- Understanding the efficacy of N,N-dimethylformamide and oxalyl chloride combination as chemoselective O-formylating agent: An unified experimental and theoretical study
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We have developed a simple but efficient synthetic protocol for the O-formylation of a wide range of aromatic hydroxyl/phenolic substrates using an N,N-dimethylformamide (DMF) and oxalyl chloride [(COCl)2] combination in dichloromethane (DCM) as solvent at ambient temperature. The DMF/(COCl)2combination was found to be highly chemoselective for the aromatic/phenolic hydroxyl group over aliphatic hydroxyl or aromatic amine/thiol groups. This chemoselectivity of DMF/(COCl)2combination towards O-formylation of aromatic alcohols was explained on the basis of outcomes of both experimental and density functional theory–based theoretical studies.
- Batuta, Shaikh,Ali, Md. Ashif,Chatterjee, Anirban,Alam, Md. Niharul,Das, Sreeparna,Mandal, Debabrata,Begum, Naznin Ara
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- Urchin-like Nb2O5 hollow microspheres enabling efficient and selective photocatalytic C–C bond cleavage in lignin models under ambient conditions
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Selective cleavage of robust C?C bonds to harvest value-added aromatic oxygenates is an intriguing but challenging task in lignin depolymerization. Photocatalysis is a promising technology with the advantages of mild reaction conditions and strong sustainability. Herein, we show a novel urchin-like Nb2O5 hollow microsphere (U-Nb2O5 HM), prepared by one-pot hydrothermal method, are highly active and selective for Cα?Cβ bond cleavage of lignin β-O-4 model compounds under mild conditions, achieving 94% substrate conversion and 96% C?C bond cleavage selectivity. Systematic experimental studies and density functional theory (DFT) calculations revealed that the superior performance of U-Nb2O5 HMs arises from more exposed active sites, more efficient free charge separation and the active (001) facet, which facilitates the activation of Cβ?H bond of lignin models and generate key Cβ radical intermediates by photogenerated holes, further inducing the Cα?Cβ bond cleavage to produce aromatic oxygenates. This work could provide some suggestions for the fabrication of hierarchical photocatalysts in the lignin depolymerization system.
- Chen, Huan,Hong, Donghui,Long, Donghui,Niu, Bo,Wan, Kun,Wang, Junjie,Zhang, Yayun
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- One-Pot Transformation of Lignin and Lignin Model Compounds into Benzimidazoles
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It is a challenging task to simultaneously achieve selective depolymerization and valorization of lignin due to their complex structure and relatively stable bonds. We herein report an efficient depolymerization strategy that employs 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as oxidant/catalyst to selectively convert different oxidized lignin models to a wide variety of 2-phenylbenzimidazole-based compounds in up to 94 % yields, by reacting with o-phenylenediamines with varied substituents. This method could take full advantage of both Cβ and/or Cγ atom in lignin structure to furnish the desirable products instead of forming byproducts, thus exhibiting high atom economy. Furthermore, this strategy can effectively transform both the oxidized hardwood (birch) and softwood (pine) lignin into the corresponding degradation products in up to 45 wt% and 30 wt%, respectively. Through a “one-pot” process, we have successfully realized the oxidation/depolymerization/valorization of natural birch lignin at the same time and produced the benzimidazole derivatives in up to 67 wt% total yields.
- Guo, Tao,He, Jianghua,Liu, Tianwei,Zhang, Yuetao
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- The Trityl Cation Embedded into a [7]Helicene-Like Backbone: Preparation and Application as a Lewis Acid Catalyst
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The synthesis of a helically chiral carbenium ion is reported. The new motif is essentially a trityl cation embedded into a [7]helicene-like framework. The key step in its preparation establishes the π-extended fluorenone system in one step by an unprecedented palladium-catalyzed carbonylative annulation of a 4,4′-biphenanthryl-3,3′-diyl precursor. The racemic form of the new carbon Lewis acid was found to catalyze a representative set of reactions typically promoted by the trityl cation.
- Gross, Benjamin M.,Oestreich, Martin
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supporting information
p. 2512 - 2516
(2021/03/22)
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- Synthesis of Indoles by Reductive Cyclization of Nitro Compounds Using Formate Esters as CO Surrogates
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Alkyl and aryl formate esters were evaluated as CO sources in the Pd- and Pd/Ru-catalyzed reductive cyclization of 2-nitrostyrenes to give indoles. Whereas the use of alkyl formates requires the presence of a ruthenium catalyst such as Ru3(CO)12, the reaction with phenyl formate can be performed by using a Pd/phenanthroline complex alone. Phenyl formate was found to be the most effective CO source and the desired products were obtained in excellent yields, often higher than those previously reported using pressurized CO. The reaction tolerates many functional groups, including sensitive ones like a free aldehydic group or a pendant pyrrole. Detailed experiments and kinetic studies allow to conclude that the activation of phenyl formate is base-catalyzed and that the metal doesn't play a role in the decarbonylation step. The reactions can be performed in a single thick-walled glass tube with as little as 0.2 mol-% palladium catalyst and even on a 2 g scale. The same protocol can be extended to other nitro compounds, affording different heterocycles.
- Ahmed Fouad, Manar,Ferretti, Francesco,Formenti, Dario,Milani, Fabio,Ragaini, Fabio
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supporting information
p. 4876 - 4894
(2021/09/20)
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- Oxidative α-C-C Bond Cleavage of 2° and 3° Alcohols to Aromatic Acids with O2at Room Temperature via Iron Photocatalysis
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The selective α-C-C bond cleavage of unfunctionalized secondary (2°) and tertiary alcohols (3°) is essential for valorization of macromolecules and biopolymers. We developed a blue-light-driven iron catalysis for aerobic oxidation of 2° and 3° alcohols to acids via α-C-C bond cleavages at room temperature. The first example of oxygenation of the simple tertiary alcohols was reported. The iron catalyst and blue light play critical roles to enable the formation of highly reactive O radicals from alcohols and the consequent two α-C-C bond cleavages.
- Zhang, Zongnan,Zhang, Guoxiang,Xiong, Ni,Xue, Ting,Zhang, Junjie,Bai, Lu,Guo, Qinyue,Zeng, Rong
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supporting information
p. 2915 - 2920
(2021/05/05)
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- Visible-light-induced oxidative lignin c-c bond cleavage to aldehydes using vanadium catalysts
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Lignin is the largest carrier of aromatics on earth, and its depolymerization can afford value-Added aromatic products. Direct cleavage of the C-C bonds in lignin linkages is significant, but it is challenging to obtain low-molecular-weight aromatic monomers. Herein, using vanadium catalysts under visible light, we selectively cleave the C-C bonds in β-1 and β-O-4 interlinkages occluded in lignin models and extracts by an oxidative protocol. Visible light irradiation triggered single electron transfer between the substrate and the catalyst, which further induced the selective Cα-Cβ bond cleavage and generated the final aromatic products through radical intermediates. Using this photocatalytic chemistry, the reactivity of lignin models and the selectivity of Cα-Cβ bond cleavage were significantly improved. More importantly, this protocol affords aromatic monomers through the fragmentation of organosolv lignins even at room temperature, indicating the potential of photocatalytic C-C bond cleavage of lignin linkages under ambient conditions.
- Liu, Huifang,Li, Hongji,Luo, Nengchao,Wang, Feng
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p. 632 - 643
(2020/01/02)
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- The formyloxyl radical: Electrophilicity, C-H bond activation and anti-Markovnikov selectivity in the oxidation of aliphatic alkenes
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In the past the formyloxyl radical, HC(O)O, had only been rarely experimentally observed, and those studies were theoretical-spectroscopic in the context of electronic structure. The absence of a convenient method for the preparation of the formyloxyl radical has precluded investigations into its reactivity towards organic substrates. Very recently, we discovered that HC(O)O is formed in the anodic electrochemical oxidation of formic acid/lithium formate. Using a [CoIIIW12O40]5- polyanion catalyst, this led to the formation of phenyl formate from benzene. Here, we present our studies into the reactivity of electrochemically in situ generated HC(O)O with organic substrates. Reactions with benzene and a selection of substituted derivatives showed that HC(O)O is mildly electrophilic according to both experimentally and computationally derived Hammett linear free energy relationships. The reactions of HC(O)O with terminal alkenes significantly favor anti-Markovnikov oxidations yielding the corresponding aldehyde as the major product as well as further oxidation products. Analysis of plausible reaction pathways using 1-hexene as a representative substrate favored the likelihood of hydrogen abstraction from the allylic C-H bond forming a hexallyl radical followed by strongly preferred further attack of a second HC(O)O radical at the C1 position. Further oxidation products are surmised to be mostly a result of two consecutive addition reactions of HC(O)O to the CC double bond. An outer-sphere electron transfer between the formyloxyl radical donor and the [CoIIIW12O40]5- polyanion acceptor forming a donor-acceptor [D+-A-] complex is proposed to induce the observed anti-Markovnikov selectivity. Finally, the overall reactivity of HC(O)O towards hydrogen abstraction was evaluated using additional substrates. Alkanes were only slightly reactive, while the reactions of alkylarenes showed that aromatic substitution on the ring competes with C-H bond activation at the benzylic position. C-H bonds with bond dissociation energies (BDE) ≤ 85 kcal mol-1 are easily attacked by HC(O)O and reactivity appears to be significant for C-H bonds with a BDE of up to 90 kcal mol-1. In summary, this research identifies the reactivity of HC(O)O towards radical electrophilic substitution of arenes, anti-Markovnikov type oxidation of terminal alkenes, and indirectly defines the activity of HC(O)O towards C-H bond activation.
- Iron, Mark A.,Khenkin, Alexander M.,Neumann, Ronny,Somekh, Miriam
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p. 11584 - 11591
(2020/11/23)
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- Direct formylation of fluorine-containing aromatics with dichloromethyl alkyl ethers
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Formylations of fluorine-containing aromatic compounds with dichloromethyl alkyl ethers have been investigated. Dichloromethyl propyl ether and dichloromethyl butyl ether have been applied for the formylation of fluorine-containing anisoles to give the corresponding aldehydes in good yields. Application of these ethers is preferable to that of methyl ether, which is prepared from volatile methyl formate. Reaction of fluorine-containing phenols with these dichloromethyl alkyl ethers did not give salicylaldehyde derivatives, leading instead to corresponding aryl formates in high yields. A plausible mechanism is discussed.
- Warashina, Takuya,Matsuura, Daisuke,Kimura, Yoshikazu
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p. 587 - 593
(2019/07/22)
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- Combining Photo-Organo Redox- and Enzyme Catalysis Facilitates Asymmetric C-H Bond Functionalization
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In this study, we combined photo-organo redox catalysis and biocatalysis to achieve asymmetric C–H bond functionalization of simple alkane starting materials. The photo-organo catalyst anthraquinone sulfate (SAS) was employed to oxyfunctionalise alkanes to aldehydes and ketones. We coupled this light-driven reaction with asymmetric enzymatic functionalisations to yield chiral hydroxynitriles, amines, acyloins and α-chiral ketones with up to 99 % ee. In addition, we demonstrate functional group interconversion to alcohols, esters and carboxylic acids. The transformations can be performed as concurrent tandem reactions. We identified the degradation of substrates and inhibition of the biocatalysts as limiting factors affecting compatibility, due to reactive oxygen species generated in the photocatalytic step. These incompatibilities were addressed by reaction engineering, such as applying a two-phase system or temporal and spatial separation of the catalysts. Using a selection of eleven starting alkanes, one photo-organo catalyst and 8 diverse biocatalysts, we synthesized 26 products and report for the model compounds benzoin and mandelonitrile > 97 % ee at gram scale.
- Zhang, Wuyuan,Fueyo, Elena Fernandez,Hollmann, Frank,Martin, Laura Leemans,Pesic, Milja,Wardenga, Rainer,H?hne, Matthias,Schmidt, Sandy
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supporting information
p. 80 - 84
(2019/01/04)
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- MATRIX METALLOPROTEINASE (MMP) INHIBITORS AND METHODS OF USE THEREOF
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Hydantoin based compounds useful as inhibitors of matrix metalloproteinases (MMPs), particularly macrophage elastase (MMP-12) are described. Also described are related compositions and methods of using the compounds to inhibit MMP-12 and treat diseases mediated by MMP-12, such as asthma, chronic obstructive pulmonary disease (COPD), emphysema, acute lung injury, idiopathic pulmonary fibrosis (IPF), sarcoidosis, systemic sclerosis, liver fibrosis, nonalcoholic steatohepatitis (NASH), arthritis, cancer, heart disease, inflammatory bowel disease (IBD), acute kidney injury (AKI), chronic kidney disease (CKD), Alport syndrome, and nephritis.
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Paragraph 0503-0504
(2019/12/02)
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- PROCESS FOR MAKING FORMIC ACID UTILIZING LOWER-BOILING FORMATE ESTERS
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Disclosed is a process for recovering formic acid from a formate ester of a C3 to C4 alcohol. Disclosed is also a process for producing formic acid by carbonylating a C3 to C4 alcohol, hydrolyzing the formate ester of the alcohol, and recovering a formic acid product. The alcohol may be dried and returned to the reactor. The process enables a more energy efficient production of formic acid than the carbonylation of methanol to produce methyl formate.
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Paragraph 00177; 00178
(2019/02/15)
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- Synthesis of phenyl esters using SiO2-SO3H catalyst in conventional heating and microwave-irradiated esterification processes
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A SiO2-SO3H amorphous catalyst containing a small surface area of 115.0 m2g-1 and 1.32 mmol H+/g was prepared from fine construction sand and sodium carbonate and sulfonated with H2SO4. In a 10% (w/w) basis, it is very efficient for catalyzing the esterification of carboxylic acids with phenol. The reaction processes were performed using conventional heating and under microwave irradiation. The yields were higher in the microwave-irradiated esterification. The catalyst could be used for three esterification sequences in both processes.
- Barbosa, Sandro L.,Ottone, Myrlene,De Freitas, Milton,Lima, Camila D.,Nelson, David L.,Clososki, Giuliano C.,Caires, Franco J.,Klein, Stanlei I.,Hurtado, Gabriela R.
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p. 3663 - 3668
(2019/05/08)
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- PdO nanoparticles supported on triazole functionalized porous triazine polymer as an efficient heterogeneous catalyst for carbonylation of aryl halides
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A well-defined triazole functionalized porous triazine based polymers act as solid heterogeneous catalyst after incorporating palladium oxide nanoparticles (PdO@TTAS) have been synthesized and thoroughly characterized by various techniques such as, FT-IR, UV-DRS, solid state 13C CP-MAS, XPS, powder X-ray diffraction, TGA, SEM and TEM analysis has been detailed illustrated. It is important to note that synthesized catalytic performance for carbonylation of aryl halides (X?=?I, Br) with EDC.HCl (N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride), and formic acid was found to be an effective CO source in the presence of triethylamine as a base and DMF as a solvent medium at 80?°C for about 3?hr. The PdO@TTAS catalyst exhibits superior catalytic performance and along with good yield (up to 90%). Moreover, studying the heterogeneity and reusability of the environmentally friendly solid catalyst can be easily separated by simple filtration and then recycled for several times. In this reaction method, we avoided ligand, additive, promoters and CO gas, due to additional problem arise by using gaseous CO, highly toxic greenhouse gases and high pressurized reaction setup.
- Sadhasivam, Velu,Balasaravanan, Rajendran,Siva, Ayyanar
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- Method for photocatalytic oxidative cleavage of lignin model compounds
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The invention relates to a method for photocatalytic oxidative cleavage of lignin model compounds. According to the method, non-metallic carbon-nitrogen materials are used as photocatalysts, various lignin model compounds are used as reaction substrates,
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Page/Page column 7-9; 11; 12
(2019/04/02)
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- Controlled Photocatalytic Hydrocarbon Oxidation by Uranyl Complexes
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Controlled, photocatalytic C?H bond activations are key reactions in the toolkits of the modern synthetic chemist. While it is known that the uranyl(VI) ion, [UVIO2]2+, the environmentally dominant form of uranium, is photoactive, most literature examines its luminescent properties, neglecting its potential synthetic utility for photocatalytic C?H bond cleavage. Here, we synthesise and fully characterise an air-stable and hydrocarbon-soluble uranyl phenanthroline complex, [UVIO2(NO3)2(Ph2phen)], UPh2phen, and demonstrate that it can catalytically abstract hydrogen atoms from a variety of organic substrates under visible light irradiation. We show that the commercially available parent complex, uranyl nitrate ([UVIO2(NO3)2(OH2)2]?4H2O; UNO3), is also competent, but from electronic spectroscopy we attribute the higher rates and selectivity of UPh2phen to ligand-mediated electronic effects. Ketones are selectively formed over other oxygenated products (alcohols, etc.), and the catalytic oxidation of substrates containing a benzylic C?H position is particularly improved for UPh2phen. We also show uranyl-mediated photocatalytic C?C bond cleavage in a model lignin compound for the first time.
- Arnold, Polly L.,Purkis, Jamie M.,Rutkauskaite, Ryte,Kovacs, Daniel,Love, Jason B.,Austin, Jonathan
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p. 3786 - 3790
(2019/03/07)
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- A cascade mechanism for a simple reaction: The gas-phase methylation of phenol with methanol
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The gas-phase alkylation of phenol with methanol, a reaction triggered for the production of o-cresol and 2,6-xylenol, is catalysed by MgO-based catalysts. Despite the industrial use of this process, the mechanism of the reaction – which is commonly believed to be based on a classical electrophilic attack of activated methanol onto the aromatic ring – is far from being fully understood. In some previous studies we reported that the reaction intermediate is salicylic alcohol, which is formed by the reaction between the adsorbed phenolate and formaldehyde, the latter being formed in-situ by methanol dehydrogenation. Here we elucidate the following steps of the reaction mechanism, by combining reactivity experiments and DFT calculation, with MgO as a model catalyst. It was found that salicylic alcohol dehydrates into quinone methide, which is then reduced via H-transfer by methanol to o-cresol. Moreover, a dehydrogenation/hydrogenation equilibrium is established between salicylic alcohol and salicylic aldehyde. The methide can also react with methanol to form 2-methoxymethylphenol, which may decompose into o-cresol, thus providing an alternative pathway for the formation of the alkylated compound.
- Tabanelli, Tommaso,Passeri, Sauro,Guidetti, Stefania,Cavani, Fabrizio,Lucarelli, Carlo,Cargnoni, Fausto,Mella, Massimo
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p. 447 - 460
(2019/01/30)
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- Synthetic method for p-hydroxybenzaldehyde
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The invention discloses a synthetic method for p-hydroxybenzaldehyde. The synthetic method comprises the following steps: with phenol and formic acid as raw materials, subjecting the raw materials toan esterification reaction under the action of a catalyst A so as to produce phenyl formate; and subjecting phenyl formate to a Fries rearrangement reaction under the action of a catalyst B so as to produce p-hydroxybenzaldehyde. According to the invention, the conversion rate of the raw materials is high, product yield is high, and the method is novel method for preparing p-hydroxybenzaldehyde from phenol and formic acid; and phenol and formic acid undergo the esterification reaction under the action of the catalyst A so as to produce phenyl formate, phenyl formate undergoes the Fries rearrangement reaction under the action of the catalyst B so as to produce p-hydroxybenzaldehyde, and then recrystallization and purification are carried out, so product purity can reach 99% or more, and overall product yield is as high as 95%. The method uses widely available raw materials and cheap and easily available catalysts, and is simple in reaction process, free of severe requirements on production equipment, low in equipment investment and convenient for industrial application.
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Paragraph 0026; 0032; 0038; 0044
(2018/06/14)
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- Photocatalytic Cleavage of C-C Bond in Lignin Models under Visible Light on Mesoporous Graphitic Carbon Nitride through π-π Stacking Interaction
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Photocatalysis is a potentially promising approach to harvest aromatic compounds from lignin. However, the development of an active and selective solid photocatalyst is still challenging for lignin transformation under ambient conditions. We herein report a mild photocatalytic oxidative strategy for C-C bond cleavage of lignin β-O-4 and β-1 linkages using a mesoporous graphitic carbon nitride catalyst. Identifications by solid-state NMR techniques and density functional theory (DFT) calculations indicate that π-π stacking interactions are most likely present between the flexible carbon nitride surface and lignin model molecule. Besides, low charge recombination efficiency and high specific surface area (206.5 m2 g-1) of the catalyst also contribute to its high catalytic activity. Mechanistic investigations reveal that photogenerated holes, as the main active species, trigger the oxidation and C-C bond cleavage of lignin models. This study sheds light on the interaction between complex lignin structures and the catalyst surface and provides a new strategy of photocatalytic cleavage of lignin models with heterogeneous photocatalysts.
- Liu, Huifang,Li, Hongji,Lu, Jianmin,Zeng, Shu,Wang, Min,Luo, Nengchao,Xu, Shutao,Wang, Feng
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p. 4761 - 4771
(2018/05/14)
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- Electrochemical Hydroxylation of Arenes Catalyzed by a Keggin Polyoxometalate with a Cobalt(IV) Heteroatom
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The sustainable, selective direct hydroxylation of arenes, such as benzene to phenol, is an important research challenge. An electrocatalytic transformation using formic acid to oxidize benzene and its halogenated derivatives to selectively yield aryl formates, which are easily hydrolyzed by water to yield the corresponding phenols, is presented. The formylation reaction occurs on a Pt anode in the presence of [CoIIIW12O40]5? as a catalyst and lithium formate as an electrolyte via formation of a formyloxyl radical as the reactive species, which was trapped by a BMPO spin trap and identified by EPR. Hydrogen was formed at the Pt cathode. The sum transformation is ArH+H2O→ArOH+H2. Non-optimized reaction conditions showed a Faradaic efficiency of 75 % and selective formation of the mono-oxidized product in a 35 % yield. Decomposition of formic acid into CO2 and H2 is a side-reaction.
- Khenkin, Alexander M.,Somekh, Miriam,Carmieli, Raanan,Neumann, Ronny
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supporting information
p. 5403 - 5407
(2018/04/19)
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- Application of polydopamine sulfamic acid-functionalized magnetic Fe3O4 nanoparticles (Fe3O4@PDA-SO3H) as a heterogeneous and recyclable nanocatalyst for the formylation of alcohols and amines under solvent-free conditions
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Herein, formylation of structurally different amines and alcohols with ethyl formate was carried out in the presence of a catalytic proportion of sulfonic acid supported on polydopamine (PDA)-encapsulated Fe3O4 nanoparticles as a heterogeneous, recyclable, and greatly efficient catalyst; this method provided the corresponding N-formyl compounds in good to excellent yields under solvent-free conditions. The magnetically catalytic system was recovered, by-passing the time-consuming filtration operation using an external magnet device. This procedure also increases the purity of the product and promises economic and ecological advantages. Furthermore, the recovery and reuse of the catalyst was demonstrated five times without detectable loss in the activity.
- Taheri, Sepideh,Veisi, Hojat,Hekmati, Malak
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p. 5075 - 5081
(2017/07/11)
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- Mechanistic Insight into Weak Base-Catalyzed Generation of Carbon Monoxide from Phenyl Formate and Its Application to Catalytic Carbonylation at Room Temperature without Use of External Carbon Monoxide Gas
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The mechanisms of the weak base-catalyzed generation of carbon monoxide (CO) and phenol from phenyl formate were investigated by experimental and theoretical methods. Kinetic studies revealed a first-order reaction in both phenyl formate and the base. The reaction was found to proceed by an E2 α-elimination pathway, which involves the abstraction of the formyl proton of phenyl formate, simultaneously generating CO and phenoxide. The reaction rate was affected by the substituents on phenyl formate, the polarity of solvents, and the basicity of bases. The mechanistic insight obtained from these studies permitted the chemical control of the rate of CO generation, which was the key to the development of the external CO-free Pd-catalyzed phenoxycarbonylation of haloarenes at room temperature. Because of the mild reaction conditions and wide substrate scope, this phenoxycarbonylation constitutes a general, safe, and practical method to synthesize arenecarboxylic acid esters. (Figure presented.).
- Konishi, Hideyuki,Matsubara, Mika,Mori, Keisuke,Tokiwa, Takaki,Arulmozhiraja, Sundaram,Yamamoto, Yuta,Ishikawa, Yoshinobu,Hashimoto, Hiroshi,Shigeta, Yasuteru,Tokiwa, Hiroaki,Manabe, Kei
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supporting information
p. 3592 - 3601
(2017/10/24)
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- Solvent- and catalyst-free N-formylations of amines at ambient condition: Exploring the usability of aromatic formates as N-formylating agents
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A solvent- and catalyst-free N-formylation protocol has been developed for amines (1s–21s) where aromatic formates (1r–6r) were used as the N-formylating agents. The amine substrates include both primary and secondary aromatic amines (1s–19s) as well as aliphatic amine (20s) and a primary amide (21s). Structures of both the aromatic formate and amine components strongly influenced the rate of the reaction and yield of the N-formamide products. The reaction condition is mild and easy to operate. This protocol can be done smoothly under ambient conditions and gives high yield of formamide products. Furthermore, the present method cannot be applied for the formylation of thiol group (22s). This signifies its possible use for the chemoselective N-formylation of amine in the presence of thiol functionality.
- Batuta, Shaikh,Begum, Naznin Ara
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p. 137 - 147
(2017/01/11)
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- Structural and catalytic characterization of a fungal baeyer-villiger monooxygenase
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Baeyer-Villiger monooxygenases (BVMOs) are biocatalysts that convert ketones to esters. Due to their high regio-, stereo- and enantioselectivity and ability to catalyse these reactions under mild conditions, they have gained interest as alternatives to chemical Baeyer-Villiger catalysts. Despite their widespread occurrence within the fungal kingdom, most of the currently characterized BVMOs are from bacterial origin. Here we report the catalytic and structural characterization of BVMOAFL838 from Aspergillus flavus. BVMOAFL838 converts linear and aryl ketones with high regioselectivity. Steady-state kinetics revealed BVMOAFL838 to show significant substrate inhibition with phenylacetone, which was more pronounced at low pH, enzyme and buffer concentrations. Para substitutions on the phenyl group significantly improved substrate affinity and increased turnover frequencies. Steady-state kinetics revealed BVMOAFL838 to preferentially oxidize aliphatic ketones and aryl ketones when the phenyl group are separated by at least two carbons from the carbonyl group. The X-ray crystal structure, the first of a fungal BVMO, was determined at 1.9 A and revealed the typical overall fold seen in type I bacterial BVMOs. The active site Arg and Asp are conserved, with the Arg found in the ginh position. Similar to phenylacetone monooxygenase (PAMO), a two residue insert relative to cyclohexanone monooxygenase (CHMO) forms a bulge within the active site. Approximately half of the gvariableh loop is folded into a short ?-helix and covers part of the active site entry channel in the non-NADPH bound structure. This study adds to the current efforts to rationalize the substrate scope of BVMOs through comparative catalytic and structural investigation of different BVMOs.
- Ferroni, Felix Martin,Tolmie, Carmien,Smit, Martha Sophia,Opperman, Diederik Johannes
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- TiCl4/Et3N-Mediated Condensation of Acetate and Formate Esters: Direct Access to β-Alkoxy- and β-Aryloxyacrylates
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A methodology to build (E)-β-alkoxy- and (E)-β-aryloxyacrylate moieties from acetate and formate esters promoted by the TiCl4/Et3N system is presented. The reaction is compatible with a broad range of structural skeletons and elapses through an unusual condensation pathway. Taking into account the obtained results, we propose a plausible mechanism involving a bimetallic titanium intermediate for this type of transformation.
- álvarez-Calero, José María,Jorge, Zacarías D.,Massanet, Guillermo M.
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supporting information
p. 6344 - 6347
(2016/12/23)
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- Palladium-Catalyzed Carbonylative Synthesis of Aryl Formates under Mild Conditions
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Aryl formates have been extensively applied as CO sources in CO-free carbonylation reactions. However, there are no catalytic synthetic procedures for their preparation. In this manuscript, we developed a convenient palladium-catalyzed procedure for the synthesis of aryl formates. Good yields were achieved under mild reaction conditions with formic acid as the formyl source. A formyl meeting: A convenient palladium-catalyzed carbonylation procedure for the synthesis of aryl formates is developed. Good yields are achieved under mild reaction conditions with formic acid as the formyl source.
- Jiang, Li-Bing,Li, Rui,Li, Hao-Peng,Qi, Xinxin,Wu, Xiao-Feng
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p. 1788 - 1791
(2016/06/01)
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- Mechanistic studies on the VO(acac)2-catalyzed oxidative cleavage of lignin model compounds in acetic acid
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Lignin is the primary source of aromatic chemicals in nature. Selective aerobic oxidation has provided a promising approach for breaking lignin into smaller aromatics. During VO(acac)2-catalyzed oxidation of lignin model compound 2-phenoxy-1-phenylethanol, benzaldehyde was unexpectedly observed as a product, in contrast to the results reported previously. The reaction pathway was studied, and a hemiacetal-like intermediate was found to be involved, and the similar intermediate was also observed during oxidation of model compound benzyl phenyl ether. Compared with direct C-O bond cleavage, prior formation of hemiacetal-like structures via oxidation would be expected to facilitate the cleavage of the aryl ether bond in aralkyl aryl ethers under mild reaction conditions.
- Ma, Yangyang,Du, Zhongtian,Xia, Fei,Ma, Jiping,Gao, Jin,Xu, Jie
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p. 110229 - 110234
(2016/11/30)
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- Fabrication of Fe3O4- l -dopa-CuII/SnIV@Micro-Mesoporous-SiO2 Catalyst Applied to Baeyer-Villiger Oxidation Reaction
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A Magnetic mFe3O4-l-dopa-CuII/SnIV@micro-mesoporous-SiO2 catalyst was successfully prepared. The catalyst exhibits high and stable catalytic activity for the Baeyer-Villiger oxidation reaction with air as oxidant. Furthermore, the selectivity can reach nearly 100 %. Meanwhile the catalyst can be easily separated by an external magnet and reused at least up to five cycles without any notable loss in catalytic activity. In addition, the effect of Sn and Cu on the oxidation of cyclohexanone is discussed.
- Huo, Hongfei,Wu, Li,Ma, Jianxin,Yang, Honglei,Zhang, Le,Yang, Yuanyuan,Li, Shuwen,Li, Rong
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p. 779 - 786
(2016/03/05)
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- Three step procedure for the preparation of aromatic and aliphatic difluoromethyl ethers from phenols and alcohols using a chlorine/fluorine exchange methodology
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Difluoromethyl ethers are prepared from phenols in three steps via their respective formate ester derivatives. The formates are first converted to dichloromethyl ethers by treatment with PCl5. These ethers are then induced to undergo chlorine/fluorine exchange to form the respective difluoromethyl ethers. The chlorine/fluorine exchange is carried out by either a room temperature, solvolytic process using THF-5HF or Et3N-3HF as exchange medium, where HF is the ultimate source of fluorine, or by a direct displacement process in sulfolane at 125 C, where KF is the source of fluorine. By one or another of these processes, virtually all phenols, electron-rich and electron-poor, can be converted to their respective difluoromethyl ethers in good yields. Aliphatic alcohols are also able to be converted to their difluoromethyl ether derivatives using the Et3N-3HF exchange medium.
- Dolbier Jr., William R.,Wang, Fei,Tang, Xiaojun,Thomoson, Charles S.,Wang, Linhua
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- Acceleration of the Dakin reaction by trifluoroacetic acid
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An acceleration of the Dakin reaction caused by addition of trifluoroacetic acid is described. The modified protocol converts aromatic aldehydes to the corresponding phenols within 4 hours at room temperature by means of hydrogen peroxide in acidic medium. This acceleration is attributed to the stability of hydrogen peroxide in an acidic medium. This modified protocol provides alternative and easy access to important phenolic precursors that have been used in the synthesis of various natural products.
- Natu, Arun D.,Burde, Ameya S.,Limaye, Rohan A.,Paradkar, Madhusudan V.
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p. 381 - 382
(2014/07/08)
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- Nickel-catalyzed hydrosilylation of CO2 in the Presence of Et3B for the synthesis of formic acid and related formates
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The reaction of CO2 with Et3SiH catalyzed by the nickel complex [(dippe)Ni(μ-H)]2 (1) afforded the reduction products Et3SiOCH2OSiEt3 (12%), Et 3SiOCH3 (3%), and CO, which were characterized by standard spectroscopic methods. Part of the generated CO was found as the complex [(dippe)Ni(CO)]2 (2), which was characterized by single-crystal X-ray diffraction. When the same reaction was carried out in the presence of a Lewis acid, such as Et3B, the hydrosilylation of CO2 efficiently proceeded to give the silyl formate (Et3SiOC(O)H) in high yields (85-89%), at 80 C for 1 h. Further reactivity of the silyl formate to yield formic acid, formamides, and alkyl formates was also investigated.
- Gonzalez-Sebastian, Lucero,Flores-Alamo, Marcos,Garcia, Juventino J.
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p. 7186 - 7194
(2014/01/06)
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- Palladacycle-catalyzed carbonylation of aryl iodides or bromides with aryl formates
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An efficient palladacycle-catalyzed aromatic carbonylation reaction of aryl formates with aryl iodides or bromides has been developed. Commercially available and easily prepared aryl formates were employed as carbonyl sources without the use of external carbon monoxide. The present catalytic system shows broad functional group tolerance and affords aryl benzoate derivatives in good to excellent yields. Copyright
- Chen, Guangwei,Leng, Yuting,Yang, Fan,Wang, Shiwei,Wu, Yangjie
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p. 1488 - 1494
(2014/01/06)
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- Preparation of α,β-unsaturated esters and amides via external-CO-free palladium-catalyzed carbonylation of alkenyl tosylates
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Palladium-catalyzed carbonylation of tosylates with phenyl formate is described. This procedure needs neither external carbon monoxide nor any pressure-resistant apparatus. A variety of cyclic and acyclic alkenyl tosylates can be converted into the corresponding phenyl esters in good yields. Furthermore, this method is effective for the one-pot synthesis of α,β-unsaturated amides.
- Ueda, Tsuyoshi,Konishi, Hideyuki,Manabe, Kei
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supporting information; experimental part
p. 5171 - 5175
(2012/09/25)
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- Synthesis and singlet oxygen reactivity of 1,2-diaryloxyethenes and selected sulfur and nitrogen analogs
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1,2-Diaryloxyethene has recently been proposed as a linker in singlet oxygen-mediated drug release. Even though 1,2-diaryloxyethenes look very simple, their synthesis was not an easy task. Previous methods are limited to symmetric molecules, lengthy step and low yield. We report on a facile synthetic method not only for 1,2-diaryloxyethenes but also their sulfur and nitrogen analogs in yields ranging from 40 to 90% with more than 90% purity at the vinylation reaction. Most recently, light-controlled drug release systems were proposed, where singlet oxygen generated from low energy light and a photosensitizer cleaves electron-rich alkenes, e.g. 1,2-diaryloxyethene. However, the synthesis of 1,2-diaryloxyethene was not well established. Herein, we report a facile synthesis of 1,2-diaryloxyethenes and its sulfur and nitrogen analogs. Model compounds were prepared in four steps from 4-phenylphenol via Ullman-type coupling reaction.
- Nkepang, Gregory,Pogula, Praveen K.,Bio, Moses,You, Youngjae
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experimental part
p. 753 - 759
(2012/09/05)
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- O-acylation of substituted phenols with various alkanoyl chlorides under phase-transfer catalyst conditions
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Esterification of several types of mono-and disubstituted phenols with various mono-and dialkanoyl chlorides was performed in phase-transfer catalysis conditions, using tetrabutylammonium chloride in a mixture of aqueous NaOH and dichloromethane. The process is particularly efficient (almost quantitative yields) as well as rapid (only 5 min reaction time, at a temperature of0°C). Taylor & Francis Group, LLC.
- Simion, Alina Marieta,Hashimoto, Iwao,Mitoma, Yoshiharu,Egashira, Naoyoshi,Simion, Cristian
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scheme or table
p. 921 - 931
(2012/02/01)
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- Palladium-catalyzed carbonylation of aryl, alkenyl, and allyl halides with phenyl formate
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Highly efficient palladium-catalyzed carbonylation of aryl, alkenyl, and allyl halides with phenyl formate is reported. This procedure does not use carbon monoxide and affords one-carbon-elongated carboxylic acid phenyl esters in excellent yields. The reaction proceeds smoothly under mild conditions and tolerates a wide range of functional groups including aldehyde, ether, ketone, ester, and cyano groups. Furthermore, a variety of heteroaromatic bromides can be converted to the corresponding phenyl esters in high yields.
- Ueda, Tsuyoshi,Konishi, Hideyuki,Manabe, Kei
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supporting information; experimental part
p. 3100 - 3103
(2012/07/27)
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- Palladium-catalyzed esterification of aryl halides using aryl formates without the use of external carbon monoxide
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Aryl formates are efficient carbon monoxide sources in palladium-catalyzed esterification of aryl halides. The carbonylation readily proceeds at ambient pressure without the use of external carbon monoxide to afford the corresponding esters in high yields.
- Fujihara, Tetsuaki,Hosoki, Tomoya,Katafuchi, Yuko,Iwai, Tomohiro,Terao, Jun,Tsuji, Yasushi
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experimental part
p. 8012 - 8014
(2012/09/08)
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- Trichlorophenyl formate: Highly reactive and easily accessible crystalline CO surrogate for palladium-catalyzed carbonylation of aryl/alkenyl halides and triflates
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The high utility of 2,4,6-trichlorophenyl formate, a highly reactive and easily accessible crystalline CO surrogate, is demonstrated. The decarbonylation with NEt3 to generate CO proceeded rapidly at rt, thereby allowing external-CO-free Pd-catalyzed carbonylation of aryl/alkenyl halides and triflates. The high reactivity of the CO surrogate enabled carbonylation at rt and significantly reduced the quantities of formate to near-stoichiometric levels. The obtained trichlorophenyl esters can be readily converted to a variety of carboxylic acid derivatives in high yields.
- Ueda, Tsuyoshi,Konishi, Hideyuki,Manabe, Kei
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supporting information
p. 5370 - 5373,4
(2012/12/12)
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- Oxidation of primary aliphatic and aromatic aldehydes with difluoro(aryl)-λ3-bromane
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Oxidation of primary aliphatic aldehydes with p- trifluoromethylphenyl(difluoro)-λ3-bromane in dichloromethane at 0 °C afforded acid fluorides selectively in good yields, while that of aromatic aldehydes in chloroform at room temperature produced aryl difluoromethyl ethers. A larger migratory aptitude of aryl groups compared to primary alkyl groups during a 1,2-shift from carbon to an electron-deficient oxygen atom in bromane(III) Criegee-type intermediates will result in these differences in the reaction courses.
- Ochiai, Masahito,Yoshimura, Akira,Hoque, Md. Mahbubul,Okubo, Takuji,Saito, Motomichi,Miyamoto, Kazunori
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supporting information; experimental part
p. 5568 - 5571
(2011/12/03)
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- Palladium-catalyzed hydroesterification of alkynes employing aryl formates without the use of external carbon monoxide
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A highly efficient hydroesterification of alkynes employing aryl formates has been developed without the use of external carbon monoxide and at ambient pressure. The reaction in the presence of a palladium-xantphos catalyst system selectively affords α,β-unsaturated esters in good to high yields. Use of an aryl formate is crucial and alkyl formates did not react at all. The hydroesterification of norbornene and terminal alkenes also readily proceeded under similar reaction conditions. A mechanistic study showed that conversion of aryl formates to carbon monoxide and phenol derivatives occurred in the hydroesterification. Xantphos is highly effective as a ligand both in the conversion of aryl formates and the hydroesterification reactions.
- Katafuchi, Yuko,Fujihara, Tetsuaki,Iwai, Tomohiro,Terao, Jun,Tsuji, Yasushi
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supporting information; experimental part
p. 475 - 482
(2011/04/22)
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- Hypervalent λ3-bromane strategy for Baeyer-Villiger oxidation: Selective transformation of primary aliphatic and aromatic aldehydes to formates, which is missing in the classical Baeyer-Villiger oxidation
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A conceptually distinct, modern strategy for Baeyer-Villiger oxidation (BVO) was developed. Our novel method involves initial hydration of water to carbonyl compounds, followed by ligand exchange of hypervalent aryl-λ3-bromane on bromane(III) with the resulting hydrate, yielding a new type of activated Criegee intermediate. The intermediate undergoes BV rearrangement and produces an ester via facile reductive elimination of an aryl-λ3-bromanyl group, because of the hypernucleofugality. The novel strategy makes it possible to induce selectively the BV rearrangement of straight chain primary aliphatic as well as aromatic aldehydes, which is missing in the classical BVO: for instance, octanal and benzaldehyde afforded rearranged formate esters with high selectivity (>95%) under our conditions, while the attempted classical BVO produced only carboxylic acids. This firmly establishes the powerful nature of new methodology for BVO.
- Ochiai, Masahito,Yoshimura, Akira,Miyamoto, Kazunori,Hayashi, Satoko,Nakanishi, Waro
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supporting information; experimental part
p. 9236 - 9239
(2010/11/02)
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- Low energy light-triggered oxidative cleavage of olefins
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A series of substituted olefins were tested for their reactivity with singlet oxygen as a singlet oxygen-mediated cleavable linker. Low intensity light of 200 mW/cm2 was irradiated to the solution of an olefin and 5,10,15-triphenyl-20-(4-hydroxyphenyl)-21H,23H-porphyrin under atmospheric condition. Among the tested olefins, 1,2-cis-diphenoxyethylene reacted fast with singlet oxygen, >80% within 15 min yielding a stoichiometric conversion to aldehyde product without any side reactions.
- Murthy, Rajesh S.,Bio, Moses,You, Youngjae
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scheme or table
p. 1041 - 1044
(2009/05/27)
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- Highly efficient formylation of alcohols, thiols and aniline derivatives by a heterogeneous (HCOOH/SiO2) system under microwave irradiation and solvent-free conditions
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A simple, rapid and efficient microwave-assisted procedure for the formylation of aniline derivatives and alcohols, using a heterogeneous (HCOOH/SiO2) system under solvent-free conditions is reported. The method is applied to a set of amines, alcohols and thiols and short reaction times (10 min) with high yields are reported. This protocol introduces a practical and viable green technology of solvent-free and catalyst-free reactions.
- Ghorbani-Vaghei, Ramin,Veisi, Hojat,Amiri, Mostafa,Chegini, Mohammad,Karimi, Mehdi,Dadamahaleh, Somayeh Akbari,Sedrpoushan, Alireza
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experimental part
p. 39 - 43
(2010/09/03)
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- A new simple method for the preparation of aryl formates from phenols
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Aryl formates are prepared in a two step one-pot procedure from phenols. Firstly the formylating reagent triformamide (1b) is generated from sodium diformamide (2) and methane-sulfonyl chloride in situ, which reacts with phenols 4a-f to give aryl formates 5a-f in good yields. Triformamide, prepared in situ, transforms anisole in the presence of aluminum chloride to the N-(diarylmethyl)formamide 7.
- Hashmi, Imran Ali,Kantlehner, Willi,Ivanov, Ivo C.
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experimental part
p. 478 - 480
(2009/01/31)
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- Aryloxy Radicals from Diaryloxydiazirines: α-Cleavage of Diaryloxycarbenes or Excited Diazirines?
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(Equation presented) The synthesis of diaryloxydiazirines, precursors to diaryloxycarbenes, is described. Thermolyses of the diazirines afford anticipated carbene products, but photolyses afford both carbenes and aryloxy radicals by α-scission. UV spectra of the carbenes and radicals are observed.
- Fede, Jean-Marie,Jockusch, Steffen,Lin, Nan,Moss, Robert A.,Turro, Nicholas J.
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p. 5027 - 5030
(2007/10/03)
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- Orthoamides, LVI [1]. A new method of wide scope for the preparation of aryl formates
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Aryl formates 4a-u, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 are prepared by formylation of hydroxyarenes 3a-u, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25 with N,N-diformylacetamide (1) or triformamide (2), respectively, in fairly good yields. The reactions can be catalyzed by sodium diformamide or praseodymium(III) triflate. The thiolformate 28 was obtained analogously from 1-thionaphthol (27).
- Ziegler, Georg,Kantlehner, Willi
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p. 1172 - 1177
(2007/10/03)
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- One-step conversion of formate esters to O-silyl ethers by means of samarium diiodide in the presence of chlorosilane reagents
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One-step conversion of various types of formate esters into the corresponding O-silyl ethers under neutral reaction conditions was established by employing samarium diiodide in the presence of chlorosilane reagents.
- Honda, Toshio,Ishikawa, Fumihiro
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p. 3323 - 3328
(2007/10/03)
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- The selective functionalization of saturated hydrocarbons. Part 44. Measurement of size of reagent by variation of steric demands of competing substrates using Gif chemistry
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Cyclohexane has been co-oxidized with a number of aromatic compounds of varying steric requirements. The oxidant was hydrogen peroxide with Fe(III)-picolinic acid in a Gif type solvent of pyridine and acetonitrile. Both the cyclohexane and the aromatic derivatives were reacting with the same iron species. From the steric requirements for the hydroxylation of the aromatic partner, it can be deduced that the iron species is of significant size. For this reason, and also because of known pulse radiolysis results, hydroxyl radicals are not involved.
- Barton, Derek H.R.,Launay, Franck
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p. 3379 - 3390
(2007/10/03)
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- Reactions of α-Chloro- and α,α-dichloro-β-oxoaldehydes with Anionic Nucleophiles
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The reaction of α-chloro and α,α-dichloro-β-oxoaldehydes with anionic nucleophiles (NaOH, MeONa, PhONa, MeCOOK) proceeds mainly via haloform splitting with elimination of the formyl group; only with the most nucleophilic sodium methoxide, the reaction at the β-carbon atom partially occurs.The intermediate anions react with benzaldehyde to give difficulty accessible polyfunctional compounds.
- Guseinov, F. I.,Tagiev, S. Sh.,Moskva, V. V.
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- Formation of Dichloromethyl Phenyl Ethers as Major Products in Photo-Reimer-Tiemann Reaction without Base
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Photolysis of phenols 1a-d in chloroform or carbon tetrachloride afforded the corresponding di- or trichloromethyl phenyl ethers (2a-d or 6a-d, respectively).In chloroform, hydroxybenzaldehydes 4a-d or 5 and phenyl formates 3a-d were obtained as minor photoproducts.In carbon tetrachloride, traces of salicyloyl chloride (7), phenyl salicylate (8) and phenyl p-hydroxybenzoate (9) were detected starting from the parent phenol (1a).The obtained results agree with the involvement of an electron transfer mechanism.
- Jimenez, M. Consuelo,Miranda, Miguel A.,Tormos, Rosa
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p. 5825 - 5830
(2007/10/02)
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