- Cu(I)-Based Metal-Organic Frameworks as Efficient and Recyclable Heterogeneous Catalysts for Aqueous-Medium C-H Oxidation
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The enantioselective transformation of ubiquitous C-H bonds into valuable C-O bonds offers an efficient synthetic approach to construct carbonyl functionalized molecules. However, the grand obstacles in the reaction are the selectivity issues and side reactions under the harsh reaction conditions. In order to overcome the limits, two Cu(I)-based MOFs {(NEt4)0.5[Cu3(TTPB)0.75(CN)0.5(H2O)]·H2O}n (1) and {[Cu2(TTPB)0.5]·DMF·2H2O}n (2) were synthesized (H4TTPB = 5,5′-(4′,5′-bis(4-(1H-tetrazol-5-yl)phenyl)-[1,1′:2′,1′′-terphenyl]-4,4′′-diyl) bis(1H-tetrazole)) under hydrothermal conditions with (triethylamine (TEA) and ethyldiisopropylamine (DIPEA) as structure-directing agents, respectively. Of these, 1 shows an anionic three-dimensional (3D) framework composed of two kinds of cagelike micropores with 7 × 17 ? and 10 × 17 ?, respectively. In comparison, 2 exhibits a 3D framework with open channels (14 × 8 ?). The stability studies showed that the crystallinity of 1 and 2 could remain in a series of organic solvents (ethanol, N,N-dimethylformamide, chloroform, dioxane, toluene) and acid and alkali aqueous solutions (pH = 1-13) at room temperature for 48 h. 1 and 2 with coordinatively unsaturated Cu(I) sites were applied as heterogeneous catalysts for the oxidation of arylacycloalkanes in aqueous medium and exhibited excellent catalytic activities, selectivities, and recyclabilities. Moreover, free-radical reaction mechanism and reversible valence-tautomeric conversions of central copper were confirmed during the process by control experiment.
- Gao, Kuan,Huang, Chao,Yang, Yisen,Li, Hong,Wu, Jie,Hou, Hongwei
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- 9.4 T and 7.05 T magnetic fields accelerate a radical oxidation reaction with a hypervalent (tert-butylperoxy)iodane
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Strong magnetic fields produced by NMR spectrometers (300 and 400 MHz) accelerate the radical oxidation of isochroman with a hypervalent (tert-butylperoxy)iodane.
- Iba, Kaori,Fukuyoshi, Shu-Ichi,Kusumi, Takenori
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- Di-tert-butyl Peroxide (DTBP)-Mediated Oxidative Cross- Coupling of Isochroman and Indole Derivatives
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A metal-free C-C bond formation method via the oxidative cross-coupling reaction of isochroman and indole derivatives was established. Various α-fuctionalized cyclic ethers were achieved in satisfactory yields using di-tert-butyl peroxide (DTBP) as the oxidant. This method is also a potentially efficient strategy for the construction of cyclic ether-containing targets.
- Jin, Likun,Feng, Jie,Lu, Guoping,Cai, Chun
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- Visible-light-catalyzed direct benzylic C(sp3)-H amination reaction by cross-dehydrogenative coupling
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A conceptually new and synthetically valuable cross-dehydrogenative benzylic C(sp3)-H amination reaction is reported by visible-light photoredox catalysis. This protocol employs DCA (9,10-dicyanoanthracene) as a visible-light-absorbing photoredox catalyst and an amide as the nitrogen source without the need of either a transition metal or an external oxidant. Amination: A metal and external oxidant-free benzylic amination driven by visible light in the presence of a sensitizer is reported (see picture). This approach is an innovative addition to the established procedures. The substrate scope and mechanistic experiments provide a good insight into the general reaction.
- Pandey, Ganesh,Laha, Ramkrishna
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- Synthesis and biological evaluation of 1-amino isochromans from 2-bromoethyl benzaldehyde and amines in acid medium
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We have developed a facile and efficient synthetic route to substituted isochromans for the first time by reacting 2-(2-bromoethyl)benzaldehyde with a variety of aryl, heteroaryl amines in AcOH. The reaction is catalyst/additive free and takes place at reflux conditions with short reaction time to furnish products in good to excellent yields. All the compounds have been characterized by spectral techniques such as IR, 1H NMR and Mass etc. Synthesized compounds were evaluated for antimicrobial activity against specific bacterial like 1) Staphylococcus strains aureus 2) Bacillus subtilis 3) Escherichia coli 4) Pseudomonas aeruginosa. Compounds 3e, 3n, 3 m, 3 l, 3 k, 3j and 3b showed most potent in vitro activity against bacterial strains.
- Fatima, Narjis,Reddy, B.V. Subba,Gowravaram, Sabitha,Yadav,Kadari, Sudhakar,Putta, Chandra Shekar
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- Microwave-Assisted Oxidation of Side Chain Arenes by Magtrieve
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A commercial tetravalent chromium dioxide (Magtrieve) as a magnetically retrievable oxidant is shown to be a very useful compound for microwave-assisted and conventional transformation of aromatic and alkyl aromatic molecules into the corresponding aryl ketones, quinones or lactones.
- Lukasiewicz, Marcin,Bogdal, Dariusz,Pielichowski, Jan
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- HCl-Catalyzed Aerobic Oxidation of Alkylarenes to Carbonyls
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The construction of C?O bonds through C?H bond functionalization remains fundamentally challenging. Here, a practical chlorine radical-mediated aerobic oxidation of alkylarenes to carbonyls was developed. This protocol employed commercially available HCl as a hydrogen atom transfer (HAT) reagent and air as a sustainable oxidant. In addition, this process exhibited excellent functional group tolerance and a broad substrate scope without the requirement for external metal and oxidants. The mechanistic hypothesis was supported by radical trapping, 18O labeling, and control experiments.
- Niu, Kaikai,Shi, Xiaodi,Ding, Ling,Liu, Yuxiu,Song, Hongjian,Wang, Qingmin
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- Two transition-metal-modified Nb/W mixed-addendum polyoxometalates for visible-light-mediated aerobic benzylic C–H oxidations
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The visible-light-induced selective oxidation of ubiquitous C–H bonds into valuable C=O bonds under aerobic conditions is one of the most attractive approaches for the construction of carbonyl-containing molecules. In this work, two transition metal-containing Nb/W mixed-addendum POMs dimers with the formula of K2Na2H5[(Fe(H2O)4)3(P2W15Nb3O62)2]?24H2O (POM[Fe]) and K2Na3H4[(Cr(H2O)4)3(P2W15Nb3O62)2]?32H2O (POM[Cr]) have been synthesized and characterized by various analytical and spectral techniques. POM[Fe] was proved to be an efficient photocatalyst for benzylic C–H oxidation under visible light and using oxygen as an oxidant to produce the corresponding carbonyl complex in good yields. A plausible mechanism involving superoxide radical was proposed for the catalytic reaction. POM[Fe] showed good reusability in the recycling experiments. IR spectroscopy and XRD analysis indicate that POM[Fe] can retain its integrity after catalysis.
- Chen, Xuenian,Gao, Fan,Li, Na,Li, Shujun,Ma, Yubin,Xiao, Wanru,Yu, Bing
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supporting information
(2022/03/27)
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- Selective Aerobic Oxidation of Csp3-H Bonds Catalyzed by Yeast-Derived Nitrogen, Phosphorus, and Oxygen Codoped Carbon Materials
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Nitrogen, phosphorus, and oxygen codoped carbon catalysts were successfully synthesized using dried yeast powder as a pyrolysis precursor. The yeast-derived heteroatom-doped carbon (yeast@C) catalysts exhibited outstanding performance in the oxidation of Csp3-H bonds to ketones and esters, giving excellent product yields (of up to 98% yield) without organic solvents at low O2pressure (0.1 MPa). The catalytic oxidation protocol exhibited a broad range of substrates (38 examples) with good functional group tolerance, excellent regioselectivity, and synthetic utility. The yeast-derived heteroatom-doped carbon catalysts showed good reusability and stability after recycling six times without any significant loss of activity. Experimental results and DFT calculations proved the important role of N-oxide (N+-O-) on the surface of yeast@C and a reasonable carbon radical mechanism.
- Ju, Zhao-Yang,Song, Li-Na,Chong, Ming-Ben,Cheng, Dang-Guo,Hou, Yang,Zhang, Xi-Ming,Zhang, Qing-Hua,Ren, Lan-Hui
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supporting information
p. 3978 - 3988
(2022/03/16)
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- Stepwise benzylic oxygenation via uranyl-photocatalysis
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Stepwise oxygenation at the benzylic position (1°, 2°, 3°) of aromatic molecules was comprehensively established under ambient conditions via uranyl photocatalysis to produce carboxylic acids, ketones, and alcohols, respectively. The accuracy of the stepwise oxygenation was ensured by the tunability of catalytic activity in uranyl photocatalysis, which was adjusted by solvents and additives demonstrated through Stern–Volmer analysis. Hydrogen atom transfer between the benzylic position and the uranyl catalyst facilitated oxygenation, further confirmed by kinetic studies. Considerably improved efficiency of flow operation demonstrated the potential for industrial synthetic application.
- Hu, Deqing,Jiang, Xuefeng
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supporting information
p. 124 - 129
(2022/01/19)
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- Mechanistic insight into the synergistic Cu/Pd-catalyzed carbonylation of aryl iodides using alcohols and dioxygen as the carbonyl source
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Pd-catalyzed carbonylation, as an efficient synthetic approach to the installation of carbonyl groups in organic compounds, has been one of the most important research fields in the past decade. Although elegant reactions that allow highly selective carbonylations have been developed, straightforward routes with improved reaction activity and broader substrate scope remain long-term challenges for new practical applications. Here, we show a new type of synergistic Cu/Pd-catalyzed carbonylation reaction using alcohols and dioxgen as the carbonyl sources. A broad range of aryl iodides and alcohols are compatible with this protocol. The reaction is concise and practical due to the ready availability of the starting materials and the scalability of the reaction. In addition, the reaction affords lactones and lactams in an intermolecular fashion. Moreover, DFT calculations have been performed to study the detailed mechanisms. [Figure not available: see fulltext.]
- Li, Junxuan,Zhou, Jinlei,Wang, Yumei,Yu, Yue,Liu, Qiang,Yang, Tilong,Chen, Huoji,Cao, Hua
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- Oxidaition of cyclic benzylic ethers by an electronically tuned nitroxyl radical
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The reactivity of an electronically tuned nitroxyl radical catalyst for the oxidation of cyclic benzylic ethers has been investigated. The oxidation of phthalan resulted in oxidative cleavage of the saturated ring to give an aromatic dialdehyde. Additionally, oxidation of isochromans afforded isochromanones, which are often seen in natural products, in a rapid manner.
- Hamada, Shohei,Yano, Kyoko,Kobayashi, Yusuke,Kawabata, Takeo,Furuta, Takumi
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supporting information
(2021/10/04)
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- Efficient Aliphatic C-H Oxidation and C═C Epoxidation Catalyzed by Porous Organic Polymer-Supported Single-Site Manganese Catalysts
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Bioinspired manganese complexes have emerged over recent decades as attractive catalysts for a number of selective oxidation reactions. However, these catalysts still suffer from oxidative degradation. In the present study, we prepared a series of porous Mn-N4 catalysts in which the catalytic units are embedded in the skeleton of porous organic polymers (POPs). These POP-based manganese catalysts demonstrated high reactivity in the oxidation of aliphatic C-H bonds and the asymmetric epoxidation of olefins. Furthermore, these catalysts could be readily recycled and reused due to their heterogeneous nature. Morphological characterization revealed that the Mn-N4 complex was individually distributed over a porous polymer network. Remarkably, the nature of the single-site catalyst prevented oxidative degradation during the reaction. The present work has thus developed a successful approach for bioinspired single-site manganese catalysts in which the oxidation reaction is confined to a specific channel in an enzyme-like mode.
- Wang, Bingyang,Lin, Jin,Sun, Qiangsheng,Xia, Chungu,Sun, Wei
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p. 10964 - 10973
(2021/09/08)
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- Selective electrochemical oxidation of aromatic hydrocarbons and preparation of mono/multi-carbonyl compounds
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A selective electrochemical oxidation was developed under mild condition. Various mono-carbonyl and multi-carbonyl compounds can be prepared from different aromatic hydrocarbons with moderate to excellent yield and selectivity by virtue of this electrochemical oxidation. The produced carbonyl compounds can be further transformed into α-ketoamides, homoallylic alcohols and oximes in a one-pot reaction. In particular, a series of α-ketoamides were prepared in a one-pot continuous electrolysis. Mechanistic studies showed that 2,2,2-trifluoroethan-1-ol (TFE) can interact with catalyst species and generate the corresponding hydrogen-bonding complex to enhance the electrochemical oxidation performance. [Figure not available: see fulltext.]
- Li, Zhibin,Zhang, Yan,Li, Kuiliang,Zhou, Zhenghong,Zha, Zhenggen,Wang, Zhiyong
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p. 2134 - 2141
(2021/09/29)
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- Integration of Earth-Abundant Photosensitizers and Catalysts in Metal-Organic Frameworks Enhances Photocatalytic Aerobic Oxidation
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We report here the construction of two metal-organic frameworks (MOFs), Zr6-Cu/Fe-1 and Zr6-Cu/Fe-2, by integrating earth-abundant cuprous photosensitizers (Cu-PSs) and Fe catalysts for photocatalytic aerobic oxidation. Site isolation and pore confinement stabilize both Cu-PSs and Fe catalysts, while the proximity between active centers facilitates electron and mass transfer. Upon visible light irradiation and using O2 as the only oxidant, Zr6-Cu/Fe-1 and Zr6-Cu/Fe-2 efficiently oxidize alcohols and benzylic compounds to afford corresponding carbonyl products with broad substrate scopes, high turnover numbers of up to 500 with a 9.4-fold enhancement over homogeneous analogues, and excellent recyclability in four consecutive runs. Control experiments, spectroscopic evidence, and computational studies revealed the photo-oxidation mechanism: Oxidative quenching of [Cu-PS]? by O2 affords [CuII-PS], which efficiently oxidizes FeIII-OH to generate a hydroxyl radical for substrate oxidation. This work highlights the potential of MOFs in promoting earth-abundant metal-based photocatalysis.
- Feng, Xuanyu,Pi, Yunhong,Song, Yang,Xu, Ziwan,Li, Zhong,Lin, Wenbin
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p. 1024 - 1032
(2021/01/26)
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- Covalent Organic Frameworks toward Diverse Photocatalytic Aerobic Oxidations
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Photoactive two-dimensional covalent organic frameworks (2D-COFs) have become promising heterogenous photocatalysts in visible-light-driven organic transformations. Herein, a visible-light-driven selective aerobic oxidation of various small organic molecules by using 2D-COFs as the photocatalyst was developed. In this protocol, due to the remarkable photocatalytic capability of hydrazone-based 2D-COF-1 on molecular oxygen activation, a wide range of amides, quinolones, heterocyclic compounds, and sulfoxides were obtained with high efficiency and excellent functional group tolerance under very mild reaction conditions. Furthermore, benefiting from the inherent advantage of heterogenous photocatalysis, prominent sustainability and easy photocatalyst recyclability, a drug molecule (modafinil) and an oxidized mustard gas simulant (2-chloroethyl ethyl sulfoxide) were selectively and easily obtained in scale-up reactions. Mechanistic investigations were conducted using radical quenching experiments and in situ ESR spectroscopy, all corroborating the proposed role of 2D-COF-1 in photocatalytic cycle.
- Liu, Shuyang,Tian, Miao,Bu, Xiubin,Tian, Hua,Yang, Xiaobo
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supporting information
p. 7738 - 7744
(2021/05/07)
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- An efficient and practical aerobic oxidation of benzylic methylenes by recyclable: N -hydroxyimide
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An efficient and practical benzylic aerobic oxidation catalyzed by cheap and simple N-hydroxyimide organocatalyst has been achieved with high yields and broad substrate scope. The organocatalyst used can be recycled and reused by simple workup and only minute amount (1 mol% in most cases) of simple iron salt is used as promoter. Phenyl substrates with mild and strong electron-withdrawing group could also be oxygenated in high yields as well as other benzylic methylenes. Influence of substituents, gram-scale application, catalysts decay and general mechanism of this methodology has also been discussed. This journal is
- Wang, Jian,Zhang, Cheng,Ye, Xiao-Qing,Du, Wenting,Zeng, Shenxin,Xu, Jian-Hong,Yin, Hong
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p. 3003 - 3011
(2021/01/28)
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- Selective Electrochemical Oxygenation of Alkylarenes to Carbonyls
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An efficient electrochemical method for benzylic C(sp3)-H bond oxidation has been developed. A variety of methylarenes, methylheteroarenes, and benzylic (hetero)methylenes could be converted into the desired aryl aldehydes and aryl ketones in moderate to excellent yields in an undivided cell, using O2 as the oxygen source and lutidinium perchlorate as an electrolyte. On the basis of cyclic voltammetry studies, 18O labeling experiments, and radical trapping experiments, a possible single-electron transfer mechanism has been proposed for the electrooxidation reaction.
- Li, Xue,Bai, Fang,Liu, Chaogan,Ma, Xiaowei,Gu, Chengzhi,Dai, Bin
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supporting information
p. 7445 - 7449
(2021/10/02)
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- A Proton-Responsive Pyridyl(benzamide)-Functionalized NHC Ligand on Ir Complex for Alkylation of Ketones and Secondary Alcohols
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A Cp*Ir(III) complex (1) of a newly designed ligand L1 featuring a proton-responsive pyridyl(benzamide) appended on N-heterocyclic carbene (NHC) has been synthesized. The molecular structure of 1 reveals a dearomatized form of the ligand. The protonation of 1 with HBF4 in tetrahydrofuran gives the corresponding aromatized complex [Cp*Ir(L1H)Cl]BF4 (2). Both compounds are characterized spectroscopically and by X-ray crystallography. The protonation of 1 with acid is examined by 1H NMR and UV-vis spectra. The proton-responsive character of 1 is exploited for catalyzing α-alkylation of ketones and β-alkylation of secondary alcohols using primary alcohols as alkylating agents through hydrogen-borrowing methodology. Compound 1 is an effective catalyst for these reactions and exhibits a superior activity in comparison to a structurally similar iridium complex [Cp*Ir(L2)Cl]PF6 (3) lacking a proton-responsive pendant amide moiety. The catalytic alkylation is characterized by a wide substrate scope, low catalyst and base loadings, and a short reaction time. The catalytic efficacy of 1 is also demonstrated for the syntheses of quinoline and lactone derivatives via acceptorless dehydrogenation, and selective alkylation of two steroids, pregnenolone and testosterone. Detailed mechanistic investigations and DFT calculations substantiate the role of the proton-responsive ligand in the hydrogen-borrowing process.
- Kaur, Mandeep,U Din Reshi, Noor,Patra, Kamaless,Bhattacherya, Arindom,Kunnikuruvan, Sooraj,Bera, Jitendra K.
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supporting information
p. 10737 - 10748
(2021/06/15)
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- Synthesis method of aromatic benzyl ketone
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The invention discloses a synthesis method of aromatic benzyl ketone, which comprises the following step: by using oxygen and/or air as an oxidant, oxidizing an aromatic benzyl compound shown in a formula (I) under the action of a catalytic system to obtain aromatic benzyl ketone shown in a formula (II). The catalytic system is formed by combining ferric ions, nitrate radicals and N-hydroxyimide derivatives and does not contain heavy metal ions harmful to human bodies, wherein the molar ratio of the ferric ions to the nitrate radicals is 1: (0.5-5), and the molar ratio of the ferric ions to the N-hydroxyimide derivatives is (0.01-0.1): (0.03-0.2). The method disclosed by the invention is wide in substrate applicability and high in atom utilization rate, avoids the use of harmful heavy metals such as copper and cobalt, and has the characteristics of high efficiency, economy and environmental protection. The formulas are as follows: Ar-CH2-R (I) and Ar-CO-R (II).
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Paragraph 0094-0103
(2020/09/12)
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- Flavin Nitroalkane Oxidase Mimics Compatibility with NOx/TEMPO Catalysis: Aerobic Oxidization of Alcohols, Diols, and Ethers
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Biomimetic flavin organocatalysts oxidize nitromethane to formaldehyde and NOx - providing a relatively nontoxic, noncaustic, and inexpensive source for catalytic NO2 for aerobic TEMPO oxidations of alcohols, diols, and ethers. Alcohols were oxidized to aldehydes or ketones, cyclic ethers to esters, and terminal diols to lactones. In situ trapping of NOx and formaldehyde suggest an oxidative Nef process reminiscent of flavoprotein nitroalkane oxidase reactivity, which is achieved by relatively stable 1,10-bridged flavins. The metal-free flavin/NOx/TEMPO catalytic cycles are uniquely compatible, especially compared to other Nef and NOx-generating processes, and reveal selectivity over flavin-catalyzed sulfoxide formation. Aliphatic ethers were oxidized by this method, as demonstrated by the conversion of (-)-ambroxide to (+)-sclareolide.
- Thapa, Pawan,Hazoor, Shan,Chouhan, Bikash,Vuong, Thanh Thuy,Foss, Frank W.
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p. 9096 - 9105
(2020/08/14)
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- Visible-light-induced selective aerobic oxidation of sp3 C-H bonds catalyzed by a heterogeneous AgI/BiVO4 catalyst
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An efficient oxidation of sp3 C-H bonds to esters and ketones has been developed using AgI/BiVO4 as the photocatalyst and O2 as the oxidant in water. Various substrates can be transformed into the desired esters and ketones in moderate to good yields. The synthetic utility of this approach has been demonstrated by gram-level experiments and consecutive oxidation experiments. A plausible mechanism has been proposed.
- Jiang, Li-Ya,Ming, Jing-Jing,Wang, Lian-Yue,Jiang, Yuan-Yuan,Ren, Lan-Hui,Wang, Zi-Cheng,Cheng, Wen-Chen
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supporting information
p. 1156 - 1163
(2020/03/11)
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- Iodine(III)-catalyzed benzylic oxidation by using the (PhIO)n/Al(NO3)3 system
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The first iodine(III)-based procedure for the benzylic oxidation of different arenes is described by using the (PhIO)n/Al(NO3)3 system under catalytic conditions leading to the formation of the corresponding carbonyl derivatives. The method proceeds under mild, operationally simple, room temperature, short reaction times, and open flask conditions. In light of the organocatalysis relevance and the novelty of our protocol, we wish to communicate our initial results of this novel oxidation.
- Yahuaca-Juárez, Berencie,González, Gerardo,Ramírez-Morales, Marco A.,Alba-Betancourt, Calara,Deveze-álvarez, Martha A.,Mendoza-Macías, Claudia L.,Ortiz-Alvarado, Rafael,Juárez-Ornelas, Kevin A.,Solorio-Alvarado, César R.,Maruoka, Keiji
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p. 539 - 548
(2020/01/22)
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- α-Angelica lactone catalyzed oxidation of benzylic sp3C-H bonds of isochromans and phthalans
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A metal-free organocatalytic system has been developed for highly efficient benzylic C-H oxygenations of cyclic ethers using oxygen as an oxidant. This oxidation reaction utilizes α-angelica lactone as a low cost/low molecular weight catalyst. The optimized reaction conditions allow the synthesis of valued isocoumarins and phthalides from readily available precursors in good yields. Mechanistic studies indicate that the reaction pathway likely involves a radical processviaa peroxide intermediate.
- Das, Utpal,Deepake, Siddharth K.,Kumar, Pawan,Thatikonda, Thanusha
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supporting information
p. 4046 - 4050
(2020/06/09)
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- (Cyclopentadienone)iron-Catalyzed Transfer Dehydrogenation of Symmetrical and Unsymmetrical Diols to Lactones
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Air-stable iron carbonyl compounds bearing cyclopentadienone ligands with varying substitution were explored as catalysts in dehydrogenative diol lactonization reactions using acetone as both the solvent and hydrogen acceptor. Two catalysts with trimethylsilyl groups in the 2- A nd 5-positions, [2,5-(SiMe3)2-3,4-(CH2)4(δ4-C4C= O)]Fe(CO)3 (1) and [2,5-(SiMe3)2-3,4-(CH2)3(δ4-C4C= O)]Fe(CO)3 (2), were found to be the most active, with 2 being the most selective in the lactonization of diols containing both primary and secondary alcohols. Lactones containing five-, six-, and seven-membered rings were successfully synthesized, and no over-oxidations to carboxylic acids were detected. The lactonization of unsymmetrical diols containing two primary alcohols occurred with catalyst 1, but selectivity was low based on alcohol electronics and modest based on alcohol sterics. Evidence for a transfer dehydrogenation mechanism was found, and insight into the origin of selectivity in the lactonization of 1°/2° diols was obtained. Additionally, spectroscopic evidence for a trimethylamine-ligated iron species formed in solution during the reaction was discovered.
- Tang, Yidan,Meador, Rowan I. L.,Malinchak, Casina T.,Harrison, Emily E.,McCaskey, Kimberly A.,Hempel, Melanie C.,Funk, Timothy W.
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p. 1823 - 1834
(2020/02/04)
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- Scalable Aerobic Oxidation of Alcohols Using Catalytic DDQ/HNO3
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A selective, practical, and scalable aerobic oxidation of alcohols is described that uses catalytic amounts of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and HNO3, with molecular oxygen serving as the terminal oxidant. The method was successfully applied to the oxidation of a wide range of benzylic, propargylic, and allylic alcohols, including two natural products, namely, carveol and podophyllotoxin. The conditions are also applicable to the selective oxidative deprotection of p-methoxybenzyl ethers.
- Arseniyadis, Stellios,Clavier, Louis,Copin, Chloé,Fournier, Jean,Giffard, Jean-Fran?ois,Jean, Alexandre,Katsina, Tania,Macedo Portela Da Silva, Nayane,Tamion, Rodolphe
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supporting information
p. 856 - 860
(2020/07/14)
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- Regioselective biocatalytic self-sufficient Tishchenko-type reactionviaformal intramolecular hydride transfer
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A self-sufficient nicotinamide-dependent intramolecular bio-Tishchenko-type reaction was developed. The reaction is catalyzed by alcohol dehydrogenases and proceeds through formal intramolecular hydride transfer on dialdehydes to deliver lactones. Regioselectivity on [1,1′-biphenyl]-2,2′-dicarbaldehyde substrates could be controlledviathe electronic properties of the substituents. Preparative scale synthesis provided access to substituted dibenzo[c,e]oxepin-5(7H)-ones.
- Buljubasic, Isa,Hall, Mélanie,Laggner, Olivia,Merusic, Kemal,Reiter, Tamara,Tassano, Erika,Vogel, Andreas
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p. 6340 - 6343
(2020/06/21)
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- Iridium-Catalyzed Enantioselective Hydrogenation of Oxocarbenium Ions: A Case of Ionic Hydrogenation
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Ionic hydrogenation has not been extensively explored, but is advantageous for challenging substrates such as unsaturated intermediates. Reported here is an iridium-catalyzed hydrogenation of oxocarbenium ions to afford chiral isochromans with high enantioselectivities. A variety of functionalities are compatible with this catalytic system. In the presence of a catalytic amount of the Br?nsted acid HCl, an α-chloroether is generated in situ and subsequentially reduced. Kinetic studies suggest first-order kinetics in the substrate and half-order kinetics in the catalyst. A positive nonlinear effect, together with the half kinetic order, revealed a dimerization of the catalyst. Possible reaction pathways based on the monomeric iridium catalyst were proposed and DFT computational studies revealed an ionic hydrogenation pathway. Chloride abstraction and the cleavage of dihydrogen occur in the same step.
- Lin, Zhenyang,Sun, Yongjie,Wang, Heng,Wen, Jialin,Yang, Tilong,Zhang, Xumu
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p. 6108 - 6114
(2020/03/04)
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- Thiyl radical promoted iron-catalyzed-selective oxidation of benzylic sp3 C-H bonds with molecular oxygen
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A ligand-free iron-catalyzed method for the oxygenation of benzylic sp3 C-H bonds by molecular oxygen (1 atm) using a thiyl radical as a cocatalyst has been developed. This transformation provides a facile access to amides, esters and ketones from readily accessible corresponding amines, ethers and alkanes. It features high regioselectivity, mild oxidative conditions and excellent functional group compatibility, providing good opportunities to the site-selective functionalization of complex molecules. Preliminary mechanistic studies suggest that this reaction may not undergo a benzylic cation intermediate pathway and the carbonyl oxygen atom in the products may be derived from molecular oxygen.
- Geng, Shasha,Xiong, Baojian,Zhang, Yun,Zhang, Juan,He, Yun,Feng, Zhang
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supporting information
p. 12699 - 12702
(2019/10/28)
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- Co(ii)-cluster-based metal-organic frameworks as efficient heterogeneous catalysts for selective oxidation of arylalkanes
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To explore metal-organic frameworks (MOFs) based on Co-clusters as heterogeneous catalysts to selectively catalyze the reaction of C-H bond oxidation of aromatic alkanes to their corresponding ketones, three MOFs {[Co5(pmbcd)2(μ3-OH)2(H2O)4(DMF)2]·4DMF}n (MOF 1), {[Co2(pmbcd)(bpea)2]·2H2O·2DMF}n (MOF 2), and {[Co2(pmbcd)(dpp)2]·3H2O·2DMF}n (MOF 3) (H4pmbcd = 9,9′-(1,4-phenylenebis(methylene))bis(9H-carbazole-3,6-dicarboxylic acid), bpea = 1,2-bis(4-pyridyl)ethane, dpp = 1,3-di(4-pyridyl)propane) were successfully synthesized and structurally characterized. MOF 1 was constructed from a pentanuclear Co(ii) cluster and exhibited a porous framework with channels of 8 × 10 ?2 along the b axis. MOF 2 was constructed from [Co2(CO2)4] units and presented a porous three-dimensional (3D) framework with channels of 11 × 13 ?2 along the b axis and of 10 × 12 ?2 along the c axis. MOF 3 was a flat two-dimensional (2D) layer based on binuclear Co(ii) units when dpp as an auxiliary ligand was introduced. The Co5-cluster-based MOF 1 exhibited excellent catalytic activity for the direct C-H bond activation of arylalkanes to ketones in H2O under room temperature because of its high density of Lewis acidic sites within the frameworks and suitable channel size to access the catalytic sites. It also presented the spatial confinement effect and catalyzed the reaction with high regioselectivity, forming mono-ketones as the sole products. Easy product separation, simple reaction procedures, and recyclability of these catalysts make the catalytic system attractive. Our work highlights the superiority of the MOF-based materials as heterogeneous catalysts.
- Fan, Yanru,Li, Xiao,Gao, Kuan,Liu, Yu,Meng, Xiangru,Wu, Jie,Hou, Hongwei
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p. 1666 - 1673
(2019/03/07)
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- A g-C3N4-based heterogeneous photocatalyst for visible light mediated aerobic benzylic C-H oxygenations
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A metal-free heterogeneous photocatalytic system has been developed for highly efficient benzylic C-H oxygenations using oxygen as an oxidant. This visible light mediated oxidation reaction utilizes graphitic carbon nitride (g-C3N4) as a recyclable, nontoxic and low cost photocatalyst. Mild reaction conditions allow for the generation of synthetically and biologically valued isochromannones, phthalides, isoquinolinones, isoindolinones and xanthones from readily accessible alkyl aromatic precursors in good yields. The heterogeneous nature of the g-C3N4 catalytic system enables easy recovery and recycling as well as the use in multiple runs without loss of activity. The synthetic utility of this "green" methodology was further demonstrated by applying in bioactive and drug valued target syntheses.
- Geng, Pengxin,Tang, Yurong,Pan, Guanglong,Wang, Wentao,Hu, Jinchuan,Cai, Yunfei
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supporting information
p. 6116 - 6122
(2019/11/20)
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- Cercosporin-bioinspired selective photooxidation reactions under mild conditions
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The development of an efficient system for selective oxidation of organic compounds to generate more valuable compounds with molecular oxygen is a significant challenge in industrial chemistry. Bioinspired by the ability of naturally occurring perylenequinonoid pigments (PQPs) to generate reactive oxygen species (ROS) upon photoirradiation, here we report that cercosporin, one of the perylenequinonoid pigments, can function as a cost-effective and environmentally friendly photocatalyst for a wide range of selective oxidations, including benzylic C-H bonds to carbonyls, amines to aldehydes, and sulfides to sulfoxides. All of the representative reactions proceeded smoothly with high efficiency under mild conditions. Owing to the use of inexpensive metal-free visible light-driven photocatalyst produced from microbial fermentation with cheap glucose as the starting material and the ease of handling, we expect that this developed method will be particularly attractive for many more applications in synthetic transformation.
- Li, Jia,Bao, Wenhao,Tang, Zhaocheng,Guo, Baodang,Zhang, Shiwei,Liu, Haili,Huang, Shuping,Zhang, Yan,Rao, Yijian
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supporting information
p. 6073 - 6081
(2019/11/20)
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- Iron-catalyzed oxidative functionalization of C(sp3)-H bonds under bromide-synergized mild conditions
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An efficient oxidation and functionalization of C-H bonds with an inorganic-ligand supported iron catalyst and hydrogen peroxide to prepare the corresponding ketones was achieved using the bromide ion as a promoter. Preliminary mechanistic investigations indicated that the bromide ion can bind to FeMo6 to form a supramolecular species (FeMo6·2Br), which can effectively catalyze the reaction.
- Yu, Han,Zhao, Qixin,Wei, Zheyu,Wu, Zhikang,Li, Qi,Han, Sheng,Wei, Yongge
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supporting information
p. 7840 - 7843
(2019/07/12)
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- Isoindolinone Synthesis: Selective Dioxane-Mediated Aerobic Oxidation of Isoindolines
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N-Alkyl and N-aryl-isoindolinones were prepared by a dioxane-mediated oxidation of isoindoline precursors. The transformation exhibits unique chemoselectivity for isoindonlines. A chiral tertiary (3°)-benzylic position was not racemized during oxidation, and methyl indoprofen was prepared by late stage oxidation. Mechanistic studies suggest a selective H atom transfer, which avoids many known oxidation (by-)products of isoindolinones.
- Thapa, Pawan,Corral, Esai,Sardar, Sinjinee,Pierce, Brad S.,Foss, Frank W.
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p. 1025 - 1034
(2019/01/24)
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- Platinum-on-Carbon-Catalyzed Aqueous Oxidative Lactonization of Diols by Using Molecular Oxygen
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A lactonization of various diols catalyzed by platinum on carbon (Pt/C) in water under an atmosphere of molecular oxygen was developed. Derivatives of 1,4- 1,5- and 1,6-diols were transformed into the corresponding five-, six-, and seven-membered lactones by the present oxidative lactonization method.
- Ban, Kazuho,Sajiki, Hironao,Sawama, Yoshinari,Takakura, Ryoya
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supporting information
p. 1919 - 1923
(2019/09/30)
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- Efficient acceptorless photo-dehydrogenation of alcohols and: N -heterocycles with binuclear platinum(ii) diphosphite complexes
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Although photoredox catalysis employing Ru(ii) and Ir(iii) complexes as photocatalysts has emerged as a versatile tool for oxidative C-H functionalization under mild conditions, the need for additional reagents acting as electron donor/scavenger for completing the catalytic cycle undermines the practicability of this approach. Herein we demonstrate that photo-induced oxidative C-H functionalization can be catalysed with high product yields under oxygen-free and acceptorless conditions via inner-sphere atom abstraction by binuclear platinum(ii) diphosphite complexes. Both alcohols (51 examples), particularly the aliphatic ones, and saturated N-heterocycles (24 examples) can be efficiently dehydrogenated under light irradiation at room temperature. Regeneration of the photocatalyst by means of reductive elimination of dihydrogen from the in situ formed platinum(iii)-hydride species represents an alternative paradigm to the current approach in photoredox catalysis.
- Zhong, Jian-Ji,To, Wai-Pong,Liu, Yungen,Lu, Wei,Che, Chi-Ming
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p. 4883 - 4889
(2019/05/16)
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- Visible light mediated oxidation of benzylic sp3 C-H bonds using catalytic 1,4-hydroquinone, or its biorenewable glucoside, arbutin, as a pre-oxidant
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Benzylic ethers undergo a visible light induced C-H activation and oxygen insertion to give the corresponding benzoate esters in moderate to good yields. The conditions employ substoichiometric amounts of 1,4-hydroquinone with copper(ii) chloride dihydrate as an electron-transfer mediator, oxygen as the terminal oxidant and dimethyl carbonate as solvent under visible light irradiation. The naturally occurring glucoside, arbutin, which is commercially available or can be accessed via extraction of the leaves of bearberry (Arctostaphylos uva-ursi) or elephant ears (Bergenia crassifolia) can be used as a biorenewable source of 1,4-hydroquinone. The methodology exploits the increase in oxidizing ability of quinones upon irradiation with visible light, and offers a sustainable alternative for the late stage oxidative functionalization of benzylic C-H bonds. It is applicable to a range of cyclic benzylic ethers such as isochromans and phthalans, and simple benzyl alkyl ethers. It can also be applied in the oxidation of benzylic amines into amides, and of diarylmethanes into the corresponding ketones. Mechanistic studies suggest that the reaction proceeds by H-abstraction by the photo-excited triplet benzoquinone to give a benzylic radical that subsequently reacts with molecular oxygen.
- Finney, Laura C.,Mitchell, Lorna J.,Moody, Christopher J.
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supporting information
p. 2242 - 2249
(2018/05/28)
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- Nitric acid-catalyzed aerobic oxidation of benzylic sp3 C–H bonds of isochromans, xanthenes and 9-fluorenone under additive-free conditions
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HNO3 was demonstrated to be an effective catalyst for aerobic oxidation of benzylic sp3 C–H bonds under additive-free conditions. A series of isochromans, xanthenes and fluorenes underwent this transformation to give the targeted products in low to high yields under the catalysis of HNO3, which provided an effective method for the synthesis of the synthetically and biologically valued isochromanones, xanthones and 9-fluorenones.
- Tian, Xinzhe,Ren, Fangping,Zhao, Bo,Ren, Yun-Lai,Zhao, Shuang,Wang, Jianji
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- Carbon monoxide is used as a source of halogen compound heterogeneous palladium catalyst in the presence of the aldehyde carbonyl compound by reaction carbonylation method (by machine translation)
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[Problem] catalyst and the presence of carbon monoxide, the halogen compound is a carbonyl compound in the carbonylation reaction, catalysts or carbon monoxide source technique has problems. [Solution] the presence of the catalyst and the carbon monoxide, the halogen compound is carbonylation reaction method for producing a carbonyl compound, As a heterogeneous palladium catalyst, carbon monoxide is produced from an aldehyde carbonyl compound used in the method. [Drawing] no (by machine translation)
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Paragraph 0070; 0071; 0072
(2018/04/06)
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- Phenylphosphinic acid-promoted addition of isocyanide to 1-methoxyisochroman derivatives
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A synthetic method for preparation of isochroman-1-carboxylamides in good to high yields by addition of isocyanides to 1-methoxyisochroman derivatives in the presence of phosphinic acid was developed. A wide range of 1-methoxyisochroman derivatives and isocyanides were suitable for this reaction.
- Soeta, Takahiro,Matsuzaki, Syunsuke,Ukaji, Yutaka
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p. 355 - 364
(2019/04/26)
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- Electron-Transfer-Induced Intramolecular Heck Carbonylation Reactions Leading to Benzolactones and Benzolactams
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A metal-catalyst-free intramolecular Heck carbonylation reaction of benzyl alcohols and benzyl amines with carbon monoxide under heating at 250 °C affords the corresponding benzolactones and benzolactams in good to excellent yields. A hybrid radical/ionic chain mechanism, involving electron transfer from radical anions generated by nucleophilic attack of alcohols or amines on intermediate acyl radicals, is proposed.
- Fukuyama, Takahide,Bando, Takanobu,Ryu, Ilhyong
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supporting information
p. 3015 - 3021
(2018/06/08)
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- Ligand-Free, Copper-Catalyzed Aerobic Benzylic sp 3 C-H Oxygenation
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A ligand-free and operationally simple copper-catalyzed aerobic benzylic sp 3 C-H oxygenation was developed. The addition of tert -butyl hydroperoxide, either in a catalytic or stoichiometric amount, was key for activating stable C-H bonds under mild conditions to furnish the corresponding ketones or esters in moderate to excellent yield.
- Tanaka, Hirotaka,Oisaki, Kounosuke,Kanai, Motomu
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supporting information
p. 1576 - 1580
(2017/08/11)
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- An Fe3O4@P4VP@FeCl3 core-shell heterogeneous catalyst for aerobic oxidation of alcohols and benzylic oxidation reaction
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A novel magnetic Fe3O4@P4VP(poly(4-vinylpyridine))@FeCl3 core-shell structure was successfully synthesized. Its Fe3O4@P4VP core was initially prepared via polymerization of 4-vinyl pyridine on the surface of Fe3O4 microspheres. The successful introduction of the FeCl3 moiety as a catalytic active site was achieved through coordination interaction between P4VP and FeCl3. The obtained Fe3O4@P4VP@FeCl3 catalyst was applied in the selective oxidation of alcohols using molecular oxygen as the oxidant. It was shown that a variety of alcohol substrates is tolerated under optimized reaction conditions. Additionally, benzylic oxidation of hydrocarbon compounds was also evaluated using Fe3O4@P4VP@FeCl3 as the catalyst and tBuOOH as the oxidant, achieving high yields and very good selectivities. The heterogeneity of the Fe3O4@P4VP@FeCl3 core-shell catalyst was tested and the initial activity was maintained after five reuses.
- Li, Ruilian,Zhao, Jian,Yang, Fengxia,Zhang, Yingchao,Ramella, Daniele,Peng, Yu,Luan, Yi
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p. 51142 - 51150
(2017/11/15)
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- Catalytic oxidation synthesis method of isochroman-4-one compounds
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The invention discloses a catalytic oxidation synthesis method of isochroman-4-one compounds. The method comprises following steps: isochroman compounds, Fe(NO3)3.9H2O and fluorine-containinginorganic salt are added to an acetonitrile solvent and react at the temperature of 75-85 DEG C for 4-10 h under the condition of normal-pressure oxygen, and the isochroman-4-one compounds are obtained; a quantity ratio of the isochroman-4-one compounds as reaction substrates, Fe(NO3)3.9H2O and theinorganic salt is 100:(8-15):(15-30); after the complete reaction, the isochroman-4-one compounds can be obtained through conventionalcolumn chromatographic separationand purification. The method is simple and safe to operate and has the main beneficial effects as follows: A), clean oxygen is utilized as an oxidizing agent, so that the environmental cost is greatly reduced; B), Fe(NO3)3.9H2O is taken as a catalyst, and the cost is low.
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Paragraph 0017; 0018; 0019; 0020; 0021; 0022; 0023-0026
(2017/08/29)
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- Method for synthesizing aromatic aldehyde, aromatic ketone and aromatic ester through catalytically oxidizing alkyl aromatic compound by iron
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The invention discloses a method for synthesizing aromatic aldehyde, aromatic ketone and aromatic ester through catalytically oxidizing an alkyl aromatic compound by iron, and belongs to the technical field of catalytic synthesis. According to the method, a low-cost and environment-friendly iron catalyst is used under a normal pressure; under the action of hydrogen and silicon reagents serving as an accelerant and an oxidant, a side chain of an aromatic hydrocarbon is oxidized into a carbonyl group for generating the corresponding aromatic aldehyde, aromatic ketone and aromatic ester. The method for preparing the aromatic aldehyde, the aromatic ketone and the aromatic ester through a catalytic oxidation reaction, which is provided by the invention, has numerous advantages that a catalyst, reaction raw materials, the oxidant and a silicon reagent are wide in sources and good in stability and is low-cost and environment-friendly; the alkyl aromatic compound is metered to participate in a reaction; the reaction condition is mild; the compatibility of functional groups is good; the scope of application is wide; the reaction selectivity is good; in an optimized reaction condition, the separation yield of a target product can be up to approximately 95 percent.
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Paragraph 0074; 0075
(2017/10/13)
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- Visible-Light Photocatalysis Employing Dye-Sensitized Semiconductor: Selective Aerobic Oxidation of Benzyl Ethers
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The aerobic oxidation is an attractive approach toward environmentally benign synthesis of fine chemicals. In addition, dye-sensitized semiconductors are underdeveloped photocatalysts for selective organic synthesis. With the aid of catalytic eosin Y-sensitized titanium dioxide, we have developed efficient aerobic photooxidation of benzyl ethers to benzoates, featuring low cost, high atom economy, broad substrate scope, and user-friendly setup. Furthermore, preliminary mechanistic studies established that the reaction pathway likely entails a photoinduced, radical-based two-step process via an isolable peroxide intermediate.
- Ren, Li,Yang, Ming-Meng,Tung, Chen-Ho,Wu, Li-Zhu,Cong, Huan
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p. 8134 - 8138
(2017/12/08)
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- MODULATORS OF CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR
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The present invention features a compound of formula I: or a pharmaceutically acceptable salt thereof, where R1, R2, R3, W, X, Y, Z, n, o, p, and q are defined herein, for the treatment of CFTR mediated diseases, such as cystic fibrosis. The present invention also features pharmaceutical compositions, method of treating, and kits thereof.
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Page/Page column 987-988
(2021/02/10)
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- Merging Photoredox with Br?nsted Acid Catalysis: The Cross-Dehydrogenative C?O Coupling for sp3 C?H Bond Peroxidation
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A photoredox and Br?nsted acid synergistically catalyzed cross-dehydrogenative C?O coupling reaction is developed in which isochroman peroxyacetals are formed through sp3 C?H bond peroxidation. The reported method is characterized by its extremely mild reaction conditions, excellent yields, and broad substrate scope. An oxocarbenium ion p-chlorobenzenesulfonate was speculated to be the reactive intermediate. The role of hemiacetals and oxygenated dimers on the effective stabilization of the oxocarbenium ion was investigated; the presence of acid appeared to establish equilibrium between hemiacetals and oxygenated dimers with the oxocarbenium ion pairs. The broad applicability of the method highlights the potential of the protocol for molecule synthesis.
- Xia, Qing,Wang, Qiang,Yan, Changcun,Dong, Jianyang,Song, Hongjian,Li, Ling,Liu, Yuxiu,Wang, Qingmin,Liu, Xiangming,Song, Haibin
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supporting information
p. 10871 - 10877
(2017/08/18)
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- Palladium on Carbon-Catalyzed Benzylic Methoxylation for Synthesis of Mixed Acetals and Orthoesters
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The palladium on carbon (Pd/C)-catalyzed direct methoxylation of the benzylic positions of linear benzyl and cyclic ether substrates proceeded in the presence of i-Pr2NEt under an oxygen atmosphere to give the corresponding mixed acetals. Cyclic acetal derivatives could also be converted into orthoesters. The present direct methoxylation via a carbon-hydrogen (C?H) functionalization can be accomplished using the easily-removed Pd/C and molecular oxygen as a green oxidant. The obtained mixed acetals were transformed into the corresponding ether products by chemoselective substitution of the methoxy group using a silyltriflate, 2,4,6-collidine, and a nucleophile. The orthoester derivative could also be transformed into the cyclic ketal under similar reaction conditions.
- Yasukawa, Naoki,Kanie, Takafumi,Kuwata, Marina,Monguchi, Yasunari,Sajiki, Hironao,Sawama, Yoshinari
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supporting information
p. 10974 - 10977
(2017/08/22)
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- Heterogeneous One-Pot Carbonylation and Mizoroki–Heck Reaction in a Parallel Manner Following the Cleavage of Cinnamaldehyde Derivatives
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Carbon monoxide (CO) and styrene derivatives that can be both generated by a palladium on carbon (Pd/C)-catalyzed carbon–carbon (C?C) bond cleavage reaction of cinnamaldehyde derivatives were effectively utilized in further palladium-catalyzed C?C bond forming reactions in a direct and practical way. CO derived from simple and affordable CO carriers such as cinnamaldehyde or terephthalaldehyde was efficiently employed in the in situ CO fixation with various aromatic iodides through a palladium-catalyzed carbonylation followed by an inter- or intramolecular coupling reaction with alcohols to afford the corresponding esters or lactones, respectively. Styrene derivatives were also efficient substrates in an in situ Mizoroki–Heck-type cross-coupling reaction with aryl iodides, leading to the effective formation of asymmetric stilbenes. The decarbonylation of cinnamaldehyde derivatives and the subsequent independent syntheses of both esters/lactones and 1,2-diarylethenes could be achieved in a virtual one-pot and in situ reaction using a H-shaped pressure-tight glass-sealed tube consisting of two independent but laterally connected reaction tubes in the gas space.
- Hattori, Tomohiro,Ueda, Shun,Takakura, Ryoya,Sawama, Yoshinari,Monguchi, Yasunari,Sajiki, Hironao
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p. 8196 - 8202
(2017/06/23)
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- P450 BM3-Catalyzed Regio- and Stereoselective Hydroxylation Aiming at the Synthesis of Phthalides and Isocoumarins
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Cytochrome P450 BM3 monooxygenases are able to catalyze the regio- and stereoselective oxygenation of a broad range of substrates, with promising potential for synthetic applications. To study the suitability of P450 BM3 variants for stereoselective benzylic hydroxylation of 2-alkylated benzoic acid esters, the biotransformation of methyl 2-ethylbenzoate, resulting in both enantiomeric forms of 3-methylphthalide, was investigated. In the case of methyl 2-propylbenzoate as a substrate the regioselectivity of the reaction was shifted towards β-hydroxylation, resulting in the synthesis of enantioenriched R- and S-configured 3-methylisochroman-1-one. The potential of P450 BM3 variants for regio- and stereoselective synthesis of phthalides and isocoumarins offers a new route to a class of compounds that are valuable synthons for a variety of natural compounds.
- Holec, Claudia,Hartrampf, Ute,Neufeld, Katharina,Pietruszka, J?rg
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p. 676 - 684
(2017/04/11)
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- NHC-Catalyzed Benzylic Csp3–H Bond Activation of Alkylarenes and N-Benzylamines for the Synthesis of 3H-Quinazolin-4-ones: Experimental and Theoretical Study
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An N-heterocyclic carbene catalyzed benzylic Csp3–H bond activation of alkylarenes and N-benzylamines under metal-free conditions was developed. This organocatalyzed oxidative transformation afforded the corresponding carbonyl derivatives in good to excellent yields. A variety of alkylarenes and N-benzylamines were tolerated under the optimized reaction conditions. The established method was further extended to the synthesis of biologically important 3H-quinazolin-4-ones in good yields. For example, NPS 53574, a potent calcium receptor antagonist, was successfully synthesized by using this oxidative protocol. DFT studies show that the benzylic C–H bond activation proceeds through the nucleophilic attack of the free carbene on the benzylic carbon atom.
- Alanthadka, Anitha,Devi, E. Sankari,Nagarajan, Subbiah,Sridharan, Vellaisamy,Suvitha, Ambigapathy,Maheswari, C. Uma
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supporting information
p. 4872 - 4880
(2016/10/13)
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- Benzylic C(sp3)-H Functionalization for C-N and C-O Bond Formation via Visible Light Photoredox Catalysis
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A visible light mediated highly selective benzylic C-H bond functionalization for intermolecular C-N and C-O bond formation is reported. This cross-dehydrogenative coupling reaction demonstrates a straightforward protocol for incorporating the heteroaromatics to the benzylic position. Benzylic oxidation of various alkyl aryls to corresponding carbonyl compounds has also been reported.
- Pandey, Ganesh,Laha, Ramkrishna,Singh, Deepak
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p. 7161 - 7171
(2016/08/30)
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- Enhanced structural variety of nonplanar N-oxyl radical catalysts and their application to the aerobic oxidation of benzylic C-H bonds
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The design and synthesis of structurally variable, nonplanar N-oxyl radical catalysts and their application to the aerobic oxidation, etherification, and acetoamidation of benzylic C-H bonds are described. The catalytic oxidation of C-H bonds represents a powerful tool to synthesize oxygenated functional molecules from simple hydrocarbons in a straightforward way. Electron-deficient N-oxyl radical catalysts, such as phthalimidoyl N-oxyl (PINO) radical, generated from N-hydroxyphthalimide (1), have attracted much attention because of their applications in the oxidation of C-H bonds with high bond dissociation energy (BDE). However, a few sites in 1 are available for structural modifications and improvements of the catalytic performance. By replacing one carbonyl group in 1 with a trifluoromethyl (CF3)-substituted sp3-carbon, we generated an additional tunable site and a nonplanar backbone, while retaining the desirable electron-withdrawing properties and increasing the lipophilicity with respect to 1. We synthesized a variety of N-hydroxy pre catalysts containing such a CF3 moiety, and investigated their utility in the aerobic oxidation of benzylic C-H bonds. Precatalysts with electron-withdrawing substituents, such as trifluoroethoxy and the acetophenone moieties, afforded higher yields than a corresponding methoxy-substituted analogue. The introduction of substituents at the aromatic ring was also effective, as evident from the performance of 7-CF3 and 4,5,6,7-tetrafluoro precatalysts. Especially the combination of trifluoroethoxy- and 4,5,6,7-tetrafluoro substitution afforded a superior performance. These catalyst systems exhibited high functional group tolerance during the aerobic oxidation of C-H bonds, and benzylic etherification and Ritter-type reactions could be carried out at room temperature when a selected precatalyst and N-bromosuccinimide (NBS) were used.
- Kadoh, Yoichi,Oisaki, Kounosuke,Kanai, Motomu
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p. 737 - 753
(2016/07/13)
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