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Vampugani NMR, Shelke AB, Singh PB, Ahmad A, Kapat A. Regioselective Synthesis of the Tetrahydrocarbazole Core of Akuammiline Alkaloids via Palladium-Catalyzed Intramolecular Arylation Reaction. J Org Chem 2024; 89:4461-4466. [PMID: 38527008 DOI: 10.1021/acs.joc.3c02619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/27/2024]
Abstract
Tetrahydrocarbazole is the central core for several biologically active alkaloids, and regioselective synthesis of this core is a challenging task. Herein, we report an efficient strategy for the synthesis of this core involving palladium-catalyzed intramolecular arylation reaction with excellent regioselectivity (>99%) starting from N-phenyl-bromoalkene without having any relocation of double bonds via competitive palladium-catalyzed isomerization reaction. Broad functional group tolerance and exclusive regioselectivity have been observed for meta-substituted halide substrates. Furthermore, this reaction can be scalable on the gram scale.
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Affiliation(s)
- Naga M R Vampugani
- Department of Chemistry, School of Natural Sciences, Shiv Nadar (Institution of Eminence Deemed to be University) Delhi-NCR, Dadri, Chithera, Gautam Buddha Nagar, Greater Noida, Uttar Pradesh 201314, India
| | - Ajay B Shelke
- Department of Chemistry, School of Natural Sciences, Shiv Nadar (Institution of Eminence Deemed to be University) Delhi-NCR, Dadri, Chithera, Gautam Buddha Nagar, Greater Noida, Uttar Pradesh 201314, India
| | - Prashant B Singh
- Department of Chemistry, School of Natural Sciences, Shiv Nadar (Institution of Eminence Deemed to be University) Delhi-NCR, Dadri, Chithera, Gautam Buddha Nagar, Greater Noida, Uttar Pradesh 201314, India
| | - Asrar Ahmad
- Department of Chemistry, School of Natural Sciences, Shiv Nadar (Institution of Eminence Deemed to be University) Delhi-NCR, Dadri, Chithera, Gautam Buddha Nagar, Greater Noida, Uttar Pradesh 201314, India
| | - Ajoy Kapat
- Department of Chemistry, School of Natural Sciences, Shiv Nadar (Institution of Eminence Deemed to be University) Delhi-NCR, Dadri, Chithera, Gautam Buddha Nagar, Greater Noida, Uttar Pradesh 201314, India
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2
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Abdellaoui M, Oppel K, Vianna A, Soleilhavoup M, Yan X, Melaimi M, Bertrand G. 1 H-1,2,3-Triazol-5-ylidenes as Catalytic Organic Single-Electron Reductants. J Am Chem Soc 2024; 146:2933-2938. [PMID: 38253007 DOI: 10.1021/jacs.3c14360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Most of the known single-electron reductants are either metal based reagents, used in a stoichiometric amount, or a combination of an organic species and a photocatalyst. Here we report that 1H-1,2,3-triazol-5-ylidenes act not only as stoichiometric one-electron donors but also as catalytic organic reducing agents, without the need of a photocatalyst. As a proof of concept, we studied the reduction of quinones, which are well-known electron conveyors that are involved in various biological and industrial processes. This work also provides experimental evidence for the formation of a bis(triazolium)carbonate adduct, which acts as the resting state of the catalytic cycle and as the carbene reservoir.
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Affiliation(s)
- Mehdi Abdellaoui
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
| | - Kai Oppel
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
| | - Adam Vianna
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
| | - Michele Soleilhavoup
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
| | - Xiaoyu Yan
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing,100872, China
| | - Mohand Melaimi
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
| | - Guy Bertrand
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
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3
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Liu QQ, Li JZ, Wang YJ, Leng YN, Huang YW, Meng XC, Leng BR, Wang DC, Zhu YL. Photocatalytic Radical Cascade Dehalogenation/Carbo-cyclization/Sulfonylation Leading to Indole- and Benzofuran-Based Benzylic Sulfones. J Org Chem 2023. [PMID: 38019169 DOI: 10.1021/acs.joc.3c02068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
This study presents a convenient approach to the synthesis of indole- and benzofuran-based benzylic sulfones using unactivated alkynes containing aryl iodides and sodium sulfinates under visible light irradiation. The procedure involves a sequential series of dehalogenation, carbo-cyclization, and radical sulfonylation. Plausible insights into the reaction mechanism are derived from control experiments, leading to the proposal of a radical cascade reaction pathway.
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Affiliation(s)
- Qing-Quan Liu
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 211816, P. R. China
| | - Jia-Zhuo Li
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 211816, P. R. China
| | - Yan-Jing Wang
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 211816, P. R. China
| | - Yan-Ning Leng
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 211816, P. R. China
| | - Yu-Wen Huang
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 211816, P. R. China
| | - Xin-Chao Meng
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 211816, P. R. China
| | - Bo-Rong Leng
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 211816, P. R. China
- College of Life and Health, Nanjing Polytechnic Institute, Nanjing 211816, P. R. China
| | - De-Cai Wang
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 211816, P. R. China
| | - Yi-Long Zhu
- School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 211816, P. R. China
- College of Life and Health, Nanjing Polytechnic Institute, Nanjing 211816, P. R. China
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4
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Jiang S, Wang W, Mou C, Zou J, Jin Z, Hao G, Chi YR. Facile access to benzofuran derivatives through radical reactions with heteroatom-centered super-electron-donors. Nat Commun 2023; 14:7381. [PMID: 37968279 PMCID: PMC10651860 DOI: 10.1038/s41467-023-43198-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 11/03/2023] [Indexed: 11/17/2023] Open
Abstract
The development of suitable electron donors is critical to single-electron-transfer (SET) processes. The use of heteroatom-centered anions as super-electron-donors (SEDs) for direct SET reactions has rarely been studied. Here we show that heteroatom anions can be applied as SEDs to initiate radical reactions for facile synthesis of 3-substituted benzofurans. Phosphines, thiols and anilines bearing different substitution patterns work well in this inter-molecular radical coupling reaction and the 3-functionalized benzofuran products bearing heteroatomic functionalities are given in moderate to excellent yields. The reaction mechanism is elucidated via control experiments and computational methods. The afforded products show promising applications in both organic synthesis and pesticide development.
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Affiliation(s)
- Shichun Jiang
- National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Guiyang, 550025, China
| | - Wei Wang
- National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Guiyang, 550025, China
| | - Chengli Mou
- Guizhou University of Traditional Chinese Medicine, Guiyang, 550025, China
| | - Juan Zou
- Guizhou University of Traditional Chinese Medicine, Guiyang, 550025, China
| | - Zhichao Jin
- National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Guiyang, 550025, China.
| | - Gefei Hao
- National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Guiyang, 550025, China.
| | - Yonggui Robin Chi
- National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Guiyang, 550025, China.
- School of Chemistry, Chemical Engineering, and Biotechnology, Nanyang Technological University, Singapore, 637371, Singapore.
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5
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Miyajima R, Ooe Y, Miura T, Ikoma T, Iwamoto H, Takizawa SY, Hasegawa E. Triarylamine-Substituted Benzimidazoliums as Electron Donor-Acceptor Dyad-Type Photocatalysts for Reductive Organic Transformations. J Am Chem Soc 2023; 145:10236-10248. [PMID: 37127911 DOI: 10.1021/jacs.3c01264] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Triarylamine-substituted benzimidazoliums (BI+-PhNAr2), new electron donor-acceptor dyad molecules, were synthesized. Their photocatalytic properties for reductive organic transformations were explored using absorption and fluorescence spectroscopy, redox potential determinations, density functional theory calculations, transient absorption spectroscopy, and reduction reactions of selected substrates. The results show that irradiation of BI+-PhNAr2 promotes photoinduced intramolecular electron transfer to form a long-lived (∼300 μs) charge shifted state (BI•-PhN•+Ar2). In the pathway for photocatalysis of reduction reactions of substrates, BI•-PhN•+Ar2 is subsequently transformed to the neutral benzimidazolyl radical (BI•-PhNAr2) by single-electron transfer from the donor 1,3-dimethyl-2-phenylbenzimidazoline (BIH-Ph) serving as a cooperative agent. Among the benzimidazoliums explored, the bromo-substituted analogue BI+-PhN(C6H4Br-p)2 in conjunction with BIH-Ph demonstrates the most consistent catalytic performance.
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Affiliation(s)
- Ryo Miyajima
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Yuuki Ooe
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Tomoaki Miura
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Tadaaki Ikoma
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Hajime Iwamoto
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Shin-Ya Takizawa
- Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Eietsu Hasegawa
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
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6
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Eckhardt P, Elliot Q, Alabugin IV, Opatz T. Two Paths to Oxidative C-H Amination Under Basic Conditions: A Theoretical Case Study Reveals Hidden Opportunities Provided by Electron Upconversion. Chemistry 2022; 28:e202201637. [PMID: 35880945 PMCID: PMC9804812 DOI: 10.1002/chem.202201637] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Indexed: 01/09/2023]
Abstract
Traditionally, cross-dehydrogenative coupling (CDC) leads to C-N bond formation under basic and oxidative conditions and is proposed to proceed via a two-electron bond formation mediated by carbenium ions. However, the formation of such high-energy intermediates is only possible in the presence of strong oxidants, which may lead to undesired side reactions and poor functional group tolerance. In this work we explore if oxidation under basic conditions allows the formation of three-electron bonds (resulting in "upconverted" highly-reducing radical-anions). The benefit of this "upconversion" process is in the ability to use milder oxidants (e. g., O2 ) and to avoid high-energy intermediates. Comparison of the two- and three-electron pathways using quantum mechanical calculations reveals that not only does the absence of a strong oxidant shut down two-electron pathways in favor of a three-electron path but, paradoxically, weaker oxidants react faster with the upconverted reductants by avoiding the inverted Marcus region for electron transfer.
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Affiliation(s)
- Paul Eckhardt
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10–1455128MainzGermany
| | - Quintin Elliot
- Department of Chemistry and BiochemistryFlorida State UniversityTallahasseeFlorida 32306USA
| | - Igor V. Alabugin
- Department of Chemistry and BiochemistryFlorida State UniversityTallahasseeFlorida 32306USA
| | - Till Opatz
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10–1455128MainzGermany
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7
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Charboneau DJ, Hazari N, Huang H, Uehling MR, Zultanski SL. Homogeneous Organic Electron Donors in Nickel-Catalyzed Reductive Transformations. J Org Chem 2022; 87:7589-7609. [PMID: 35671350 DOI: 10.1021/acs.joc.2c00462] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Many contemporary organic transformations, such as Ni-catalyzed cross-electrophile coupling (XEC), require a reductant. Typically, heterogeneous reductants, such as Zn0 or Mn0, are used as the electron source in these reactions. Although heterogeneous reductants are highly practical for preparative-scale batch reactions, they can lead to complications in performing reactions on process scale and are not easily compatible with modern applications, such as flow chemistry. In principle, homogeneous organic reductants can address some of the challenges associated with heterogeneous reductants and also provide greater control of the reductant strength, which can lead to new reactivity. Nevertheless, homogeneous organic reductants have rarely been used in XEC. In this Perspective, we summarize recent progress in the use of homogeneous organic electron donors in Ni-catalyzed XEC and related reactions, discuss potential synthetic and mechanistic benefits, describe the limitations that inhibit their implementation, and outline challenges that need to be solved in order for homogeneous organic reductants to be widely utilized in synthetic chemistry. Although our focus is on XEC, our discussion of the strengths and weaknesses of different methods for introducing electrons is general to other reductive transformations.
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Affiliation(s)
- David J Charboneau
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520, United States
| | - Nilay Hazari
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520, United States
| | - Haotian Huang
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520, United States
| | - Mycah R Uehling
- Discovery Chemistry, HTE and Lead Discovery Capabilities, Merck & Co., Inc., Kenilworth, New Jersey 07033, United States
| | - Susan L Zultanski
- Department of Process Research and Development, Merck & Co., Inc., Kenilworth, New Jersey 07033, United States
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9
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Franco M, Vargas EL, Tortosa M, Cid MB. Coupling of thiols and aromatic halides promoted by diboron derived super electron donors. Chem Commun (Camb) 2021; 57:11653-11656. [PMID: 34668910 DOI: 10.1039/d1cc05294b] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We have proven that pyridine-boryl complexes can be used as superelectron donors to promote the coupling of thiols and aromatic halides through a SRN1 mechanism. The reaction is efficient for a broad substrate scope, tolerating heterocycles including pyridines, enolizable or reducible functional groups. The method has been applied to intermediates in drug synthesis as well as interesting functionalized polythioethers through a controlled and consecutive intramolecular electron transfer process.
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Affiliation(s)
- Mario Franco
- Department of Organic Chemistry, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
| | - Emily L Vargas
- Department of Organic Chemistry, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
| | - Mariola Tortosa
- Department of Organic Chemistry, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain. .,Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - M Belén Cid
- Department of Organic Chemistry, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain. .,Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain
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10
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Yu D, To WP, Liu Y, Wu LL, You T, Ling J, Che CM. Direct photo-induced reductive Heck cyclization of indoles for the efficient preparation of polycyclic indolinyl compounds. Chem Sci 2021; 12:14050-14058. [PMID: 34760188 PMCID: PMC8565399 DOI: 10.1039/d1sc04258k] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 09/16/2021] [Indexed: 12/15/2022] Open
Abstract
The photo-induced cleavage of C(sp2)-Cl bonds is an appealing synthetic tool in organic synthesis, but usually requires the use of high UV light, photocatalysts and/or photosensitizers. Herein is described a direct photo-induced chloroarene activation with UVA/blue LEDs that can be used in the reductive Heck cyclization of indoles and without the use of a photocatalyst or photosensitizer. The indole compounds examined display room-temperature phosphorescence. The photochemical reaction tolerates a panel of functional groups including esters, alcohols, amides, cyano and alkenes (27 examples, 50-88% yields), and can be used to prepare polycyclic compounds and perform the functionalization of natural product analogues in moderate to good yields. Mechanistic experiments, including time-resolved absorption spectroscopy, are supportive of photo-induced electron transfer between the indole substrate and DIPEA, with the formation of radical intermediates in the photo-induced dearomatization reaction.
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Affiliation(s)
- Daohong Yu
- Department of Chemistry, Southern University of Science and Technology Shenzhen Guangdong 518055 China
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong China
- Key Laboratory of Organo-Pharmaceutical Chemistry of Jiangxi Province, Gannan Normal University Ganzhou 341000 China
| | - Wai-Pong To
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong China
| | - Yungen Liu
- Department of Chemistry, Southern University of Science and Technology Shenzhen Guangdong 518055 China
| | - Liang-Liang Wu
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong China
| | - Tingjie You
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong China
| | - Jesse Ling
- Laboratory for Synthetic Chemistry and Chemical Biology Limited Units 1503-1511, 15/F, Building 17W, Hong Kong Science Park New Territories Hong Kong China
| | - Chi-Ming Che
- Department of Chemistry, Southern University of Science and Technology Shenzhen Guangdong 518055 China
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong China
- HKU Shenzhen Institute of Research and Innovation Shenzhen Guangdong 518057 China
- Laboratory for Synthetic Chemistry and Chemical Biology Limited Units 1503-1511, 15/F, Building 17W, Hong Kong Science Park New Territories Hong Kong China
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11
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Okumura S, Uozumi Y. Photocatalytic Carbinol Cation/Anion Umpolung: Direct Addition of Aromatic Aldehydes and Ketones to Carbon Dioxide. Org Lett 2021; 23:7194-7198. [PMID: 34468148 DOI: 10.1021/acs.orglett.1c02592] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We have developed a new photocatalytic umpolung reaction of carbonyl compounds to generate anionic carbinol synthons. Aromatic aldehydes or ketones reacted with carbon dioxide in the presence of an iridium photocatalyst and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzimidazole (DMBI) as a reductant under visible-light irradiation to furnish the corresponding α-hydroxycarboxylic acids through nucleophilic addition of the resulting carbinol anions to electrophilic carbon dioxide.
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Affiliation(s)
- Shintaro Okumura
- Institute for Molecular Science (IMS), Myodaiji, Okazaki 444-8787, Japan
| | - Yasuhiro Uozumi
- Institute for Molecular Science (IMS), Myodaiji, Okazaki 444-8787, Japan
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12
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Frenette BL, Arsenault N, Walker SL, Decken A, Dyker CA. Bis(Iminophosphorano)-Substituted Pyridinium Ions and their Corresponding Bispyridinylidene Organic Electron Donors. Chemistry 2021; 27:8528-8536. [PMID: 33834560 DOI: 10.1002/chem.202100318] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Indexed: 12/22/2022]
Abstract
Optimized synthetic procedures for pyridinium ions featuring iminophosphorano (-N=PR3 ; R=Ph, Cy) π-donor substituents in the 2- and 4- positions are described. Crystallographic and theoretical studies reveal that the strongly donating substituents severely polarize the π-electrons of the pyridyl ring at the expense of aromaticity. Moreover, the pyridinium ions are readily deprotonated to generate powerful bispyridinylidene (BPY) organic electron donors. Electrochemical studies show exceptionally low redox potentials for the two-electron BPY/BPY2+ couples, ranging from -1.71 V vs the saturated calomel electrode for 3PhPh (with four Ph3 P=N- groups) to -1.85 V for 3CyCy (with four Cy3 P=N- groups). These new compounds represent the most reducing neutral organic electron donors (OEDs) currently known. Some preliminary reductions involving 3CyCy showed enhanced capability owing to its low redox potential, such as the thermally activated reduction of an aryl chloride, but purification challenges were often encountered.
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Affiliation(s)
- Brandon L Frenette
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - Nadine Arsenault
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - Sarah L Walker
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - Andreas Decken
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - C Adam Dyker
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
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13
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14
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Hasegawa E, Nakamura S, Oomori K, Tanaka T, Iwamoto H, Wakamatsu K. Competitive Desulfonylative Reduction and Oxidation of α-Sulfonylketones Promoted by Photoinduced Electron Transfer with 2-Hydroxyaryl-1,3-dimethylbenzimidazolines under Air. J Org Chem 2021; 86:2556-2569. [PMID: 33492136 DOI: 10.1021/acs.joc.0c02666] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Desulfonylation reactions of α-sulfonylketones promoted by photoinduced electron transfer with 2-hydroxyarylbenzimidazolines (BIH-ArOH) were investigated. Under aerobic conditions, photoexcited 2-hydroxynaphthylbenzimidazoline (BIH-NapOH) promotes competitive reduction (forming alkylketones) and oxidation (producing α-hydroxyketones) of sulfonylketones through pathways involving the intermediacy of α-ketoalkyl radicals. The results of an examination of the effects of solvents, radical trapping reagents, substituents of sulfonylketones, and a variety of hydroxyaryl- and aryl-benzimidazolines (BIH-ArOH and BIH-Ar) suggest that the oxidation products are produced by dissociation of α-ketoalkyl radicals from the initially formed solvent-caged radical ion pairs followed by reaction with molecular oxygen. In addition, the observations indicate that the reduction products are generated by proton or hydrogen atom transfer in solvent-caged radical ion pairs derived from benzimidazolines and sulfonylketones. The results also suggest that arylsulfinate anions arising by carbon-sulfur bond cleavage of sulfonylketone radical anions act as reductants in the oxidation pathway to convert initially formed α-hydroperoxyketones to α-hydroxyketones. Finally, density functional theory calculations were performed to explore the structures and properties of radical ions of sulfonylketones as well as BIH-NapOH.
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Affiliation(s)
- Eietsu Hasegawa
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Shyota Nakamura
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Kazuki Oomori
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Tsukasa Tanaka
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Hajime Iwamoto
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Kan Wakamatsu
- Department of Chemistry, Faculty of Science, Okayama University of Science, 1-1 Ridaicho, Kita-ku, Okayama 700-0005, Japan
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15
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Tintori G, Fall A, Assani N, Zhao Y, Bergé-Lefranc D, Redon S, Vanelle P, Broggi J. Generation of powerful organic electron donors by water-assisted decarboxylation of benzimidazolium carboxylates. Org Chem Front 2021. [DOI: 10.1039/d0qo01488e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
In situ and easy generation of organic electron donors from water-activation of carboxylate precursors allows OED-promoted intermolecular radical addition reactions.
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Affiliation(s)
- Guillaume Tintori
- Aix Marseille Univ
- CNRS
- Institut de Chimie Radicalaire ICR
- Faculté de Pharmacie
- 13005 Marseille
| | - Arona Fall
- Aix Marseille Univ
- CNRS
- Institut de Chimie Radicalaire ICR
- Faculté de Pharmacie
- 13005 Marseille
| | - Nadhrata Assani
- Aix Marseille Univ
- CNRS
- Institut de Chimie Radicalaire ICR
- Faculté de Pharmacie
- 13005 Marseille
| | - Yuxi Zhao
- Aix Marseille Univ
- CNRS
- Institut de Chimie Radicalaire ICR
- Faculté de Pharmacie
- 13005 Marseille
| | | | - Sébastien Redon
- Aix Marseille Univ
- CNRS
- Institut de Chimie Radicalaire ICR
- Faculté de Pharmacie
- 13005 Marseille
| | - Patrice Vanelle
- Aix Marseille Univ
- CNRS
- Institut de Chimie Radicalaire ICR
- Faculté de Pharmacie
- 13005 Marseille
| | - Julie Broggi
- Aix Marseille Univ
- CNRS
- Institut de Chimie Radicalaire ICR
- Faculté de Pharmacie
- 13005 Marseille
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16
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Messelberger J, Kumar M, Goodner SJ, Munz D. Wanzlick's equilibrium in tri- and tetraaminoolefins. Org Chem Front 2021. [DOI: 10.1039/d1qo01320c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
How to isolate small carbenes, previously reported to from dimers instantaneously, and how to split triaminoolefins into free carbenes.
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Affiliation(s)
- Julian Messelberger
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
| | - Manoj Kumar
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
| | - Stephen J. Goodner
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
- Friedrich-Alexander Universität Erlangen-Nürnberg, Department of Chemistry and Pharmacy: Chair of Inorganic and General Chemistry, Egerlandstraße 1, D-91058 Erlangen, Germany
| | - Dominik Munz
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
- Friedrich-Alexander Universität Erlangen-Nürnberg, Department of Chemistry and Pharmacy: Chair of Inorganic and General Chemistry, Egerlandstraße 1, D-91058 Erlangen, Germany
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17
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Gimeno L, Queffélec C, Mall Haidaraly K, Blart E, Pellegrin Y. Dehalogenation reaction photocatalyzed by homoleptic copper(i) complexes associated with strongly reductive sacrificial donors. Catal Sci Technol 2021. [DOI: 10.1039/d1cy01209f] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
To perform challenging reduction reactions with light at low cost and low toxicity, we use for the first time a reductive quenching cycle with a simple, strongly colored homoleptic copper(i) complex [Cu(dipp)2]+ (dipp = 2,9-diisopropyl-1,10-phen).
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Affiliation(s)
- Lea Gimeno
- CEISAM, UMR 6230, Université de Nantes, CNRS, 2 chemin de la Houssinière, Nantes F-44000, France
| | - Clémence Queffélec
- CEISAM, UMR 6230, Université de Nantes, CNRS, 2 chemin de la Houssinière, Nantes F-44000, France
| | - Kevin Mall Haidaraly
- CEISAM, UMR 6230, Université de Nantes, CNRS, 2 chemin de la Houssinière, Nantes F-44000, France
| | - Errol Blart
- CEISAM, UMR 6230, Université de Nantes, CNRS, 2 chemin de la Houssinière, Nantes F-44000, France
| | - Yann Pellegrin
- CEISAM, UMR 6230, Université de Nantes, CNRS, 2 chemin de la Houssinière, Nantes F-44000, France
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18
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Das A, Ahmed J, Rajendran NM, Adhikari D, Mandal SK. A Bottleable Imidazole-Based Radical as a Single Electron Transfer Reagent. J Org Chem 2021; 86:1246-1252. [PMID: 33280378 DOI: 10.1021/acs.joc.0c02465] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Reduction of 1,3-bis(2,6-diisopropylphenyl)-2,4-diphenyl-1H-imidazol-3-ium chloride (1) resulted in the formation of the first structurally characterized imidazole-based radical 2. 2 was established as a single electron transfer reagent by treating it with an acceptor molecule tetracyanoethylene. Moreover, radical 2 was utilized as an organic electron donor in a number of organic transformations such as in activation of an aryl-halide bond, alkene hydrosilylation, and in catalytic reduction of CO2 to methoxyborane, all under ambient temperature and pressure.
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Affiliation(s)
- Arpan Das
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, India
| | - Jasimuddin Ahmed
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, India
| | - N M Rajendran
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, India
| | - Debashis Adhikari
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, SAS Nagar, 140306, India
| | - Swadhin K Mandal
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, India
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19
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Richard NA, Khor CK, Hetherington SM, Mills SL, Decken A, Dyker CA. Iminophosphorano-Substituted Bispyridinylidenes: Redox Potentials and Substituent Constants from Tolman Electronic Parameters. Chemistry 2020; 26:17371-17375. [PMID: 33022780 DOI: 10.1002/chem.202004153] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 09/26/2020] [Indexed: 12/21/2022]
Abstract
Bispyridinylidenes (BPYs) have emerged as an important class of neutral organic electron donors, with redox potentials that vary widely with choice of substituent. Methods to predict the effect of substitution on the redox potential are therefore highly desirable. Here we show that the redox potential of BPYs featuring iminophosphorano substituents (R3 P=N-), which represent the most reducing class of BPYs, can be predicted based on the well-known Tolman electronic parameter (TEP) for the respective phosphine fragment (R3 P). Moreover, building on earlier work relating redox potentials to Hammett-type substituent constants, it is now possible to quantitatively predict σp + values for iminophosphorano substituents from TEP values. These results provide a path for precisely tailoring redox potentials of iminophosphorano-substituted BPYs, but also give quantitative descriptors for how these highly versatile iminophosphorano substituents can impact the properties of any molecular scaffold.
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Affiliation(s)
- Nicholas A Richard
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - Chun Keat Khor
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - Sydney M Hetherington
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - Scott L Mills
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - Andreas Decken
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - C Adam Dyker
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
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20
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Gualandi A, Nenov A, Marchini M, Rodeghiero G, Conti I, Paltanin E, Balletti M, Ceroni P, Garavelli M, Cozzi PG. Tailored Coumarin Dyes for Photoredox Catalysis: Calculation, Synthesis, and Electronic Properties. ChemCatChem 2020. [DOI: 10.1002/cctc.202001690] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Andrea Gualandi
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
| | - Artur Nenov
- Dipartimento di Chimica Industriale “T. Montanari” Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Marianna Marchini
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
| | - Giacomo Rodeghiero
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
- Cyanagen Srl Via Stradelli Guelfi 40/C 40138 Bologna Italy
| | - Irene Conti
- Dipartimento di Chimica Industriale “T. Montanari” Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Ettore Paltanin
- Dipartimento di Chimica Industriale “T. Montanari” Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Matteo Balletti
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
| | - Paola Ceroni
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
| | - Marco Garavelli
- Dipartimento di Chimica Industriale “T. Montanari” Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Pier Giorgio Cozzi
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
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21
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Zhang J, Yang JD, Cheng JP. Diazaphosphinyl radical-catalyzed deoxygenation of α-carboxy ketones: a new protocol for chemo-selective C-O bond scission via mechanism regulation. Chem Sci 2020; 11:8476-8481. [PMID: 34123107 PMCID: PMC8163385 DOI: 10.1039/d0sc03220d] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 07/27/2020] [Indexed: 11/22/2022] Open
Abstract
C-O bond cleavage is often a key process in defunctionalization of organic compounds as well as in degradation of natural polymers. However, it seldom occurs regioselectively for different types of C-O bonds under metal-free mild conditions. Here we report a facile chemo-selective cleavage of the α-C-O bonds in α-carboxy ketones by commercially available pinacolborane under the catalysis of diazaphosphinane based on a mechanism switch strategy. This new reaction features high efficiency, low cost and good group-tolerance, and is also amenable to catalytic deprotection of desyl-protected carboxylic acids and amino acids. Mechanistic studies indicated an electron-transfer-initiated radical process, underlining two crucial steps: (1) the initiator azodiisobutyronitrile switches originally hydridic reduction to kinetically more accessible electron reduction; and (2) the catalytic phosphorus species upconverts weakly reducing pinacolborane into strongly reducing diazaphosphinane.
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Affiliation(s)
- Jingjing Zhang
- Department of Chemistry, Center of Basic Molecular Science, Tsinghua University Beijing 100084 China
| | - Jin-Dong Yang
- Department of Chemistry, Center of Basic Molecular Science, Tsinghua University Beijing 100084 China
| | - Jin-Pei Cheng
- Department of Chemistry, Center of Basic Molecular Science, Tsinghua University Beijing 100084 China
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University Tianjin 300071 China
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22
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Glaser F, Larsen CB, Kerzig C, Wenger OS. Aryl dechlorination and defluorination with an organic super-photoreductant. Photochem Photobiol Sci 2020; 19:1035-1041. [PMID: 32588869 DOI: 10.1039/d0pp00127a] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Direct excitation of the commercially available super-electron donor tetrakis(dimethylamino)ethylene (TDAE) with light-emitting diodes at 440 or 390 nm provides a stoichiometric reductant that is able to reduce aryl chlorides and fluorides. The method is very simple and requires only TDAE, substrate, and solvent at room temperature. The photoactive excited state of TDAE has a lifetime of 17.3 ns in cyclohexane at room temperature and an oxidation potential of ca.-3.4 V vs. SCE. This makes TDAE one of the strongest photoreductants able to operate on the basis of single excitation with visible photons. Direct substrate activation occurs in benzene, but acetone is reduced by photoexcited TDAE and substrate reduction takes place by a previously unexplored solvent radical anion mechanism. Our work shows that solvent can have a leveling effect on the photochemically available redox power, reminiscent of the pH-leveling effect that solvent has in acid-base chemistry.
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Affiliation(s)
- Felix Glaser
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Christopher B Larsen
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Christoph Kerzig
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland.
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23
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Messelberger J, Grünwald A, Goodner SJ, Zeilinger F, Pinter P, Miehlich ME, Heinemann FW, Hansmann MM, Munz D. Aromaticity and sterics control whether a cationic olefin radical is resistant to disproportionation. Chem Sci 2020; 11:4138-4149. [PMID: 34760147 PMCID: PMC8562513 DOI: 10.1039/d0sc00699h] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 03/28/2020] [Indexed: 12/14/2022] Open
Abstract
We elucidate why some electron rich-olefins such as tetrathiafulvalene (TTF) or paraquat (1,1'-dimethyl-4,4'-bipyridinylidene) form persistent radical cations, whereas others such as the dimer of N,N'-dimethyl benzimidazolin-2-ylidene (benzNHC) do not. Specifically, three heterodimers derived from cyclic (alkyl) (amino) carbenes (CAAC) with N,N'-dimethyl imidazolin-2-ylidene (NHC), N,N'-dimethyl imidazolidin-2-ylidene (saNHC) and N-methyl benzothiazolin-2-ylidene (btNHC) are reported. Whereas the olefin radical cations with the NHC and btNHC are isolable, the NHC compound with a saturated backbone (saNHC) disproportionates instead to the biscation and olefin. Furthermore, the electrochemical properties of the electron-rich olefins derived from the dimerization of the saNHC and btNHC were assessed. Based on the experiments, we propose a general computational method to model the electrochemical potentials and disproportionation equilibrium. This method, which achieves an accuracy of 0.07 V (0.06 V with calibration) in reference to the experimental values, allows for the first time to rationalize and predict the (in)stability of olefin radical cations towards disproportionation. The combined results reveal that the stability of heterodimeric olefin radical cations towards disproportionation is mostly due to aromaticity. In contrast, homodimeric radical cations are in principle isolable, if lacking steric bulk in the 2,2' positions of the heterocyclic monomers. Rigid tethers increase accordingly the stability of homodimeric radical cations, whereas the electronic effects of substituents seem much less important for the disproportionation equilibrium.
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Affiliation(s)
- Julian Messelberger
- Lehrstuhl für Allgemeine und Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Annette Grünwald
- Lehrstuhl für Allgemeine und Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Stephen J Goodner
- Lehrstuhl für Allgemeine und Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Florian Zeilinger
- Lehrstuhl für Allgemeine und Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Piermaria Pinter
- Lehrstuhl für Allgemeine und Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Matthias E Miehlich
- Lehrstuhl für Allgemeine und Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Frank W Heinemann
- Lehrstuhl für Allgemeine und Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Max M Hansmann
- Institut für Organische und Biomolekulare Chemie, Georg-August Universität Göttingen Tammannstraße 2 37077 Göttingen Germany
- Organische Chemie, Technische Universität Dortmund Otto-Hahn-Str. 6 44227 Dortmund Germany
| | - Dominik Munz
- Lehrstuhl für Allgemeine und Anorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 1 91058 Erlangen Germany
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24
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Zhang J, Yang JD, Cheng JP. Exploiting the radical reactivity of diazaphosphinanes in hydrodehalogenations and cascade cyclizations. Chem Sci 2020; 11:4786-4790. [PMID: 34122935 PMCID: PMC8159257 DOI: 10.1039/d0sc01352h] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 04/22/2020] [Indexed: 12/19/2022] Open
Abstract
The remarkable reducibility of diazaphosphinanes has been extensively applied in various hydrogenations, based on and yet limited by their well-known hydridic reactivity. Here we exploited their unprecedented radical reactivity to implement hydrodehalogenations and cascade cyclizations originally inaccessible by hydride transfer. These reactions feature a broad substrate scope, high efficiency and simplicity of manipulation. Mechanistic studies suggested a radical chain process in which a phosphinyl radical is generated in a catalytic cycle via hydrogen-atom transfer from diazaphosphinanes. The radical reactivity of diazaphosphinanes disclosed here differs from their well-established hydridic reactivity, and hence, opens a new avenue for diazaphosphinane applications in organic syntheses.
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Affiliation(s)
- Jingjing Zhang
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University Beijing 100084 China
| | - Jin-Dong Yang
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University Beijing 100084 China
| | - Jin-Pei Cheng
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University Beijing 100084 China
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University Tianjin 300071 China
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25
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Hasegawa E, Yoshioka N, Tanaka T, Nakaminato T, Oomori K, Ikoma T, Iwamoto H, Wakamatsu K. Sterically Regulated α-Oxygenation of α-Bromocarbonyl Compounds Promoted Using 2-Aryl-1,3-dimethylbenzimidazolines and Air. ACS OMEGA 2020; 5:7651-7665. [PMID: 32280909 PMCID: PMC7144160 DOI: 10.1021/acsomega.0c00509] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 03/05/2020] [Indexed: 05/08/2023]
Abstract
A debrominative oxygenation protocol has been developed for the conversion of α-bromo-α,α-dialkyl-substituted carbonyl compounds to their corresponding α-hydroxy analogues. For example, stirring a solution of α-bromoisobutyrophenone and 2-aryl-1,3-dimethylbenzimidazoline (BIH-Ar) at room temperature under an air atmosphere leads to the efficient formation of α-hydroperoxyisobutyrophenone, which can be converted to α-hydroxyisobutyrophenone using Me2S reduction. In contrast, reaction of α-bromoacetophenone under the same conditions produces the α-hydrogenated product acetophenone. α-Keto-alkyl and benzimidazolyl radicals (BI•-Ar), generated via dissociative electron transfer from BIH-Ar to α-bromoketone substrates, serve as key intermediates in the oxidation and reduction processes. The dramatic switch from hydrogenation to oxygenation is attributed to a steric effect of α-alkyl substituents, which causes hydrogen atom abstraction from sterically crowded BIH-Ar to α-keto-alkyl radicals to be slow and enable preferential reaction with molecular oxygen. Generation of the α-keto-alkyl radical and BI•-Ar intermediates in these process and their sterically governed hydrogen atom transfer reactions are supported by results arising from DFT calculations. Moreover, an electron spin resonance study showed that visible light irradiation of phenyl benzimidazoline (BIH-Ph) in the presence of molecular oxygen produces the benzimidazolyl radical (BI•-Ph). The addition of thiophenol into the reaction of α-bromoisobutyrophenone and BIH-Ph predominantly produced α-phenylthiolated isobutyrophenone even if a high concentration of molecular oxygen exists. Furthermore, the developed protocol was applied to other α-bromo-α,α-dialkylated carbonyl compounds.
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Affiliation(s)
- Eietsu Hasegawa
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
- E-mail:
| | - Naoki Yoshioka
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Tsukasa Tanaka
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Taisei Nakaminato
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Kazuki Oomori
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Tadaaki Ikoma
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Hajime Iwamoto
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Kan Wakamatsu
- Department
of Chemistry, Faculty of Science, Okayama
University of Science, 1-1 Ridaicho, Kita-ku, Okayama 700-0005, Japan
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26
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Hasegawa E, Tanaka T, Izumiya N, Kiuchi T, Ooe Y, Iwamoto H, Takizawa SY, Murata S. Protocol for Visible-Light-Promoted Desulfonylation Reactions Utilizing Catalytic Benzimidazolium Aryloxide Betaines and Stoichiometric Hydride Donor Reagents. J Org Chem 2020; 85:4344-4353. [PMID: 32073264 DOI: 10.1021/acs.joc.0c00038] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
An unprecedented photocatalytic system consisting of benzimidazolium aryloxide betaines (BI+-ArO-) and stoichiometric hydride reducing reagents was developed for carrying out desulfonylation reactions of N-sulfonyl-indoles, -amides, and -amines, and α-sulfonyl ketones. Measurements of absorption spectra and cyclic voltammograms as well as density functional theory (DFT) calculations were carried out to gain mechanistic information. In the catalytic system, visible-light-activated benzimidazoline aryloxides (BIH-ArO-), generated in situ by hydride reduction of the corresponding betaines BI+-ArO-, donate both an electron and a hydrogen atom to the substrates. A modified protocol was also developed so that a catalytic quantity of more easily prepared hydroxyaryl benzimidazolines (BIH-ArOH) is used along with a stoichiometric hydride donor to promote the photochemical desulfonylation reactions.
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Affiliation(s)
- Eietsu Hasegawa
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Tsukasa Tanaka
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Norihiro Izumiya
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Takehiro Kiuchi
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Yuuki Ooe
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Hajime Iwamoto
- Department of Chemistry, Faculty of Science, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Shin-Ya Takizawa
- Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Shigeru Murata
- Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
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27
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Nozawa-Kumada K, Ito S, Noguchi K, Shigeno M, Kondo Y. Super electron donor-mediated reductive desulfurization reactions. Chem Commun (Camb) 2019; 55:12968-12971. [PMID: 31603153 DOI: 10.1039/c9cc06775b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The desulfurization of thioacetals and thioethers by a pyridine-derived electron donor is described. This methodology provides efficient access to the reduced products in high yields and does not require the use of transition-metals, elemental alkali-metals, or hydrogen atom donors.
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Affiliation(s)
- Kanako Nozawa-Kumada
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
| | - Shungo Ito
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
| | - Koto Noguchi
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
| | - Masanori Shigeno
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
| | - Yoshinori Kondo
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
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