- Two-photon-induced cycloreversion reaction of coumarin photodimers
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Photochemical reactions induced by two-photon-absorption processes offer several advantages over common one-photon initiated photoreactions, e.g., three-dimensional spatial control. We present the photocleavage reaction of coumarin photodimers via a two-photon process using pulsed frequency-doubled Nd:YAG-laser light. The two-photon-induced cycloreversion reaction leads selectively to the cleavage of the coumarin photodimers resulting in the formation of monomeric coumarin molecules. The two-photon cross section of the coumarin photodimer was determined to be of 1.6×10-52 cm4 s photon-1. The presented reaction is of interest, e.g., for the photo-triggered release of chemicals in areas which cannot be directly optically addressed due to cover layers which have a high absorption at the single-photon-absorption wavelength.
- Kim,Kreiling,Greiner,Hampp
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- Visible-light-driven, photoredox-catalyzed cascade of ortho-hydroxycinnamic esters to access 3-fluoroalkylated coumarins
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A general and straightforward protocol for di-/perfluoroalkylation of ortho-hydroxycinnamic esters via a photoredox-catalyzed cascade was developed to access a variety of 3-fluoroalkylated coumarins. This method was characterized by all-in-one synthetic design, simplified operation, mild reaction conditions, and broad substrate scope. Moreover, a sequential one-pot procedure starting from commercially available salicylaldehyde was also successfully realized to synthesize 3-fluoroalkylated coumarins.
- Song, Dan,Wang, Chao-Ming,Ye, Zhi-Peng,Xia, Peng-Ju,Deng, Zhi-Xiong,Xiao, Jun-An,Xiang, Hao-Yue,Yang, Hua
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- The Copper-Catalyzed Reaction of 2-(1-Hydroxyprop-2-yn-1-yl)phenols with Sulfonyl Azides Leading to C3-Unsubstituted N-Sulfonyl-2-iminocoumarins
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An operationally simple synthesis of Z-configured and C3-unsubstituted N-sulfonyl-2-iminocoumarins (e.g., 8a) that proceeds under mild conditions is achieved by reacting 2-(1-hydroxyprop-2-yn-1-yl)phenols (e.g., 6a) with sulfonyl azides (e.g., 7a). The cascade process involved likely starts with a copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction. This is followed by ring-opening of the resulting metalated triazole (with accompanying loss of nitrogen), reaction of the ensuing ketenimine with the pendant phenolic hydroxyl group, and finally dehydration of the (Z)-N-(4-hydroxychroman-2-ylidene)sulfonamide so formed.
- Zhao, Yu,Zhou, Zitong,Liu, Lvling,Chen, Man,Yang, Weiguang,Chen, Qi,Gardiner, Michael G.,Banwell, Martin G.
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- Quantification of free coumarin and its liberation from glucosylated precursors by stable isotope dilution assays based on liquid chromatography-tandem mass spectrometry detection
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A stable isotope dilution assay for the quantification of free coumarin and glucosylated coumarin precursors has been developed using [13C 2]-coumarin as the internal standard. The doubly labeled coumarin was synthesized by reacting [13C2]-acetic anhydride with salicylic aldehyde and characterized by means of mass spectrometry and nuclear magnetic resonance (NMR) experiments. The specifity of liquid chromatography-tandem mass spectrometry enabled unequivocal determination and sensitive quantitation of the odorant. Because of the very simple extraction procedure, free coumarin could be analyzed within 1h. For quantification of total coumarin, the odorant was liberated from its precursors by an incubation with hydrochloric acid or β-glucosidase. In analyses of breakfast cereals, the intra-assay coefficient of variation was 9.9% (n = 5) for total coumarin. When coumarin was added to butter cookies at a level of 10 μg/kg, a recovery of 94.1% was found. Further addition studies revealed a detection limit of 2.9 μg/kg and a quantification limit of 8.6 μg/kg. Application of the stable isotope dilution assay to several plants, foods, and essential oils revealed high contents in cassia products and those foods in which cassia has been used as an ingredient. In contrast to this, Ceylon cinnamon contained much less coumarin. The odorant was also quantified in woodruff, clover seeds, and the essential oils of lavender, citron, and chamomile. Only trace amounts were detected in carrots and the essential oils of peppermint and dill, whereas in bilberries, black raspberries, and Angelica roots, coumarin was below detectable levels. In Ceylon cinnamon and cassia, the odorant occurred mainly in its free form, whereas in fenugreek seeds and woodruff, 68 and 88% of the total coumarin content was liberated from glucosylated precursors, respectively.
- Rychlik, Michael
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- Photocatalytic Oxidative [2+2] Cycloelimination Reactions with Flavinium Salts: Mechanistic Study and Influence of the Catalyst Structure
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Flavinium salts are frequently used in organocatalysis but their application in photoredox catalysis has not been systematically investigated to date. We synthesized a series of 5-ethyl-1,3-dimethylalloxazinium salts with different substituents in the positions 7 and 8 and investigated their application in light-dependent oxidative cycloelimination of cyclobutanes. Detailed mechanistic investigations with a coumarin dimer as a model substrate reveal that the reaction preferentially occurs via the triplet-born radical pair after electron transfer from the substrate to the triplet state of an alloxazinium salt. The very photostable 7,8-dimethoxy derivative is a superior catalyst with a sufficiently high oxidation power (E=2.26 V) allowing the conversion of various cyclobutanes (with Eox up to 2.05 V) in high yields. Even compounds such as all-trans dimethyl 3,4-bis(4-methoxyphenyl)cyclobutane-1,2-dicarboxylate can be converted, whose opening requires a high activation energy due to a missing pre-activation caused by bulky adjacent substituents in cis-position.
- Hartman, Tomá?,Reisnerová, Martina,Chudoba, Josef,Svobodová, Eva,Archipowa, Nataliya,Kutta, Roger Jan,Cibulka, Radek
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p. 373 - 386
(2021/02/01)
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- Cyclobutane-cleavage of anti-head-to-head coumarin and quinolinone homo- and cross-dimers via single- and two-photon-absorption photochemistry
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The light-driven cleavage of cyclobutane containing systems via [2 + 2] cycloreversion, such as di-coumarin, is an important yet poorly investigated photochemical reaction. Its applications can be found in smart crosslinking polymers or light-activated drug release. We report the increased cleavage efficiencies of the coumarins lactam analog quinolinone for single-photon as well as two-photon-absorption experiments. To investigate the structure-function relationship of the molecular substitution pattern and its influence on the photoactivity, a coumarin-quinolinone cross-dimer was synthesized and investigated towards its cleavage efficiencies in single-photon as well as two-photon photocleavage. The cross-dimer shows a lower cleavage efficiency than both homo-dimers. The presented results are of interest, e.g., for applications utilizing highly efficient cleavage reactions in symmetric or asymmetric molecular frameworks.
- Bieniek, Nikolai,Inacker, Sebastian,Kim, Hee-Cheol,Hampp, Norbert
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- Ruthenium-Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism
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The direct dehydrogenation of alkanes is among the most efficient ways to access valuable alkene products. Although several catalysts have been designed to promote this transformation, they have unfortunately found limited applications in fine chemical synthesis. Here, we report a conceptually novel strategy for the catalytic, intermolecular dehydrogenation of alkanes using a ruthenium catalyst. The combination of a redox-active ligand and a sterically hindered aryl radical intermediate has unleashed this novel strategy. Importantly, mechanistic investigations have been performed to provide a conceptual framework for the further development of this new catalytic dehydrogenation system.
- Huang, Lin,Bismuto, Alessandro,Rath, Simon A.,Trapp, Nils,Morandi, Bill
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supporting information
p. 7290 - 7296
(2021/03/01)
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- Iron-Catalyzed ?±,?-Dehydrogenation of Carbonyl Compounds
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An iron-catalyzed α,β-dehydrogenation of carbonyl compounds was developed. A broad spectrum of carbonyls or analogues, such as aldehyde, ketone, lactone, lactam, amine, and alcohol, could be converted to their α,β-unsaturated counterparts in a simple one-step reaction with high yields.
- Zhang, Xiao-Wei,Jiang, Guo-Qing,Lei, Shu-Hui,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 1611 - 1615
(2021/03/03)
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- Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis
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The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.
- Zhou, Min-Jie,Zhang, Lei,Liu, Guixia,Xu, Chen,Huang, Zheng
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supporting information
p. 16470 - 16485
(2021/10/20)
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- Gold(I)-Catalyzed Intramolecular Hydroarylation of Phenol-Derived Propiolates and Certain Related Ethers as a Route to Selectively Functionalized Coumarins and 2 H-Chromenes
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Methods are reported for the efficient assembly of a series of phenol-derived propiolates, including the parent system 56, and their Au(I)-catalyzed cyclization (intramolecular hydroarylation) to give the corresponding coumarins (e.g., 1). Simple syntheses of natural products such as ayapin (144) and scoparone (145) have been realized by such means, and the first of these subject to single-crystal X-ray analysis. A related process is described for the conversion of propargyl ethers such as 156 into the isomeric 2H-chromene precocene I (159), a naturally occurring inhibitor of juvenile hormone biosynthesis.
- Cervi, Aymeric,Vo, Yen,Chai, Christina L. L.,Banwell, Martin G.,Lan, Ping,Willis, Anthony C.
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p. 178 - 198
(2020/12/22)
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- Exploiting a silver-bismuth hybrid material as heterogeneous noble metal catalyst for decarboxylations and decarboxylative deuterations of carboxylic acids under batch and continuous flow conditions
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Herein, we report novel catalytic methodologies for protodecarboxylations and decarboxylative deuterations of carboxylic acids utilizing a silver-containing hybrid material as a heterogeneous noble metal catalyst. After an initial batch method development, a chemically intensified continuous flow process was established in a simple packed-bed system which enabled gram-scale protodecarboxlyations without detectable structural degradation of the catalyst. The scope and applicability of the batch and flow processes were demonstrated through decarboxylations of a diverse set of aromatic carboxylic acids. Catalytic decarboxylative deuterations were achieved on the basis of the reaction conditions developed for the protodecarboxylations using D2O as a readily available deuterium source.
- ?tv?s, Sándor B.,Fül?p, Ferenc,Kónya, Zoltán,Kukovecz, ákos,Márton, András,Mészáros, Rebeka,Pálinkó, István,Szabados, Márton,Varga, Gábor
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p. 4685 - 4696
(2021/07/12)
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- Preparation method of photoresponse phase change material
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The invention relates to the field of phase change materials, in particular to a preparation method of a photoresponse phase change material, and provides the preparation method of the photoresponse phase change material, the structural formula of the prepared phase change material is shown as a formula I, and the photoresponse phase change material has the advantages of cheap and easily availableraw materials, simple process, mild reaction conditions and suitability for large-scale production.
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Paragraph 0080-0081
(2021/03/30)
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- Visible-Light-Induced C(sp2)-C(sp3) Coupling Reaction for the Regioselective Synthesis of 3-Functionalized Coumarins
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A photocatalysis strategy for the regioselective synthesis of 3-functionalized coumarins is reported. With visible light irradiation, a direct and regioselective C(sp2)-C(sp3) coupling reaction of 3-(2-hydroxyphenyl)acrylates with ethers or thioethers occurs by using Ru(bpy)3Cl2·6H2O as a photocatalyst and TBHP as an oxidant. The cascade process involves alkenylation of the C(sp3)-H bond of ethers and lactonization, furnishing 3-alkylated coumarins as the final products. This approach is characterized by a broad substrate scope, mild reaction conditions, and simplified operation. The synthesis of 3-alkylated coumarins could be realized by a one-pot procedure, starting from commercially available salicylaldehyde.
- Li, Hanjie,Lin, Zhenwei,Lu, Ping,Qiao, Li,Wang, Yanguang,Xie, Jianwei,Zhang, Ke
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p. 9552 - 9562
(2021/07/26)
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- Visible-light promoted oxidative cyclization of cinnamic acid derivatives using xanthone as the photocatalyst
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We have developed an efficient photocatalytic synthesis of coumarin derivativesviaa tandem double bond isomerization/oxidative cyclization of cinnamic acids. Inexpensive and stable xanthone was used as the photocatalyst, and readily available Selectfluor was used as the oxidant. This method tolerates a wide range of functional groups and offers excellent chemical yields in general. Besides, the photocatalytic oxidative cyclization of cinnamic acid esters gives dimerized lignan-type products.
- Zhao, Bin,Xu, Bo
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supporting information
p. 568 - 573
(2021/02/06)
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- Electrochemically driven desaturation of carbonyl compounds
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Electrochemical techniques have long been heralded for their innate sustainability as efficient methods to achieve redox reactions. Carbonyl desaturation, as a fundamental organic oxidation, is an oft-employed transformation to unlock adjacent reactivity through the formal removal of two hydrogen atoms. To date, the most reliable methods to achieve this seemingly trivial reaction rely on transition metals (Pd or Cu) or stoichiometric reagents based on I, Br, Se or S. Here we report an operationally simple pathway to access such structures from enol silanes and phosphates using electrons as the primary reagent. This electrochemically driven desaturation exhibits a broad scope across an array of carbonyl derivatives, is easily scalable (1–100 g) and can be predictably implemented into synthetic pathways using experimentally or computationally derived NMR shifts. Systematic comparisons to state-of-the-art techniques reveal that this method can uniquely desaturate a wide array of carbonyl groups. Mechanistic interrogation suggests a radical-based reaction pathway. [Figure not available: see fulltext.]
- Gnaim, Samer,Takahira, Yusuke,Wilke, Henrik R.,Yao, Zhen,Li, Jinjun,Delbrayelle, Dominique,Echeverria, Pierre-Georges,Vantourout, Julien C.,Baran, Phil S.
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p. 367 - 372
(2021/03/31)
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- Cycloreversion performance of coumarin and hetero-coumarin dimers under aerobic conditions: Unexpected behavior triggered by UV-A light
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Photochemical [2+2]-cycloadditions of coumarin-like monomers are the textbook paradigms of photo-formation and photo-cleavage reactions. The electronic conjugation length of monomers and dimers is quite different which results in almost fully separated UV/Vis absorption bands in the UV-A and UV-C. This feature enables the selective light-controlled conversion between monomeric and dimeric forms by the choice of the appropriate wavelengths. Several applications are based on this kind of reversible photo linker without absorption in the visible range. But which is the best molecule from the coumarin family for such an application? Within this study, we compared the photochemical cleavage behavior of twelve coumarin-type cyclobutane dimers. In particular, the influence of isomer structure and substitution pattern was studied. Two dimers with an unexpected high quantum yield for cyclobutane cleavage were identified. This behavior is explained through the differing ring strain of the cyclobutane moiety. Electron donating substitutions of the framework, e.g. with a methoxy function (+M-effect), leads to a decreased oxidation potential, making the dimers sensitive towards oxidative dimer splitting. This result disqualifies coumarins, e.g. attached to a polymer backbone via an ether bond, often in the 7-position, because of their instabilities and side reactions in an aerobic environment. The methylated dimers (+I-effect) show excellent stability towards this undesired side reaction as well as a high cleavage efficiency upon irradiation with 265 nm. All twelve investigated dimers are ranked for their quantum efficiency and rate constant for cleavage at 265 nm, as well as their oxygen tolerance. As the most promising derivative within our scope for applications the methylated coumarin dimer was identified.
- Bieniek, Nikolai,Hampp, Norbert,Inacker, Sebastian
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p. 17703 - 17712
(2021/08/30)
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- Design, synthesis, and antifungal evaluation of novel coumarin-pyrrole hybrids
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A series of coumarin derivatives bearing a pyrrole scaffold were designed, prepared, and assessed for their in vitro antifungal activities against six phytopathogenic fungi. The antifungal activity screening results suggest that some synthesized hybrids exhibited potential fungicidal activities against the tested fungi. In particular, compounds 6j, 6k, 6o, 6p, and 6r displayed significant antifungal effects against Rhizoctorzia solani, and possessed EC50 values of 3.94, 7.75, 6.38, 6.25, and 7.67 μg/ mL, respectively. The above activities are more potent than the commercialized fungicide Boscalid (11.52 μg/mL) and Osthole (9.79 μg/mL). These results provide a significant reference for further rational design of coumarin-based fungicides.
- Zhang, Shuguang,Tan, Xin,Liang, Chaogen,Zhang, Weihua
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p. 450 - 458
(2020/11/30)
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- Coumarins by Direct Annulation: β-Borylacrylates as Ambiphilic C3-Synthons
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Modular β-borylacrylates have been validated as programmable, ambiphilic C3-synthons in the cascade annulation of 2-halo-phenol derivatives to generate structurally and electronically diverse coumarins. Key to this [3+3] disconnection is the BPin unit which serves a dual purpose as both a traceless linker for C(sp2)–C(sp2) coupling, and as a chromophore extension to enable inversion of the alkene geometry via selective energy transfer catalysis. Mild isomerisation is a pre-condition to access 3-substituted coumarins and provides a handle for divergence. The method is showcased in the synthesis of representative natural products that contain this venerable chemotype. Facile entry into π-expanded estrone derivatives modified at the A-ring is disclosed to demonstrate the potential of the method in bioassay development or in drug repurposing.
- Wienhold, Max,Molloy, John J.,Daniliuc, Constantin G.,Gilmour, Ryan
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supporting information
p. 685 - 689
(2020/11/30)
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- Second-coordination sphere effects on the reactivities of Hoveyda-Grubbs-type catalysts: A ligand exchange study using phenolic moiety-functionalized ligands
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The Hoveyda-Grubbs (HG) second-generation catalyst (HG-II), a Ru complex with a 2-isopropoxybenzylidene ligand, is extensively used for olefin metathesis, the rearrangement of carbon-carbon double bonds. A well-known strategy to control its complex reactivity is to modify the phenyl ring in the ligand, thereby directly influencing the coordination of the phenolic oxygen to the metal center. We, herein, report that a functional group attached to the phenolic moiety in the 2-alkoxybenzylidene ligand can indirectly affect the reactivities of HG-type complexes. In this work, the ligand exchange reactions between HG-II and phenolic moiety-modified 2-alkoxybenzylidene ligands are useful for evaluating the structural effects of the ligands. Specifically, an ethylene amide or an ester group at the terminal phenolic moiety in the benzylidene ligand was found to influence the relative stabilities of HG-type complexes compared to that of the HG-II complex. The structural analyses proved that the observed effects of the functional groups on the complex stabilities originate from the interactions with a chlorido ligand in HG-type complexes without changes in coordination fashions at the metal centers. It was found that the outer-sphere interactions also influence the catalytic activities of HG-type complexes, namely, the properties of HG-type complexes can be controlled by outer-sphere structural factors toward the metal center (i.e., "the second-coordination sphere effect"). In the design of functionalized HG-type complexes, the outer-sphere structural effects need to be considered in addition to the optimization of the metal coordination site.
- Akiyama, Naoki,Goshima, Kenta,Hirota, Shun,Jatmika, Catur,Matsuo, Takashi,Wakabayashi, Kazumo
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supporting information
p. 11618 - 11627
(2020/09/09)
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- Polyphosphoric acid-promoted synthesis of coumarins lacking substituents at positions 3 and 4
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Coumarins have recently emerged as a hot topic of research due to their diverse pharmacological properties. This work described a method for the synthesis of 3,4-diunsubstituted coumarins promoted by polyphosphoric acid (PPA) from salicylaldehydes and acetic anhydride. Various coumarins were produced in good to excellent yields.
- Yang, Li-Shou,Wang, Yu,Wang, En-Hua,Yang, Jan,Pan, Xiong,Liao, Xiu,Yang, Xiao-Sheng
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supporting information
p. 1 - 6
(2020/07/25)
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- Synthesis method of coumarin derivatives
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The invention provides a synthesis method of coumarin derivatives. The synthesis method comprises the following steps: adding polyphosphoric acid PPA and a solvent N,N-dimethylformamide DMF, sequentially adding substituted salicylaldehyde and acetic anhydride, and carrying out a heating stirring reaction for 3-6 h under nitrogen protection; and after the reaction is finished, separating and purifying to obtain the coumarin derivative pure products. The synthesis method disclosed by the invention is disclosed for the first time, is short in reaction time, simple to operate, low in catalyst usage amount, cheap, easy to obtain and relatively good in derivative yield, not only provides a new method for synthesizing coumarin derivatives, but also provides more possibilities for large-scale production of products and improvement of production efficiency.
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Paragraph 0021-0024; 0027-0029
(2020/09/23)
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- Fe(III)-Catalyzed Decarboxylative C3-Difluoroarylmethylation of Coumarins with α,α-Difluoroarylacetic Acids
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A facile Fe(III)-catalyzed oxidative decarboxylative radical coupling reaction of α,α-difluoroarylacetic acids with coumarins has been developed. This transformation, which provides a series of C-3 difluoroarylmethylated coumarins containing various functional groups in moderate-to-good yields, features easily accessible starting materials and operational simplicity.
- Chen, Zhiwei,Bai, Xiang,Sun, Jie,Xu, Yicheng
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supporting information
p. 7674 - 7682
(2020/07/15)
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- Facile one-pot synthetic access to libraries of diversely substituted 3-aryl (Alkyl)-coumarins using ionic liquid (IL) or conventional base/solvent, and an IL-mediated approach to novel coumarin-bearing diaryl-ethynes
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The in-situ formed carbonylimidazole derivatives of Ar(alkyl)-CH2COOH react at r.t. with substituted salicylaldehydes in [BMIM][PF6] or [BMIM][BF4] as solvent, and [PAIM][NTf2] as basic-IL, to produce libraries of 3-aryl(alkyl)coumarins. Whereas these reactions can also be performed with similar efficiency in THF by employing DBU, the IL approach offers easier work-up and recycling of the IL solvent. An IL-mediated approach to the synthesis of novel coumarin-bearing diaryl-ethynes by the Sonogshira reaction is also reported, and the potential for recycling/reuse of the IL solvent is shown.
- Kalkhambkar, Rajesh G.,Laali, Kenneth K.,Malunavar, Shruti S.,Prabhala, Pavankumar,Savanur, Hemantkumar M.,Sutar, Suraj M.
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supporting information
(2020/04/08)
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- Visible-light-induced regioselective alkylation of coumarins via decarboxylative coupling with N-hydroxyphthalimide esters
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An efficient photocatalytic decarboxylative 3-position alkylation of coumarins by using alkyl N-hydroxyphthalimide esters as alkylation reagents has been developed. A variety of NHP esters derived from aliphatic carboxylic acids (primary, secondary, and tertiary) has been proved to be tolerated for this decarboxylation process, affording a broad scope of 3-alkylated coumarin derivatives in moderate to excellent yields. This protocol was highlighted by its mild conditions, readily available starting materials, operational simplicity, and wide functional group tolerance.
- Jin, Can,Yan, Zhiyang,Sun, Bin,Yang, Jin
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supporting information
p. 2064 - 2068
(2019/04/11)
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- Iron-Catalyzed Regioselective Decarboxylative Alkylation of Coumarins and Chromones with Alkyl Diacyl Peroxides
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A facile iron-catalyzed decarboxylative radical coupling of alkyl diacyl peroxides with coumarins or chromones has been developed, affording a highly efficient approach to synthesize a variety of α-alkylated coumarins and β-alkylated chromones. The reaction proceeded smoothly without adding any ligand or additive and provided the corresponding products containing a wide scope of functional groups in moderate to excellent yields. This protocol was highlighted by its high regioselectivity, readily available starting materials, and operational simplicity.
- Jin, Can,Sun, Bin,Xu, Tengwei,Yan, Zhiyang,Zhang, Xun
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supporting information
p. 1585 - 1591
(2019/08/07)
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- Late-Stage Direct o-Alkenylation of Phenols by PdII-Catalyzed C?H Functionalization
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o-Alkenylation of unprotected phenols has been developed by direct C?H functionalization catalyzed by PdII. This work features phenol group as a directing group and realizes highly site-selective C?H bond functionalization of phenols to achieve the corresponding products in moderate to excellent yields at 60 °C. The advantages of this reaction include unprecedented C?H functionalization using phenol as a directing group, high regioselectivity, good substrate scope, mild reaction conditions, and high efficiency. To the best of our knowledge, this is the first example of a regioselective C?H alkenylation of unprotected phenols utilizing phenolic hydroxyl group as a directing group. The alkenylation of unprotected tyrosine and intramolecular cyclization are also successfully carried out under this catalytic system in good yields. Furthermore, this novel method enables a late-stage modification of complex phenol-containing bioactive molecules toward a diversity-oriented drug discovery.
- Dou, Yandong,Kenry,Liu, Jiang,Jiang, Jianze,Zhu, Qing
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p. 6896 - 6901
(2019/05/07)
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- On/Off O2 Switchable Photocatalytic Oxidative and Protodecarboxylation of Carboxylic Acids
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Photoredox catalysis in recent years has manifested a powerful branch of science in organic synthesis. Although merging photoredox and metal catalysts has been a widely used method, switchable heterogeneous photoredox catalysis has rarely been considered. Herein, we open a new window to use a switchable heterogeneous photoredox catalyst which could be turned on/off by changing a simple stimulus (O2) for two opponent reactions, namely, oxidative and protodecarboxylation. Using this strategy, we demonstrate that Au@ZnO core-shell nanoparticles could be used as a switchable photocatalyst which has good catalytic activity to absorb visible light due to the localized surface plasmon resonance effect of gold, can decarboxylate a wide range of aromatic and aliphatic carboxylic acids, have multiple reusability, and are a reasonable candidate for synthesizing both aldehydes/ketones and alkane/arenes in a large-scale set up. Some biologically active molecules are also shown via examples of the direct oxidative and protodecarboxylation which widely provided pharmaceutical agents.
- Bazyar, Zahra,Hosseini-Sarvari, Mona
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p. 13503 - 13515
(2019/10/11)
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- Platinum-Catalyzed Desaturation of Lactams, Ketones, and Lactones
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The development of a general platinum-catalyzed desaturation of N-protected lactams, ketones, and lactones to their conjugated α,β-unsaturated counterparts is reported. The reaction operates under mildly acidic conditions at room temperature or 50 °C. It is scalable and tolerates a wide range of functional groups. The complementary reactivity to the palladium-catalyzed desaturation is demonstrated in the efficient conversion of iodide, bromide, and sulfur-containing substrates.
- Chen, Ming,Rago, Alexander J.,Dong, Guangbin
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supporting information
p. 16205 - 16209
(2018/11/23)
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- Synthesis of 7-Azido-3-Formylcoumarin – A Key Precursor in Bioorthogonally Applicable Fluorogenic Dye Synthesis
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Coumarins represent an important group of natural products and a common part of various drugs and fluorescent dyestuffs. Herein, we present the synthesis of a coumarin that can serve as a key starting material in the design and synthesis of bioorthogonally applicable fluorogenic dyes. The synthesis of 7-azido-3-formylcoumarin started from 7-diallylaminocoumarin. This allyl protected aminocoumarin is otherwise hard to obtain by conventional methods but was conveniently accessed in good yields by a sequential, Wittig-reaction–UV isomerization process. This sequential approach was studied in more details and applied for the synthesis of a series of substituted coumarins even in one-pot.
- Pünk?sti, Zoltán,Kele, Péter,Herner, András
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supporting information
p. 1183 - 1188
(2018/03/21)
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- Rhodium(I)-Catalyzed Decarbonylative Aerobic Oxidation of Cyclic α-Diketones: A Regioselective Single Carbon Extrusion Strategy
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A rhodium-catalyzed decarbonylative aerobic oxidation of cyclic α-diketones has been developed for the first time, where the regioselective formations of α-pyrones and isocoumarins have been achieved. The current decarbonylative aerobic oxidation pathway proceeds via the C-C bond cleavage followed by a C-O bond formation, representing a biomimetic oxidation approach to unsaturated six-membered cyclic lactones. The unique ability of rhodium catalysts to induce the decarbonylative aerobic oxidation opens up a new synthetic toolbox that utilizes the "regioselective single carbon" extrusion strategy.
- Golime, Gangadhararao,Kim, Hun Young,Oh, Kyungsoo
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supporting information
p. 942 - 945
(2018/02/22)
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- Generation and Confinement of Long-Lived N-Oxyl Radical and Its Photocatalysis
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Generation of controllable carbon radical under the assistance of N-oxyl radical is an efficient method for the activation of C-H bonds in hydrocarbons. We herein report that irradiation of α-Fe2O3 and N-hydroxyphthalimide (NHPI) under 455 nm light generates phthalimide-N-oxyl radical (PINO), which after being formed by oxidation with holes, is confined on α-Fe2O3 surface. The half-life time of the confined radical reaches 22 s as measured by in situ electron paramagnetic resonance (EPR) after the light being turned off. This allows the long-lived N-oxyl radical to abstract the H from C-H bond to form a carbon radical that reacts with molecular oxygen to form R3C-OO· species, decomposition of which leads to oxygenated products.
- Zhang, Chaofeng,Huang, Zhipeng,Lu, Jianmin,Luo, Nengchao,Wang, Feng
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p. 2032 - 2035
(2018/02/19)
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- Cp?Ir-Catalyzed Acceptorless Dehydrogenation of Carbon-Carbon Single Bonds
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Pentamethylcyclopentadienyl (Cp?) iridium(III) chloride catalyzed acceptorless dehydrogenation of α-tetralone is reported. Cp? iridium chloride showed higher activity in comparison to other Cp? iridium complexes having bromide, iodide, or hydride or complexes without a Cp ring. The desired product, naphthol, was obtained in up to 71% yield from α-tetralone. The dehydrogenation by Cp? iridium catalyst could be applied to not only α-tetralone but also dihydrocoumarin, dihydroquinolinone, dimethylcyclohexanone, dihydrobenzofuran and 1-isochromanone, although the conversion stayed moderate. The catalytic turnover was not limited by the increased concentration of the product but by catalyst decomposition.
- Ando, Hideaki,Kusumoto, Shuhei,Wu, Weiwei,Nozaki, Kyoko
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supporting information
p. 2317 - 2322
(2017/06/30)
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- Palladium-Catalyzed C?H Functionalization of Phenyl 2-Pyridylsulfonates
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An efficient palladium(II)-catalyzed intermolecular direct ortho-alkenylation and acetoxylation of phenols has been developed. The reaction proceeded via a seven-membered cyclopalladated intermediate and showed complete regio- and diastereoselectivity. The approach also provided an efficient route for the synthesis of coumarins and benzofurans.
- Li, Bin,Guo, Dong-Dong,Guo, Shi-Huan,Pan, Gao-Fei,Gao, Ya-Ru,Wang, Yong-Qiang
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p. 130 - 144
(2017/01/06)
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- Bichromatic Photosynthesis of Coumarins by UV Filter-Enabled Olefin Metathesis
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Herein, we report on a two-step bichromatic synthesis of coumarins involving UV-A and UV-C light. The first step is a UV-A-photoinduced ruthenium-catalyzed cross-metathesis (CM) reaction of 2-nitrobenzyl-protected 2-hydroxystyrenes with acrylates, using an external solution of 1-pyrenecarboxaldehyde as a UV filter. Irradiation in the absence of the filter permanently inhibits the light-activated catalyst due to photocleavage of the photolabile protecting group (PPG) and ensuing phenolate chelation to the ruthenium. The simple removal of the external filter after CM allows further photochemical reactions with UV-C light to achieve more complex architectures, such as the coumarins presented in this work. (Figure presented.).
- Eivgi, Or,Sutar, Revannath L.,Reany, Ofer,Lemcoff, N. Gabriel
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p. 2352 - 2357
(2017/07/22)
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- Silver-Mediated Oxidative Decarboxylative Trifluoromethylthiolation of Coumarin-3-carboxylic Acids
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The introduction of trifluoromethylthio groups into organic compounds, in particular heterocycles, is important because of the prevalence of these structures in medicinally and agriculturally relevant molecules. Herein, the silver-mediated oxidative decarboxylative trifluoromethylthiolation of coumarin-3-carboxylic acids is reported. This methodology utilizes existing carboxylic acid functionalities for the direct conversion to CF3S groups and results in a broad scope of 3-trifluoromethylthiolated coumarins, including analogues of natural products, in moderate to excellent yields.
- Li, Minghao,Petersen, Jeffrey L.,Hoover, Jessica M.
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supporting information
p. 638 - 641
(2017/02/10)
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- Synthesis method for coumarins compound
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The invention discloses a synthesis method for a coumarins compound. The structural formula is shown in the specification, wherein R1 is selected from one or more of -H, -CH3, -OCH3, -F, -Cl, -Br, -OH, -NO2 and N(CH2CH3)2 and R2 is selected from one of -H, -CH3 or CH2CH3. According to the invention, a 2-hydroxy cinnamate compound is directly utilized as a raw material and the coumarins compound is synthesized in one step under the catalytic effect of visible light. Compared with the present synthesis method, the synthesis method for the coumarins compound disclosed by the invention has the characteristics of simple method, mild condition and high yield; the reaction is carried out under normal temperature; and the visible light is utilized as a reaction energy source and is green and pollution-free.
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Paragraph 0040; 0041; 0042; 0043; 0044; 0045; 0046; 0047
(2017/08/29)
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- Microwave-Assisted Synthesis of Phenylpropanoids and Coumarins: Total Synthesis of Osthol
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Herein we describe a one-pot microwave-assisted method for the synthesis of cinnamic acid and coumarin derivatives. The synthesis begins with an aldehyde synthon, and the chosen reaction conditions determine whether a cinnamic acid or coumarin derivative is formed. A regioselective Claisen rearrangement was also efficiently incorporated into the synthetic sequence to further increase the complexity of the product. Notably, this approach provides high product yields and selectivities without the need of a phenol protecting group.
- Konrádová, Daniela,Kozubíková, Hana,Dole?al, Karel,Pospí?il, Ji?í
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supporting information
p. 5204 - 5213
(2017/09/29)
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- Synthetic method for 9,10-benzophenanthrene compound
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The invention discloses a synthetic method for a 9,10-benzophenanthrene compound. The synthetic method comprises the following concrete steps: dissolving a compound as shown in a formula (2) which is described in the specification and another compound as shown in a formula (4) which is described in the specification in N,N-dimethyl formamide under the protection of inert gas; and carrying out a reaction at 120 to 140 DEG C under the action of copper trifluoromethanesulfonate, sodium carbonate and caesium acetate so as to obtain the 9,10-benzophenanthrene compound as shown in a formula (I) which is described in the specification. According to the invention, 2-bromobiphenyl is used as a raw material, diaryl iodate is used as an arylation reagent, bivalent copper is used as a catalyst, and sodium carbonate and caesium acetate are used as mixed base; the synthetic method has the characteristics of usage of easily available raw materials, short reaction time, high yield, etc.; and as a simplest graphene monomer, the synthesized 9,10-benzophenanthrene compound good application prospects in the field of organic photoelectricity.
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Paragraph 0031; 0032
(2018/01/09)
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- Photocatalytic Systems with Flavinium Salts: From Photolyase Models to Synthetic Tool for Cyclobutane Ring Opening
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Two new photocatalytic systems based on flavinium species formed in situ by protonation of riboflavin-tetraacetate (1) with triflic acid or prepared in advance via alloxazine quaternization are presented as effective tools for oxidative cyclobutane ring [2 + 2] cycloreversion using visible light. The system with 1,3-dimethyl-8-trifluoromethylalloxazinium perchlorate (2c) was found to be superior allowing an acid-free mild procedure, which results in the opening of cyclobutanes with high oxidation potential (up to 2.14 V) and/or with sensitive groups (e.g., furan) without side reactions.
- Hartman, Tomá?,Cibulka, Radek
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supporting information
p. 3710 - 3713
(2016/08/16)
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- CARBAZOLE-BASED COMPOUND AND ORGANIC LIGHT EMITTING DEVICE INCLUDING THE SAME
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A carbazole compound represented by Formula 1: wherein in Formula 1, groups and variables are the same as described in the specification.
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- CONDENSED-CYCLIC COMPOUND AND ORGANIC LIGHT-EMITTING DEVICE INCLUDING THE SAME
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A condensed cyclic compound is represented by Formula 1: where R1 to R12 are as defined in the specification and at least one of R1 to R12 is a group represented by Formula 2, and at least one of R1 to R12 is a group represented by Formula 3; where L1, L2, Ar1 to Ar4, a1 and a1 are as defined in the specification. An organic light-emitting device including the condensed cyclic compound.
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- Coumarin derivative, and preparation method and use thereof
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The invention relates to a coumarin derivative and a use thereof. The coumarin derivative is a compound represented by formula I. The compound represented by formula I can be applied as an organic pigment. The application field of the coumarin derivative with a large pi conjugated system is developed, and foundation is laid for commercial preparation of like coumarin derivatives. In the formula I, R1-R7 are respectively independently selected from hydrogen, halogens, C1-C4 linear or branched alkyl groups, fluorine-containing C1-C4 linear or branched alkyl groups, hydroxyl groups, C1-C3 linear or branched alkyloxy groups, trifluoromethylsulfo groups or C6-C10 aryl groups; or R1, R4, R5, R6 and R7 are respectively independently selected from one of H and C1-C3 linear or branched alkyl groups, and a combination of R2 and R3 is a bivalent phenyl group.
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-
Paragraph 0046; 0047; 0048
(2016/10/09)
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- Industrial synthesis method for coumarin
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The invention discloses an industrial synthesis method for coumarin and relates to the technical field of organic synthesis. The method comprises the steps of adding salicylaldehyde and potassium carbonate into a reactor, slowly adding acetic anhydride into the reactor from an overhead tank, carrying out a condensation reaction while controlling the reaction temperature to be below 200 DEG C, putting the obtained crude coumarin product into a relay tank, then, transferring the crude coumarin product to a water washing kettle for water washing, then, pumping the crude coumarin product into a rectifying still, condensing the obtained cut, then, feeding the condensed cut to a crystallization kettle, adding ethanol into the crystallization kettle, carrying out crystallizing and centrifuging, rectifying a centrifuging stock solution by a rectifying still so as to recover the ethanol, and drying centrifuging solid, thereby obtaining the refined coumarin product. According to the method, the operation is simple, and intermediate products are not subjected to refining treatment and are directly applied to next-step reactions, so that the loss of intermediate products and production workload are reduced, the volume of wastewater produced is low, the raw materials are cheap and readily available, and the prepared coumarin product is high in purity and can be directly applied to flavorings.
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Paragraph 0009; 0010
(2017/05/02)
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- A simple protocol for Cu-catalyzed protodecarboxylation of (hetero)aromatic carboxylic acids
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A simple and practical protodecarboxylation of o-nitrobenzoic acids as well as heteroaromatic carboxylic acids with various substituents via using CuI/Et3N has been established. This transformation provides a viable and low-cost approach to generating previously unavailable substituted arenes from readily accessible aryl carboxylic acids as the starting materials.
- Li, Zhaojie,Fu, Zhengjiang,Zhang, Haixia,Long, Jiao,Song, Yuanyuan,Cai, Hu
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supporting information
p. 3014 - 3018
(2016/05/09)
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- Ytterbium triflate promoted coupling of phenols and propiolic acids: Synthesis of coumarins
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Coumarins are a well-known class of natural occurring and semi-synthetic products with reported important and effective pharmacological activities. In this Letter an improved method for the chemical synthesis of such compounds is described. Coumarins have been obtained in good to excellent yields under microwave irradiation and solvent-free conditions in a short time from differently substituted phenols and propiolic acids used as starting materials in the presence of Yb(OTf)3 hydrate 10% mol as the catalyst.
- Fiorito, Serena,Epifano, Francesco,Taddeo, Vito A.,Genovese, Salvatore
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supporting information
p. 2939 - 2942
(2016/06/14)
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- Metal-free, Br?nsted acid-mediated synthesis of coumarin derivatives from phenols and propiolic acids
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A novel synthesis of coumarin derivatives by Br?nsted acid-mediated condensation and intramolecular cyclization of phenols and propiolic acids was reported. This transformation requires the use of TfOH in place of a conventional metal mediator, and it occurs under mild conditions and provides rapid access to coumarin derivatives in good yields.
- Choi, Hyuck,Kim, Jaehyun,Lee, Kooyeon
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supporting information
p. 3600 - 3603
(2016/07/21)
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- Process for preparing coumarin derivatives using phenol and propiolic acid
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Provided is a manufacturing method of coumarin derivative. The manufacturing method of coumarin derivative comprises a step of making a phenol compound react with a propiolic acid compound. According to the present invention, the manufacturing method of coumarin derivative is quick and efficient, and is useful to fields requiring synthesis of coumarin derivatives of various structures.COPYRIGHT KIPO 2016
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Paragraph 0098; 0099
(2017/01/12)
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- One Photocatalyst, n Activation Modes Strategy for Cascade Catalysis: Emulating Coumarin Biosynthesis with (-)-Riboflavin
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Generating molecular complexity using a single catalyst, where the requisite activation modes are sequentially exploited as the reaction proceeds, is an attractive guiding principle in synthesis. This requires that each substrate transposition exposes a catalyst activation mode (AM) to which all preceding or future intermediates are resistant. While this concept is exemplified by MacMillan's beautiful merger of enamine and iminium ion activation, examples in other fields of contemporary catalysis remain elusive. Herein, we extend this tactic to organic photochemistry. By harnessing the two discrete photochemical activation modes of (-)-riboflavin, it is possible to sequentially induce isomerization and cyclization by energy transfer (ET) and single-electron transfer (SET) activation pathways, respectively. This catalytic approach has been utilized to emulate the coumarin biosynthesis pathway, which features a key photochemical E → Z isomerization step. Since the ensuing SET-based cyclization eliminates the need for a prefunctionalized aryl ring, this constitutes a novel disconnection of a pharmaceutically important scaffold.
- Metternich, Jan B.,Gilmour, Ryan
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p. 1040 - 1045
(2016/02/05)
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- Hantzsch Ester as a Photosensitizer for the Visible-Light-Induced Debromination of Vicinal Dibromo Compounds
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The debromination of vicinal dibromo compounds to generate alkenes usually requires harsh reaction conditions and the addition of catalysts. Just recently the visible-light-induced debromination of vicinal dibromo compounds emerged as a possible alternative to commonly used methods, but the substrate scope of this reaction is limited and a photocatalyst is necessary for the successful conversion of the starting compounds. A catalyst-free visible-light-induced debromination of vicinal dibromo compounds with a base-activated Hantzsch ester as photosensitizer is reported. The method has a wide substrate scope and a broad functional-group compatibility.
- Chen, Wenxin,Tao, Huachen,Huang, Wenhao,Wang, Guoqiang,Li, Shuhua,Cheng, Xu,Li, Guigen
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supporting information
p. 9546 - 9550
(2016/07/14)
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- Nickel-Catalyzed Boron Insertion into the C2-O Bond of Benzofurans
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Treatment of benzofurans with bis(pinacolato)diboron and Cs2CO3 under nickel-NHC catalysis resulted in the insertion of a boron atom into the C2-O bond of benzofurans to afford the corresponding oxaborins. The scope of benzofuran substrates is wide, and the reactions proceeded without loss of functional groups such as fluoro, methoxy, and ester that are potentially reactive under nickel catalysis. The boron-inserted products proved to be useful building blocks and subsequently underwent a series of transformations, one of which led to the synthesis of fluorescent π-expanded oxaborins.
- Saito, Hayate,Otsuka, Shinya,Nogi, Keisuke,Yorimitsu, Hideki
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p. 15315 - 15318
(2016/12/09)
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- A PROCESS FOR THE SYNTHESIS OF CARBOXYLIC ACID DERIVATIVES
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The present invention discloses one-pot synthesis of various carboxylic acid derivatives using copper catalyst and sodium cyanide as the cyanide source for bringing in carbonylative coupling in a single step.
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Page/Page column 8-9; 14
(2015/05/19)
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- Rh-Catalyzed Synthesis of Coumarin Derivatives from Phenolic Acetates and Acrylates via C-H Bond Activation
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An efficient annulation strategy involving the reaction of phenolic acetates with acrylates in the presence of [Rh2(OAc)4] as catalyst and formic acid as reducing agent, leading to the high yield synthesis of coumarin derivatives, has been developed. The addition of NaOAc as a base increased the yield of the products. The reaction is quite successful for both electron-rich as well as electron-deficient phenolic acetates, affording coumarins with excellent regioselectivity, and proceeds via C-H bond activation proven by deuterium incorporation studies.
- Gadakh, Sunita K.,Dey, Soumen,Sudalai, Arumugam
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p. 11544 - 11550
(2015/12/04)
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