- 7,10-Dibromo-2,3-dicyanopyrazinophenanthrene Aggregates as a Photosensitizer for Nickel-Catalyzed Aryl Esterification
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Self-assembled aggregates of 7,10-dibromo-2,3-dicyanopyrazinophenanthrene which act as a new organophotocatalyst in combination with Ni catalyst for the C aryl-O acylcross-coupling reactions of carboxylic acids with aryl halides are described. This visible-light-induced C aryl-O acylbond-formation reaction proceeds smoothly to afford aryl esters with satisfactory to excellent yields.
- Bao, Ming,He, Min,Yang, Shilei,Yu, Xiaoqiang
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supporting information
(2021/10/05)
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- Conversion of esters to thioesters under mild conditions
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We report conversion of esters to thioestersviaselective C-O bond cleavage/weak C-S bond formation under transition-metal-free conditions. The method is notable for a general and practical transition-metal-free system, broad substrate scope and excellent functional group tolerance. The strategy was successfully deployed in late-stage thioesterification, site-selective cross-coupling/thioesterification/decarbonylation and easy-to-handle gram scale thioesterification. Selectivity and computational studies were performed to gain insight into the formation of weak C-S bonds by C-O bond cleavage, which contrasts with the traditional trend of nucleophilic additions to carboxylic acid derivatives.
- Shi, Yijun,Liu, Xuejing,Cao, Han,Bie, Fusheng,Han, Ying,Yan, Peng,Szostak, Roman,Szostak, Michal,Liu, Chengwei
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supporting information
p. 2991 - 2996
(2021/04/14)
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- PEROVSKITES FOR PHOTOCATALYTIC ORGANIC SYNTHESIS
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Nature is capable of storing solar energy in chemical bonds via photosynthesis through a series of C—C, C—O and C—N bond-forming reactions starting from CO2 and light. Direct capture of solar energy for organic synthesis is a promising approach
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- Energy-Transfer-Mediated Photocatalysis by a Bioinspired Organic Perylenephotosensitizer HiBRCP
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Energy transfer plays a special role in photocatalysis by utilizing the potential energy of the excited state through indirect excitation, in which a photosensitizer determines the thermodynamic feasibility of the reaction. Bioinspired by the energy-transfer ability of natural product cercosporin, here we developed a green and highly efficient organic photosensitizer HiBRCP (hexaisobutyryl reduced cercosporin) through structural modification of cercosporin. After structural manipulation, its triplet energy was greatly improved, and then, it could markedly promote the efficient geometrical isomerization of alkenes from the E-isomer to the Z-isomer. Moreover, it was also effective for energy-transfer-mediated organometallic catalysis, which allowed realization of the cross-coupling of aryl bromides and carboxylic acids through efficient energy transfer from HiBRCP to nickel complexes. Thus, the study on the relationship between structural manipulation and their photophysical properties provided guidance for further modification of cercosporin, which could be applied to more meaningful and challenging energy-transfer reactions.
- Zhang, Yan,Xia, Mingze,Li, Min,Ping, Qian,Yuan, Zhenbo,Liu, Xuanzhong,Yin, Huimin,Huang, Shuping,Rao, Yijian
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supporting information
p. 15284 - 15297
(2021/11/01)
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- Esterification of Carboxylic Acids with Aryl Halides via the Merger of Paired Electrolysis and Nickel Catalysis
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Electrochemistry has been successfully applied in metal catalysis to avoid the usage of chemical redox agents. This strategy proved to be a powerful approach to construct carbon-carbon (C-C) and carbon-heteroatom (C-X) bonds. However, most of the developed methods are based on either anodic oxidation or cathodic reduction, in which a sacrificial reaction occurs at the counter electrode. Paired electrolysis merging with metal catalysis is underdeveloped, wherein both anodic and cathodic processes are taking place simultaneously. Herein, we demonstrated that by using esterification of carboxylic acids with aryl halides via paired electrolysis using nickel as the catalyst the respective aryl esters were obtained in good to excellent yields at room temperature in an undivided electrochemical cell.
- Wei, Lei,Wang, Zhen-Hua,Jiao, Ke-Jin,Liu, Dong,Ma, Cong,Fang, Ping,Mei, Tian-Sheng
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p. 15906 - 15913
(2021/05/05)
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- Dual aminoquinolate diarylboron and nickel catalysed metallaphotoredox platform for carbon-oxygen bond construction
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Herein, aminoquinolate diarylboron complexes are utilized as photocatalysts in dual Ni/photoredox catalyzed carbon-oxygen construction reactions. Via this unified metallaphotoredox platform, diverse (hetero)aryl halides can be conveniently coupled with acids, alcohols and water. This method features operational simplicity, broad substrate scope and good compatibility with functional groups. This journal is
- Day, Craig,Jia, Xin,Wei, Lanfeng,Xu, Liang,Zu, Weisai
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supporting information
p. 8273 - 8276
(2020/08/17)
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- Ligand-Controlled C?O Bond Coupling of Carboxylic Acids and Aryl Iodides: Experimental and Computational Insights
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Palladium-catalyzed cross-coupling reactions between carboxylic acids and aryl halides have several possible competitive pathways. Decarboxylative C?C bond coupling and C?H arylation are well established in the literature. However, direct C?O bond coupling between carboxylic acids and aryl halides has received little success. In this report, we describe a protocol for exclusive C?O bond formation, enabled by a bidentate N,N-ligand such as 1,10-phenanthroline. The reaction is general for a broad range of carboxylic acids and iodoarenes. Experimental evidence and computational results suggest a high energy barrier for the alternative pathway of decarboxylative carbon-carbon bond coupling. (Figure presented.).
- Li, Li,Song, Feifei,Zhong, Xiumei,Wu, Yun-Dong,Zhang, Xinhao,Chen, Jiean,Huang, Yong
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supporting information
p. 126 - 132
(2019/11/28)
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- Visible light-mediated transition metal-free esterification of amides with boronic acids
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A novel strategy for visible light-mediated esterification of amides with boronic acids in air has been described. This method is characterized by mild reaction conditions and low cost owing to no need of any catalyst, which implies high potential utility in late-stage functionalization of amide drugs and materials.
- Ding, Hao,Qi, Wan-Ying,Zhen, Jing-Song,Ding, Qiuping,Luo, Yong
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- General Paradigm in Photoredox Nickel-Catalyzed Cross-Coupling Allows for Light-Free Access to Reactivity
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Self-sustained NiI/III cycles are established as a potentially general paradigm in photoredox Ni-catalyzed carbon–heteroatom cross-coupling reactions through a strategy that allows us to recapitulate photoredox-like reactivity in the absence of light across a wide range of substrates in the amination, etherification, and esterification of aryl bromides, the latter of which has remained, hitherto, elusive under thermal Ni catalysis. Moreover, the accessibility of esterification in the absence of light is especially notable because previous mechanistic studies on this transformation under photoredox conditions have unanimously invoked energy-transfer-mediated pathways.
- Nocera, Daniel G.,Qin, Yangzhong,Sun, Rui
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supporting information
p. 9527 - 9533
(2020/04/08)
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- Semi-heterogeneous Dual Nickel/Photocatalysis using Carbon Nitrides: Esterification of Carboxylic Acids with Aryl Halides
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Cross-coupling reactions mediated by dual nickel/photocatalysis are synthetically attractive but rely mainly on expensive, non-recyclable noble-metal complexes as photocatalysts. Heterogeneous semiconductors, which are commonly used for artificial photosynthesis and wastewater treatment, are a sustainable alternative. Graphitic carbon nitrides, a class of metal-free polymers that can be easily prepared from bulk chemicals, are heterogeneous semiconductors with high potential for photocatalytic organic transformations. Here, we demonstrate that graphitic carbon nitrides in combination with nickel catalysis can induce selective C?O cross-couplings of carboxylic acids with aryl halides, yielding the respective aryl esters in excellent yield and selectivity. The heterogeneous organic photocatalyst exhibits a broad substrate scope, is able to harvest green light, and can be recycled multiple times. In situ FTIR was used to track the reaction progress to study this transformation at different irradiation wavelengths and reaction scales.
- Pieber, Bartholom?us,Malik, Jamal A.,Cavedon, Cristian,Gisbertz, Sebastian,Savateev, Aleksandr,Cruz, Daniel,Heil, Tobias,Zhang, Guigang,Seeberger, Peter H.
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supporting information
p. 9575 - 9580
(2019/06/25)
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- Palladium-Catalyzed Aerobic Oxidative Coupling of Amides with Arylboronic Acids by Cooperative Catalysis
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The first fluoride and palladium co-catalyzed conversion of amide to ester through an aerobic oxidative coupling pathway is reported. This new approach presents a practical process that employs easily available oxygen and commercially available arylboronic acids as coupling partners, uses a wide range of N- tosylamides, and proceeds under mild reaction conditions. This protocol demonstrates broad functional group tolerance, and provides an alternative option to synthesize esters from N-tosylamides which obtained by simply N-functionalization of secondary amides.
- Li, Yue,Wu, Hongxiang,Zeng, Zhuo
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p. 4357 - 4361
(2019/07/09)
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- Synthesis and amelioration of inflammatory paw edema by novel benzophenone appended oxadiazole derivatives by exhibiting cyclooxygenase-2 antagonist activity
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Ten new 2(4-hydroxy-3-benzoyl) benzamide-5-phenyl-1,3,4-oxadiazole derivatives (10a–j) were synthesized by coupling 3-benzoyl-4-hydroxybenzoic acid (5) with 2-amino-5-phenyl-1,3,4-oxadiazoles (9a–j). The structures of these compounds were confirmed by IR, 1H, 13C NMR, and mass spectra, and also by elemental analyses. The anti-inflammatory activity of the compounds 10a–j were investigated by screening them against human red blood cells (HRBC) in-vitro. The results reveal that among this series, compound 10j with hydroxy substituent, particularly at the ortho position of the phenyl ring attached to the 5th carbon atom of the oxadiazole ring possess significant membrane stabilizing activity in comparison with the control. Further, in-vivo chick chorioallantoic membrane (CAM) and rat corneal anti-angiogenesis assays were performed to assess the effect of compound 10j on endothelial cell migration. This confirmed that compound 10j inhibits the proliferation of endothelial cells. Anti-inflammatory studies detected the amelioration of carrageen induced rat hind paw edema. Further in-vivo and in-silico approaches revealed the inhibition of inflammatory marker enzyme cyclooxygenase-2 (Cox-2) and myleoperoxidase (MPO). The study reports that the compound 10j effectively act against the inflammatory mediated anti-angiogenic disorders which could be translated into a new drug in future.
- Puttaswamy, Naveen,Malojiao, Vikas H.,Mohammed, Yasser Hussein Eissa,Sherapura, Ankith,Prabhakar,Khanum, Shaukath Ara
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p. 1446 - 1455
(2018/05/22)
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- Cu(OTf)2-mediated Chan-Lam reaction of carboxylic acids to access phenolic esters
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A Cu(OTf)2-mediated Chan-Lam reaction of carboxylic acids with arylboronic acids is described. It represents a facile and practical methodology to access phenolic esters in moderate to good yields. The procedure tolerates a series of functional groups, such as methoxycarbonyl, acetoxy, free phenolic hydroxyl, vinyl, nitro, trifluoromethyl, methoxyl, bromo, chloro, iodo, and acetyl groups.
- Zhang, Lingli,Zhang, Guoying,Zhang, Manli,Cheng, Jiang
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experimental part
p. 7472 - 7474
(2011/01/03)
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- Investigation of aromatic polyester synthesis by the chain-growth polycondensation method
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Synthesis of aromatic polyesters by chain-growth polycondensation of activated 4-hydroxybenzoic acid derivatives (1) was investigated. Model reactions of ester formation between active compounds (6 and 7) and phenolic nucleophile (8) gave the best result when 3-arylcarbonyl-2-benzothiazolone derivatives were used with tertiary amines in CH2Cl2. Therefore, we designed an synthesized 3-(4-hydroxy-3-octylbenzoyl)-2-benzothiazolone (1h) as a monomer. The Mn- and Mw/Mn-conversion curves of the polymerization of 1h with initiator suggested that transesterification between polymer and monomer occurred in the late stage of polymerization. Investigation of the effects of bases and initiators revealed that the transesterification at the initiator end was minimized by using 3-(4-benzoyloxybenzoyl)-2-benzothiazolone (7h) and diisopropylethylamine as an initiator and a base, respectively. When the ratio of initiator 7h to monomer 1h was 20 mol %, the polycondensation proceeded in a chain-growth manner to give aromatic polyester having a controlled molecular weight and a low polydispersity. However, the polymerization of 1h with 10 mol % or less of 7h could not be controlled and gave step-growth polymer as well as chain-growth polymer. The model reaction demonstrated that transesterification would occur at the polymer main chain even by use of weak tertiary amines as a base.
- Yokoyama, Akihiro,Iwashita, Ken-Ichi,Hirabayashi, Kyota,Aiyama, Kazushige,Yokozawa, Tsutomu
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p. 4328 - 4336
(2007/10/03)
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- Synthesis and biological screening of 2-substituted 5,6-dihydro-5-oxo-4H-1,3,4-oxadiazine-4-propanenitriles and of their intermediates
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To evaluate the effect of substituents on biological activities of electron-rich N-containing heterocycles, the variably 2-substituted 5,6-dihydro-5-oxo-4H-1,3,4-oxadiazine-4-propanenitriles 26-33 were synthesized and evaluated for antibacterial, antifungal, and enzyme-inhibition activities. The target compounds were obtained from alkyl 4- or 3-hydroxy benzoates 1 and 2, respectively, and from methyl indoleacetate 3. The phenolic OH group of benzoates 1 and 2 were substituted with p-toluenesulfonyl (→ 4 and 5), benzoyl (→ 6 and 7), and benzyl groups (→ 8 and 9) and then converted to 5,6-dihydro-5-oxo-4H-1,3,4-oxadiazine-4-propanenitriles. To establish structure-activity relationships (SAR), a pharmacological screening of the intervening intermediates was also conducted, which revealed that the intermediate hydrazide 11 possesses significant antimicrobial and MAO-A inhibiting properties and intermediates 12, 24, 28, and 29 appreciable antifungal activities. Compound 7 inhibits α-chymotrypsin.
- Khan, Khalid Mohammed,Rahat, Shagufta,Choudhary, Muhammad Iqbal,Atta-ur-Rahman,Ghani, Usman,Perveen, Shahnaz,Khatoon, Shagufta,Dar, Ahsana,Malik, Abdul
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p. 559 - 570
(2007/10/03)
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- Lewis acid-catalyzed cleavage of carbamate and carbonate resins
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A procedure for the preparation of amides and esters on a Merrifield resin-bound benzyloxycarbonyl equivalent has been developed. Polymer-supported carbamates react cleanly with zinc bromide and the appropriate acyl halide in the presence of triethylamine to provide their corresponding amides in high yields and purities. Cleavage of resin-bound carbonates was carried out using the similar reagent systems in the absence of triethylamine to give acetates or benzoates. (C) 2000 Elsevier Science Ltd.
- Li,Lin,Yo
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p. 6619 - 6622
(2007/10/03)
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- Efficient one-pot formation of amides from benzyl carbamates: Application to solid-phase synthesis
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A convenient one-pot protocol for the conversion of benzyl carbamates to amides is described. The general applicability of the procedure is illustrated using various types of substrates. This new method proceeds rapidly under mild conditions, in good yields, and without noticeable racemization. This protocol was applied to solid-phase synthesis to prepare amides and esters from Merrifield resin-bound carbamates and carbonates. (C) 2000 Elsevier Science Ltd.
- Li, Wen-Ren,Yo, Ying-Chih,Lin, Yu-Sheng
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p. 8867 - 8875
(2007/10/03)
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