- EXCEPTIONAL REACTIVITY OF THE AROMATIC RING IN 8-SUBSTITUTED 1-NAPHTHOL DERIVATIVES. READY REDUCTION TO TETRALINS.
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8-Lithio-1-methoxynaphthalene is acylated and alkylated to give 8-CO2H, COCH3 and Me2C(OH) derivatives in only poor yields.Methyl lithium does not add to the 8-acetyl compound, converting it instead to the lithium enolate.Compounds with secondary or tertiary alkyl peri-substituents undergo rapid protodealkylation, and are readily reduced to tetralins by H2/Pd at atmospheric pressure.
- Kirby, Anthony J.,Percy, Jonathan M.
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- Dediazoniation of 1-naphthalenediazonium tetrafluoroborate in aqueous acid and in micellar solutions
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We have measured the rates and product yields of dediazoniation of 1-naphthalenediazonium (1ND) tetrafluoroborate in the presence and absence of sodium dodecyl sulfate (SDS) micellar aggregates by employing a combination of UV-vis spectroscopy and high-performance liquid chromatography (HPLC) measurements. Kinetic data were obtained by a derivatization procedure with product yields were determined by HPLC. HPLC chromatograms show that in aqueous acid and in micellar solutions only one dediazoniation product is formed in significant quantities, 1-naphthol (NOH), and the observed rate constants (kobs) are tne same when IND loss is monitored spectrometrically and when NOH formation is monitored by HPLC. Activation parameters were obtained both in the presence and absence of SDS micellar aggregates. In both the systems, the enthalpies of activation are high and the entropies of activation are positive. The enthalpy of activation in the absence of SDS is very similar to that in the presence of SDS micelles, but the entropy of activation is lower by a factor of 4. As a consequence, SDS micelles speed up the thermal decomposition of 1 ND and increase kobs by a factor of 1.5 when [SDS] = 0.02 M. In contrast, results obtained in the presence of complexing systems such as crown ethers and polyethers show significant stabilization of the parent arenediazonium ions. Kinetic and HPLC data are consistent with the heterolytic DN + AN mechanism that involves the rate-determining fragmentation of the arenediazonium ion into a very reactive phenyl cation that reacts competitively with available nucleophiles.
- Bravo-Diaz, Carlos,Pastoriza-Gallego, Maria Jose,Losada-Barreiro, Sonia,Sanchez-Paz, Veronica,Fernandez-Alonso, Alejandra
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- Ultrasensitive self-enhanced electrochemiluminescence sensor based on novel PAN?Ru?PEI?Nafion nanofiber mat
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In the present work, a novel self-enhanced electrochemiluminescence (ECL) composite was for the first time prepared by simply electrospinning a mixture of polyacrylonitrile (PAN), Ru(bpy)32+, poly(ethylenimine) (PEI) and Nafion, and defined as PAN?Ru?PEI?Nafion nanofiber mat (PAN?Ru?PEI?Nafionnfm). Herein, Ru(bpy)32+was applied as an ECL reagent, and PEI was selected as a co-reactant due to the abundant tertiary amine groups in its backbone. In order to further improve the ECL efficiency of the Ru(bpy)32+-PEI system, we innovatively loaded Ru(bpy)32+and PEI into PAN nanofibers simultaneously by a one-step electrospinning technique. As a result, the electronic transmission distance between them was sharply shortened. Meanwhile, with the help of electrostatic interaction between positively charged Ru(bpy)32+or PEI and negatively charged Nafion, exfoliation of Ru(bpy)32+and PEI from the PAN nanofiber mat was effectively avoided. As expected, the luminous nanofibers exhibited excellent ECL performance including high efficiency and good stability. On this basis, we fabricated a new self-enhanced ECL sensor with excellent analysis performance. Using a-naphthol as an analytical probe, the sensor showed a wide linear range from 1.0 × 10-12to 1.0 × 10-7M with a low detection limit of 1.0 × 10-12M. When it was applied to detect a-naphthol from carbaryl hydrolysis, the results were well consistent with those obtained from the high efficiency liquid chromatography-diode array detector (HPLC-DAD) method, indicating the potential application of the ECL sensor in real sample assays.
- Li, Libo,Liu, Xiaohong,You, Tianyan,Zhou, Limin
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- A validated stability indicating rapid LC method for duloxetine HCl
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The present paper describes the development of a reversed phase liquid chromatographic (RPLC) analytical method for duloxetine HCl in the presence of its impurities and degradation products generated from forced decomposition studies. The drug substance w
- Srinivasulu,Srinivas,Reddy,Mukkanti,Buchireddy
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- Serum albumins and detoxication of anti-cholinesterase agents
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Serum albumin displays an esterase activity that is capable of hydrolysing the anti-cholinesterase compounds carbaryl, paraoxon, chlorpyrifos-oxon, diazoxon and O-hexyl, O-2,5-dichlorphenyl phosphoramidate. The detoxication of all these anti-cholinesterase compounds takes place at significant rates with substrate concentrations in the same order of magnitude as expected during in vivo exposures, even when these substrate concentrations are between 15 and 1300 times lower than the recorded Km constants. Our data suggest that the efficacy of this detoxication system is based on the high concentration of albumin in plasma (and in the rest of the body), and not on the catalytic efficacy itself, which is low for albumin. We conclude the need for a structure-activity relationship study into the albumin-associated esterase activities because this protein is universally present in vertebrates and could compensate for reduced levels of other esterases, i.e., lipoprotein paraoxonase, in some species. It is also remarkable that the biotransformation of xenobiotics can be reliably studied in vitro, although conditions as similar as possible to in vivo situations are necessary.
- Sogorb, Miguel A.,Vilanova, Eugenio
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- Rabbit serum albumin hydrolyzes the carbamate carbaryl
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One of the main detoxification processes of the carbamate insecticides is the hydrolysis of the carbamic ester bond. Carboxylesterases seem to play important roles in the metabolization of carbamates. This study performs a biochemical characterization of the capabilities of rabbit serum albumin (RSA) to hydrolyze the carbamate carbaryl. Rabbit serum albumin was able to hydrolyze carbaryl with a Kcat of 7.1 × 10-5 s-1. The Km for this hydrolysis reaction was 240 μM. Human, chicken, and bovine serum albumins were also able to hydrolyze carbaryl. The divalent cation Cu2+ at 1 mM concentration inhibited around 50% of the hydrolysis of carbaryl by RSA. Other mono- and divalent cations at 1 mM concentration and 5 mM EDTA exerted no significant effects on the hydrolysis of carbaryl by RSA. The inhibition of the carbaryl hydrolysis by sulfydril blocking agents suggests that a cysteine residue plays an important role in the active center of the catalytic activity. Both caprylic and palmitic acids were noncompetitive inhibitors of the carbaryl hydrolysis by RSA. The carboxyl ester p-nitrophenyl butyrate is a substrate of RSA and competitively inhibited the hydrolysis of carbaryl by this protein, suggesting that the hydrolysis of carbaryl and the hydrolysis of carboxyl esters occur in the same catalytic site and through a similar mechanism. This mechanism might be based on the carbamylation of a tyrosine residue of the RSA. Serum albumin is a protein universally present in nontarget species of insecticides; therefore, the capability of this protein to hydrolyze other carbamates must be studied because it might have important toxicological and ecotoxicological implications.
- Sogorb, Miguel A.,Carrera, Victoria,Benabent, Monica,Vilanova, Eugenio
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- Selective hydroxylation of naphthalene using the H2O2-dependent engineered P450BM3 driven by dual-functional small molecules
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We herein report the H2O2-dependent selective hydroxylation of naphthalene catalyzed by engineered P450BM3 with the assistance of dual-functional small molecules (DFSMs). The mutation at position 268 significantly improved the hydroxylation activity of P450BM3, which is quite different from those engineered P450BM3 peroxygenases and NADPH-dependent P450BM3 mutants previously reported, implicating the unique role of the residue at position 268. This study provides a potential approach to develop the practical hydroxylation biocatalyst of P450s for aromatic hydrocarbons using the DFSM-facilitated P450BM3-H2O2 system.
- Chen, Zhifeng,Chen, Jie,Ma, Nana,Zhou, Haifeng,Cong, Zhiqi
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- Photocatalytic conversion of naphthalene to α-naphthol using nanometer-sized TiO2
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The effects of various parameters (co-solvents, electron acceptors, and surface modification) on the direct synthesis of α-naphthol from naphthalene using photocatalytic processes were investigated. The OH radicals generated on UV-illuminated TiO2 photocatalysts led to the direct hydroxylation of naphthalene to α-naphthol. The addition of Fe 3+, Fe2+, Fe3+ + H2O2, and Fe2+ + H2O2 greatly increases the conversion of naphthalene and the yield of α-naphthol in TiO2 suspensions. The addition of Fe3+ + H2O2 to a TiO2 suspension increased the yield to 22.2. Surface modified-TiO2 had a significant influence on the hydroxylation reaction. La-Eu/TiO2, La-Y/TiO2, H3PW 12O40/TiO2, H3PMo12O 40/TiO2, Fe/TiO2, Ag/TiO2, Cu/TiO2, and N/TiO2 enhanced the conversion and yield more than TiO2. Fe/TiO2 has the highest photocatalytic efficiency among these species.
- Shi, Huixian,Zhang, Tianyong,Wang, Hongliang,Wang, Xiao,He, Meng
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- Palladium/zinc co-catalyzed syn-stereoselectively asymmetric ring-opening reaction of oxabenzonorbornadienes with phenols
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A new palladium/zinc co-catalyst system associated with chiral (R)-Difluorphos for asymmetric ring-opening reaction of oxabenzonorbornadienes with phenols is reported. This catalyst system allows the formation of cis-2-aryloxy-1,2-dihydronaphthalen-1-ol products in good yields (up to 95-% yield) with excellent enantioselectivities (up to 99-% ee). The cis-configuration of the product has been confirmed by X-ray crystal structure analysis. To the best of our knowledge, it represents the first example in ring-opening reactions of bicycloalkenes with heteronucleophiles in a syn-stereoselective manner. Open the ring: A new palladium/zinc co-catalyst associated with chiral (R)-Difluorphos for asymmetric ring-opening reaction of oxabenzonorbornadienes with phenolic or naphtholic nucleophiles was developed, which afforded the corresponding cis-2-aryloxy-1,2-dihydronaphthalen-1-ol products in good yields (up to 95-% yield) with excellent enantioselectivities (up to 99-% ee).
- Li, Sifeng,Xu, Jianbin,Fan, Baomin,Lu, Zhiwu,Zeng, Chaoyuan,Bian, Zhaoxiang,Zhou, Yongyun,Wang, Jun
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- Determination of the hydrolysis kinetics of α-naphthyl acetate in micellar systems and the effect of HPMC (catalyst present)
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The change in the hexadecyltrimethylammonium bromide (CTAB) critical aggregation concentration (CAC) was studied in the presence of various concentrations and grades of hydroxypropylmethyl cellulose (HPMC) using surface tension measurement (duNouey ring and Wilhelmy plate) and oil red O solubilization. According to the surface tension methods, the CAC was higher than the CTAB critical micelle concentration (CMC). CAC and CMC were not different when the solubilization method was used. Micellar solutions of CTAB have been found to accelerate the hydrolysis of α-naphthyl acetate (α-NA) by o-iodosobenzoic acid (IBA), a strong nucleophile. Pseudo-first-order kinetics were utilized for rate constant determination. The observed rate constants for the degradation of α-NA in the presence of varying CTAB concentrations with and without HPMC were analyzed according to the pseudophase model. The micellar rate constants and the micellar binding constants for the substrates were obtained. The presence of HPMC retarded the reaction rate, and the rate constant decreased as the polymer concentration increased. However, there was no obvious difference in the observed rate constants among the different grades of HPMC (Methocel E5, Methocel E15, Methocel E50). The decrease in the rate constant was likely due to the polymer-micelle interaction interfering with substrate binding to the CTAB micelles.
- Werawatganone, Pornpen,Wurster, Dale Eric
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- Imidazolium-urea low transition temperature mixtures for the UHP-promoted oxidation of boron compounds
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Different carboxy-functionalized imidazolium salts have been considered as components of low transition temperature mixtures (LTTMs) in combination with urea. Among them, a novel LTTM based on 1-(methoxycarbonyl)methyl-3-methylimidazolium chloride and urea has been prepared and characterized by differential scanning calorimetry throughout its entire composition range. This LTTM has been employed for the oxidation of boron reagents using urea-hydrogen peroxide adduct (UHP) as the oxidizer, thus avoiding the use of aqueous H2O2, which is dangerous to handle. This metal-free protocol affords the corresponding alcohols in good to quantitative yields in up to 5 mmol scale without the need of further purification. The broad composition range of the LTTM allows for the reaction to be carried out up to three consecutive times with a single imidazolium salt loading offering remarkable sustainability with an E-factor of 7.9, which can be reduced to 3.2 by the threefold reuse of the system.
- Martos, Mario,Pastor, Isidro M.
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- A mild and practical method for deprotection of aryl methyl/benzyl/allyl ethers with HPPh2andtBuOK
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A general method for the demethylation, debenzylation, and deallylation of aryl ethers using HPPh2andtBuOK is reported. The reaction features mild and metal-free reaction conditions, broad substrate scope, good functional group compatibility, and high chemical selectivity towards aryl ethers over aliphatic structures. Notably, this approach is competent to selectively deprotect the allyl or benzyl group, making it a general and practical method in organic synthesis.
- Pan, Wenjing,Li, Chenchen,Zhu, Haoyin,Li, Fangfang,Li, Tao,Zhao, Wanxiang
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p. 7633 - 7640
(2021/09/22)
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- Me3SI-promoted chemoselective deacetylation: a general and mild protocol
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A Me3SI-mediated simple and efficient protocol for the chemoselective deprotection of acetyl groups has been developedviaemploying KMnO4as an additive. This chemoselective deacetylation is amenable to a wide range of substrates, tolerating diverse and sensitive functional groups in carbohydrates, amino acids, natural products, heterocycles, and general scaffolds. The protocol is attractive because it uses an environmentally benign reagent system to perform quantitative and clean transformations under ambient conditions.
- Gurawa, Aakanksha,Kashyap, Sudhir,Kumar, Manoj
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p. 19310 - 19315
(2021/06/03)
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- PREPARING METHODE FOR NAPHTHOL
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The present invention provides a method for producing naphthol by oxidizing naphthalene and an oxidizing agent in the presence of a catalyst. According to the present invention, naphthol can be produced in a single process of direct oxidation of naphthalene, and the yield and selectivity of naphthalene can be improved by controlling process variables such as the molar ratio of the oxidizing agent and naphthalene, catalyst input amount, and reaction time.
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Paragraph 0032-0048
(2021/01/28)
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- Aryl phenol compound as well as synthesis method and application thereof
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The invention discloses a synthesis method of an aryl phenol compound shown as a formula (3). All systems are carried out in an air or nitrogen atmosphere, and visible light is utilized to excite a photosensitizer for catalyzation. In a reaction solvent, ArNR1R2 as shown in a formula (1) and water as shown in a formula (2) are used as reaction raw materials and react under the auxiliary action of acid to obtain the aryl phenol compound as shown in a formula (3). The ArNR1R2 in the formula (1) can be primary amine and tertiary amine, can also be steroid and amino acid derivatives, and can also be drugs or derivatives of propofol, paracetamol, ibuprofen, oxaprozin, indomethacin and the like. The synthesis method has the advantages of cheap and easily available raw materials, simple reaction operation, mild reaction conditions, high reaction yield and good compatibility of substrate functional groups. The fluid reaction not only can realize amplification of basic chemicals, but also can realize amplification of fine chemicals, such as synthesis of drugs propofol and paracetamol. The invention has wide application prospect and use value.
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Paragraph 0173-0176
(2021/05/12)
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- Ligand compound for copper catalyzed aryl halide coupling reaction, catalytic system and coupling reaction
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The invention provides a ligand compound capable of being used for copper catalyzed aryl halide coupling reaction, the ligand compound is a three-class compound containing a 2-(substituted or non-substituted) aminopyridine nitrogen-oxygen group, and the invention also provides a catalytic system for the aryl halide coupling reaction. Thecatalytic system comprises a copper catalyst, a compound containing a 2-(substituted or non-substituted) aminopyridine nitrogen-oxygen group adopted as a ligand, alkali and a solvent, and meanwhile, the invention also provides a system for the aryl halide coupling reaction adopting the catalyst system. The compound containing the 2-(substituted or non-substituted) aminopyridine nitrogen oxygen group can be used as the ligand for the copper catalyzed aryl chloride coupling reaction, and the ligand is stable under a strong alkaline condition and can well maintain catalytic activity when being used for the copper-catalyzed aryl chloride coupling reaction. In addition, the copper catalyst adopting the compound as the ligand can particularly effectively promote coupling of copper catalyzed aryl chloride and various nucleophilic reagents which are difficult to generate under conventional conditions, C-N, C-O and C-S bonds are generated, and numerous useful small molecule compounds are synthesized. Therefore, the aryl halide coupling reaction has a very good large-scale application prospect by adopting the copper catalysis system of the ligand.
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Paragraph 0152-0158
(2021/05/29)
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- Photocatalytic Reductive C-O Bond Cleavage of Alkyl Aryl Ethers by Using Carbazole Catalysts with Cesium Carbonate
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Methods to activate the relatively stable ether C-O bonds and convert them to other functional groups are desirable. One-electron reduction of ethers is a potentially promising route to cleave the C-O bond. However, owing to the highly negative redox potential of alkyl aryl ethers (Ered -2.6 V vs SCE), this mode of ether C-O bond activation is challenging. Herein, we report the visible-light-induced photocatalytic cleavage of the alkyl aryl ether C-O bond using a carbazole-based organic photocatalyst (PC). Both benzylic and non-benzylic aryl ethers underwent C-O bond cleavage to form the corresponding phenol products. Addition of Cs2CO3 was beneficial, especially in reactions using a N-H carbazole PC. The reaction was proposed to occur via single-electron transfer (SET) from the excited-state carbazole to the substrate ether. Interaction of the N-H carbazole PC with Cs2CO3 via hydrogen bonding exists, which enables a deprotonation-assisted electron-transfer mechanism to operate. In addition, the Lewis acidic Cs cation interacts with the substrate alkyl aryl ether to activate it as an electron acceptor. The high reducing ability of the carbazole combined with the beneficial effects of Cs2CO3 made this otherwise formidable SET event possible.
- Yabuta, Tatsushi,Hayashi, Masahiko,Matsubara, Ryosuke
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p. 2545 - 2555
(2021/02/01)
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- Green preparation method of menadione sodium bisulfite
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The invention provides a preparation method of menadione sodium bisulfite. The method comprises the following steps of: by using cheap and easily available 3, 4-dihydro-1 (2H)-naphthalenone as a raw material, carrying out halogenation-elimination to obtain 1-naphthol; carrying out methylation reaction to generate 2-methyl-1-naphthol; carrying out air oxidation on the 2-methyl-1-naphthol to obtain 2-methyl-1, 4-naphthoquinone; and carrying out addition reaction on the 2-methyl-1, 4-naphthoquinone and sodium hydrogen sulfite so as to obtain the menadione sodium bisulfite. The method has the advantages of cheap and easily available raw materials, low cost, safe, simple and convenient process operation, less process wastewater generation, green and environment-friendly performance, high stability of raw materials and intermediate products, high reaction activity and selectivity, easy realization of reaction conditions, few side reactions and high product purity and yield, and can facilitate the industrial production of the menadione sodium bisulfite.
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Page/Page column 0064-0069
(2021/07/31)
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- Nickel-catalyzed deallylation of aryl allyl ethers with hydrosilanes
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An efficient and mild catalytic deallylation method of aryl allyl ethers is developed, with commercially available Ni(COD)2 as catalyst precursor, simple substituted bipyridine as ligand and air-stable hydrosilanes. The process is compatible with a variety of functional groups and the desired phenol products can be obtained with excellent yields and selectivity. Besides, by detection or isolation of key intermediates, mechanism studies confirm that the deallylation undergoes η3-allylnickel intermediate pathway.
- Ding, Guangni,Fan, Sijie,Wang, Jingyang,Wang, Yu,Wu, Xiaoyu,Xie, Xiaomin,Yang, Liqun,Zhang, Zhaoguo
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supporting information
(2021/09/28)
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- A copper nitride catalyst for the efficient hydroxylation of aryl halides under ligand-free conditions
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Copper nitride (Cu3N) was used as a heterogeneous catalyst for the hydroxylation of aryl halides under ligand-free conditions. The cubic Cu3N nanoparticles showed high catalytic activity, comparable to those of conventional Cu catalysts with nitrogen ligands, demonstrating that the nitrogen atoms in Cu3N act as functional ligands that promote hydroxylation.
- Mitsudome, Takato,Mizugaki, Tomoo,Xu, Hang,Yamaguchi, Sho
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supporting information
p. 6593 - 6597
(2021/08/10)
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- Radical-anion coupling through reagent design: hydroxylation of aryl halides
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The design and development of an oxime-based hydroxylation reagent, which can chemoselectively convert aryl halides (X = F, Cl, Br, I) into phenols under operationally simple, transition-metal-free conditions is described. Key to the success of this approach was the identification of a reducing oxime anion which can interact and couple with open-shell aryl radicals. Experimental and computational studies support the proposed radical-nucleophilic substitution chain mechanism.
- Chechik, Victor,Greener, Andrew J.,James, Michael J.,Oca?a, Ivan,Owens-Ward, Will,Smith, George,Ubysz, Patrycja,Whitwood, Adrian C.
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p. 14641 - 14646
(2021/11/17)
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- Highly recyclable Ti0.97Ni0.03O1.97catalyst coated on cordierite monolith for efficient transformation of arylboronic acids to phenols and reduction of 4-nitrophenol
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A stable Ni2+substituted TiO2catalyst (Ti0.97Ni0.03O1.97) has been synthesized by a solution combustion method with an average crystallite size of 7.5 nm. Ti1?xNixO2?x(x= 0.01-0.06) crystallizes in the TiO2anatase structure with Ni2+substituted in Ti4+ion sites and Ni taking a nearly square planar geometry. This catalyst is found to be highly active in the transformation of diverse arylboronic acids to the corresponding phenols. The catalyst coated cordierite monolith can even be recycled for up to 20 cycles with a cumulative TOF of 1.8 × 105h?1. In scale-up reactions, various phenols are synthesized by employing a single cordierite monolith. It also shows high performance in the reduction of 4-nitrophenol.
- Hegde, M. S.,Prasanna,Usha, K. M.
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supporting information
p. 14223 - 14234
(2021/10/25)
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- Isotruxene-based porous polymers as efficient and recyclable photocatalysts for visible-light induced metal-free oxidative organic transformations
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Two new isotruxene-based porous polymers were prepared and demonstrated to be highly efficient, metal-free heterogeneous photocatalysts for oxidative transformations using air as the mild oxidant under visible-light irradiation. Both catalysts show excellent recyclability. In addition, the reactions can be performed in water, further indicating the greenness of this method. This journal is
- Zhang, Haowen,Zhang, Xiao,Zheng, Ying,Zhou, Cen
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supporting information
p. 8878 - 8885
(2021/11/27)
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- Cu2O/TiO2 as a sustainable and recyclable photocatalyst for gram-scale synthesis of phenols in water
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A green and straightforward protocol was developed for the synthesis of phenols from aryl boronic acid using an inexpensive and available Cu2O/TiO2 photocatalyst under visible light and sunlight. This approach proceeded in mild reaction conditions in water and the presence of air as a green oxidant, resulting in the corresponding phenols in good to excellent yields. Sunlight was also a sustainable source for this photochemical reaction. Heterogeneous nano photocatalyst was successfully recovered in 8 consecutive runs. It is noteworthy that, the photocatalyst exhibited high activity for the large-scale synthesis of phenols.
- Hosseini-Sarvari, Mona,Keshavarz, Kimia,Tavakolian, Mina
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- The graphite-catalyzed: ipso -functionalization of arylboronic acids in an aqueous medium: metal-free access to phenols, anilines, nitroarenes, and haloarenes
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An efficient, metal-free, and sustainable strategy has been described for the ipso-functionalization of phenylboronic acids using air as an oxidant in an aqueous medium. A range of carbon materials has been tested as carbocatalysts. To our surprise, graphite was found to be the best catalyst in terms of the turnover frequency. A broad range of valuable substituted aromatic compounds, i.e., phenols, anilines, nitroarenes, and haloarenes, has been prepared via the functionalization of the C-B bond into C-N, C-O, and many other C-X bonds. The vital role of the aromatic π-conjugation system of graphite in this protocol has been established and was observed via numerous analytic techniques. The heterogeneous nature of graphite facilitates the high recyclability of the carbocatalyst. This effective and easy system provides a multipurpose approach for the production of valuable substituted aromatic compounds without using any metals, ligands, bases, or harsh oxidants.
- Badgoti, Ranveer Singh,Dandia, Anshu,Parewa, Vijay,Rathore, Kuldeep S.,Saini, Pratibha,Sharma, Ruchi
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p. 18040 - 18049
(2021/05/29)
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- Blacklight-Induced Hydroxylation of Arylboronic Acids Leading to Hydroxyarenes Using Molecular Oxygen and Tetrabutylammonium Borohydride
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A new simple protocol for the conversion of arylboronic acids to hydroxyarenes was achieved using molecular oxygen in the presence of tetrabutylammonium borohydride under blacklight irradiation (360 nm). A radical chain mechanism in which a superoxide ion (O2?.) plays a key role is proposed.
- Kawamoto, Takuji,Ryu, Ilhyong
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- Homogeneous Palladium-Catalyzed Selective Reduction of 2,2′-Biphenols Using HCO 2H as Hydrogen Source
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An efficient homogeneous palladium-catalyzed selective deoxygenation of 2,2′-biphenols by reduction of aryl triflates with HCO 2H as the hydrogen source is reported. This protocol complements the current method based on heterogeneous Pd/C-catalyzed hydrogenation with hydrogen gas. This process provided the reduction products in good to excellent yields, which could be readily converted to various synthetically useful molecules, especially ligands for catalytic synthesis.
- Li, Ruoling,Li, Chenchen,Yang, Wen,Zhao, Wanxiang
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p. 1605 - 1618
(2021/02/01)
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- How the external solvent in biocompatible reverse micelles can improve the alkaline phosphatase behavior
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In the last decade, the nature of the nonpolar solvents that can be part of reverse micelles (RMs) has been the topic of several investigations to improve their applications. In this sense, the hydrolysis of 1-naphthyl phosphate catalyzed by the enzyme alkaline phosphatase (AP) was used as a probe to investigate the effect of the change of the external solvent on RMs formulated with the anionic surfactant sodium diethylhexyl sulfosuccinate (AOT). As external nonpolar solvents, two biocompatible lipophilic esters, isopropyl myristate and methyl laurate, and the traditional nonpolar solvents,n-heptane and benzene, were used. The results were compared among the RMs investigated and with the reaction in homogeneous media. Thus, the effect of the nanoconfinement as well as the impact of the replacement of a conventional external nonpolar solvent by biocompatible solvents were analyzed. The results indicate that the catalytic efficiency in the AOT RMs is larger than that in homogeneous media, denoting a different hydration level over the AP enzyme, which is directly related to the different degrees of nonpolar solvent penetration to the RM interface. Our findings demonstrated that toxic solvents such asn-heptane and benzene can be replaced by nontoxic ones (isopropyl myristate or methyl laurate) in AOT RMs without affecting the performance of micellar systems as nanoreactors, making them a green and promising alternative toward efficient and sustainable chemistry.
- Dib, Nahir,Girardi, Valeria R.,Silber, Juana J.,Correa, N. Mariano,Falcone, R. Dario
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p. 4969 - 4977
(2021/06/16)
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- Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis
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The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.
- Zhou, Min-Jie,Zhang, Lei,Liu, Guixia,Xu, Chen,Huang, Zheng
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supporting information
p. 16470 - 16485
(2021/10/20)
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- Anchimerically Assisted Selective Cleavage of Acid-Labile Aryl Alkyl Ethers by Aluminum Triiodide and N, N-Dimethylformamide Dimethyl Acetal
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Aluminum triiodide is harnessed by N,N-dimethylformamide dimethyl acetal (DMF-DMA) for the selective cleavage of ethers via neighboring group participation. Various acid-labile functional groups, including carboxylate, allyl, tert-butyldimethylsilyl (TBS), and tert-butoxycarbonyl (Boc), suffer the conditions intact. The method offers an efficient approach to cleaving catechol monoalkyl ethers and to uncovering phenols from acetal-type protecting groups such as methoxymethyl (MOM), methoxyethoxymethyl (MEM), and tetrahydropyranyl (THP) chemoselectively.
- Sang, Dayong,Yue, Huaxin,Zhao, Zhengdong,Yang, Pengtao,Tian, Juan
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p. 6429 - 6440
(2020/07/14)
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- Selective ether bond breaking method of aryl alkyl ether
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The invention discloses a selective aryl alkyl ether cracking method, which comprises that aryl alkyl ether, aluminum iodide and an additive are subjected to a selective ether bond cleavage reaction in an organic solvent at a temperature of -20 DEG C to a reflux temperature to generate phenol and derivatives thereof. The method is mild in condition and simple and convenient to operate, is suitablefor cracking aryl alkyl ether containing o-hydroxyl and o-carbonyl and acetal ether, and can also be used for removing tertiary carbon hydroxyl protecting groups with higher steric hindrance, such astriphenylmethyl, tertiary butyl and the like.
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Paragraph 0207-0211
(2020/09/16)
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- Development and Mechanistic Studies of Iron-Catalyzed Construction of Csp2-B Bonds via C-O Bond Activation
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Herein we describe an iron-catalyzed borylation of alkenyl and aryl carbamates through the activation of a C-O bond. This protocol exhibits high efficiency, a broad substrate scope, and the late-stage borylation of biorelevant compounds, thus providing potential applications in medicinal chemistry. Moreover, this method enables orthogonal transformations of phenol derivatives and also offers good opportunities for the synthesis of multisubstituted arenes. Preliminary mechanistic studies suggest that a FeII/FeIII catalytic cycle via a radical pathway might be involved in the reaction.
- Geng, Shasha,Zhang, Juan,Chen, Shuo,Liu, Zhengli,Zeng, Xiaoqin,He, Yun,Feng, Zhang
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supporting information
p. 5582 - 5588
(2020/07/08)
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- Functional Analyses of House Fly Carboxylesterases Involved in Insecticide Resistance
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Carboxylesterase-mediated metabolism is one of major mechanisms involved in insecticide resistance. Our previous study has identified multiple carboxylesterase genes with their expression levels were significantly upregulated in pyrethroid resistant house flies. To further explore their metabolic functions, we used insect Spodoptera frugiperda (Sf9) cells to express these carboxylesterases in vitro and measure their hydrolytic activities toward esterase substrates. Our results indicated that these carboxylesterases can efficiently hydrolyze α-naphthyl acetate rather than β- naphthyl acetate. A cell based MTT cytotoxicity assay indicated that carboxylesterase-expressing cells show enhanced tolerance to permethrin, suggesting important roles of these carboxylesterases in metabolizing permethrin and thereby protecting cells from permethrin treatments. The metabolic functions of carboxylesterases were further verified by conducting in vitro metabolism studies toward permethrin and its potential metabolites 3-phenoxybenzyl alcohol and 3-phenoxybenzaldehyde, which not only suggested the potential metabolic pathway of permethrin in insects, but also important roles of these candidate carboxylesterases in metabolizing permethrin and conferring resistance in house flies. Homology modeling and docking were finally conducted to reflect interactions between permethrin ligand and carboxylesterase proteins, visually confirming the metabolic functions of carboxylesterases to insecticides in house flies.
- Feng, Xuechun,Liu, Nannan
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- Mechanistic Insights into Hydrogen Evolution by Photocatalytic Reforming of Naphthalene
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Heterogeneous photocatalysis has been widely considered, among other applications, for environmental remediation and hydrogen production. While these applications have been traditionally seen as well-separated areas, recent examples have highlighted the possibility of coupling them. Here, we demonstrate the simultaneous production of H2 and naphthalene removal from aqueous solutions with (unoptimized) photonic efficiencies of 0.97 and 0.33percent, respectively, over Pt-TiO2 under simulated sunlight. Photocatalytic and spin-trapping experiments in the presence of a hydroxyl radical and hole scavengers evinced that only the photogenerated holes play a significant role in the oxidation of naphthalene. Isotopic labeling analyses showed that the evolved H2 isotopologues match those of the solvent and that deuterated water (but not deuterated naphthalene) decreases the reaction rate, suggesting its involvement in the rate-determining step. Moreover, the use of Ti18O2 does not lead to the significant formation of 18O-enriched CO2, suggesting that water is the source of the oxygen atoms. Ultimately, by considering the stable and transient reaction intermediates, we propose a plausible reaction pathway. Our work illustrates that environmental remediation can be effectively coupled to solar fuel production, providing a double purpose to photocatalytic reactions, while the mechanistic insights will be of use for the further development of this strategy.
- Al-Madanat, Osama,Alsalka, Yamen,Bahnemann, Detlef W.,Curti, Mariano,Dillert, Ralf
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p. 7398 - 7412
(2020/07/21)
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- Reductive Cross-Coupling between Unactivated C(aryl)-N and C(aryl)-O Bonds by Chromium Catalysis Using a Bipyridyl Ligand
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Reductive cross-coupling between two chemically inert bonds remains a great challenge in synthetic chemistry. We report here the reductive cross-coupling between unactivated C(aryl)-N and C(aryl)-O bonds that was achieved by chromium catalysis. The simple and inexpensive CrCl2 salt, combined with important bipyridyl ligand and magnesium reductant, shows high reactivity in the successive cleavage of C(aryl)-N bonds of aniline derivatives and C(aryl)-O bonds of aryl esters, allowing the cross-coupling of these two unactivated and different bonds to occur in a reductive fashion to form a C(aryl)-C(aryl) bond. Mechanistic studies by deuterium-labeling experiments indicate that the C(aryl)-N bonds in anilines are preferentially cleaved by reactive Cr species, in which the ligation of bipyridyl with Cr by adopting a coordination model in 1:1 ratio can be considered.
- Cong, Xuefeng,Fan, Fei,Luo, Meiming,Tang, Jinghua,Zeng, Xiaoming,Zhao, Lixing
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p. 12834 - 12840
(2020/08/21)
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- Copper and L-(?)-quebrachitol catalyzed hydroxylation and amination of aryl halides under air
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L-(?)-Quebrachitol, a natural product obtained from waste water of the rubber industry, was utilized as an efficient ligand for the copper-catalyzed hydroxylation and amination of aryl halides to selectively give phenols and aryl amines in water or 95percent ethanol. In addition, the hydroxylation of 2-chloro-4-hydroxybenzoic acid was validated on a 100-g scale under air.
- Bao, Xuefei,Chen, Guoliang,Dong, Jinhua,Du, Fangyu,Li, Hui,Liang, Xinjie,Wu, Ying,Zhang, Yongsheng
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supporting information
(2020/08/03)
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- Aerobic photooxidative hydroxylation of boronic acids catalyzed by anthraquinone-containing polymeric photosensitizer
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We report herein the synthesis of a polymeric photosensitizer and its application in aerobic photooxidative hydroxylation of boronic acids. The polymeric photosensitizer was synthesized by the condensation of anthraquinone-2-carbonyl chloride (AQ-2-COCl) with poly (2-hydroxyethyl methacrylate) (PHEMA). The photo-oxidative hydroxylation of boronic acids using anthraquinone-containing-poly (2-hydroxyethyl methacrylate) (AQ-PHEMA) was then explored and shown to exhibit high efficiency and broad scope. Moreover, AQ-PHEMA could be easily recovered and reused for more than 20 times without significant loss of the catalytic activity.
- Chen, Yang,Ding, Aishun,Hu, Jianhua
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p. 7927 - 7932
(2020/03/11)
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- Rongalite-promoted metal-free aerobic ipso-hydroxylation of arylboronic acids under sunlight: DFT mechanistic studies
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A novel rongalite-promoted metal-free aerobic ipso-hydroxylation of arylboronic acids has been developed. This method employs low-cost rongalite as a radical initiator and O2 as a green oxidizing agent for ipso-hydroxylation. This protocol is compatible with a wide variety of functional groups with good to excellent yields at room temperature. Furthermore, mechanistic insight into the role of superoxide radical anions in C-B cleavage has also been provided based on DFT studies.
- Golla, Sivaparwathi,Poshala, Soumya,Pawar, Ravinder,Kokatla, Hari Prasad
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supporting information
(2019/12/27)
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- Nickel-catalyzed oxidative hydroxylation of arylboronic acid: Ni(HBTC)BPY MOF as an efficient and ligand-free catalyst to access phenolic motifs
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A straightforward and mild oxidative ipso-hydroxylation of arylboronic acids has been achieved using a simple and non-noble metal, nickel-based reusable heterogeneous catalyst Ni(HBTC)BPY MOF (HBTC = benzene-1,3,5-tricarboxylate, BPY = 4,4′-bipyridine) in the presence of benign hydrogen peroxide as an oxidant under ambient reaction condition. The Ni(HBTC)BPY MOF exhibits excellent catalytic activity towards the formation of phenols from diverse arylboronic acids within short time and can be reused up to five times without any notable loss in its activity as well as shown high functional group tolerance even in the presence of sensitive functionalities and useful to achieve hydroxyl group in heterocycles.
- Latha, Ganesapandian,Devarajan, Nainamalai,Karthik, Murugan,Suresh, Palaniswamy
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- Method for preparing alcohol and phenol through aerobic hydroxylation reaction of boric acid derivative in absence of photocatalyst
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The invention discloses a method for preparing alcohol and phenol through aerobic hydroxylation reaction of a boric acid derivative in the absence of a photocatalyst, wherein the boric acid derivativeis aryl boronic acid or alkyl boronic acid, and the corresponding target compounds are respectively a phenol-based compound and an alcohol-based compound. According to the method, by using a boric acid derivative as a reaction substrate, an additive is added under a solvent condition, and a hydroxylation reaction is performed under aerobic and illumination conditions to obtain a corresponding target compound. According to the invention, the new strategy is provided for the synthesis of phenols through aerobic hydroxylation of aryl boronic acid without a photocatalyst; the catalyst-free aerobic hydroxylation method for photocatalysis of aryl boronic acid or alkyl boronic acid by using triethylamine as an additive is firstly disclosed; and the new method has advantages of photocatalyst-freecondition, wide substrate range and good functional group compatibility.
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Paragraph 0025-0028; 0030-0032
(2020/01/25)
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- Copper nanoparticles supported on highly nitrogen-rich covalent organic polymers as heterogeneous catalysts for the ipso -hydroxylation of phenyl boronic acid to phenol
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This work describes a simple procedure for the synthesis of highly nitrogen-rich covalent organic polymers using commercially available starting materials like melamine and cyanuric chloride as a solid heterogeneous catalyst Cu/TCOP under solvothermal conditions. The structural properties of the as-synthesized solid heterogeneous catalyst were determined by X-ray diffraction (XRD), diffuse reflectance spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), 13C-CP MAS nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. The catalytic activity of Cu/TCOP was investigated by focusing on the oxidation of phenylboronic acid under atmospheric conditions in an aqueous medium, achieving a very good yield up to 99%. The reaction performance was evaluated considering the effect of various parameters, such as the amount of the catalyst, reaction time, temperature, and the amount of the base and solvent. The Cu/TCOP catalyst is completely recoverable in a facile manner from the reaction mixture and the efficiency of the copper nanocatalyst can be recovered after five cycles.
- Sadhasivam, Velu,Harikrishnan, Muniyasamy,Elamathi, Ganesan,Balasaravanan, Rajendran,Murugesan, Sepperumal,Siva, Ayyanar
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supporting information
p. 6222 - 6231
(2020/05/13)
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- Bimetallic photoredox catalysis: Visible light-promoted aerobic hydroxylation of arylboronic acids with a dirhodium(ii) catalyst
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We report the use of a rhodium(II) dimer in visible light photoredox catalysis for the aerobic oxidation of arylboronic acids to phenols under mild conditions. Spectroscopic and computational studies indicate that the catalyst Rh2(bpy)2(OAc)4 (1) undergoes metal-metal to ligand charge transfer upon visible light irradiation, which is responsible for catalytic activity. Further reactivity studies demonstrate that 1 is a general photoredox catalyst for diverse oxidation reactions.
- Campbell, Michael G.,Chuang, Gary Jing,Liu, Ming-Lun,Miura-Stempel, Emily,Tu, Jing-Wen,Yang, Hsiang-Ming
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p. 2040 - 2047
(2020/03/13)
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- Optimizing the crystallization process of conjugated polymer photocatalysts to promote electron transfer and molecular oxygen activation
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Photocatalytic reactive oxygen species (ROS)-induced reactions provide an appealing method to solve the environmental and energy issues, whereas the current oxidation reaction generally suffered from low efficiency and poor selectivity due to uncontrollable O2 activation process. In view of the existence of competitive electron and energy transfer pathway, we propose that highly efficient superoxide radical anion (·O2?) generation can be achieved by optimizing the order degree of the photocatalyst. Herein, by taking carbon nitride polymer as an example, we optimized the crystallization process of carbon nitride polymer by selecting precursors of different polymerization degrees with a molten salt method. Benefiting from the high crystallinity, extended π-conjugated system and strong van der-Waals interactions between interlayers, the modified carbon nitride polymer exhibited accelerated charge transport and enhancement in electron induced molecular oxygen activation reactions under visible light. Consequently, the CCN-P exhibits about 1.5 times higher conversion rate in hydroxylation of phenylboronic acid and over 6-fold faster degradation rate in Rh B organic pollutants photodegradation with respect to pristine carbon nitride. This study provides an in-depth understanding on the optimization of the O2 activation process and the design of advanced photocatalysts.
- Anpo, Masakazu,Cheng, Jiajia,Huang, Caijin,Ou, Honghui,Ren, Wei,Wang, Xinchen
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p. 636 - 645
(2020/07/27)
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- Oxalic amide ligands, and uses thereof in copper-catalyzed coupling reaction of aryl halides
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The present invention provides oxalic amide ligands and uses thereof in copper-catalyzed coupling reaction of aryl halides. Specifically, the present invention provides a use of a compound represented by formula I, wherein definitions of each group are described in the specification. The compound represented by formula I can be used as a ligand in copper-catalyzed coupling reaction of aryl halides for the formation of C—N, C—O and C—S bonds.
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Page/Page column 122
(2020/01/09)
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- Photocatalytic hydrogen evolution of 1-tetralones to α-naphthols by continuous-flow technology
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Taking advantage of the synergy between photocatalysis and cobaloxime catalysis, the keto-enol radical cation of 1-tetralones becomes compatible with the transformation of various 1-tetralones into α-naphthols and H2 by virtue of the continuous-flow approach without any sacrificial oxidants under unusually mild conditions.
- He, Xu,Zheng, Yi-Wen,Lei, Tao,Liu, Wen-Qiang,Chen, Bin,Feng, Ke,Tung, Chen-Ho,Wu, Li-Zhu
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p. 3337 - 3341
(2019/07/10)
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- Identification of an Oxalamide Ligand for Copper-Catalyzed C?O Couplings from a Pharmaceutical Compound Library
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A typical pharmaceutical compound library is stocked with molecular diversity and could provide a platform for the discovery of new ligand structures. Herein, we describe the use of this approach in combination with high throughput screening to identify N,N’-bis(thiophene-2-ylmethyl)oxalamide as a ligand that is generally effective for copper-catalyzed C?O cross-couplings to prepare both biarylethers as well as phenols under mild conditions.
- Chan, Vincent S.,Krabbe, Scott W.,Li, Changfeng,Sun, Lijie,Liu, Yue,Nett, Alex J.
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- Nickel-Catalyzed C(sp2)?C(sp3) Kumada Cross-Coupling of Aryl Tosylates with Alkyl Grignard Reagents
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Aryl tosylates are an attractive class of electrophiles for cross-coupling reactions due to ease of synthesis, low price, and the employment of C?O electrophiles, however, the reactivity of aryl tosylates is low. Herein, we report the Ni-catalyzed C(sp2)?C(sp3) Kumada cross-coupling of aryl tosylates with primary and secondary alkyl Grignard reagents. The method delivers valuable alkyl arenes by cross-coupling with challenging alkyl organometallics possessing β-hydrogens that are prone to β-hydride elimination and homo-coupling. The reaction is catalyzed by an air- and moisture stable-Ni(II) precatalyst. A broad range of electronically-varied aryl tosylates, including bis-tosylates, underwent this transformation, and many examples are suitable at mild room temperature conditions. The combination of Ar?X cross-coupling with the facile Ar?OH activation/cross-coupling strategy permits for orthogonal cross-coupling with challenging alkyl organometallics. Furthermore, we demonstrate that the method operates with TON reaching 2000, which is one of the highest turnovers observed to date in Ni-catalyzed cross-couplings. (Figure presented.).
- Piontek, Aleksandra,Och?dzan-Siod?ak, Wioletta,Bisz, Elwira,Szostak, Michal
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supporting information
p. 2329 - 2336
(2019/04/13)
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- Palladium–Borane Cooperation: Evidence for an Anionic Pathway and Its Application to Catalytic Hydro-/Deutero-dechlorination
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Metal–Lewis acid cooperation provides new opportunities in catalysis. In this work, we report a new type of palladium–borane cooperation involving anionic Pd0 species. The air-stable DPB palladium complex 1 (DPB=diphosphine-borane) was prepared and reacted with KH to give the Pd0 borohydride 2, the first monomeric anionic Pd0 species to be structurally characterized. The boron moiety acts as an acceptor towards Pd in 1 via Pd→B interaction, but as a donor in 2 thanks to B-H-Pd bridging. This enables the activation of C?Cl bonds and the system is amenable to catalysis, as demonstrated by the hydro-/deutero-dehalogenation of a variety of (hetero)aryl chlorides (20 examples, average yield 85 %).
- Kameo, Hajime,Yamamoto, Jun,Asada, Ayaka,Nakazawa, Hiroshi,Matsuzaka, Hiroyuki,Bourissou, Didier
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supporting information
p. 18783 - 18787
(2019/11/19)
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- Phthalocyanine Zinc-catalyzed Hydroxylation of Aryl Boronic Acids under Visible Light
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A visible-light-promoted aerobic oxidative hydroxylation of boronic acids using phthalocyanine zinc as an easily available photosensitizer has been developed. It provided a direct access to synthesize aliphatic alcohols and phenols from boronic acids. The advantages of this approach included the low catalyst loading (0.5 mol%), high efficient, the use of O2 as an oxygen source, wide substrate range, the simple operational process, and mild conditions. (Figure presented.).
- Luo, Dong-Ping,Huang, Yang-Feng,Hong, Xiao-Yi,Chen, Dingben,Li, Guo-Xing,Huang, Xiao-Bo,Gao, Wen-Xia,Liu, Miao-Chang,Zhou, Yun-Bing,Wu, Hua-Yue
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supporting information
p. 961 - 964
(2019/01/25)
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- Cellulose as recyclable organocatalyst for ipso-hydroxylation of arylboronic acids
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Cellulose catalyzed oxidative hydroxylation of aryl and hetero-arylboronic acids to the corresponding phenols under metal and base free strategy has been demonstrated. The sustainable ipso-hydroxylation takes place using hydrogen peroxide as an oxidant in water under mild condition in shorter period of time. Interestingly, easy recovery and reusability of heterogeneous catalyst without significant loss in catalytic yield makes the protocol environmentally benign.
- Laskar, Khairujjaman,Paul, Subham,Bora, Utpal
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- Heterogeneous Palladium–Chitosan–CNT Core–Shell Nanohybrid Composite for Ipso-hydroxylation of Arylboronic Acids
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Abstract: A novel palladium-nanohybrid (Pd–Chitosan–CNT) catalytic composite has been developed using CNT–chitosan nanocomposite and palladium nitrate. The prepared catalytic platform displays excellent catalytic reactivity for the ipso-hydroxylation of various arylboronic acids with a mild oxidant aqueous H2O2 at room temperature, affording the corresponding phenols in excellent yields. Significantly, the easy recovery and reusability by simple manipulation demonstrate the green credentials of this catalytic platform. Graphical Abstract: [Figure not available: see fulltext.]
- Shin, Eun-Jae,Kim, Han-Sem,Joo, Seong-Ryu,Shin, Ueon Sang,Kim, Seung-Hoi
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- The highly efficient air oxidation of aryl and alkyl boronic acids by a microwave-assisted protocol under transition metal-free conditions
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Molecular oxygen is the most important green-oxidant due to its excellent properties. However, the effective utilization of molecular oxygen remains a major challenge in modern chemistry. Herein, we report the development a rapid, green and efficient microwave-assisted protocol for the air oxidation of boronic acids to phenols and alcohols under transition metal-free conditions. In the presence of KOH and DMSO, high yields of the expected phenols and alcohol were obtained with microwave-assistance, and a variety of functional groups were tolerated in this procedure. Notably, this transition metal-free method represents a breakthrough in both organic synthesis and green chemistry for the oxidative hydroxylation of boronic acids to phenols and alcohols.
- Yin, Weiyan,Pan, Xizhi,Leng, Wenxi,Chen, Jian,He, Haifeng
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supporting information
p. 4614 - 4618
(2019/09/09)
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- Trichloroacetonitrile as an efficient activating agent for the: Ipso -hydroxylation of arylboronic acids to phenolic compounds
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A metal-free and base-free Cl3CCN mediated method was developed for the ipso-hydroxylation of aryl boronic acids to their corresponding phenols, which was promoted by a key unstable Lewis adduct intermediate. This transformation has broad functional group tolerance, and late-stage functionalization was successful as well. After simple investigation, two pathways (radical/ionic mechanism) were suggested, and the beneficial action of blue light needs to be further studied.
- Fang, Yuanding,Zhao, Rong,Yao, Yuan,Liu, Yang,Chang, Denghu,Yao, Ming,Shi, Lei
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p. 7558 - 7563
(2019/08/20)
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- A Green Alternative for the Conversion of Arylboronic Acids/Esters into Phenols Promoted by a Reducing Agent, Sodium Sulfite
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Hydroxylation of arylboronic acids and arylboronic esters using sodium sulfite and oxygen as the source of ultimate oxidant proceeds rapidly in water under transition metal-free conditions. This remarkable mild and environmentally benign protocol represents a green alternative to synthesize phenols using inexpensive starting materials in a simple methodology. This new application for sodium sulfite shows a wide tolerance of functional groups, and it is compatible with oxidizable functionalities.
- Castro-Godoy, Willber D.,Schmidt, Luciana C.,Argüello, Juan E.
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p. 3035 - 3039
(2019/05/15)
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- Room-Temperature Ionic Liquids (RTILs) as Green Media for Metal- and Base-Free ipso -Hydroxylation of Arylboronic Acids
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The oxidative hydroxylation of arylboronic acids to the corresponding phenolic compounds under metal- and base-free aerobic conditions is successfully demonstrated on a greener media. Hydrogen peroxide, as an eco-friendly oxidant, is compatible with green mediates room-temperature ionic liquids (RTIL)s, providing hydroxylation products of arylboronic acids in an efficient manner. The RTIL support is particularly interesting for its reusability.
- Kim, Seung-Hoi,Kwon, Gyu-Tae,Shin, Eun-Jae
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supporting information
p. 1815 - 1819
(2019/09/09)
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- Photoinduced hydroxylation of arylboronic acids with molecular oxygen under photocatalyst-free conditions
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Photoinduced hydroxylation of boronic acids with molecular oxygen under photocatalyst-free conditions is reported, providing a green entry to a variety of phenols and aliphatic alcohols in a highly concise fashion. This new protocol features photocatalyst-free conditions, wide substrate scope and excellent functional group compatibility.
- Xu, Yu-Ting,Li, Chen-Yuan,Huang, Xiao-Bo,Gao, Wen-Xia,Zhou, Yun-Bing,Liu, Miao-Chang,Wu, Hua-Yue
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supporting information
p. 4971 - 4975
(2019/09/30)
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