- Sodium Trimethylsilanethiolate in Novel Cyclizations for Synthesis of Aromatic Heterotricyclic Compounds
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A new method was developed for synthesis of aromatic heterotricyclic compounds in 50-64percent yields from diaryls bearing a functionality including OMe, COOMe, and CN, and a leaving group (i.e., F and OMe) by use of Me3SiSNa in 1,3-dimethyl-2-imidazolidinone at 120-150 deg C.
- Lai, Long-Li,Lin, Pen-Yuan,Huang, Wen-Hong,Shiao, Min-Jen,Hwu, Jih Ru
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- New strategies for the synthesis and functionalization of tetrahydroxanthones
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Two strategies for the functionalization of simple tetrahydroxanthones (THX) on either of the carbocyclic rings are reported. By application of palladium catalysis, concomitant assembly of this heterocyclic scaffold with controlled introduction of substituents on the aromatic ring at C-5, C-6 or C-7 can be achieved. Variation in the nature of the added carbon fragment (aryl, alkenyl and alkynyl) is explored through use of different cross-coupling partners. Separately, functionalization at C-4 of the saturated carbocyclic ring is demonstrated through use of the extended enolate derived from 1-hydroxytetrahydroxanthone.
- Turner, Penelope A.,Samiullah,Geden, Joanna V.,White, Alexander,Clarkson, Guy J.,Shipman, Michael
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- A new method for the preparation of 2,3-cycloalkeno-5,6-cycloalkeno-4H-pyran-4-ones
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Several 2,3-cycloalkeno-5,6-cycloalkeno-4H-pyran-4-ones, such as 2,3,5,6-bicyclopenteno-4H-pyran-4-one and 1,2-dihydronaphtho[3,4-b]cyclopenteno[1,2-e]-4H-pyran-4-one, were synthesized conveniently by the reaction of a cyclic ketone enamine and diacylchloride. This reaction allows a new method for preparation of these compounds, which may be the precursors for the synthesis of some useful heterocycles. (C) 2000 Elsevier Science Ltd.
- Xu, Fan,Cao, Xueqin,Cao, Zhengbai,Zou, Lei
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- Multicomponent Reaction of Phosphines, Benzynes, and CO2: Facile Synthesis of Stable Zwitterionic Phosphonium Inner Salts
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The first synthesis of benzyne-derived stable zwitterions is reported. Benzynes generated in situ from 2-(trimethylsilyl)aryl triflates undergo a multicomponent reaction with phosphines and CO2 to produce the stable 1,5-zwitterionic species in moderate to excellent isolated yields, which provides a novel method for the preparation of phosphonium inner salts under mild and transition-metal-free conditions.
- Xie, Pei,Yang, Shoushan,Guo, Yuyu,Cai, Zhihua,Dai, Bin,He, Lin
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- Reaction of thioketones with (R)-2-vinyloxirane: Regio- and stereoselective formation of (sS)-4-vinyl-1,3-oxathiolanes
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The reactions of 4,4′-dimethoxythiobenzophenone (1), 9H-xanthene-9-thione (2), and adamantane-2-thlone (3) with (R)-2-vinyloxirane [(R)-6] in the presence of SiO2 in anhydrous CH2Cl 2 at 0°C or room temperature afforded th
- Fedorov, Alexey,Fu, Changchun,Linden, Anthony,Heimgartner, Heinz
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- Photoionization of xanthone via its triplet state or via its radical anion
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The photoionization of xanthone in methanol-water by light of wavelength 308, 355 and 532 nm was investigated by single-pulse and two-pulse laser-flash photolysis with optical detection of the hydrated electron and the ketone-based intermediates. Kinetic constants and quantum yields were obtained from the intensity dependences of the concentrations. In the absence of an electron donor, the mechanism is sequential. A first photon produces the triplet state, which is then ionized by a second photon with a quantum yield φion of 8 × 10-3 at both 308 and 355 nm; at 532 nm photoionization is undetectable (φion -6). When an electron donor (triethylamine or DABCO) is added in large excess, excitation of the ketone and quenching are followed by photoionization of the radical anion X.-. The latter regenerates the starting carbonyl compound, so in effect the donor is ionized by a catalytic cycle. The competition of both ionization pathways was studied quantitatively by varying the donor concentration. The ionization of X.- is monophotonic at 308 and 355 nm with a wavelength-independent quantum yield of 7 × 10-2. A biphotonic ionization was found at 532 nm; φion of the excited radical anion must be larger than 5 × 10-5. At that wavelength, nonabsorbing products are also formed with a quantum yield that is higher than φion by a factor of 3.2. The consistently lower quantum yields of photoionization in the absence of a donor were explained by reverse intersystem crossing of the upper excited triplet states as an efficient deactivation channel that is not accessible to the excited radical anions.
- Goez, Martin,Hussein, Belal Hussein Mohammed
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- Synthesis of Xanthones by Palladium-Catalyzed Tandem Carbonylation/C–H Activation via 2-Iodo Diaryl Ethers
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The ring closure of 2-iodo diaryl ether in the presence of a palladium catalyst to xanthone under carbon monoxide atmosphere is studied. A series of xanthones could be successfully obtained through this protocol, with Pd(OAc)2 as the catalyst, P(Cy)3 as ligand, PivONa.H2O as base, and PivOH and tetrabutylamonium bromide as additives in DMSO, in moderate to good yields.
- Ma, Rui-Yue,Chen, Ya-Fang,Wang, Jun-Ru,Du, Zhen-Ting
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- Intermolecular Electrochemical C(sp3)-H/N-H Cross-coupling of Xanthenes with N-alkoxyamides: Radical Pathway Mediated by Ferrocene as a Redox Catalyst
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Efficient intermolecular dehydrogenative cross-coupling of N-alkyloxyamides with xanthenes is reported. The protocol is carried out in an undivided cell under constant current conditions employing simple, cheap and readily available ferrocene (Fc) as a redox catalyst. Cyclic voltammetry and control experiments disclosed that the dehydrogenative cross-coupling reaction may proceed via an amidyl radical. (Figure presented.).
- Lin, Meng-Ying,Xu, Kun,Jiang, Yang-Ye,Liu, Yong-Guo,Sun, Bao-Guo,Zeng, Cheng-Chu
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- 1,3-Dichloro-tetra-n-butyl-distannoxane: A new application for catalyzing the direct substitution of 9H-xanthen-9-ol at room temperature
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1,3-Dichloro-tetra-n-butyl-distannoxane was firstly used to catalyze the direct substitution of 9H-xanthen-9-ol with indoles at room temperature to afford a class of 3-(9H-xanthen-9-yl)-1H-indole derivatives in good to excellent isolating yield. Moreover, other nucleophiles (such as diketone and pyrrole) could also proceed smoothly in this methodology. Copyright
- Liu, Ling-Yan,Zhang, Yan,Huang, Kai-Meng,Chang, Wei-Xing,Li, Jing
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- A highly efficient thiourea catalyzed dehydrative nucleophilic substitution reaction of 3-substituted oxindoles with xanthydrols
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We report a highly efficient thiourea catalyzed dehydrative nucleophilic substitution reaction. The Schreiner's thiourea catalyst A1 catalyzed the alkylation of 3-substituted oxindoles with xanthydrols well, to furnish quaternary oxindoles in high yield. The ESI-MS analysis confirms the interaction of 3-substituted oxindole 1 with the thiourea, which might facilitate the oxindole-hydroxindole tautomerization for the alkylation. The Royal Society of Chemistry 2013.
- Chen, Long,Zhu, Feng,Wang, Cui-Hong,Zhou, Jian
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- N-Rich 2D Heptazine Covalent Organic Frameworks as Efficient Metal-Free Photocatalysts
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Heptazine serves as the solely repetitive unit of graphitic carbon nitride (g-C3N4), which represents a progressive metal-free photocatalyst. However, synthesizing high-quality 2D heptazine-based covalent organic frameworks (COFs) remains a formidable challenge, probably due to the scarcity of suitable and ample reactive heptazine-based building blocks. Herein, we designed and synthesized a 4-(methylene diacetate)phenyl-substituted heptazine monomer (HEP-OAc) by oxidation of tris(4-tolyl)heptazine. Accordingly, two highly ordered N-rich COFs (HEP-TAPT-COF and HEP-TAPB-COF) were readily prepared by the direct condensation of HEP-OAc with two C3-symmetric aromatic amines under solvothermal conditions. In comparison to the pristine g-C3N4, HEP-TAPT-COF exhibited greatly enhanced photocatalytic performance for benzylic C–H oxidation and selective sulfoxidation under mild conditions. This work provides meaningful insights into developing highly crystalline N-rich COFs with better photocatalytic capacities.
- Chen, Dan,Chen, Long,Chen, Weiben,Chen, Weihua,Li, Shen,Xing, Guolong,Zhang, Guang
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p. 616 - 623
(2022/01/12)
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- A radical-radical cross-coupling reaction of xanthene with sulfonyl hydrazides: Facile access to xanthen-9-sulfone derivatives
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A straightforward strategy for direct incorporation of sulfonyl units into a xanthene moiety for accessing xanthen-9-sulfone derivatives in good to excellent yields has been established via metal-free radical-radical cross-coupling reaction of xanthenes and sulfonyl hydrazides. Using easily accessible starting materials, this methodology proceeds efficiently with a high degree of functional group compatibility and with a wide scope of both xanthenes and sulfonyl hydrazides under operationally simple reaction conditions. Mechanistic investigations revealed that sulfonyl radicals could be generated from sulfonyl hydrazides in the presence of TBHP under an oxygen atmosphere.
- Bhowmik, Arup,Das, Sumit,Deb, Indubhusan,Karmakar, Sudip,Mishra, Aniket,Mondal, Imtiaj,Roy, Shantonu,Saha, Shubhra Jyoti,Sarkar, Writhabrata
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supporting information
p. 2902 - 2905
(2022/03/09)
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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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- 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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- 4CzIPN catalyzed photochemical oxidation of benzylic alcohols
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A green photoredox oxidation of benzylic primary and secondary alcohols to aldehydes and ketones with air as an oxidant was reported. The oxidation shows broad substrate scope and excellent selectivity over benzylic alcohols to the aliphatic alcohols. Further mechanistic studies revealed a quinuclidine mediated HAT process, and blue LEDs promoted 4CzlPN (1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene) photoredox cycle were involved in our oxidation.
- Zhang, Heng,Guo, Tianyun,Wu, Mingzhong,Huo, Xing,Tang, Shouchu,Wang, Xiaolei,Liu, Jian
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supporting information
(2021/02/20)
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- Synthesis of xanthones, thioxanthones and Acridones by a metal-free photocatalytic oxidation using visible light and molecular oxygen
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9H-Xanthenes, 9H-thioxanthenes and 9,10-dihydroacridines can be easily oxidized to the corresponding xanthones, thioxanthones and acridones, respectively, by a simple photo-oxidation procedure carried out using molecular oxygen as oxidant under the irradiation of visible blue light and in the presence of riboflavin tetraacetate as a metal-free photocatalyst. The obtained yields are high or quantitative.
- Chinchilla, Rafael,Torregrosa-Chinillach, Alejandro
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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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- 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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- 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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- V2O5@TiO2 Catalyzed Green and Selective Oxidation of Alcohols, Alkylbenzenes and Styrenes to Carbonyls
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The versatile application of different functional groups such as alcohols (1° and 2°), alkyl arenes, and (aryl)olefins to construct carbon-oxygen bond via oxidation is an area of intense research. Here, we report a reusable heterogeneous V2O5@TiO2 catalyzed selective oxidation of various functionalities utilizing different mild and eco-compatible oxidants under greener reaction conditions. The method was successfully applied for the alcohol oxidation, oxidative scission of styrenes, and benzylic C?H oxidation to their corresponding aldehydes and ketones. The utilization of mild and eco-friendly oxidizing reagents such as K2S2O8, H2O2 (30 % aq.), TBHP (70 % aq.), broad substrate scope, gram-scale synthesis, and catalyst recyclability are notable features of the developed protocol.
- Upadhyay, Rahul,Kumar, Shashi,Maurya, Sushil K.
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p. 3594 - 3600
(2021/07/02)
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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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- Ultraviolet-light-induced aerobic oxidation of benzylic C(sp3)-H of alkylarenes under catalyst- and additive-free conditions
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A mild and efficient system has been discovered for the synthesis of α-aryl carbonyl compounds via oxidation of benzylic C–H to C[dbnd]O bonds. This ultraviolet-light-mediated oxygenation reaction exhibited excellent substrate scope including various xanthenes, thioxanthenes and 9, 10-dihydroacridines and afforded the corresponding ketones with good to excellent yields under catalyst- and additive-free conditions at room temperature.
- Zhou, Jiacheng,Li, Meichao,Li, Tianci,Li, Chunmei,Hu, Xinquan,Jin, Liqun,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu
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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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- Cu2O-CuO/Chitosan Composites as Heterogeneous Catalysts for Benzylic C?H Oxidation at Room Temperature
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Recently, in catalysis, chitosan has been exploited as a macrochelating ligand for metal active species due to the presence of various functional groups in its structure. Moreover, copper-based catalysts are classified as one of the most environmentally friendly catalytic systems and their use for the oxidation of alkylarene has not been established much. Therefore, in this work, the hydrothermal synthesis of copper oxide-chitosan composites as heterogeneous catalysts for the benzylic C?H oxidation of alkylarene was investigated. Characterization results reveal mixed phases of CuO and Cu2O, inferring the ability of chitosan to act as a reducing sugar under the hydrothermal condition. The pre-existing interaction between copper species and chitosan as well as the co-existence of the Cu2O and CuO structures give rise to the efficient performance of the catalysts. The synthesized composites exhibit high activity for the oxidation of fluorene to 9-fluorenone at room temperature and small catalyst loading (1 mol % of Cu, >90 % conversion and 100 % selectivity). Superior TOF was observed, and a good scope of substrates can be converted to corresponding ketones in 48–97 % yields with these copper oxide-chitosan catalysts. In addition, the catalysts can be used for up to nine cycles without significant decrease of the activity.
- Kanarat, Jurin,Bunchuay, Thanthapatra,Klysubun, Wantana,Tantirungrotechai, Jonggol
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p. 4833 - 4840
(2021/10/07)
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- Visible-Light-Driven Selective Air-Oxygenation of C?H Bond via CeCl3 Catalysis in Water
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Visible-light-induced C?H aerobic oxidation is an important chemical transformation that can be applied for the synthesis of aromatic ketones. High-cost catalysts and toxic solvents were generally needed in the present methodologies. Here, an efficient aqueous C?H aerobic oxidation protocol was reported. Through CeCl3-mediated photocatalysis, a series of aromatic ketones were produced in moderate to excellent yields. With air as the oxidant, this reaction could be performed under mild conditions in water and demonstrated high activity and functional group tolerance. This method is economical, highly efficient, and environmentally friendly, and it will provide inspiration for the development of aqueous photochemical synthesis reactions.
- Xie, Pan,Xue, Cheng,Shi, Sanshan,Du, Dongdong
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p. 2689 - 2693
(2021/05/07)
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- Ferric ion concentration-controlled aerobic photo-oxidation of benzylic C–H bond with high selectivity and conversion
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A Fe(III)-promoted highly selective photo-oxidation of benzylic C–H bond delivering relative carbonyl products is reported. By altering the concentration of ferric salt, methylarenes can be selectively oxidized under UV irradiation to furnish aromatic aldehydes or acids, respectively. By this protocol, the oxidation of ethylarenes provides the corresponding acetophenones. The reaction is inferred to involve divergent pathways in different concentrations of catalyst for the alternative selectivity between aldehydes and aicds. The reusable catalyst, high conversion and selectivity make this oxidation a green and economic protocol for the synthesis of aromatic carbonyl compounds.
- Bu, Hongzhong,Gu, Jiefan,Li, Yufeng,Ma, Hongfei,Wan, Yuting,Wu, Zheng-Guang,Zhang, Weijian,Zhou, Ying'ao,Zhu, Hongjun
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- COMPOUND FOR ORGANIC ELECTRONIC ELEMENT, ORGANIC ELECTRONIC ELEMENT USING THE SAME, AND AN ELECTRONIC DEVICE THEREOF
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The present invention relates to a compound for an organic electronic element. To the present invention, an organic electronic element having high luminous efficiency, low driving voltage, and high heat resistance can be provided, and color purity and lifetime of the organic electronic element can be improved.
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Paragraph 0360-0361; 0364-0365; 0372-0373; 0376-0377
(2021/03/23)
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- Formation and Disproportionation of Xanthenols to Xanthenes and Xanthones and Their Use in Synthesis
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A facile and versatile strategy employing TiCl4-mediated cyclization followed by a Cannizzaro reaction has been developed for the synthesis of various xanthene derivatives. The reaction proceeded smoothly to afford both xanthenes/xanthones or their sulfur derivatives and tolerated a wide range of electronically diverse substrates. Using this methodology, pranoprofen was synthesized in three steps in 59% overall yield from commercially available starting materials.
- Shi, Zeyu,Chen, Si,Xiao, Qiong,Yin, Dali
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p. 3334 - 3343
(2021/02/05)
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- Insight into the chemoselective aromatic: Vs. side-chain hydroxylation of alkylaromatics with H2O2catalyzed by a non-heme imine-based iron complex
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The oxidation of a series of alkylaromatic compounds with H2O2 catalyzed by an imine-based non-heme iron complex prepared in situ by reaction of 2-picolylaldehyde, 2-picolylamine, and Fe(OTf)2 in a 2?:?2?:?1 ratio leads to a marked chemoselectivity for aromatic ring hydroxylation over side-chain oxidation. This selectivity is herein investigated in detail. Side-chain/ring oxygenated product ratio was found to increase upon decreasing the bond dissociation energy (BDE) of the benzylic C-H bond in line with expectation. Evidence for competitive reactions leading either to aromatic hydroxylation via electrophilic aromatic substitution or side-chain oxidation via benzylic hydrogen atom abstraction, promoted by a metal-based oxidant, has been provided by kinetic isotope effect analysis. This journal is
- Ticconi, Barbara,Capocasa, Giorgio,Cerrato, Andrea,Di Stefano, Stefano,Lapi, Andrea,Marincioni, Beatrice,Olivo, Giorgio,Lanzalunga, Osvaldo
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p. 171 - 178
(2021/01/28)
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- Formation of cobalt-oxygen intermediates by dioxygen activation at a mononuclear nonheme cobalt(ii) center
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A mononuclear nonheme cobalt(ii) complex, [(TMG3tren)CoII(OTf)](OTf) (1), activates dioxygen in the presence of hydrogen atom donor substrates, such as tetrahydrofuran and cyclohexene, resulting in the generation of a cobalt(ii)-alkylperoxide intermediate (2), which then converts to the previously reported cobalt(iv)-oxo complex, [(TMG3tren)CoIV(O)]2+-(Sc(OTf)3)n(3), in >90% yield upon addition of a redox-inactive metal ion, Sc(OTf)3. Intermediates2and3represent the cobalt analogues of the proposed iron(ii)-alkylperoxide precursor that converts to an iron(iv)-oxo intermediateviaO-O bond heterolysis in pterin-dependent nonheme iron oxygenases. In reactivity studies,2shows an amphoteric reactivity in electrophilic and nucleophilic reactions, whereas3is an electrophilic oxidant. To the best of our knowledge, the present study reports the first example showing the generation of cobalt-oxygen intermediates by activating dioxygen at a cobalt(ii) center and the reactivities of the cobalt-oxygen intermediates in oxidation reaction.
- Chandra, Anirban,Dau, Holger,Farquhar, Erik R.,Lee, Yong-Min,Malik, Deesha D.,Mebs, Stefan,Nam, Wonwoo,Ray, Kallol,Seo, Mi Sook
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supporting information
p. 11889 - 11898
(2021/09/06)
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- The Oxo-Wall Remains Intact: A Tetrahedrally Distorted Co(IV)-Oxo Complex
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In this paper, we report the preparation, spectroscopic and theoretical characterization, and reactivity studies of a Co(IV)-oxo complex bearing an N4-macrocyclic coligand, 12-TBC (12-TBC = 1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacyclododecane). On the basis of the ligand and the structure of the Co(II) precursor, [CoII(12-TBC)(CF3SO3)2], one would assume that this species corresponds to a tetragonal Co(IV)-oxo complex, but the spectroscopic data do not support this notion. Co K-edge XAS data show that the treatment of the Co(II) precursor with iodosylbenzene (PhIO) as an oxidant at -40 °C in the presence of a proton source leads to a distinct shift in the Co K-edge, in agreement with the formation of a Co(IV) intermediate. The presence of the oxo group is further demonstrated by resonance Raman (rRaman) spectroscopy. Interestingly, the EPR data of this complex show a high degree of rhombicity, indicating structural distortion. This is further supported by the EXAFS data. Using DFT calculations, a structural model is developed for this complex with a ligand-protonated structure that features a Co?O···HN hydrogen bond and a four-coordinate Co center in a seesaw-shaped coordination geometry. Magnetic circular dichroism (MCD) spectroscopy further supports this finding. The hydrogen bond leads to an interesting polarization of the Co-oxo ?-bonds, where one O(p) lone-pair is stabilized and leads to a regular Co(d) interaction, whereas the other ?-bond shows an inverted ligand field. The reactivity of this complex in hydrogen atom and oxygen atom transfer reactions is discussed as well.
- Dong, Hai T.,Larson, Virginia A.,Lee, Yong-Min,Lehnert, Nicolai,Nam, Wonwoo,Seo, Mi Sook,Shearer, Jason,Yang, Jindou
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supporting information
p. 16943 - 16959
(2021/10/25)
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- Sustainable System for Hydrogenation Exploiting Energy Derived from Solar Light
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Herein described is a sustainable system for hydrogenation that uses solar light as the ultimate source of energy. The system consists of two steps. Solar energy is captured and chemically stored in the first step; exposure of a solution of azaxanthone in ethanol to solar light causes an energy storing dimerization of the ketone to produce a sterically strained 1,2-diol. In the second step, the chemical energy stored in the vicinal diol is released and used for hydrogenation; the diol offers hydrogen onto alkenes and splits back to azaxanthone, which is easily recovered and reused repeatedly for capturing solar energy.
- Ishida, Naoki,Kamae, Yoshiki,Ishizu, Keigo,Kamino, Yuka,Naruse, Hiroshi,Murakami, Masahiro
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supporting information
p. 2217 - 2220
(2021/02/16)
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- New acridone-and (Thio)xanthone-derived 1,1-donor–acceptor-substituted alkenes: Ph-dependent fluorescence and unusual photooxygenation properties
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A synthetic route to new heterocyclic 1,1-donor–acceptor-substituted alkenes starting with N-methyl-acridone, xanthone, and thioxanthone was investigated, leading to the acridone-and xanthone-derived products methyl 2-methoxy-2-(10-methylacridin-9 (10H)-ylidene)acetate (7) and methyl 2-methoxy-2-(9H-xanthen-9-ylidene)acetate (10) in low yields with the de-methoxylated product methyl 2-(10-methylacridin-9 (10H)-ylidene)acetate (8) and the reduced compound methyl 2-methoxy-2-(9H-xanthen-9-yl)acetate (11) as the major products from N-methyl acridone and xanthone. From thioxanthone, only the rearrangement and reduction products (14) and (15) resulted. The photophysical properties of compounds (7), (8), and (10) were investigated in the presence and absence of the Br?nsted acid TFA by NMR, UV–VIS absorption, and fluorescence spectroscopy. Protonation of the acridone-derived alkenes (7) and (8) led to strong bathochromic and hyperchromic fluorescence shifts and a substantial increase in Stokes shift. The photooxygenation experiments with these substrates showed an unusual reactivity pattern in the singlet oxygen processes: whereas the electron-rich enolether (7) was chemically unreactive, (8) and (10) were oxidatively cleaved, presumably via intermediate 1,2-dioxetanes.
- Griesbeck, Axel,Lippold, Tim,Neud?rfl, J?rg M.
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- Palladium-catalyzed intramolecular aromatic C-H acylation of 2-arylbenzoyl fluorides
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The catalytic intramolecular cyclization of acyl fluorides using a Pd(OAc)2/PCy3 system is described. A wide range of 2-arylbenzoyl fluoride derivatives can be used as fluorenone precursors and the reaction proceeds via an intramolecular coupling between aromatic C-H bonds with acyl C-F bonds. The reaction can be applied to the synthesis of indenofluorenedione derivatives and to the construction of other molecules with fivemembered rings.
- Hayakawa, Kazuki,Ikai, Kana,Ogiwara, Yohei,Sakai, Norio,Sakurai, Yuka
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supporting information
p. 1882 - 1893
(2021/08/13)
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- C-H Activation by RuCo3O4Oxo Cubanes: Effects of Oxyl Radical Character and Metal-Metal Cooperativity
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High-valent multimetallic-oxo/oxyl species have been implicated as intermediates in oxidative catalysis involving proton-coupled electron transfer (PCET) reactions, but the reactive nature of these oxo species has hindered the development of an in-depth understanding of their mechanisms and multimetallic character. The mechanism of C-H oxidation by previously reported RuCo3O4 cubane complexes bearing a terminal RuV-oxo ligand, with significant oxyl radical character, was investigated. The rate-determining step involves H atom abstraction (HAA) from an organic substrate to generate a Ru-OH species and a carbon-centered radical. Radical intermediates are subsequently trapped by another equivalent of the terminal oxo to afford isolable radical-trapped cubane complexes. Density functional theory (DFT) reveals a barrierless radical combination step that is more favorable than an oxygen-rebound mechanism by 12.3 kcal mol-1. This HAA reactivity to generate organic products is influenced by steric congestion and the C-H bond dissociation energy of the substrate. Tuning the electronic properties of the cubane (i.e., spin density localized on terminal oxo, basicity, and redox potential) by varying the donor ability of ligands at the Co sites modulates C-H activations by the RuV-oxo fragment and enables construction of structure-activity relationships. These results reveal a mechanistic pathway for C-H activation by high-valent metal-oxo species with oxyl radical character and provide insights into cooperative effects of multimetallic centers in tuning PCET reactivity.
- Amtawong, Jaruwan,Balcells, David,Handford, Rex C.,Skjelstad, Bastian Bjerkem,Suslick, Benjamin A.,Tilley, T. Don
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supporting information
p. 12108 - 12119
(2021/08/20)
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- Synthesis of xanthones from 4-(2-phenoxyphenyl)-1-tosyl-1H-1,2,3-triazole via rhodium-catalyzed annulation/oxidation
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A series of xanthone derivatives were synthesized by rhodium-catalyzed cycloaddition and sequential oxidation. The derivatives synthesized for excellent yields, including electron-withdrawing and electron-donating substituents, demonstrated the wide applicability of the proposed approach. The xanthones synthesized with different substituent electron effects may go through the same intermediate via two cycloadditions. It is highlighted that the protocol was exemplified by its successful integration into a one-pot synthesis directly from 1-ethynyl-2-phenoxybenzene. We believe that the current method may be an attractive option for the synthesis of xanthone and its derivatives.
- Anna,Chen, Zhaohang,Gao, Juanhong,Li, Chao,Qiao, Hongwei,Zhu, Mengyao
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- Photodriven Dehydrogenative Homocoupling of Benzylic C-H Bonds Forming Strained C-C Bonds
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A photoinduced dehydrogenative homocoupling reaction of alkylarenes is reported. Gaseous hydrogen is evolved as the sole byproduct and neither oxidants nor hydrogen acceptors are required. The present reaction offers an environmentally benign and atom-economical means for forming sterically strained C-C single bonds. It also gives a remarkable example of photodriven reactions overcoming a considerable rise in energy.
- Ishida, Naoki,Son, Mingon,Kawasaki, Tairin,Ito, Misato,Murakami, Masahiro
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supporting information
p. 2067 - 2070
(2021/10/14)
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- Deeper Understanding of Mononuclear Manganese(IV)-Oxo Binding Br?nsted and Lewis Acids and the Manganese(IV)-Hydroxide Complex
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Binding of Lewis acidic metal ions and Br?nsted acid at the metal-oxo group of high-valent metal-oxo complexes enhances their reactivities significantly in oxidation reactions. However, such a binding of Lewis acids and proton at the metal-oxo group has been questioned in several cases and remains to be clarified. Herein, we report the synthesis, characterization, and reactivity studies of a mononuclear manganese(IV)-oxo complex binding triflic acid, {[(dpaq)MnIV(O)]-HOTf}+ (1-HOTf). First, 1-HOTf was synthesized and characterized using various spectroscopic techniques, including resonance Raman (rRaman) and X-ray absorption spectroscopy/extended X-ray absorption fine structure. In particular, in rRaman experiments, we observed a linear correlation between the Mn-O stretching frequencies of 1-HOTf (e.g., νMn-O at a 793 cm-1) and 1-Mn+ (Mn+ = Ca2+, Zn2+, Lu3+, Al3+, or Sc3+) and the Lewis acidities of H+ and Mn+ ions, suggesting that H+ and Mn+ bind at the metal-oxo moiety of [(dpaq)MnIV(O)]+. Interestingly, a single-crystal structure of 1-HOTf was obtained by X-ray diffraction analysis, but the structure was not an expected Mn(IV)-oxo complex but a Mn(IV)-hydroxide complex, [(dpaq)MnIV(OH)](OTf)2 (4), with a Mn-O bond distance of 1.8043(19) ? and a Mn-O stretch at 660 cm-1. More interestingly, 4 reverted to 1-HOTf upon dissolution, demonstrating that 1-HOTf and 4 are interconvertible depending on the physical states, such as 1-HOTf in solution and 4 in isolated solid. The reactivity of 1-HOTf was investigated in hydrogen atom transfer (HAT) and oxygen atom transfer (OAT) reactions and then compared with those of 1-Mn+ complexes; an interesting correlation between the Mn-O stretching frequencies of 1-HOTf and 1-Mn+ and their reactivities in the OAT and HAT reactions is reported for the first time in this study.
- Fukuzumi, Shunichi,Karmalkar, Deepika G.,Kim, Youngsuk,Lee, Eunsung,Lee, Yong-Min,Nam, Wonwoo,Sarangi, Ritimukta,Seo, Mi Sook
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supporting information
p. 16996 - 17007
(2021/11/16)
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- Rapid Iron(III)?Fluoride-Mediated Hydrogen Atom Transfer
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We anticipate high-valent metal–fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H?F bond (in the product) that drives HAT oxidation. We prepared a dimeric FeIII(F)?F?FeIII(F) complex (1) by reacting [FeII(NCCH3)2(TPA)](ClO4)2 (TPA=tris(2-pyridylmethyl)amine) with difluoro(phenyl)-λ3-iodane (difluoroiodobenzene). 1 was a sluggish oxidant, however, it was readily activated by reaction with Lewis or Br?nsted acids to yield a monomeric [FeIII(TPA)(F)(X)]+ complex (2) where X=F/OTf. 1 and 2 were characterized using NMR, EPR, UV/Vis, and FT-IR spectroscopies and mass spectrometry. 2 was a remarkably reactive FeIII reagent for oxidative C?H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive FeIII and FeIV oxidants.
- Doyle, Lorna M.,Gericke, Robert,McDonald, Aidan R.,Panda, Chakadola
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supporting information
p. 26281 - 26286
(2021/11/12)
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- Photoredox-Catalyzed Simultaneous Olefin Hydrogenation and Alcohol Oxidation over Crystalline Porous Polymeric Carbon Nitride
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Booming of photocatalytic water splitting technology (PWST) opens a new avenue for the sustainable synthesis of high-value-added hydrogenated and oxidized fine chemicals, in which the design of efficient semiconductors for the in-situ and synergistic utilization of photogenerated redox centers are key roles. Herein, a porous polymeric carbon nitride (PPCN) with a crystalline backbone was constructed for visible light-induced photocatalytic hydrogen generation by photoexcited electrons, followed by in-situ utilization for olefin hydrogenation. Simultaneously, various alcohols were selectively transformed to valuable aldehydes or ketones by photoexcited holes. The porosity of PPCN provided it with a large surface area and a short transfer path for photogenerated carriers from the bulk to the surface, and the crystalline structure facilitated photogenerated charge transfer and separation, thus enhancing the overall photocatalytic performance. High reactivity and selectivity, good functionality tolerance, and broad reaction scope were achieved by this concerted photocatalysis system. The results contribute to the development of highly efficient semiconductor photocatalysts and synergistic redox reaction systems based on PWST for high-value-added fine chemical production.
- Qiu, Chuntian,Sun, Yangyang,Xu, Yangsen,Zhang, Bing,Zhang, Xu,Yu, Lei,Su, Chenliang
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p. 3344 - 3350
(2021/07/26)
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- Nitrosoarene-Catalyzed HFIP-Assisted Transformation of Arylmethyl Halides to Aromatic Carbonyls under Aerobic Conditions
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A rare metal-free nucleophilic nitrosoarene catalysis accompanied by highly hydrogen-bond-donor (HBD) solvent, 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), organocatalytically converts arylmethyl halides to aromatic carbonyls. This protocol offers an effective means to access a diverse array of aromatic carbonyls with good chemoselectivity under mild reaction conditions. The activation of arylmethyl halides by HFIP to generate stable carbocation and autoxidation of in situ generated hydroxylamine to nitrosoarene in the presence of atmospheric O2 are the keys to success.
- Pradhan, Suman,Sharma, Vishali,Chatterjee, Indranil
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supporting information
p. 6148 - 6152
(2021/08/03)
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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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- Photochemical oxidation of benzylic primary and secondary alcohols utilizing air as the oxidant
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A mild and green photochemical protocol for the oxidation of alcohols to aldehydes and ketones was developed. Utilizing thioxanthenone as the photocatalyst, molecular oxygen from air as the oxidant and cheap household lamps or sunlight as the light source, a variety of primary and secondary alcohols were converted into the corresponding aldehydes or ketones in low to excellent yields. The reaction mechanism was extensively studied.
- Nikitas, Nikolaos F.,Tzaras, Dimitrios Ioannis,Triandafillidi, Ierasia,Kokotos, Christoforos G.
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supporting information
p. 471 - 477
(2020/02/13)
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- A sodium trifluoromethanesulfinate-mediated photocatalytic strategy for aerobic oxidation of alcohols
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A sodium trifluoromethanesulfinate-mediated photocatalytic strategy for the aerobic oxidation of alcohols has been developed for the first time, and the photoredox aerobic oxidation of secondary and primary alcohols provided the corresponding ketones and carboxylic acids, respectively, in high to excellent yields.
- Zhu, Xianjin,Liu, Can,Liu, Yong,Yang, Haijun,Fu, Hua
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p. 12443 - 12446
(2020/10/30)
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- Base-free oxidation of alcohols enabled by nickel(ii)-catalyzed transfer dehydrogenation
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An efficient nickel(ii)-catalyzed transfer dehydrogenation oxidation of alcohols is reported that relies on cyclohexanone as the formal oxidant and does not require the use of an external base. The synthetic utility of this protocol is demonstratedviathe facile oxidation of structurally complicated natural products.
- Ye, Danfeng,Liu, Zhiyuan,Sessler, Jonathan L.,Lei, Chuanhu
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supporting information
p. 11811 - 11814
(2020/10/13)
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- Photochemical Transformations with Iodine Azide after Release from an Ion-Exchange Resin
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This report discloses the photochemical homolytic cleavage of iodine azide after its formation following release from polymer-bound bisazido iodate(I) anions. A series of radical reactions are reported including the 1,2-functionlization of alkenes and the unprecedented chemoselective oxidation of secondary alcohols in the presence of primary alcohols.
- Dr?ger, Gerald,K?sel, Teresa,Kirschning, Andreas,Schulz, G?ran
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supporting information
p. 12376 - 12380
(2020/05/08)
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- Iodine-catalyzed efficient synthesis of xanthene/thioxanthene-indole derivatives under mild conditions
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An iodine-catalyzed nucleophilic substitution reaction of xanthen-9-ol and thioxanthen-9-ol with indoles has been developed, providing an efficient procedure for the synthesis of xanthene/thioxanthene-indole derivatives with good to excellent yields. This protocol offers several advantages, such as short reaction times, green solvent, operational simplicity, easily available catalyst and mild reaction conditions. Moreover, this method showed good tolerance of functional groups and a wide range of substrates.
- Bai, Mengjiao,Duan, Hengpan,Duan, Suyue,Miao, Weihang,Wang, Xuequan,Yang, Zhixin,Ye, Pingting
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p. 25165 - 25169
(2020/07/14)
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- Manganese(Ⅲ)-iodosylbenzene complex, preparation method thereof and oxidant comprising the same
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The present invention relates to a manganese(III)-iodosylbenzene complex, a preparation method thereof, and an oxidant comprising the same. The manganese(III)-iodosylbenzene complex provided in one aspect of the present invention has an effect of inducing a hydrogen atom abstraction (HAA) reaction of cyclohexadiene, dihydroanthracene and xanthine, and an oxygen atom transfer (OAT) reaction of thioanisole and stilbene with excellent electrophilic reactivity. The manganese(III)-iodosylbenzene complex is represented by a compound of formula 1: [Mn^III(L)(OIPh)(OH)]^2+.COPYRIGHT KIPO 2020
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Paragraph 0130-0136; 0141; 0166
(2020/09/22)
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- Copper-catalyzed aerobic asymmetric cross-dehydrogenative coupling of C(sp3)-H bonds driven by visible light
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Asymmetric cross-dehydrogenative coupling (CDC) of C(sp3)-H bonds shows great potential for rapid and stereoselective construction of C-C bonds and use of molecular oxygen as the oxidant for such transformations is appealing in the context of green synthetic methodologies. However, the poor reactivity of oxygen at the ground state and the challenges in controlling the stereochemistry make it extremely difficult to access highly enantioselective aerobic CDC reactions of C(sp3)-H precursors. Herein we report our effort towards this goal via copper-based asymmetric photocatalysis. A chiral-copper catalyst initiates the visible-light-driven oxidative CDC reaction by molecular oxygen, and governs the stereochemistry. In this way, a diastereo- and enantioselective cross-dehydrogenative coupling between carbonyl compounds and xanthene derivatives has been achieved. This work provides an economic and manageable approach to stereoselective C-C bond formation, and demonstrates a potential application of chiral copper catalysts in difficult asymmetric photochemical reactions.
- Gong, Lei,Li, Yanjun,Lin, Yu-Mei,Yu, Ying,Zhou, Kexu
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p. 4597 - 4603
(2020/08/10)
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- Tuning Flavin-Based Photocatalytic Systems for Application in the Mild Chemoselective Aerobic Oxidation of Benzylic Substrates
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New flavin-based photocatalytic systems used for chemoselective aerobic visible-light oxidations have been developed by tuning the flavin structure and reaction conditions. 1,3-Dimethyl-7-trifluoromethylalloxazine (2) and 10-butyl-3-methyl-7-trifluoromethylisoalloxazine (3) were shown to mediate the selective oxidation of benzyl alcohols to form aldehydes in the presence of Cs2CO3. Flavin 3 was superior in the oxidation of toluene derivatives to form aldehydes in the presence of trifluoroacetic acid. On the other hand, photooxidations provided by ethylene-bridged quaternary flavinium salt 1 gave the corresponding carboxylic acids. The usefulness of the developed catalytic systems using 1–3 was also demonstrated in the oxidation of secondary benzylic and aliphatic alcohols, and benzylic methylene groups to form the corresponding ketones. The systems have the advantage of a broad substrate scope and metal-free conditions, which distinguish them from the previously reported flavin photooxidation reactions.
- Tolba, Amal Hassan,Vávra, Franti?ek,Chudoba, Josef,Cibulka, Radek
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supporting information
p. 1579 - 1585
(2019/12/24)
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- Highly Active and Robust Ruthenium Complexes Based on Hemilability of Hybrid Ligands for C-H Oxidation
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Evaluation of the hemilability of hybrid ligands provides a key to understand the metal-ligand cooperation in transition metal catalysis. Here, we design and synthesize a type of RuII complexes based on the hemilability of N-heterocyclic carbenes (NHCs), pyridine, and pyrazole, to compare their activity with other reported Ru catalysts in benzylic C-H oxidation. The RuII catalysts showed ultrastrong catalytic activity in water at room temperature and achieved a turnover frequency (TOF) of 114 h-1, which is the highest TOF value ever reported for Ru-catalyzed benzylic C-H oxidation. The addition of tridentate hybrid ligands in the Ru central position has two beneficial effects: NHCs with a stronger donor ability stabilize the Ru center; however, nitrogen ligands with a relatively weaker donor ability release from the Ru center, so that they induce a reaction. UV-vis, high-resolution electrospray ionization mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR) spectrometry, the trapping of radicals, and the density functional theory calculations (DFT) suggested that a cation catalyst L-RuII-tBuO2H is formed via the reaction between starting RuII catalysts and tert-butyl hydroperoxide, which further undergoes a cleavage of the O-O bond to generate a radical and a cation L-RuIII-OH active intermediate.
- Bo, Chun-Bo,Bu, Qingqing,Li, Xue,Ma, Ge,Wei, Donghui,Guo, Cheng,Dai, Bin,Liu, Ning
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p. 4324 - 4334
(2020/03/05)
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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 0088-0093
(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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- Benzylic oxidation and functionalizations of xanthenes by ligand trasfer reactions of hypervalent iodine reagents
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The benzylic oxidation, amidation, and unprecedented heteroarylation proceed at room temperature using iodosobenzene, (sulfonylimido)iodobenzenes, and diaryliodonium(III) salts are described for the direct Csp3-H functionalizations of xanthene molecules. This study has demonstrated that hypervalent iodine reagents serve as unified synthetic tools for versatile xanthene Csp3-H transformations based on the radical and SET oxidation processes.
- Dohi, Toshifumi,Ito, Motoki,Kita, Yasuyuki,Komiyama, Keina,Ueda, Shohei,Yamaoka, Nobutaka
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- Ultraviolet light promoted synthesis method of xanthone compounds
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The invention discloses an ultraviolet light promoted synthesis method of a xanthone compound. The method comprises the steps: by taking a xanthene compound as a reaction substrate and oxygen in air as an oxidant, carrying out a reaction on the reaction substrate in an organic solvent at normal temperature under the condition of 380-385 nm ultraviolet irradiation, and after the reaction is finished, carrying out separation treatment to obtain the xanthone compound. According to the synthesis method disclosed by the invention, a traditional heating reaction is replaced by an illumination reaction, so that energy sources can be saved; no catalyst is used.
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Paragraph 0025-0028
(2020/05/05)
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- Cu (II) Schiff base complex grafted guar gum: Catalyst for benzophenone derivatives synthesis
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In this study Guar gum based Cu(II) Schiff's base complex (GG-Cu) has been synthesized and characterized by FT-IR, PXRD, UV–vis, TGA, XPS, FESEM, TEM, EDAX, solid-state NMR, Elemental mapping, CHNS and AAS analysis. This moiety has been found to be an efficient heterogeneous catalyst for selective oxidation reactions. Fifteen model reactions have been carried to establish the catalytic behavior of GG-Cu, and five of these yield novel products. The ease of separation of catalyst from the reaction mixture simply by filtration is an added advantage; furthermore the catalyst can be reused up to five times without significant loss of catalytic activity. The overall concept of developing newer, efficient and environmental benign catalysts with ease of separation and recycling ability has been successfully demonstrated. All of the isolated products were fully characterized on the basis of their physical and spectral data.
- Krishna,Kumari, Shweta,Sharma, Sunil K.,Yadav, Deepak
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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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- COMPOUND FOR ORGANIC ELECTRONIC ELEMENT, ORGANIC ELECTRONIC ELEMENT USING THE SAME, AND AN ELECTRONIC DEVICE THEREOF
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The present invention provides a compound represented by chemical formula 1, an organic electric device including a first electrode, a second electrode, and an organic material layer between the first electrode and the second electrode, and an electronic device including the organic electric device. By including the compound represented by chemical formula 1 in the organic material layer, the driving voltage of the organic electric device can be lowered, luminous efficiency and lifespan can be improved, and in particular, the lifespan can be improved.COPYRIGHT KIPO 2021
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Paragraph 0144; 0238; 0247-0248; 0251-0252; 0271-0272; 0275
(2020/10/31)
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