1
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Luo Z, Lu C, Histand G, Lin D. One-Step Visible Light Photoredox-Catalyzed Purine C8 Alkoxylation with Alcohol. J Org Chem 2022; 87:11558-11564. [PMID: 35984935 DOI: 10.1021/acs.joc.2c01146] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A cross-dehydrogenation coupling reaction between purines and alcohols, induced by visible light, using an acridinium photocatalyst and air as the sole oxidant, to synthesize a series of C8-alkoxy purine derivatives was developed. This protocol is a green and novel method to construct the C8-O bond on a purine ring with high step and atom economy.
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Affiliation(s)
- Zhe Luo
- Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641, China
| | - Changtong Lu
- Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641, China
| | - Gary Histand
- The International School of Advanced Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
| | - Dongen Lin
- Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641, China
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2
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Abstract
The fields of C-H functionalization and photoredox catalysis have garnered enormous interest and utility in the past several decades. Many different scientific disciplines have relied on C-H functionalization and photoredox strategies including natural product synthesis, drug discovery, radiolabeling, bioconjugation, materials, and fine chemical synthesis. In this Review, we highlight the use of photoredox catalysis in C-H functionalization reactions. We separate the review into inorganic/organometallic photoredox catalysts and organic-based photoredox catalytic systems. Further subdivision by reaction class─either sp2 or sp3 C-H functionalization─lends perspective and tactical strategies for use of these methods in synthetic applications.
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Affiliation(s)
- Natalie Holmberg-Douglas
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - David A Nicewicz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
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3
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Rivero AR, Fodran P, Ondrejková A, Wallentin CJ. Alcohol Etherification via Alkoxy Radicals Generated by Visible-Light Photoredox Catalysis. Org Lett 2020; 22:8436-8440. [PMID: 33040526 PMCID: PMC7653678 DOI: 10.1021/acs.orglett.0c03058] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
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A mechanistically divergent method
is described that, employing
a commercially available hypervalent iodine(III) reagent, generates
alkoxy radicals from 1°, 2°, and 3° alcohols and allows
their use in the functionalization of C(sp3)–H and
C(sp2)–H bonds. This visible-light photoredox catalysis
produces alkyl ethers via 1,5/6-hydrogen atom transfer or aryl ethers
via 1,5-addition. This mild methodology provides a practical strategy
for the synthesis of acetals, orthoesters, tetrahydrofurans, and chromanes.
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Affiliation(s)
- Alexandra R Rivero
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemigården 4, 412 96 Gothenburg, Sweden
| | - Peter Fodran
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemigården 4, 412 96 Gothenburg, Sweden
| | - Alica Ondrejková
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemigården 4, 412 96 Gothenburg, Sweden
| | - Carl-Johan Wallentin
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemigården 4, 412 96 Gothenburg, Sweden
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4
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Kodama T, Kubo M, Shinji W, Ohkubo K, Tobisu M. Phenylene-bridged bis(benzimidazolium) (BBIm 2+): a dicationic organic photoredox catalyst. Chem Sci 2020; 11:12109-12117. [PMID: 34094425 PMCID: PMC8162872 DOI: 10.1039/d0sc03958f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 10/07/2020] [Indexed: 12/30/2022] Open
Abstract
A dicationic photoredox catalyst composed of phenylene-bridged bis(benzimidazolium) (BBIm2+) was designed, synthesised and demonstrated to promote the photochemical decarboxylative hydroxylation and dimerisation of carboxylic acids. The catalytic activity of BBIm2+ was higher than that for a monocation analogue, suggesting that the dicationic nature of BBIm2+ plays a key role in these decarboxylative reactions. The rate constant for the decay of the triplet-triplet absorption of the excited BBIm2+ increased with increasing concentration of the carboxylate anion with a saturated dependence, suggesting that photoinduced electron transfer occurs within the ion pair complex composed of the triplet excited state of BBIm2+ and a carboxylate anion.
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Affiliation(s)
- Takuya Kodama
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University Suita Osaka 565-0871 Japan
| | - Maiko Kubo
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University Suita Osaka 565-0871 Japan
| | - Wataru Shinji
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University Suita Osaka 565-0871 Japan
| | - Kei Ohkubo
- Institute for Advanced Co-Creation Studies, Osaka University Suita Osaka 565-0871 Japan
- Institute for Open and Transdisciplinary Research Initiatives, Osaka University Suita Osaka 565-0871 Japan
| | - Mamoru Tobisu
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University Suita Osaka 565-0871 Japan
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5
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Cheng LC, Chen WC, Santhoshkumar R, Chao TH, Cheng MJ, Cheng CH. Synthesis of Quinolinium Salts from N
-Substituted Anilines, Aldehydes, Alkynes, and Acids: Theoretical Understanding of the Mechanism and Regioselectivity. European J Org Chem 2020. [DOI: 10.1002/ejoc.202000178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Lin-Chieh Cheng
- Department of Chemistry; National Tsing Hua University; 30013 Hsinchu Taiwan
| | - Wei-Chen Chen
- Department of Chemistry; National Tsing Hua University; 30013 Hsinchu Taiwan
| | | | - Tzu-Hsuan Chao
- Department of Chemistry; National Cheng Kung University; 70101 Tainan Taiwan
| | - Mu-Jeng Cheng
- Department of Chemistry; National Cheng Kung University; 70101 Tainan Taiwan
| | - Chien-Hong Cheng
- Department of Chemistry; National Tsing Hua University; 30013 Hsinchu Taiwan
- Department of Chemistry; National Sun Yat-sen University; 80424 Kaohsiung Taiwan
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6
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Petzold D, Giedyk M, Chatterjee A, König B. A Retrosynthetic Approach for Photocatalysis. European J Org Chem 2020. [DOI: 10.1002/ejoc.201901421] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Daniel Petzold
- Department of Organic Chemistry University of Regensburg Universitätsstraße 31 93053 Regensburg Germany
| | - Maciej Giedyk
- Department of Organic Chemistry University of Regensburg Universitätsstraße 31 93053 Regensburg Germany
- Institute of Organic Chemistry Polish Academy of Sciences Kasprzaka 44/52 01‐224 Warsaw Poland
| | - Anamitra Chatterjee
- Department of Organic Chemistry University of Regensburg Universitätsstraße 31 93053 Regensburg Germany
| | - Burkhard König
- Department of Organic Chemistry University of Regensburg Universitätsstraße 31 93053 Regensburg Germany
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7
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Ming XX, Tian ZY, Zhang CP. Base-Mediated O-Arylation of Alcohols and Phenols by Triarylsulfonium Triflates. Chem Asian J 2019; 14:3370-3379. [PMID: 31464363 DOI: 10.1002/asia.201900968] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 07/29/2019] [Indexed: 12/15/2022]
Abstract
A mild and efficient protocol for O-arylation of alcohols and phenols (ROH) by triarylsulfonium triflates was developed under transition-metal-free conditions. Various alcohols, including primary, secondary and tertiary, and phenols bearing either electron-donating or electron-withdrawing groups on the aryl rings were smoothly converted to form the corresponding aromatic ethers in moderate to excellent yields. The reactions were conducted at 50 or 80 °C for 24 h in the presence of a certain base and showed good functional group tolerance. The base-mediated arylation with asymmetric triarylsulfonium salts could selectively transfer the aryl groups of sulfoniums to ROH, depending on their inherent electronic nature. The mechanistic studies revealed that the reaction might proceed through the nucleophilic attack of the in situ formed alkoxy or phenoxy anions at the aromatic carbon atoms of the C-S bonds of triarylsulfonium cations to furnish the target products.
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Affiliation(s)
- Xiao-Xia Ming
- School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, 205 Luoshi Road, Wuhan, 430070, P. R. China
| | - Ze-Yu Tian
- School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, 205 Luoshi Road, Wuhan, 430070, P. R. China
| | - Cheng-Pan Zhang
- School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, 205 Luoshi Road, Wuhan, 430070, P. R. China
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8
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Lukyanov DA, Funt LD, Konev AS, Povolotskiy AV, Vereshchagin AA, Levin OV, Khlebnikov AF. Novel homogeneous photocatalyst for oxygen to hydrogen peroxide reduction in aqueous media. Photochem Photobiol Sci 2019; 18:1982-1989. [PMID: 31237303 DOI: 10.1039/c9pp00206e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
An isoquinolinium-pyrrole donor-acceptor dyad was found to exhibit photocatalytic activity in oxygen-to-peroxide photoreduction with oxalate as a sacrificial electron donor. The concentration of hydrogen peroxide was shown to reach a plateau of 0.57 mM. The screening of related pyridinium-pyrrole dyads showed the importance of the isoquinoline moiety in securing the photocatalytic activity.
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Affiliation(s)
- Daniil A Lukyanov
- Institute of Chemistry, Saint Petersburg University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.
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9
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Tang H, Luo J, Xie P. Advances on the Synthesis of Aryl Ethers via Dehydrogenative Coupling. CHINESE J ORG CHEM 2019. [DOI: 10.6023/cjoc201904011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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10
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Zhang H, Lei A. Visible-Light-Induced C−H Functionalization and C−C/C−X Bond-Forming Oxidative Cross-Coupling Reactions. ASIAN J ORG CHEM 2018. [DOI: 10.1002/ajoc.201800214] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Heng Zhang
- College of Chemistry and Molecular Sciences; Wuhan University; Wuhan Hubei 430072 P. R. China
| | - Aiwen Lei
- College of Chemistry and Molecular Sciences; Wuhan University; Wuhan Hubei 430072 P. R. China
- State Key Laboratory and Institute of Elemento-Organic Chemistry; Nankai University; Tianjin 300071 P. R. China
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11
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Corrigan N, Shanmugam S, Xu J, Boyer C. Photocatalysis in organic and polymer synthesis. Chem Soc Rev 2018; 45:6165-6212. [PMID: 27819094 DOI: 10.1039/c6cs00185h] [Citation(s) in RCA: 466] [Impact Index Per Article: 77.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This review, with over 600 references, summarizes the recent applications of photoredox catalysis for organic transformation and polymer synthesis. Photoredox catalysts are metallo- or organo-compounds capable of absorbing visible light, resulting in an excited state species. This excited state species can donate or accept an electron from other substrates to mediate redox reactions at ambient temperature with high atom efficiency. These catalysts have been successfully implemented for the discovery of novel organic reactions and synthesis of added-value chemicals with an excellent control of selectivity and stereo-regularity. More recently, such catalysts have been implemented by polymer chemists to post-modify polymers in high yields, as well as to effectively catalyze reversible deactivation radical polymerizations and living polymerizations. These catalysts create new approaches for advanced organic transformation and polymer synthesis. The objective of this review is to give an overview of this emerging field to organic and polymer chemists as well as materials scientists.
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Affiliation(s)
- Nathaniel Corrigan
- Centre for Advanced Macromolecular Design (CAMD), School of Chemical Engineering, UNSW Australia, Sydney, NSW 2052, Australia. and Australian Centre for NanoMedicine, School of Chemical Engineering, UNSW Australia, Sydney, NSW 2052, Australia
| | - Sivaprakash Shanmugam
- Centre for Advanced Macromolecular Design (CAMD), School of Chemical Engineering, UNSW Australia, Sydney, NSW 2052, Australia.
| | - Jiangtao Xu
- Centre for Advanced Macromolecular Design (CAMD), School of Chemical Engineering, UNSW Australia, Sydney, NSW 2052, Australia. and Australian Centre for NanoMedicine, School of Chemical Engineering, UNSW Australia, Sydney, NSW 2052, Australia
| | - Cyrille Boyer
- Centre for Advanced Macromolecular Design (CAMD), School of Chemical Engineering, UNSW Australia, Sydney, NSW 2052, Australia. and Australian Centre for NanoMedicine, School of Chemical Engineering, UNSW Australia, Sydney, NSW 2052, Australia
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12
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Zheng YW, Ye P, Chen B, Meng QY, Feng K, Wang W, Wu LZ, Tung CH. Benzene C-H Etherification via Photocatalytic Hydrogen-Evolution Cross-Coupling Reaction. Org Lett 2017; 19:2206-2209. [PMID: 28409933 DOI: 10.1021/acs.orglett.7b00463] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Aryl ethers can be constructed from the direct coupling between the benzene C-H bond and the alcohol O-H bond with the evolution of hydrogen via the synergistic merger of photocatalysis and cobalt catalysis. Utilizing the dual catalyst system consisting of 3-cyano-1-methylquinolinum photocatalyst and cobaloxime, intermolecular etherification of arenes with various alcohols and intramolecular alkoxylation of 3-phenylpropanols with formation of chromanes are accomplished. These reactions proceed at remarkably mild conditions, and the sole byproduct is equivalent hydrogen gas.
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Affiliation(s)
- Yi-Wen Zheng
- Key Laboratory of Colloid and Interface Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University , Jinan 250100, PR China.,Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry & University of Chinese Academy of Sciences, Chinese Academy of Sciences , Beijing 100190, PR China
| | - Pan Ye
- Key Laboratory of Colloid and Interface Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University , Jinan 250100, PR China
| | - Bin Chen
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry & University of Chinese Academy of Sciences, Chinese Academy of Sciences , Beijing 100190, PR China
| | - Qing-Yuan Meng
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry & University of Chinese Academy of Sciences, Chinese Academy of Sciences , Beijing 100190, PR China
| | - Ke Feng
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry & University of Chinese Academy of Sciences, Chinese Academy of Sciences , Beijing 100190, PR China
| | - Wenguang Wang
- Key Laboratory of Colloid and Interface Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University , Jinan 250100, PR China
| | - Li-Zhu Wu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry & University of Chinese Academy of Sciences, Chinese Academy of Sciences , Beijing 100190, PR China
| | - Chen-Ho Tung
- Key Laboratory of Colloid and Interface Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University , Jinan 250100, PR China.,Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry & University of Chinese Academy of Sciences, Chinese Academy of Sciences , Beijing 100190, PR China
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13
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Affiliation(s)
- Nathan A. Romero
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - David A. Nicewicz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
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14
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Affiliation(s)
- Shunichi Fukuzumi
- Department of Material and Life Science; Graduate School of Engineering; Osaka University, ALCA and SENTAN; Japan Science and Technology Agency (JST); 2-1 Yamada-oka, Suita Osaka 565-0871 Japan
- Department of Bioinspired Science; Ewha Womans University; Seoul 120-750 Korea
- Faculty of Science and Technology; Meijo University and ALCA and SENTAN, Japan Science and Technology Agency (JST); Tempaku Nagoya, Aichi 468-8502 Japan
| | - Kei Ohkubo
- Department of Material and Life Science; Graduate School of Engineering; Osaka University, ALCA and SENTAN; Japan Science and Technology Agency (JST); 2-1 Yamada-oka, Suita Osaka 565-0871 Japan
- Department of Bioinspired Science; Ewha Womans University; Seoul 120-750 Korea
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15
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Ohkubo K, Hirose K, Fukuzumi S. Solvent-Free One-Step Photochemical Hydroxylation of Benzene Derivatives by the Singlet Excited State of 2,3-Dichloro-5,6-dicyano-p-benzoquinone Acting as a Super Oxidant. Chemistry 2014; 21:2855-61. [DOI: 10.1002/chem.201404810] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Indexed: 11/08/2022]
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16
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Fukuzumi S, Ohkubo K. Organic synthetic transformations using organic dyes as photoredox catalysts. Org Biomol Chem 2014; 12:6059-71. [PMID: 24984977 DOI: 10.1039/c4ob00843j] [Citation(s) in RCA: 327] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The oxidizing ability of organic dyes is enhanced significantly by photoexcitation. Radical cations of weak electron donors can be produced by electron transfer from the donors to the excited states of organic dyes. The radical cations thus produced undergo bond formation reactions with various nucleophiles. For example, the direct oxygenation of benzene to phenol was made possible under visible-light irradiation of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in an oxygen-saturated acetonitrile solution of benzene and water via electron transfer from benzene to the triplet excited state of DDQ. 3-Cyano-1-methylquinolinium ion (QuCN(+)) can also act as an efficient photocatalyst for the selective oxygenation of benzene to phenol using oxygen and water under homogeneous and ambient conditions. Alkoxybenzenes were also obtained when water was replaced by alcohol under otherwise identical experimental conditions. QuCN(+) can also be an effective photocatalyst for the fluorination of benzene with O2 and fluoride anion. Photocatalytic selective oxygenation of aromatic compounds was achieved using an electron donor-acceptor-linked dyad, 9-mesityl-10-methylacridinium ion (Acr(+)-Mes), as a photocatalyst and O2 as the oxidant under visible-light irradiation. The electron-transfer state of Acr(+)-Mes produced upon photoexcitation can oxidize and reduce substrates and dioxygen, respectively, leading to the selective oxygenation and halogenation of substrates. Acr(+)-Mes has been utilized as an efficient organic photoredox catalyst for many other synthetic transformations.
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Affiliation(s)
- Shunichi Fukuzumi
- Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan.
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17
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Ohkubo K, Fujimoto A, Fukuzumi S. Photocatalytic Monofluorination of Benzene by Fluoride via Photoinduced Electron Transfer with 3-Cyano-1-methylquinolinium. J Phys Chem A 2013; 117:10719-25. [DOI: 10.1021/jp408315a] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Kei Ohkubo
- Department
of Material and Life Science, Graduate School of Engineering, Osaka University and ALCA, Japan Science and Technology Agency (JST), 2-1 Yamada-oka,
Suita, Osaka 565-0871, Japan
| | - Atsushi Fujimoto
- Department
of Material and Life Science, Graduate School of Engineering, Osaka University and ALCA, Japan Science and Technology Agency (JST), 2-1 Yamada-oka,
Suita, Osaka 565-0871, Japan
| | - Shunichi Fukuzumi
- Department
of Material and Life Science, Graduate School of Engineering, Osaka University and ALCA, Japan Science and Technology Agency (JST), 2-1 Yamada-oka,
Suita, Osaka 565-0871, Japan
- Department
of Bioinspired Science, Ewha Womans University, Seoul 120-750, Korea
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19
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Yamada Y, Maeda K, Ohkubo K, Karlin KD, Fukuzumi S. Improvement of durability of an organic photocatalyst in p-xylene oxygenation by addition of a Cu(II) complex. Phys Chem Chem Phys 2012; 14:9654-9. [PMID: 22692585 DOI: 10.1039/c2cp41207a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The catalytic durability of an organic photocatalyst, 9-mesityl-10-methyl acridinium ion (Acr(+)-Mes), has been dramatically improved by the addition of [{tris(2-pyridylmethyl)amine}Cu(II)](ClO(4))(2) ([(tmpa)Cu(II)](2+)) in the photocatalytic oxygenation of p-xylene by molecular oxygen in acetonitrile. Such an improvement is not observed by the addition of Cu(ClO(4))(2) in the absence of organic ligands. The addition of [(tmpa)Cu](2+) in the reaction solution resulted in more than an 11 times higher turnover number (TON) compared with the TON obtained without [(tmpa)Cu(II)](2+). In the photocatalytic oxygenation, a stoichiometric amount of H(2)O(2) formation was observed in the absence of [(tmpa)Cu(II)](2+), however, much less H(2)O(2) formation was observed in the presence of [(tmpa)Cu(II)](2+). The photocatalytic mechanism was investigated by laser flash photolysis measurements in order to detect intermediates. The reaction of O(2)˙(-) with [(tmpa)Cu(II)](2+) monitored by UV-vis spectroscopy in propionitrile at 203 K suggested formation of [{(tmpa)Cu(II)}(2)O(2)](2+), a transformation which is crucial for the overall 4-electron reduction of molecular O(2) to water, and a key in the observed improvement in the catalytic durability of Acr(+)-Mes.
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Affiliation(s)
- Yusuke Yamada
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
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