- Cerium Ammonium Nitrate-Mediated Access to Biaryl Lactones: Substrate Scopes and Mechanism Studies
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Herein we described an access to biaryl lactones from ortho-aryl benzoic acids via intramolecular O-H/C-H oxidative coupling with the commonly used cerium ammonium nitrate (CAN) as the one-electron oxidant under a thermal condition. The radical interrupting experiment suggested a radical process, while the kinetic isotope effect (KIE) showed that the C-H cleavage likely was not involved in the rate-determining step. Competitive reactions, especially the strikingly different ρ values of Hammett equations, indicated that the reaction rate was more sensitive to the electronic properties on the aryl moiety rather than the carboxylic moiety, which corresponded to the first single electron transfer (SET) step. In addition, the quite negative ρ values (-4.7) of the aryl moiety unveiled the remarkable electrophilic nature of the second intramolecular radical addition process, which was also consistent with product yields and regioselectivity. Moreover, control experiments disclosed that the single electron in the third step was also transferred to CeIV instead of molecular oxygen. Besides, the possible role of co-solvents trifluoroethanol (TFE) and its influences on the CeIV species were discussed. This work elucidated the possible mechanism by proposing the step that had more effects on the total reaction rate and the species that was responsible for the last single electron transfer.
- Chao, Mianran,Wang, Fang,Xu, Linlin,Ju, Yanping,Chen, Zixuan,Wang, Bin,Gong, Peiwei,You, Jinmao,Jin, Ming,Shen, Duyi
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p. 13371 - 13380
(2021/10/01)
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- Facile preparation of 3,4-benzocoumarins from 2-arylbenzoic acids with NCS and NAI
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– Treatment of 2-arylbenzoic acids with N-chlorosuccinimide (NCS) and NaI at 70 °C under fluorescent lighting condition gave the corresponding 3,4-benzocoumarins in good yields under transition-metal-free condition. It was found that the reactivity of NCS
- Nakamura, Momoko,Togo, Hideo
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- 3, 4-benzocoumarin derivative as well as preparation method and application thereof
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The general formula of the 3, 4-benzocoumarin derivative is shown as a formula I, and definitions of substituent groups are shown in the specification in detail. The 3, 4-benzocoumarin derivative witha novel structure provided by the invention is simple in preparation method, nontoxic and harmless, has blue fluorescence, and can be used as a potential organic functional material. The structure ofthe compound has modifiability, and has high optical stability and thermal stability.
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Paragraph 0178-0180
(2020/08/02)
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- Palladium-Catalyzed Site-Selective Benzocylization of Aromatic Acids with o-Fluoro-Substituted Diaryliodonium Salts toward 3,4-Benzocoumarins
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By using 2-fluoro-substituted diaryliodonium salts, a novel benzocylization has been accomplished for the synthesis of 3,4-benzocoumarin derivatives via a cascade of ortho-arylation and defluorination in the presence of palladium catalysts. The reaction exhibits a broad compatibility of readily available aromatic acids with an excellent level of site-selectivity. Mechanistic investigations revealed a unique reactivity of carboxylic acid directed arylation by followed nucleophilic substitution of aromatic fluoride in the present system.
- Pan, Cheng,Wang, Limin,Han, Jianwei,Han, Jianwei
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p. 4776 - 4780
(2020/07/02)
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- Visible-Light-Induced Arene C(sp 2)-H Lactonization Promoted by DDQ and tert -Butyl Nitrite
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A visible-light photocatalytic aerobic oxidative lactonization of arene C(sp 2)-H bonds proceeds in the presence of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and tert -butyl nitrite (TBN). Under the optimized conditions, a range of 2-arylbenzoic acids is converted into the corresponding benzocoumarin derivatives in moderate to excellent yields. This method is characterized by its atom economy, mild reaction conditions, the use of a green oxidant and metal-free catalysis.
- Chen, Bajin,Hu, Baoxiang,Hu, Xinquan,Jin, Liqun,Li, Meichao,Shen, Zhenlu,Sun, Nan,Wang, Shengpeng,Wang, Yiqing
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p. 261 - 266
(2020/02/18)
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- Cerium photocatalyzed dehydrogenative lactonization of 2-arylbenzoic acids
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The first cerium photocatalyzed dehydrogenative lactonization of 2-arylbenzoic acids has been developed. This operationally simple protocol allows rapid access to synthetically useful coumarins on gram scale by employing CeCl3 as a photocatalyst and O2 as a terminal oxidant. Overall, this delivers an economical and environmentally amiable entry to diversely substituted coumarins, important structural motifs in bioactive molecules.
- Wadekar, Ketan,Aswale, Suraj,Yatham, Veera Reddy
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supporting information
p. 983 - 987
(2020/02/15)
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- Photocatalytic oxidation synthesis method of benzocoumarin compound
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The synthesis method disclosed by the invention takes,aryl-aryl formic acid compound as a reaction raw material 2 - to react the substrate in an organic solvent, DEG C - 5555,6-dinitrile - 1111, 4-benzoquinone 2,3 - and tert-butyl nitrite (DDQ) as a catal
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Paragraph 0037; 0038
(2020/03/17)
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- Intramolecular Aromatic C-H Acyloxylation Enabled by Iron Photocatalysis
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A mild and efficient protocol for the intramolecular aromatic C-H oxygenation of 2-biphenylcarboxylic acids has been achieved via iron photocatalysis. The 2-biphenylcarboxylic acids with a diverse array of substituents at both phenyl rings could furnish the oxygenation products in good to excellent yields. We speculate that the aryl carboxylate-iron(III) complexes should generate the aroyloxy radicals and iron(II) upon visible light irradiation.
- Xia, Siqi,Hu, Kunjun,Lei, Chuanhu,Jin, Jian
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supporting information
p. 1385 - 1389
(2020/02/13)
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- Visible light mediated oxidative lactonization of 2-methyl-1,1′-biaryls for the synthesis of benzocoumarins
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A visible light mediated oxidative lactonization of 2-methyl-1,1′-biaryls was developed, giving benzocoumarins in good yields. The reaction features multiple C-H functionalization processes with oxygen as the final oxidant. The corresponding 2-aldehdyes, alcohols and carboxylic acids of the 1,1′-biaryls also worked well for the reaction.
- Luo, Zhi,Gao, Zhong-Hua,Song, Zhi-Yong,Han, You-Feng,Ye, Song
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supporting information
p. 4212 - 4215
(2019/05/06)
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- Organocatalytic Electrochemical C-H Lactonization of Aromatic Carboxylic Acids
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An electrochemical strategy has been developed for radical arene carbon-oxygen bond formation. This reaction utilizes DDQ as a redox mediator, with inexpensive glassy carbon electrodes to facilitate an intramolecular lactonization of biphenyl-2-carboxylic
- Li, Longji,Yang, Qi,Jia, Zongbin,Luo, Sanzhong
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supporting information
p. 2924 - 2929
(2018/04/05)
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- Method for synthesizing of isocoumarin compounds
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The present invention provides a preparation method for isocoumarin compounds. The method comprises the following steps: using 2-arylbenzaldehyde represented by a formula I in the description as a rawmaterial, performing a reaction at the temperature of 0-50 DEG C for 6-36h in an organic solvent under the actions of a copper catalyst, an oxidant and alkaline matter, and performing separation purification on an obtained reaction liquid to obtain the isocoumarin compounds represented by a formula II in the description. According to the invention, the raw materials are cheap and easy to obtain,the reaction conditions are mild, the tolerance of the functional groups is good, the operation is simple and environmentally friendly, and a novel method is provided for synthesizing isocoumarin containing various substituent groups.
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Paragraph 0054; 0058; 0062; 0064; 0065; 0066
(2018/04/02)
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- Vitamin Catalysis: Direct, Photocatalytic Synthesis of Benzocoumarins via (-)-Riboflavin-Mediated Electron Transfer
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An operationally simple protocol is disclosed to facilitate entry to benzo-3,4-coumarins directly from biaryl carboxylic acids without the need for substrate prefunctionalization. Complementary to classic lactonization strategies, this disconnection relies on the oxidation competence of photoactivated (-)-riboflavin (vitamin B2) to generate the heterocyclic core via photoinduced single electron transfer. Collectively, the inexpensive nature of the catalyst, ease of execution, and absence of external metal additives are a convincing endorsement for the incorporation of simple vitamins in contemporary catalysis.
- Morack, Tobias,Metternich, Jan B.,Gilmour, Ryan
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p. 1316 - 1319
(2018/03/09)
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- Electrochemical C?O Bond Formation: Facile Access to Aromatic Lactones
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An efficient and robust methodology based on electrochemical techniques for the direct synthesis of aromatic lactones through dehydrogenative C?O cyclization is described. This new and useful electrochemical reaction can tolerate a variety of functional groups, and is scalable to 100 g under mild conditions. Remarkably, heterocycle-containing substrates can be employed, thus expanding the scope of radical C?O cyclization reactions.
- Tao, Xiang-Zhang,Dai, Jian-Jun,Zhou, Jie,Xu, Jun,Xu, Hua-Jian
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supporting information
p. 6932 - 6935
(2018/04/30)
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- External oxidant-free dehydrogenative lactonization of 2-arylbenzoic acids via visible-light photocatalysis
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An external oxidant-free C-H functionalization/C-O bond formation reaction for constructing benzo-3,4-coumarins accompanied by quantitative H2 evolution has been developed. High functional group tolerance and excellent reaction efficiency are s
- Shao, Ailong,Zhan, Jirui,Li, Na,Chiang, Chien-Wei,Lei, Aiwen
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p. 3582 - 3589
(2018/04/14)
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- Scalable Electrochemical Dehydrogenative Lactonization of C(sp2/sp3)-H Bonds
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A practical, electrochemical method is developed for the direct dehydrogenative lactonization of C(sp2/sp3)-H bonds under external oxidant- and metal-free conditions, delivering diverse lactones, including coumarin derivatives with excellent regioselectivity. The scalable nature of this newly developed electrochemical process was demonstrated on a 40 g scale following an operationally simple protocol. The remote lactonization of C(sp3)-H bonds would constitute an important synthetic advance toward electrochemical C-O bond formation.
- Zhang, Sheng,Li, Lijun,Wang, Huiqiao,Li, Qian,Liu, Wenmin,Xu, Kun,Zeng, Chengchu
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supporting information
p. 252 - 255
(2018/01/17)
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- Electrochemical Intramolecular C—H/O—H Cross-Coupling of 2-Arylbenzoic Acids
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A synthetic protocol to lactones by electro-oxidative induced C—H activation of 2-arylbenzoic acids has been developed. By using Na2SO4 aqueous solution as a cheap and green supporting electrolyte, different 2-arylbenzoic acids could provide the corresponding lactones in 30%—90% yields. This reaction could be conducted on a gram scale with a good efficiency as well as a high utility for natural product synthesis.
- Shao, Ailong,Li, Na,Gao, Yong,Zhan, Jirui,Chiang, Chien-Wei,Lei, Aiwen
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supporting information
p. 619 - 624
(2018/05/30)
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- Synthesis of dibenzopyranones and pyrazolobenzopyranones through copper(0)/Selectfluor system-catalyzed double C[sbnd]H activation/oxygen insertion of 2-arylbenzaldehydes and 5-arylpyrazole-4-carbaldehydes
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A mild and efficient protocol for the synthesis of dibenzopyranones and pyrazolobenzopyranones was developed involving a copper(0)/Selectfluor system-catalyzed double C[sbnd]H activation/oxygen insertion of 2-arylbenzaldehydes and 5-arylpyrazole-4-carbaldehydes. Preliminary mechanistic studies suggest that both water and dioxygen act as the oxygen source in the formation of pyranone scaffolds.
- Zhang, Jian,Shi, Dongdong,Zhang, Haifeng,Xu, Zheng,Bao, Hanyang,Jin, Hongwei,Liu, Yunkui
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p. 154 - 163
(2016/12/23)
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- Silver-Catalyzed C(sp2)-H Functionalization/C-O Cyclization Reaction at Room Temperature
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Silver-catalyzed C(sp2)-H functionalization/C-O cyclization has been developed. The scalable reaction proceeds at room temperature in an open flask. The present method exhibits good functional-group compatibility because of the mild reaction conditions. Using a AgNO3 catalyst and a (NH4)2S2O8 oxidant in CH2Cl2/H2O solvent, various lactones are obtained in good to excellent yields. A kinetic isotope effect (KIE) study indicates that the reaction may occur via a radical process.
- Dai, Jian-Jun,Xu, Wen-Tao,Wu, Ya-Dong,Zhang, Wen-Man,Gong, Ying,He, Xia-Ping,Zhang, Xin-Qing,Xu, Hua-Jian
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p. 911 - 919
(2015/01/30)
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- Photocatalytic Dehydrogenative Lactonization of 2-Arylbenzoic Acids
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A metal-free dehydrogenative lactonization of 2-arylbenzoic acids at room temperature was developed. This work illustrates the first application of visible-light photoredox catalysis in the preparation of benzo-3,4-coumarins, an important structural motif in bioactive molecules. The combination of photocatalyst [Acr+-Mes] with (NH4)2S2O8 as a terminal oxidant provides an economical and environmentally benign entry to different substituted benzocoumarins. Preliminary mechanistic studies suggest that this reaction most likely occurs through a homolytic aromatic substitution pathway.
- Ramirez, Nieves P.,Bosque, Irene,Gonzalez-Gomez, Jose C.
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p. 4550 - 4553
(2015/09/28)
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- NIS-mediated oxidative lactonization of 2-arylbenzoic acids for the synthesis of dibenzopyranones under metal-free conditions
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A series of dibenzopyranones were synthesized from 2-arylbenzoic acids by a radical oxidative cyclization procedure mediated by N-iodosuccinimide (NIS). The methodology is distinguished by its practicality in terms of its wide substrate scope, good functi
- Gao, Peng,Wei, Yunyang
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supporting information
p. 343 - 347
(2014/02/14)
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- The fungal phytotoxin alternariol 9-methyl ether and some of its synthetic analogues inhibit the photosynthetic electron transport chain
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Alternariol and monomethylalternariol are natural phytotoxins produced by some fungal strains, such as Nimbya and Alternaria. These substances confer virulence to phytopathogens, yet no information is available concerning their mode of action. Here we show that in the micromolar range alternariol 9-methyl ether is able to inhibit the electron transport chain (IC50 = 29.1 ± 6.5 μM) in isolated spinach chloroplasts. Since its effectiveness is limited by poor solubility in water, several alternariol analogues were synthesized using different aromatic aldehydes. The synthesized 6H-benzo[c]cromen-6-ones, 5H-chromene[4,3-b]pyridin-5-one, and 5H-chromene[4,3-c]pyridin-5-one also showed inhibitory properties, and three 6H-benzo[c]cromen-6-ones were more effective (IC50 = 12.8-22.8 μM) than the lead compound. Their addition to the culture medium of a cyanobacterial model strain was found to inhibit algal growth, with a relative effectiveness that was consistent with their activity in vitro. In contrast, the growth of a nonphotosynthetic plant cell culture was poorly affected. These compounds may represent a novel lead for the development of new active principles targeting photosynthesis.
- Demuner, Antonio Jacinto,Barbosa, Luiz Claudio Almeida,Miranda, Ana Cristina Mendes,Geraldo, Guilherme Carvalho,Da Silva, Cleiton Moreira,Giberti, Samuele,Bertazzini, Michele,Forlani, Giuseppe
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p. 2234 - 2245
(2014/01/17)
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- One pot synthesis of bioactive benzopyranones through palladium-catalyzed C-H activation and CO insertion into 2-arylphenols
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Palladium-catalyzed oxidative carbonylation of 2-arylphenols through C-H bond activation and C-C and C-O bond formation under acid-base free and mild conditions has been developed. The reaction tolerates a variety of substrates and provides biologically important benzopyranone derivatives in up to 87% isolated yield.
- Lee, Tai-Hua,Jayakumar, Jayachandran,Cheng, Chien-Hong,Chuang, Shih-Ching
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p. 11797 - 11799
(2013/12/04)
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- Pd-catalyzed C-H lactonization for expedient synthesis of biaryl lactones and total synthesis of cannabinol
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A practical Pd(II)/Pd(IV)-catalyzed carboxyl-directed C-H activation/C-O cyclization to construct biaryl lactones has been developed. The synthetic utility of this new reaction was demonstrated in an atom-economical and operationally convenient total synthesis of the natural product cannabinol from commercially available starting materials, with the newly developed method used for two key steps.
- Li, Yan,Ding, Yan-Jun,Wang, Jian-Yong,Su, Yi-Ming,Wang, Xi-Sheng
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p. 2574 - 2577
(2013/07/11)
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- General and practical carboxyl-group-directed remote C-H oxygenation reactions of arenes
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Two methods for remote aromatic C-H oxygenation reactions, have been developed. Method1, the Cu-catalyzed oxygenation reaction, is highly efficient for cyclization of electron-neutral and electron-rich biaryl carboxylic acids into 3,4-benzocoumarins. Method2, the K2S2O 8-mediated oxygenation reaction, is more general and practical for cyclization of substrates with electron-donating and -withdrawing groups (see scheme). Copyright
- Wang, Yang,Gulevich, Anton V.,Gevorgyan, Vladimir
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p. 15836 - 15840
(2014/04/03)
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