino groups to palladium exhibits an excellent catalytic activity and low Pd leaching for the Suzuki-Miyaura coupling reaction. The catalyst can also be reused at least six recycles in air with only a minor loss of activity.[Figure not available: see fulltext.]
- Zhang, Guoheng,Wang, Peiyu,Wei, Xiufang
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Read Online
- D-Glucosamine based-phosphine for Suzuki-Miyaura cross-coupling reactions in the supported aqueous phase catalysis system
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A d-glucosamine-based phosphine/Pd(OAc)2 complex has been applied to the Suzuki-Miyaura coupling reaction of aryl bromides with arylboronic acids using the supported aqueous phase catalysis, SAPC, concept. The recyclability of the catalyst was investigated and revealed a very high activity during the 4 runs.
- Wójcik, Karolina,Goux-Henry, Catherine,Andrioletti, Bruno,Micha? Pietrusiewicz,Framery, Eric
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Read Online
- A graphdiyne-based carbon material for electroless deposition and stabilization of sub-nanometric Pd catalysts with extremely high catalytic activity
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The development of sub-nanometric metal particles (1 nm) as advanced heterogeneous catalysts has received considerable interest due to their outstanding catalytic performance, while the synthesis and stabilization of sub-nanometric catalysts (SNCs) without using additional surface capping agents remains a challenge. Herein, we report the synthesis of novel three-dimensional pyrenyl graphdiyne (Pyr-GDY) ultrafine nanofibers (3-10 nm), which can serve as an ideal substrate for electroless deposition and stabilization of Pd SNCs through the terminal uncoupled acetenyl groups in Pyr-GDY, with an average Pd particle size of only 0.83 nm. The as-synthesized Pd/Pyr-GDY composite shows extremely high catalytic activities for the reduction of nitroarenes to arylamines and Suzuki coupling reactions, 300 and 25 times higher than those of commercial Pd/C, respectively. The outstanding catalytic performance can be ascribed to the sub-nanometric Pd particles with a "clean surface", and the unique three-dimensional network structure of Pyr-GDY, being favorable for rapid mass transfer. Our result provides an ideal carbon material for electroless deposition and stabilization of other SNCs with a "clean surface", which will display outstanding catalytic activity for various catalytic reactions.
- Yang, Liang-Liang,Wang, Hong-Juan,Wang, Juan,Li, Yu,Zhang, Wen,Lu, Tong-Bu
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Read Online
- Direct Acetoxylation of Arenes
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Acetoxylation of arenes is an important reaction and an unmet need in chemistry. We report a metal-free, direct acetoxylation reaction using sodium nitrate under an anhydrous environment of trifluoroacetic acid, acetic acid, and acetic anhydride. Arenes (31 examples), with oxidation potentials (Eox, in V vs SCE) lower than benzene (2.48 V), were acetoxylated with good yields and regioselectivity. A stepwise, single electron-transfer mechanism is proposed.
- Hong Nguyen, Thi Anh,Hou, Duen-Ren
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supporting information
p. 8127 - 8131
(2021/08/23)
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- Rhodium-Catalyzed Carbonylative Coupling of Alkyl Halides with Phenols under Low CO Pressure
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A rhodium-catalyzed carbonylative transformation of alkyl halides under low pressure of CO has been developed. This robust catalyst system allows using phenols as the carbonylative coupling partner and, meanwhile, exhibits high functional group tolerance and good chemoselectivity. Substrates even with a large steric hindrance group or multiple reaction sites can be selectively converted into the desired products in good to excellent yields. A gram-scale experiment was performed and delivered an almost quantitative amount of the product. Control experiments were performed as well, and a possible reaction mechanism is proposed.
- Ai, Han-Jun,Li, Chong-Liang,Wang, Hai,Wu, Xiao-Feng
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p. 5147 - 5152
(2020/05/27)
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- Synthesis and anti-inflammatory activity of 2-oxo-2H-chromenyl and 2H-chromenyl-5-oxo-2,5-dihydrofuran-3-carboxylates
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Cycloaddition reaction of 4-chloro-2-oxo-2H-chromene-3-carbaldehydes (3a-g) and 4-chloro-2H-chromene-3-carbaldehydes (7a-h) with activated alkynes (4a-b) provided the 2-oxo-2H-chromenyl-5-oxo-2,5-dihydrofuran-3-carboxylates (5a-n) and 2H-chromenyl-5-oxo-2,5-dihydrofuran-3-carboxylates (8a-p). All the prepared compounds were screened for anti-inflammatory activity. In vitro anti-inflammatory activity data demonstrated that the compounds 5g, 5i, 5k-l and 8f are effective among the tested compounds against TNF-α (1.108 ± 0.002, 0.423 ± 0.022, 0.047 ± 0.001, 0.070 ± 0.002 and 0.142 ± 0.001 μM) in comparison with standard compound Prednisolone (0.033 ± 0.002 μM). Based on in vitro results, three compounds (5i, 5k and 8f) have been selected for in vivo experiments and these compounds are identified as better compounds with respect to anti-inflammatory activity in LPS induced mice model. Compound 5i was identified as potent and showed significant reduction in TNF-α and IL-6.
- Bhimapaka, China Raju,Karri, Shailaja,Kuncha, Madhusudana,Kurma, Siva Hariprasad,Sistla, Ramakrishna
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- Visible-Light-Induced [4+2] Annulation of Thiophenes and Alkynes to Construct Benzene Rings
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The [4+2] annulation represents an elegant and versatile synthetic protocol for the construction of benzene rings. Herein, a strategy for visible-light induced [4+2] annulation of thiophenes and alkynes, to afford benzene rings, is presented. Under simple and mild reaction conditions, the ready availability and structural diversity of thiophenes and alkynes permit the facile synthesis of several substituted aromatic rings. Valuable drugs and amino acids are also well tolerated. Moreover, DFT calculations explain the high regioselectivity of the reaction.
- Song, Chunlan,Dong, Xin,Wang, Zhongjie,Liu, Kun,Chiang, Chien-Wei,Lei, Aiwen
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supporting information
p. 12206 - 12210
(2019/07/31)
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- Metal-Free and Redox-Neutral Conversion of Organotrifluoroborates into Radicals Enabled by Visible Light
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Converting organoboron compounds into the corresponding radicals has broad synthetic applications in organic chemistry. To achieve these transformations, various strong oxidants such as Mn(OAc)3, AgNO3/K2S2O8, and Cu(OAc)2, in stoichiometric amounts are required, proceeding by a single-electron transfer mechanism. Established herein is a distinct strategy for generating both aryl and alkyl radicals from organotrifluoroborates through an SH2 process. This strategy is enabled by using water as the solvent, visible light as the energy input, and diacetyl as the promoter in the absence of any metal catalyst or redox reagent, thereby eliminating metal waste. To demonstrate its synthetic utility, an efficient acetylation to prepare valuable aryl (alkyl) methyl ketones is described and applications to construct C?C, C?I, C?Br, and C?S bonds are also feasible. Experimental evidence suggests that triplet diacetyl serves as the key intermediate in this process.
- Liu, Wenbo,Liu, Peng,Lv, Leiyang,Li, Chao-Jun
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supporting information
p. 13499 - 13503
(2018/09/25)
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- C-C cross-coupling reactions by palladium on barium and potassium polyoxotungstate supports
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A heterogeneous catalyst system for Suzuki and Heck coupling reactions was developed using polyoxometalates as supports for palladium. The catalyst system was synthesized in a one step process using sodium phosphotungstate and palladium acetate. We used the supported catalyst in organic media without the need for special ligands. Substantial activity was observed after several recycles. The catalyst showed high product selectivity with yields up to > 95 % in both Suzuki and Heck reactions.
- Karume,Tebandeke,Mbabazi,Ssekaalo,Wendt
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p. 2357 - 2360
(2018/09/09)
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- Synthetic method of 4-hydroxy-4'-biphenyl nitrile
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The invention discloses a preparation method of 4-hydroxy-4'-biphenyl nitrile. The method comprises: reacting 4-hydroxybiphenyl (2) with acetyl chloride to generate 4-acetic acid biphenyl (3), reacting 4-acetic acid biphenyl (3) with oxalyl chloride under aluminium trichloride catalysis to generate 4-chlorocarbonyl-4'-acetic acid biphenyl (4), reacting 4-chlorocarbonyl-4'-acetic acid biphenyl (4)with ammonia water to generate 4-formamido-4'-acetic acid biphenyl (5), dehydrating 4-formamido-4'-acetic acid biphenyl (5) under phosphorus oxychloride catalysis to generate 4-cyano-4'-acetic acid biphenyl (6), and deacetylating 4-cyano-4'-acetic acid biphenyl (6) in the presence of sodium hydroxide to generate 4-hydroxy-4'-biphenyl nitrile (1). The method is simple in process, is economic and eco-friendly, and is suitable for industrial amplification requirement.
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Paragraph 0007; 0025
(2018/09/21)
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- Amino propylene glycol derivatives, its preparation method and its pharmaceutical composition and use thereof
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The invention discloses a class of amino propanediol derivatives, a preparation method, drug compositions and uses thereof, and particularly relates to a class of new immunoloregulation agents represented by a general formula (I), a preparation method, drug compositions containing the immunoloregulation agents, and especially uses of the immunoloregulation agents as immunoloregulation drugs. The compound with characteristics of excellent treatment effect and low toxicity can be used in the fields of immunologic derangement and immunosuppression, and can further be used for treatment of hypoimmunity, organ transplant rejection and autoimmune diseases. The formula I is defined in the instruction.
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Paragraph 0318; 0321; 0322; 0323
(2018/11/22)
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- A PdII Carbene Complex with Anthracene Side-Arms for π-Stacking on Reduced Graphene Oxide (rGO): Activity towards Undirected C–H Oxygenation of Arenes
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An N-heterocyclic carbene palladium(II) complex containing two anthracene side arms was immobilized on the surface of reduced graphene oxide (rGO) by π-stacking. The activity of the homogeneous analogue and the supported complex in undirected C–H acetoxylation reaction of arenes was studied. The results show that the catalytic efficiency in acetoxylation of benzene is improved in the immobilized materials compared to the homogeneous analogue. According to XPS analysis, the immobilized catalyst maintains the original oxidation state of PdII after the catalytic reaction.
- Majeed, Maitham H.,Shayesteh, Payam,Persson, Axel R.,Wallenberg, L. Reine,Schnadt, Joachim,Wendt, Ola F.
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supporting information
p. 4742 - 4746
(2018/11/27)
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- Size-selective catalysts in five functionalized porous coordination polymers with unsaturated zinc centers
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The five reported structural isomorphic porous coordination polymers (PCPs) 1-5, namely, [Zn(L)(ip) (1), Zn(L)(aip) (2), Zn(L)(hip) (3), Zn(L)(nip) (4), and Zn(L)(HBTC) (5) (L = N4,N4′-di(pyridine-4-yl)biphenyl-4,4′-dicarboxamide, H2ip = isophthalic acid, H2aip = 5-aminoisophthalic acid, H2hip = 5-hydroxyisophthalic acid, H2nip = 5-nitroisophthalic acid, H3BTC = 1,3,5-benzenetricarboxylic acid)] were used to catalyze the acetylation of phenol. All these heterogeneous catalysts exhibit good catalytic efficiency and size-selectivity toward the acetylation of phenols owing to their unsaturated metal centers, non-coordinated amide, and suitable channel size and shape. Among them, 2 displays the highest catalytic activity and excellent cooperative catalysis due to the presence of basic non-coordinated amide groups.
- Deng, Dongsheng,Guo, Hui,Ji, Baoming,Wang, Weizhou,Ma, Lufang,Luo, Feng
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p. 12611 - 12616
(2017/11/06)
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- Polymer-Supported Palladium(II) Carbene Complexes: Catalytic Activity, Recyclability, and Selectivity in C?H Acetoxylation of Arenes
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Heterogeneous catalysts for selective oxidation of C?H bonds were synthesized by co-polymerization of new N-heterocyclic carbene-palladium(II) (NHC-PdII) monomers with divinylbenzene. The polymer-supported NHC-PdII-catalysed undirect
- Majeed, Maitham H.,Shayesteh, Payam,Wallenberg, L. Reine,Persson, Axel R.,Johansson, Niclas,Ye, Lei,Schnadt, Joachim,Wendt, Ola F.
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supporting information
p. 8457 - 8465
(2017/06/28)
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- Inherent vs Apparent Chemoselectivity in the Kumada-Corriu Cross-Coupling Reaction
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The Kumada-Corriu reaction is a powerful tool for C-C bond formation, but is seldom utilized due to perceived chemoselectivity issues. Herein, we demonstrate that high-yielding couplings can occur in the presence of many electrophilic and heterocyclic functional groups. Our strategy is mechanically based, matching oxidative addition rates with the rate of syringe pump addition of the Grignard reagent. The mechanistic reason for the effectiveness of this strategy is uncovered by continuous-infusion ESI-MS studies.
- Hua, Xiye,Masson-Makdissi, Jeanne,Sullivan, Ryan J.,Newman, Stephen G.
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p. 5312 - 5315
(2016/11/02)
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- Palladium-Catalyzed Desilylative Acyloxylation of Silicon-Carbon Bonds on (Trimethylsilyl)arenes: Synthesis of Phenol Derivatives from Trimethylsilylarenes
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A strategy for desilylative acetoxylation of (trimethylsilyl)arenes has been developed in which (trimethylsilyl)arenes are converted into acetoxyarenes. The direct acetoxylation is performed in the presence of 5 mol % of Pd(OAc)2 and PhI(OCOCF3)2 (1.5 equiv) in AcOH at 80°C for 17 h. The acetoxyarenes are obtained in good to high yields (67-98%). The synthetic utility is demonstrated with a one-pot transformation of (trimethylsilyl)arenes to phenols by successive acetoxylation and hydrolysis. Furthermore, desilylative acyloxylation of 2-(trimethylsilyl)naphthalene using several carboxylic acids has been conducted.
- Gondo, Keisuke,Oyamada, Juzo,Kitamura, Tsugio
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supporting information
p. 4778 - 4781
(2015/10/12)
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- L-pyrrolidine-2-carboxylic acid-4-hydrogen sulfate (supported on silica gel) as a new and efficient catalyst for acylation of alcohols, phenols and amines under solvent-free conditions
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In the present work, L-pyrrolidine-2-carboxylic acid-4-hydrogen sulfate, supported on silica gel was prepared and characterized by Mass spectroscopy, 1H NMR, 13CNMR, FT IR and elemental analysis (CHN) methods. This heterogenized catalyst can be used as an efficient catalyst for the acylation of alcohols, phenols, and amines with acetic anhydride under mild and solvent-free conditions. Simple work-up, stability of the catalyst, nontoxicity and good to high yields are the advantages of this work.
- Hajjami, Maryam,Ghorbani-Choghamarani, Arash,Khani, Zahra
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p. 324 - 329
(2013/07/26)
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- NOVEL TRISPHENOL COMPUND
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A trisphenol compound is expressed by formula (1), wherein R represents an alkyl group or alkoxyl group with 1 to 8 carbon atoms, phenyl group or hydroxyl group; R1 represents an alkyl group or alkoxyl group with 1 to 8 carbon atoms, or phenyl
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Page/Page column 7
(2012/09/10)
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- Copper-catalyzed trifluoromethylation of aryl boronic acids using a CF 3+ reagent
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A copper-catalyzed process for trifluoromethylation of aryl, heteroaryl, and vinyl boronic acids has been developed. The reaction is conducted under mild conditions and shows tolerance to moisture and a variety of functional groups.
- Xu, Jun,Luo, Dong-Fen,Xiao, Bin,Liu, Zhao-Jing,Gong, Tian-Jun,Fu, Yao,Liu, Lei
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scheme or table
p. 4300 - 4302
(2011/06/21)
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- WB4101-related compounds: New, subtype-selective α1- adrenoreceptor antagonists (or inverse agonists?)
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Our previous structure-affinity relationship study had considered the enantiomers of the naphthodioxane, tetrahydronaphthodioxane, and 2-methoxy-1-naphthoxy analogues (compounds 1, 3, and 2, respectively) of 2-(2,6-dimethoxyphenoxyethylaminomethyl)-1,4-be
- Pallavicini, Marco,Budriesi, Roberta,Fumagalli, Laura,Ioan, Pierfranco,Chiarini, Alberto,Bolchi, Cristiano,Ugenti, Maria Paola,Colleoni, Simona,Gobbi, Marco,Valoti, Ermanno
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p. 7140 - 7149
(2007/10/03)
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- Zinc oxide (ZnO) as a new, highly efficient, and reusable catalyst for acylation of alcohols, phenols and amines under solvent free conditions
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Zinc oxide (ZnO) is a highly efficient catalyst for the acylation of a variety of alcohols, phenols and amines with acid chlorides or acid anhydrides under solvent free conditions. Primary, secondary, tertiary, allylic and benzylic alcohols, diols and phenols with electron donating or withdrawing substituents can be easily acylated in good to excellent yield.
- Hosseini Sarvari, Mona,Sharghi, Hashem
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p. 10903 - 10907
(2007/10/03)
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- Cesium fluoride-Celite: A solid base for efficient syntheses of aromatic esters and ethers
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Coupling reactions of a number of aromatic and heteroaromatic phenols with alkyl, acyl or benzoyl halides in acetonitrile with cesium fluoride-Celite are described, demonstrating that this reagent provides an efficient, convenient and practical method for the syntheses of aromatic esters and ethers.
- Shah, Syed Tasadaque Ali,Khan, Khalid Mohammed,Hussain, Hidayat,Anwar, Muhammad Usman,Fecker, Miriam,Voelter, Wolfgang
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p. 6652 - 6656
(2007/10/03)
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- Formylchromone derivatives as a novel class of protein tyrosine phosphatase 1B inhibitors
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Formylchromone inhibits a human protein tyrosine phosphatase PTP1B with a IC50 value of 73 μM. The chemical reactivity of formylchromone was adjusted by substitution at various positions of the formylchromone skeleton. In an initial assessment of the structure-activity relationship, the most potent inhibitor showed an IC50 of 4.3 μM against PTP1B and strong or medium selectivity against other human PTPases, LAR and TC-PTP. This compound, however, was not selective against microbial PTPases, YPTP1 and YOP. The potency and selectivity of the formylchromone derivatives expecting further improvements provides a novel pharmacophore for the design of drugs for the treatmenrt of type 2 diabetes and obesity.
- Shim, Yi Sup,Kim, Ki Chul,Chi, Dae Yoon,Lee, Keun-Hyeung,Cho, Hyeongjin
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p. 2561 - 2563
(2007/10/03)
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- Conversion of N-aromatic amides to O-aromatic esters
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(Matrix Presented) N-Aromatic secondary amides can be transformed into O-aromatic esters in high yield via N-nitrosamide intermediates. The amides can be generated in situ from the corresponding aromatic amines or nitro compounds, and phenols can easily be made from the esters. The reaction can be modified by addition of methyl methacrylate or toluene at 0 °C to give polymerization or deamination, respectively. The rearrangement mechanism may involve radical formation and recombination.
- Glatzhofer, Daniel T.,Roy, Raymond R.,Cossey, Kimberly N.
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p. 2349 - 2352
(2007/10/03)
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- An efficient approach towards syntheses of ethers and esters using CsF-Celite as a solid base
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The coupling reactions of a number of alcohols and phenols with alkyl, acyl or benzoyl halides in acetonitrile with cesium fluoride-Celite are described. It has been found that CsF-Celite combinations provide an efficient, convenient and practical method for syntheses of both, ethers and esters.
- Shah, Syed Tasadaque A,Khan, Khalid M,Heinrich, Angelica M,Choudhary, M.Iqbal,Voelter
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p. 8603 - 8606
(2007/10/03)
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- Sulfonamide-substituted chromans, processes for their preparation, their use as a medicament or diagnostic, and medicament comprising them
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Sulfonamide-substituted chromans, processes for their preparation, their use as a medicament or a diagnostic, and medicament comprising them Chromans of the formula I and of the formula 1a having the meanings R(A), R(B), R(C) and R(1) to R(8) indicated in the claims are outstandingly suitable for preparing a medicament for blocking the K+channel which is opened by cyclic adenosine monophosphate (cAMP); and further for preparing a medicament for inhibiting gastric acid secretion; for the treatment of ulcers of the stomach and of the intestinal region, in particular of the duodenum, for the treatment of reflux esophagitis, for the treatment of diarrheal illnesses, for the treatment and prevention of all types of arrhythmias including ventricular and supraventricular arrhythmias, and for the control of reentry arrhythmias and for the prevention of sudden heart death as a result of ventricular fibrillation.
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- Synthesis and property of liquid crystalline 4-alkoxyl-4″-cyano-p-terphenyls
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The synthesis of some new 4-alkoxyl-4″-cyano-p-terphenyls is described. The preliminary characterization by means of polarized optical microscopy, differential scanning calorimetry and X-ray diffraction shows that all these compounds are thermotropically liquid-crystalline and can form both the nematic and smectic mesophases.
- Zang, Zhi-Qian,Zhang, Dong,Wan, Xin-Hua,Zhou, Qi-Feng
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p. 145 - 158
(2007/10/03)
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- Synthesis of unsymmetrical biaryls by palladium-catalyzed cross coupling reactions of arenes with tetrabutylammonium triphenyldifluorosilicate, a hypervalent silicon reagent
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Palladium-catalyzed cross coupling of arenes with tetrabutylammonium triphenyldifluorosilicate, a hypervalent silicon reagent, to give unsymmetrical biaryls is reported. The Pd(0)-catalyzed process proceeds in good yield with aryl iodides, most aryl trifiates, and electron-deficient aryl bromides.
- Mowery, Molly E.,DeShong, Philip
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p. 3266 - 3270
(2007/10/03)
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- Norrish Type I Photoreaction in the Presence of Phenols; an Intermolecular Photo-Fries Rearrangement
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Pinacolone photolysis in the presence of phenols leads to phenyl acetates and hydroxy acetophenones; Norrish type I cleavage and subsequent hydrogen abstraction from the phenol by the tert-butyl radical gives rise to acyl-aryloxy radical pairs which recombined constituting an intermolecular photo-Fries rearrangement.
- Jimenez, M. Consuelo,Leal, Pablo,Miranda, Miguel A.,Tormos, Rosa
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p. 2009 - 2010
(2007/10/02)
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- Structural and Substituent Effect on (+.) vs. (+) Formation in Fast Atom Bombardment Mass Spectra of Simple Organic Compounds
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The peak intensity ratios of (+.) vs. (+) were measured in the fast atom bombardment (FAB) mass spectra of readily available test compounds with 3-nitrobenzyl alcohol as the matrix.For simple aromatic amines, the ratio increases as the ionization energy of the substrate decreases. 4-Subsituted benzophenones showed preferential formation of (+) ions, regardless of the nature of the substituents.This is probably due to the fact that the benzophenones have carbonyl groups which can form hydrogen bonds with the matrix molecule.The peak intensity ratio is roughly proportional to the Hammett ?+.Among 4-substituted biphenyls, both bromo and chloro substituents afforded abnormally high peak intensity ratios.The effects of the substituents in these compounds are discussed semi-quantitatively in terms of the Hammett correlation and the hard and soft acids and bases principle.The mechanism of ion formation in FAB and chemical ionization (CI) ion sources appeared to be different because some of the compounds studied showed an intense (+.) peak with a relatively weak (+) peak in FAB spectra but exhibited a strong (+) peak in ordinary CI spectra.
- Nakata, Hisao,Tanaka, Katsunori
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p. 283 - 288
(2007/10/02)
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- Acetylation of phenols in organic solvent catalyzed by a lipase from chromobacterium viscosum
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Lipase from Chromobacterium viscosum, absorbed on an inert support, was employed as catalyst for the esterification of monohydric phenols in organic solvent, with vinyl acetate as acyl donor. The effect of aromatic ring substitution on the initial rate of transesterification was investigated.
- Nicolosi,Piatelli,Sanfilippo
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p. 2477 - 2482
(2007/10/02)
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- FUNCTIONAL GROUP OXIDATION USING SODIUM PERBORATE
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Sodium perborate in acetic acid is an effective reagent for the oxidation of anilines to nitroarenes and of sulphides to either sulphoxides or sulphones.It is also an excellent reagent for the oxidative deprotection of ketone dimethylhydrazones.Baeyer-Villiger oxidation of ketones can be carried out with sodium perborate in either trifluoroacetic acid or acetic acid/trifluoroacetic acid mixtures, and hydroquinones and certain highly substituted phenols are smoothly converted into quinones.
- McKillop, Alexander,Tarbin, Jonathan A.
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p. 1753 - 1758
(2007/10/02)
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- Electron Transfer Reactions in Organic Chemistry. VII. Oxidative Acetoxylation of Aromatic Compounds by Tungsten Hexachloride
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Tungsten hexachloride, a high-potential oxidant, causes fast oxidative acetoxylation of ring and/or α positions of aromatic compounds, even as difficalty oxidizable ones as mesitylene and p-xylene.Chlorination is a completing reaction which cannnot be completely suppressed.The acetoxylation process in all likelihood proceeds via an electron transfer mechanism, involving initial formation of the radical cation of the substrate.
- Eberson, Lennart,Joensson, Lennart,Saenneskog, Owe
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p. 113 - 122
(2007/10/02)
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- Reductive elimination of aryl carboxylates from acyl(aryloxy)nickel(II) and -palladium(II) complexes
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Acyl(p-cyanophenoxy)nickel(II) and -palladium(II) complexes, M(COR)(OC6H4-p-CN)L2 (M = Ni, Pd; L2 = bpy, (PEt3)2), have been prepared by insertion reactions of CO into the metal-carbon bonds of the corresponding methylnickel(II) and -palladium(II) complexes. Addition of π-acids such as CO, maleic anhydride, and acrylonitrile selectively induces reductive elimination of p-cyanophenyl acetate from acylnickel(II) complexes, whereas thermolysis of the complexes mainly results in decarbonylation. In contrast, reductive elimination from the palladium analogue proceeds smoothly on thermolysis, and no apparent accelerating effect of added π-acids is observed. Kinetic studies of both reductive eliminations reveal that the former proceeds via an associative mechanism involving a five-coordinate intermediate, whereas the latter proceeds via two mechanisms, one being a dissociative pathway involving a three-coordinate species and the other being a direct reductive elimination from a four-coordinate species.
- Komiya, Sanshiro,Akai, Yasushi,Tanaka, Kohkichi,Yamamoto, Takakazu,Yamamoto, Akio
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p. 1130 - 1136
(2008/10/08)
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- Metal Ion Oxidation. XI. Oxidation of Aromatic Hydroarbons and Arylacetic Acids by Heteropoly Anions Containing Ni(IV), Mn(IV) and Co(III) Ions as Central Atoms
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Heteropoly ions containing Ni(IV) and Mn(IV) as central atoms have been shown to oxidize aromatic hydrocarbons and arylacetic acids in acetic acid and acetic acid-water, yielding acetates and alcohols.The product patternof these reactions supports an outer-sphere electron transfer mechanism.Substituted arylacetic acids are decarboxylated when treated with 12-tungstocobalt(III)ate ion and 9-molybdonickel(IV)ate ion.These decarboxylation reactions are proposed to be outer-sphere electron transfer processes.
- Joensson, Lennart
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p. 761 - 768
(2007/10/02)
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- Metal Ion Oxidation. VII. Oxidation of Aromatic Hydrocarbons by Potassium 12-Wolframocobalt(III)ate, a "Soluble Anode"
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The oxidation of aromatic compounds with potassium 12-wolframocobalt(II)ate in acetic acid media has been investigated.A wide range of alkylaromatics can be acetoxylated in the α position, whereas nuclear substitution can be effected in the presence of acetate ion.In a few cases acetoxymethylation is observed, presumably via intermediate arylacetic acid. 4-Fluoroanisole is converted to 4-acetoxyanisole.In all preparative aspects, the reaction is closely similar to anodic and Ag(II) mediated acetoxylation.A study of substituted effects upon α acetoxylation showed a good linear relationship between log krel and Eo for oxidation of the alkylaromatic substrates (slope -3.2 V-1).A strong deuterium isotope effect (KH/kD ca. 6) is indicative of a rate-determining step involving hydrogen atom transfer ("concerted electron/proton transfer") from the α C-H bond to an oxygen of the heteropoly ion.
- Eberson, Lennart,Wistrand, Lars-Goeran
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p. 349 - 358
(2007/10/02)
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