1
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Shilov RA, Podkorytov IS, Kisel KS, Galenko EE, Karpitskaya DO, Rodionov IA, Shakirova JR, Tunik SP. DPPM-Bridged Binuclear Pt(II) Pincer Complexes: Chemistry, Structure, and Photophysics in Solution Revisited. Inorg Chem 2024; 63:11194-11208. [PMID: 38836300 DOI: 10.1021/acs.inorgchem.4c00984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
A series of luminescent binuclear ([dppm{Pt(NNC)}2]2+) and mononuclear ([PPh3Pt(NNC)]+) complexes containing pincer ligands were synthesized and characterized. Photophysical characteristics of both types of complexes were studied in dichloromethane solution. In the solid phase, the binuclear compounds adopt a syn configuration where the {Pt(NNC)} fragments are held together due to intramolecular Pt-Pt bonding and π-stacking of the pincer ligand aromatic systems. Analysis of the complexes' molecular structure in solution by multinuclear NMR spectroscopy showed that the stacked intramolecular configuration is retained in fluid media, which is in complete agreement with a considerable red shift of the emission wavelength due to formation of the intramolecular Pt-Pt bond, leading to the transformation of an emissive excited state to 3MMLCT. It was also found that triethylamine quenches the emission of both types of complexes; the mechanism of quenching is a combination of dynamic and static channels of excited-state deactivation. In the case of binuclear complexes, deprotonation of the dppm methylene bridge by triethylamine also contributes to the chromophore quenching. To explain the observed chemistry of binuclear complex interactions with Et3N, a chemical equilibrium scheme was suggested, which was confirmed by quantitative monitoring of the 31P signal variations as a function of triethylamine concentration.
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Affiliation(s)
- Roman A Shilov
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Ivan S Podkorytov
- Biomolecular NMR Laboratory, St. Petersburg State University, 7-9 Universitetskaya Emb., 199034 Saint Petersburg, Russia
| | - Kristina S Kisel
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Ekaterina E Galenko
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Daria O Karpitskaya
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Ivan A Rodionov
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Julia R Shakirova
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Sergey P Tunik
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
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2
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Papadopoulos I, Bosveli A, Montagnon T, Zachilas I, Kalaitzakis D, Vassilikogiannakis G. Eosin, blue LEDs and DIPEA are employed in a simple synthesis of (poly)cyclic O, O- and N, O-acetals. Chem Commun (Camb) 2024; 60:5494-5497. [PMID: 38712582 DOI: 10.1039/d4cc01175a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
A simple procedure for the synthesis of (poly)cyclic O,O- and N,O-acetals from various enol ethers, N-acyl enamines or Boc-protected enamines has been developed. The key step is a photocatalytic Stork-Ueno-type cylization using the very simple metal-free conditions of catalytic eosin, diisopropylamine in the green solvent ethanol with blue LED irradition.
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Affiliation(s)
- Ioannis Papadopoulos
- Department of Chemistry, University of Crete, Vasilika Vouton, 71003, Iraklion, Crete, Greece.
| | - Artemis Bosveli
- Department of Chemistry, University of Crete, Vasilika Vouton, 71003, Iraklion, Crete, Greece.
| | - Tamsyn Montagnon
- Department of Chemistry, University of Crete, Vasilika Vouton, 71003, Iraklion, Crete, Greece.
| | - Ioannis Zachilas
- Department of Chemistry, University of Crete, Vasilika Vouton, 71003, Iraklion, Crete, Greece.
| | - Dimitris Kalaitzakis
- Department of Chemistry, University of Crete, Vasilika Vouton, 71003, Iraklion, Crete, Greece.
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3
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Li B, Zhang HH, Luo Y, Yu S, Goddard Iii WA, Dang Y. Interception of Transient Allyl Radicals with Low-Valent Allylpalladium Chemistry: Tandem Pd(0/II/I)-Pd(0/II/I/II) Cycles in Photoredox/Pd Dual-Catalytic Enantioselective C(sp 3)-C(sp 3) Homocoupling. J Am Chem Soc 2024; 146:6377-6387. [PMID: 38385755 DOI: 10.1021/jacs.4c00676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
We present comprehensive computational and experimental studies on the mechanism of an asymmetric photoredox/Pd dual-catalytic reductive C(sp3)-C(sp3) homocoupling of allylic electrophiles. In stark contrast to the canonical assumption that photoredox promotes bond formation via facile reductive elimination from high-valent metal-organic species, our computational analysis revealed an intriguing low-valent allylpalladium pathway that features tandem operation of Pd(0/II/I)-Pd(0/II/I/II) cycles. Specifically, we propose that (i) the photoredox/Pd system enables the in situ generation of allyl radicals from low-valent Pd(I)-allyl species, and (ii) effective interception of the fleeting allyl radical by the chiral Pd(I)-allyl species results in the formation of an enantioenriched product. Notably, the cooperation of the two pathways highlights the bifunctional role of Pd(I)-allyl species in the generation and interception of transient allyl radicals. Moreover, the mechanism implies divergent substrate-activation modes in this homocoupling reaction, suggesting a theoretical possibility for cross-coupling. Combined, the current study offers a novel mechanistic hypothesis for photoredox/Pd dual catalysis and highlights the use of low-valent allylpalladium as a means to efficiently intercept radicals for selective asymmetric bond constructions.
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Affiliation(s)
- Bo Li
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China
- Materials and Process Simulation Center, Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States
| | - Hong-Hao Zhang
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, People's Republic of China
| | - Yongrui Luo
- Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, PR China
| | - Shouyun Yu
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, People's Republic of China
| | - William A Goddard Iii
- Materials and Process Simulation Center, Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States
| | - Yanfeng Dang
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China
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4
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Hu LY, Zhang SY, Zhu L, Li Y, Luo K, Wu L. "Boomerang" Strategy in Carbohydrate Chemistry: Diastereoselective Synthesis of C-Glycosylated Benzothiazoles from ortho-Isocyanophenyl Thioglycosides. Org Lett 2024; 26:215-220. [PMID: 38117978 DOI: 10.1021/acs.orglett.3c03817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
This paper reveals a novel "boomerang" strategy in the expedient and diastereoselective synthesis of C-nucleoside analogues. Bench-stable ortho-isocyanophenyl thioglycosides can be converted to glycosyl radicals through rapid and efficient C-S bond homolysis when they are irradiated by visible light. The glycosyl radicals are subsequently trapped by the corresponding leaving group or other radical acceptors to provide diverse C-nucleoside analogues under mild conditions.
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Affiliation(s)
- Li-Yan Hu
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Shen-Yuan Zhang
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Li Zhu
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Yang Li
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Kai Luo
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Lei Wu
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China
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5
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Bosveli A, Griboura N, Kampouropoulos I, Kalaitzakis D, Montagnon T, Vassilikogiannakis G. The Rapid Synthesis of Colibactin Warhead Model Compounds Using New Metal-Free Photocatalytic Cyclopropanation Reactions Facilitates the Investigation of Biological Mechanisms. Chemistry 2023; 29:e202301713. [PMID: 37452669 DOI: 10.1002/chem.202301713] [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: 05/30/2023] [Revised: 07/06/2023] [Accepted: 07/11/2023] [Indexed: 07/18/2023]
Abstract
Herein, we report the synthesis of a series of colibactin warhead model compounds using two newly developed metal-free photocatalytic cyclopropanation reactions. These mild cyclopropanations expand the known applications of eosin within synthesis. A halogen atom transfer reaction mode has been harnessed so that dihalides can be used as the cyclopropanating agents. The colibactin warhead models were then used to provide new insight into two key mechanisms in colibactin chemistry. An explanation is provided for why the colibactin warhead sometimes undergoes a ring expansion-addition reaction to give fused cyclobutyl products while at other times nucleophiles add directly to the cyclopropyl unit (as when DNA adds to colibactin). Finally, we provide some evidence that Cu(II) chelated to colibactin may catalyze an important oxidation of the colibactin-DNA adduct. The Cu(I) generated as a result could then also play a role in inducing double strand breaks in DNA.
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Affiliation(s)
- Artemis Bosveli
- Department of Chemistry, University of Crete, Vasilika Vouton, 71003, Iraklion, Crete
| | - Nefeli Griboura
- Department of Chemistry, University of Crete, Vasilika Vouton, 71003, Iraklion, Crete
| | | | - Dimitris Kalaitzakis
- Department of Chemistry, University of Crete, Vasilika Vouton, 71003, Iraklion, Crete
| | - Tamsyn Montagnon
- Department of Chemistry, University of Crete, Vasilika Vouton, 71003, Iraklion, Crete
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6
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Tagami K, Ofuji Y, Kanbara T, Yajima T. Metal-free visible-light-induced hydroxy-perfluoroalkylation of conjugated olefins using enamine catalyst. RSC Adv 2022; 12:32790-32795. [PMID: 36425182 PMCID: PMC9667149 DOI: 10.1039/d2ra06679c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Accepted: 11/05/2022] [Indexed: 07/22/2023] Open
Abstract
We developed a simple and sustainable method for the hydroxy-perfluoroalkylation of electron-deficient conjugated olefins and styrenes. In this protcol, in situ generated enamine forms electron-donor-accepter (EDA) complexes with perfluoroalkyl iodide, and reaction proceed with visible-light irradiation. Tertiary amine also interacts with perfluoroalkyl iodide via halogen-bonding, promoting the perfluoroalkyl radical generation. This reaction does not require any transition-metal or photoredox catalyst, and gaseous oxygen is used as the green hydroxy source. Moreover, various commercially available substrates and perfluoroalkyl iodides were tolerated, affording the desired hydroxy-perfluoroalkylated products in good to moderate yields (>50 examples, up to 90%).
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Affiliation(s)
- Koto Tagami
- Department of Chemistry, Faculty of Science, Ochanomizu University Otsuka, Bunkyo-ku Tokyo 112-8610 Japan
| | - Yu Ofuji
- Department of Chemistry, Faculty of Science, Ochanomizu University Otsuka, Bunkyo-ku Tokyo 112-8610 Japan
| | - Tadashi Kanbara
- Department of Chemistry, Faculty of Science, Ochanomizu University Otsuka, Bunkyo-ku Tokyo 112-8610 Japan
| | - Tomoko Yajima
- Department of Chemistry, Faculty of Science, Ochanomizu University Otsuka, Bunkyo-ku Tokyo 112-8610 Japan
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7
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Zhou H, Fan R, Yang J, Sun X, Liu X, Wang XC. N, N-Diisopropylethylamine-Mediated Electrochemical Reduction of Azobenzenes in Dichloromethane. J Org Chem 2022; 87:14536-14543. [PMID: 36269896 DOI: 10.1021/acs.joc.2c01949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report a cathodic reduction-dominated electrochemical approach for the hydrogenation of azobenzenes in dichloromethane. With cheap and readily available N,N-diisopropylethylamine as a catalytic mediator, the reaction proceeded smoothly in a simple undivided cell under constant-current electrolysis. A series of azobenzenes were successfully reduced to the corresponding hydrazobenzenes in moderate to high yields at room temperature. Preliminarily mechanistic studies indicate that solvent dichloromethane acts as a hydrogen source. The use of a common solvent as a hydrogen source, no need for stoichiometric mediators or metallic reductants, and mild conditions make this work a more straightforward and sustainable protocol for hydrogenation of azobenzenes.
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Affiliation(s)
- Hongyan Zhou
- College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China.,College of Science, Gansu Agricultural University, Lanzhou 730070, China
| | - Rundong Fan
- College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China
| | - Jingya Yang
- College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China
| | - Ximei Sun
- College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China
| | - Xiaojun Liu
- College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China
| | - Xi-Cun Wang
- College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China
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8
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Zeng W, Li L, Wang C, Wang D, Zhou L. Synthesis of 3‐Amino‐1‐(difluoromethylidene)‐tetralins via Relay Photocatalytic Cascade Reactions of Arylalanines and 2‐Bromo‐3,3,3‐trifluoropropene. Adv Synth Catal 2022. [DOI: 10.1002/adsc.202200612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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9
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Immel JR, Bloom S. carba-Nucleopeptides (cNPs): A Biopharmaceutical Modality Formed through Aqueous Rhodamine B Photoredox Catalysis. Angew Chem Int Ed Engl 2022; 61:e202205606. [PMID: 35507689 PMCID: PMC9256812 DOI: 10.1002/anie.202205606] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Indexed: 12/14/2022]
Abstract
Exchanging the ribose backbone of an oligonucleotide for a peptide can enhance its physiologic stability and nucleic acid binding affinity. Ordinarily, the eneamino nitrogen atom of a nucleobase is fused to the side chain of a polypeptide through a new C-N bond. The discovery of C-C linked nucleobases in the human transcriptome reveals new opportunities for engineering nucleopeptides that replace the traditional C-N bond with a non-classical C-C bond, liberating a captive nitrogen atom and promoting new hydrogen bonding and π-stacking interactions. We report the first late-stage synthesis of C-C linked carba-nucleopeptides (cNPs) using aqueous Rhodamine B photoredox catalysis. We prepare brand-new cNPs in batch, in parallel, and in flow using three long-wavelength photochemical setups. We detail the mechanism of our reaction by experimental and computational studies and highlight the essential role of diisopropylethylamine as a bifurcated two-electron reductant.
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Affiliation(s)
- Jacob R Immel
- Department of Medicinal Chemistry, University of Kansas, Lawrence, KS 66045, USA
| | - Steven Bloom
- Department of Medicinal Chemistry, University of Kansas, Lawrence, KS 66045, USA
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10
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Immel JR, Bloom S. carba
‐Nucleopeptides (
c
NPs): A Biopharmaceutical Modality Formed through Aqueous Rhodamine B Photoredox Catalysis. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202205606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Jacob R. Immel
- Department of Medicinal Chemistry University of Kansas Lawrence KS 66045 USA
| | - Steven Bloom
- Department of Medicinal Chemistry University of Kansas Lawrence KS 66045 USA
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11
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Kwon K, Simons RT, Nandakumar M, Roizen JL. Strategies to Generate Nitrogen-centered Radicals That May Rely on Photoredox Catalysis: Development in Reaction Methodology and Applications in Organic Synthesis. Chem Rev 2022; 122:2353-2428. [PMID: 34623809 PMCID: PMC8792374 DOI: 10.1021/acs.chemrev.1c00444] [Citation(s) in RCA: 116] [Impact Index Per Article: 58.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
For more than 70 years, nitrogen-centered radicals have been recognized as potent synthetic intermediates. This review is a survey designed for use by chemists engaged in target-oriented synthesis. This review summarizes the recent paradigm shift in access to and application of N-centered radicals enabled by visible-light photocatalysis. This shift broadens and streamlines approaches to many small molecules because visible-light photocatalysis conditions are mild. Explicit attention is paid to innovative advances in N-X bonds as radical precursors, where X = Cl, N, S, O, and H. For clarity, key mechanistic data is noted, where available. Synthetic applications and limitations are summarized to illuminate the tremendous utility of photocatalytically generated nitrogen-centered radicals.
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Affiliation(s)
- Kitae Kwon
- Duke University, Department of Chemistry, Box 90346, Durham, North Carolina 27708-0354, United States
| | - R Thomas Simons
- Duke University, Department of Chemistry, Box 90346, Durham, North Carolina 27708-0354, United States
| | - Meganathan Nandakumar
- Duke University, Department of Chemistry, Box 90346, Durham, North Carolina 27708-0354, United States
| | - Jennifer L Roizen
- Duke University, Department of Chemistry, Box 90346, Durham, North Carolina 27708-0354, United States
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12
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Murray PD, Cox JH, Chiappini ND, Roos CB, McLoughlin EA, Hejna BG, Nguyen ST, Ripberger HH, Ganley JM, Tsui E, Shin NY, Koronkiewicz B, Qiu G, Knowles RR. Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis. Chem Rev 2022; 122:2017-2291. [PMID: 34813277 PMCID: PMC8796287 DOI: 10.1021/acs.chemrev.1c00374] [Citation(s) in RCA: 150] [Impact Index Per Article: 75.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Indexed: 12/16/2022]
Abstract
We present here a review of the photochemical and electrochemical applications of multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms in which both an electron and a proton are exchanged together, often in a concerted elementary step. As such, MS-PCET can function as a non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from a wide variety of common organic functional groups. We present an introduction to MS-PCET and a practitioner's guide to reaction design, with an emphasis on the unique energetic and selectivity features that are characteristic of this reaction class. We then present chapters on oxidative N-H, O-H, S-H, and C-H bond homolysis methods, for the generation of the corresponding neutral radical species. Then, chapters for reductive PCET activations involving carbonyl, imine, other X═Y π-systems, and heteroarenes, where neutral ketyl, α-amino, and heteroarene-derived radicals can be generated. Finally, we present chapters on the applications of MS-PCET in asymmetric catalysis and in materials and device applications. Within each chapter, we subdivide by the functional group undergoing homolysis, and thereafter by the type of transformation being promoted. Methods published prior to the end of December 2020 are presented.
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Affiliation(s)
- Philip
R. D. Murray
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - James H. Cox
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Nicholas D. Chiappini
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Casey B. Roos
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | | | - Benjamin G. Hejna
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Suong T. Nguyen
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Hunter H. Ripberger
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Jacob M. Ganley
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Elaine Tsui
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Nick Y. Shin
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Brian Koronkiewicz
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Guanqi Qiu
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Robert R. Knowles
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
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13
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Aydogan A, Bangle RE, Cadranel A, Turlington MD, Conroy DT, Cauët E, Singleton ML, Meyer GJ, Sampaio RN, Elias B, Troian-Gautier L. Accessing Photoredox Transformations with an Iron(III) Photosensitizer and Green Light. J Am Chem Soc 2021; 143:15661-15673. [PMID: 34529421 DOI: 10.1021/jacs.1c06081] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Efficient excited-state electron transfer between an iron(III) photosensitizer and organic electron donors was realized with green light irradiation. This advance was enabled by the use of the previously reported iron photosensitizer, [Fe(phtmeimb)2]+ (phtmeimb = {phenyl[tris(3-methyl-imidazolin-2-ylidene)]borate}, that exhibited long-lived and luminescent ligand-to-metal charge-transfer (LMCT) excited states. A benchmark dehalogenation reaction was investigated with yields that exceed 90% and an enhanced stability relative to the prototypical photosensitizer [Ru(bpy)3]2+. The initial catalytic step is electron transfer from an amine to the photoexcited iron sensitizer, which is shown to occur with a large cage-escape yield. For LMCT excited states, this reductive electron transfer is vectorial and may be a general advantage of Fe(III) photosensitizers. In-depth time-resolved spectroscopic methods, including transient absorption characterization from the ultraviolet to the infrared regions, provided a quantitative description of the catalytic mechanism with associated rate constants and yields.
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Affiliation(s)
- Akin Aydogan
- Université Catholique de Louvain (UCLouvain), Institut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Place Louis Pasteur 1, bte L4.01.02, 1348 Louvain-la-Neuve, Belgium
| | - Rachel E Bangle
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Alejandro Cadranel
- Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.,Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Inorgánica, Analítica y Química Física, Pabellón 2, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina.,CONICET - Universidad de Buenos Aires. Instituto de Química Física de Materiales, Medio Ambiente y Energía (INQUIMAE), Pabellón 2, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina
| | - Michael D Turlington
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Daniel T Conroy
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Emilie Cauët
- Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (CP 160/09), Université Libre de Bruxelles, 50 av. F. D. Roosevelt, B-1050 Brussels, Belgium
| | - Michael L Singleton
- Université Catholique de Louvain (UCLouvain), Institut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Place Louis Pasteur 1, bte L4.01.02, 1348 Louvain-la-Neuve, Belgium
| | - Gerald J Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Renato N Sampaio
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
| | - Benjamin Elias
- Université Catholique de Louvain (UCLouvain), Institut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Place Louis Pasteur 1, bte L4.01.02, 1348 Louvain-la-Neuve, Belgium
| | - Ludovic Troian-Gautier
- Université Catholique de Louvain (UCLouvain), Institut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Place Louis Pasteur 1, bte L4.01.02, 1348 Louvain-la-Neuve, Belgium.,Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States.,Laboratoire de Chimie Organique, Université Libre de Bruxelles (ULB), CP 160/06, 50 avenue F.D. Roosevelt, 1050 Brussels, Belgium
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14
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Zhang HH, Tang M, Zhao JJ, Song C, Yu S. Enantioselective Reductive Homocoupling of Allylic Acetates Enabled by Dual Photoredox/Palladium Catalysis: Access to C2-Symmetrical 1,5-Dienes. J Am Chem Soc 2021; 143:12836-12846. [PMID: 34351745 DOI: 10.1021/jacs.1c06271] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Transition-metal-catalyzed reductive coupling reactions have emerged as powerful protocols to construct C-C bonds. However, the development of enantioselective C(sp3)-C(sp3) reductive coupling remains challenging. Herein, we report a highly regio-, diastereo-, and enantioselective reductive homocoupling of allylic acetates through cooperative palladium and photoredox catalysis using diisopropylethylamine or Hantzsch ester as a homogeneous organic reductant. This straightforward protocol enables the stereoselective construction of C(sp3)-C(sp3) bonds under mild reaction conditions. A series of C2-symmetrical chiral 1,5-dienes were easily prepared with excellent enantioselectivities (up to >99% ee), diastereoselectivities (up to >95:5 dr), and regioselectivities (up to >95:5 rr). The resultant chiral 1,5-dienes can be directly used as chiral ligands in asymmetric synthesis, and they can be also transformed into other valuable chiral ligands.
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Affiliation(s)
- Hong-Hao Zhang
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, People's Republic of China
| | - Menghan Tang
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, People's Republic of China
| | - Jia-Jia Zhao
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, People's Republic of China
| | - Changhua Song
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, People's Republic of China
| | - Shouyun Yu
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, People's Republic of China
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15
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Dewanji A, Bülow RF, Rueping M. Photoredox/Nickel Dual-Catalyzed Reductive Cross Coupling of Aryl Halides Using an Organic Reducing Agent. Org Lett 2020; 22:1611-1617. [DOI: 10.1021/acs.orglett.0c00199] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Abhishek Dewanji
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
| | - Raoul F. Bülow
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
| | - Magnus Rueping
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
- King Abdullah University of Science and Technology (KAUST), KAUST Catalysis Center (KCC), Thuwal 23955-6900, Saudi Arabia
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16
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Supranovich VI, Chernov GN, Levin VV, Dilman AD. Photoredox Fluoroalkylation of Arylidene and Alkylidene Amidrazones. European J Org Chem 2019. [DOI: 10.1002/ejoc.201901672] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Grigory N. Chernov
- N. D. Zelinsky Institute of Organic Chemistry; Leninsky prosp. 47 119991 Moscow Russian Federation
- Department of Chemistry; Moscow State University; Leninskie Gory 1-3 119991 Moscow Russian Federation
| | - Vitalij V. Levin
- N. D. Zelinsky Institute of Organic Chemistry; Leninsky prosp. 47 119991 Moscow Russian Federation
| | - Alexander D. Dilman
- N. D. Zelinsky Institute of Organic Chemistry; Leninsky prosp. 47 119991 Moscow Russian Federation
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17
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Deguchi M, Fujiya A, Yamaguchi E, Tada N, Uno B, Itoh A. Organic dye-catalyzed radical ring expansion reaction. RSC Adv 2018; 8:15825-15830. [PMID: 35539500 PMCID: PMC9080073 DOI: 10.1039/c8ra02383b] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 04/23/2018] [Indexed: 12/03/2022] Open
Abstract
Herein, we reported an attractive method for synthesizing medium-sized rings that are catalyzed by erythrosine B under fluorescent light irradiation. This synthetic approach featured mild conditions, a facile procedure, a broad substrate scope, and moderate-to-good yields. Herein, we reported an attractive method for synthesizing medium-sized rings that are catalyzed by erythrosine B under fluorescent light irradiation.![]()
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Affiliation(s)
- Masato Deguchi
- Gifu Pharmaceutical University 1-25-4, Daigaku-nishi Gifu 501-1196 Japan
| | - Akitoshi Fujiya
- Gifu Pharmaceutical University 1-25-4, Daigaku-nishi Gifu 501-1196 Japan
| | - Eiji Yamaguchi
- Gifu Pharmaceutical University 1-25-4, Daigaku-nishi Gifu 501-1196 Japan
| | - Norihiro Tada
- Gifu Pharmaceutical University 1-25-4, Daigaku-nishi Gifu 501-1196 Japan
| | - Bunji Uno
- Gifu Pharmaceutical University 1-25-4, Daigaku-nishi Gifu 501-1196 Japan
| | - Akichika Itoh
- Gifu Pharmaceutical University 1-25-4, Daigaku-nishi Gifu 501-1196 Japan
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18
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Lee KN, Ngai MY. Recent developments in transition-metal photoredox-catalysed reactions of carbonyl derivatives. Chem Commun (Camb) 2017; 53:13093-13112. [PMID: 29125152 PMCID: PMC5930931 DOI: 10.1039/c7cc06287g] [Citation(s) in RCA: 102] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Single-electron reduction of C[double bond, length as m-dash]O and C[double bond, length as m-dash]N bonds of aldehydes, ketones, and imines results in the formation of ketyl and α-aminoalkyl anion radicals, respectively. These reactive intermediates are characterized by an altered electronic character with respect to their parent molecules and undergo a diverse range of synthetically useful transformations, which are not available to even-electron species. This Review summarizes the reactions of ketyl and α-aminyl radicals generated from carbonyl derivatives under transition-metal photoredox-catalysed conditions. We primarily focus on recent developments in the field, as well as give a brief overview of catalytic enantioselective transformations that provide a means to achieve precise stereocontrol over the reactivity of ion radicals.
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Affiliation(s)
- Katarzyna N Lee
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA.
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19
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Michelet B, Deldaele C, Kajouj S, Moucheron C, Evano G. A General Copper Catalyst for Photoredox Transformations of Organic Halides. Org Lett 2017; 19:3576-3579. [PMID: 28598630 DOI: 10.1021/acs.orglett.7b01518] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
A broadly applicable copper catalyst for photoredox transformations of organic halides is reported. Upon visible light irradiation in the presence of catalytic amounts of [(DPEphos)(bcp)Cu]PF6 and an amine, a range of unactivated aryl and alkyl halides were shown to be smoothly activated through a rare Cu(I)/Cu(I)*/Cu(0) catalytic cycle. This complex efficiently catalyzes a series of radical processes, including reductions, cyclizations, and direct arylation of arenes.
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Affiliation(s)
- Bastien Michelet
- Laboratoire de Chimie Organique and ‡Laboratoire de Chimie Organique et Photochimie, Service de Chimie et PhysicoChimie Organiques, Université libre de Bruxelles (ULB) , Avenue F. D. Roosevelt 50, CP160/06, 1050 Brussels, Belgium
| | - Christopher Deldaele
- Laboratoire de Chimie Organique and ‡Laboratoire de Chimie Organique et Photochimie, Service de Chimie et PhysicoChimie Organiques, Université libre de Bruxelles (ULB) , Avenue F. D. Roosevelt 50, CP160/06, 1050 Brussels, Belgium
| | - Sofia Kajouj
- Laboratoire de Chimie Organique and ‡Laboratoire de Chimie Organique et Photochimie, Service de Chimie et PhysicoChimie Organiques, Université libre de Bruxelles (ULB) , Avenue F. D. Roosevelt 50, CP160/06, 1050 Brussels, Belgium
| | - Cécile Moucheron
- Laboratoire de Chimie Organique and ‡Laboratoire de Chimie Organique et Photochimie, Service de Chimie et PhysicoChimie Organiques, Université libre de Bruxelles (ULB) , Avenue F. D. Roosevelt 50, CP160/06, 1050 Brussels, Belgium
| | - Gwilherm Evano
- Laboratoire de Chimie Organique and ‡Laboratoire de Chimie Organique et Photochimie, Service de Chimie et PhysicoChimie Organiques, Université libre de Bruxelles (ULB) , Avenue F. D. Roosevelt 50, CP160/06, 1050 Brussels, Belgium
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20
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Bertocchi MJ, Bajpai A, Moorthy JN, Weiss RG. New Insights into an Old Problem. Fluorescence Quenching of Sterically-Graded Pyrenes by Tertiary Aliphatic Amines. J Phys Chem A 2017; 121:458-470. [DOI: 10.1021/acs.jpca.6b11382] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Alankriti Bajpai
- Department
of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India
| | - Jarugu N. Moorthy
- Department
of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India
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21
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Yoshioka E, Kohtani S, Jichu T, Fukazawa T, Nagai T, Kawashima A, Takemoto Y, Miyabe H. Aqueous-Medium Carbon-Carbon Bond-Forming Radical Reactions Catalyzed by Excited Rhodamine B as a Metal-Free Organic Dye under Visible Light Irradiation. J Org Chem 2016; 81:7217-29. [PMID: 27314306 DOI: 10.1021/acs.joc.6b01102] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The utility of rhodamine B as a water-soluble organic photocatalyst was studied in the cascade radical addition-cyclization-trapping reactions under visible light irradiation. In the presence of (i-Pr)2NEt, the electron transfer from the excited rhodamine B to perfluoroalkyl iodides proceeded smoothly to promote the carbon-carbon bond-forming radical reactions in aqueous media. When i-C3F7I was employed as a radical precursor, the aqueous-medium radical reactions proceeded even in the absence of (i-Pr)2NEt. In these reactions, the direct electron transfer from the excited singlet state of rhodamine B would take place. Furthermore, the cleavage of the C-I bond in less reactive i-PrI could be achieved by the reductive electron transfer from the excited rhodamine B, which was confirmed by the fluorescence quenching of rhodamine B with the addition of i-PrI.
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Affiliation(s)
- Eito Yoshioka
- School of Pharmacy, Hyogo University of Health Sciences , Minatojima, Chuo-ku, Kobe, 650-8530, Japan
| | - Shigeru Kohtani
- School of Pharmacy, Hyogo University of Health Sciences , Minatojima, Chuo-ku, Kobe, 650-8530, Japan
| | - Takahisa Jichu
- School of Pharmacy, Hyogo University of Health Sciences , Minatojima, Chuo-ku, Kobe, 650-8530, Japan
| | - Takuya Fukazawa
- School of Pharmacy, Hyogo University of Health Sciences , Minatojima, Chuo-ku, Kobe, 650-8530, Japan
| | - Toyokazu Nagai
- School of Pharmacy, Hyogo University of Health Sciences , Minatojima, Chuo-ku, Kobe, 650-8530, Japan
| | - Akira Kawashima
- School of Pharmacy, Hyogo University of Health Sciences , Minatojima, Chuo-ku, Kobe, 650-8530, Japan
| | - Yoshiji Takemoto
- Graduate School of Pharmaceutical Sciences, Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hideto Miyabe
- School of Pharmacy, Hyogo University of Health Sciences , Minatojima, Chuo-ku, Kobe, 650-8530, Japan
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22
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Rautela R, Arora P, Joshi NK, Pant S, Joshi HC. Fluorescence quenching of 8-methyl quinolinium: An efficient halide indicator mechanism. J Mol Liq 2016. [DOI: 10.1016/j.molliq.2016.03.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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23
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Yagafarov NZ, Kolesnikov PN, Usanov DL, Novikov VV, Nelyubina YV, Chusov D. The synthesis of sterically hindered amines by a direct reductive amination of ketones. Chem Commun (Camb) 2016; 52:1397-400. [DOI: 10.1039/c5cc08577b] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An atom-economical methodology for the synthesis of sterically hindered tertiary amines was developed, which is based on a complementary Rh- and Ru-catalyzed direct reductive amination of ketones with primary and secondary amines using carbon monoxide as a deoxygenating agent.
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Affiliation(s)
- Niyaz Z. Yagafarov
- A.N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences
- Moscow
- Russian Federation
| | - Pavel N. Kolesnikov
- A.N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences
- Moscow
- Russian Federation
| | - Dmitry L. Usanov
- A.N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences
- Moscow
- Russian Federation
| | - Valentin V. Novikov
- A.N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences
- Moscow
- Russian Federation
| | - Yulia V. Nelyubina
- A.N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences
- Moscow
- Russian Federation
| | - Denis Chusov
- A.N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences
- Moscow
- Russian Federation
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24
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Singh A, Kubik JJ, Weaver JD. Photocatalytic C-F alkylation; facile access to multifluorinated arenes. Chem Sci 2015; 6:7206-7212. [PMID: 29861956 PMCID: PMC5947535 DOI: 10.1039/c5sc03013g] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 09/14/2015] [Indexed: 01/09/2023] Open
Abstract
C-F functionalizations that provide C-C bonds are challenging synthetic transformations, due in part to the large C-F bond strength, short bond length, nonpolarizable nature, the production of fluoride, and the regioselectivity-in the case of multifluorinated substrates. However, commercially available highly fluorinated arenes possess great synthetic potential because they already possess the C-F bonds in the desired locations that would be difficult to selectively fluorinate. In order to take advantage of this potential, selective C-F functionalizations must be developed. Herein, we disclose conditions for the photocatalytic reductive alkylation of highly fluorinated arenes with ubiquitous and unactivated alkenes. The mild reaction conditions provide for a broad functional group scope, and the reaction is remarkably efficient using just 0.25 mol% catalyst. Finally, we demonstrate the utility of the strategy by converting highly fluorinated arenes to elaborate (hetero)arenes that contain 2-5 Caryl-F bonds via synergistic use of photocatalysis and SNAr chemistry.
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Affiliation(s)
- A Singh
- 107 Physical Science , Department of Chemistry , Oklahoma State University , USA .
| | - J J Kubik
- 107 Physical Science , Department of Chemistry , Oklahoma State University , USA .
| | - J D Weaver
- 107 Physical Science , Department of Chemistry , Oklahoma State University , USA .
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25
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Photohydrogenation of Acetophenone Using Coumarin Dye-Sensitized Titanium Dioxide under Visible Light Irradiation. Catalysts 2015. [DOI: 10.3390/catal5031417] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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26
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Jeffrey JL, Petronijević FR, MacMillan DWC. Selective Radical-Radical Cross-Couplings: Design of a Formal β-Mannich Reaction. J Am Chem Soc 2015; 137:8404-7. [PMID: 26075347 PMCID: PMC4629778 DOI: 10.1021/jacs.5b05376] [Citation(s) in RCA: 192] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A direct β-coupling of cyclic ketones with imines has been accomplished via the synergistic combination of photoredox catalysis and organocatalysis. Transient β-enaminyl radicals derived from ketones via enamine and oxidative photoredox catalysis readily combine with persistent α-amino radicals in a highly selective hetero radical-radical coupling. This novel pathway to γ-aminoketones is predicated upon the use of DABCO as both a base and an electron transfer agent. This protocol also formally allows for the direct synthesis of β-Mannich products via a chemoselective three-component coupling of aryl aldehydes, amines, and ketones.
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Affiliation(s)
| | | | - David W. C. MacMillan
- Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States
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27
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Yoshioka E, Kohtani S, Tanaka E, Hata Y, Miyabe H. Carbon radical addition–cyclization reaction induced by ruthenium-photocatalyst under visible light irradiation. Tetrahedron 2015. [DOI: 10.1016/j.tet.2014.12.068] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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28
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Fagnoni M, Protti S, Ravelli D, Albini A. Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes. Beilstein J Org Chem 2013; 9:800-8. [PMID: 23766793 PMCID: PMC3678633 DOI: 10.3762/bjoc.9.91] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 04/03/2013] [Indexed: 11/23/2022] Open
Abstract
Steady-state irradiation in neat acetonitrile of some aromatic nitriles, imides and esters (10(-5)-10(-3) M solution) in the presence of tertiary amines allowed the accumulation of the corresponding radical anions, up to quantitative yield for polysubstituted benzenes and partially with naphthalene and anthracene derivatives. The condition for such an accumulation was that the donor radical cation underwent further evolution that precluded back electron transfer and any chemical reaction with the radical anion. In fact, no accumulation occurred with 1,4-diazabicyclo[2.2.2]octane (DABCO), for which this condition is not possible. The radical anions were produced from benzene polyesters too, but decomposition began early. Ipso substitution was one of the paths with secondary amines and the only reaction with tetrabutylstannane. The results fully support the previously proposed mechanism for electron transfer (ET) mediated photochemical alkylation of aromatic acceptors via radical ions and radical intermediates.
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Affiliation(s)
- Maurizio Fagnoni
- PhotoGreen Lab, Department of Chemistry, University of Pavia, V. Le Taramelli 12, 27100 Pavia, Italy
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29
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Goez M, Frisch I, Sartorius I. Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP. Beilstein J Org Chem 2013; 9:437-46. [PMID: 23504286 PMCID: PMC3596088 DOI: 10.3762/bjoc.9.46] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 02/06/2013] [Indexed: 11/26/2022] Open
Abstract
The photoreactions of diazabicyclo[2,2,2]octane (DABCO) and triisopropylamine (TIPA) with the sensitizers anthraquinone (AQ) and xanthone (XA) or benzophenone (BP) were investigated by time-resolved photo-CIDNP (photochemically induced dynamic nuclear polarization) experiments. By varying the radical-pair concentration, it was ensured that these measurements respond only to self-exchange reactions of the free amine-derived radicals (radical cations DH•+ or α-amino alkyl radicals D•) with the parent amine DH; the acid–base equilibrium between DH•+ and D• also plays no role. Although the sensitizer does not at all participate in the observed processes, it has a pronounced influence on the CIDNP kinetics because the reaction occurs through successive radical pairs. With AQ, the polarizations stem from the initially formed radical-ion pairs, and escaping DH•+ then undergoes electron self-exchange with DH. In the reaction sensitized with XA (or BP), the polarizations arise in a secondary pair of neutral radicals that is rapidly produced by in-cage proton transfer, and the CIDNP kinetics are due to hydrogen self-exchange between escaping D• and DH. For TIPA, the activation parameters of both self-exchange reactions were determined. Outer-sphere reorganization energies obtained with the Marcus theory gave very good agreement between experimental and calculated values of ∆G‡298.
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Affiliation(s)
- Martin Goez
- Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, Kurt-Mothes-Str. 2, 06120 Halle/Saale, Germany
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30
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Chen CH, Huang YC, Liao WC, Lim TS, Liu KL, Chen IC, Luh TY. Controlling Conformations in Alternating Dialkylsilylene-Spaced Donor-Acceptor Copolymers by a Cooperative Thorpe-Ingold Effect and Polymer Folding. Chemistry 2011; 18:334-46. [DOI: 10.1002/chem.201102032] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 08/25/2011] [Indexed: 11/06/2022]
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31
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Jie Y, Livant P, Li H, Yang M, Zhu W, Cammarata V, Almond P, Sullens T, Qin Y, Bakker E. An Acyclic Trialkylamine Virtually Planar at Nitrogen. Some Chemical Consequences of Nitrogen Planarity. J Org Chem 2010; 75:4472-9. [DOI: 10.1021/jo100628v] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yuanping Jie
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312
| | - Peter Livant
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312
| | - Hui Li
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312
| | - Minmin Yang
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312
| | - Wei Zhu
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312
| | - Vince Cammarata
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312
| | - Philip Almond
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312
| | - Tyler Sullens
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312
| | - Yu Qin
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312
| | - Eric Bakker
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312
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32
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Jager WF, Hammink TS, van den Berg O, Grozema FC. Highly Sensitive Water-Soluble Fluorescent pH Sensors Based on the 7-Amino-1-methylquinolinium Chromophore. J Org Chem 2010; 75:2169-78. [DOI: 10.1021/jo902225k] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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33
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Yousefi R, Gaudin JC, Chobert JM, Pourpak Z, Moin M, Moosavi-Movahedi AA, Haertle T. Micellisation and immunoreactivities of dimeric β-caseins. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1794:1775-83. [DOI: 10.1016/j.bbapap.2009.08.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Revised: 07/26/2009] [Accepted: 08/13/2009] [Indexed: 11/28/2022]
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34
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Kim D, Scranton AB, Stansbury JW. Effect of the electron donor structure on the shelf-lifetime of visible-light activated three-component initiator systems. J Appl Polym Sci 2009. [DOI: 10.1002/app.30770] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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35
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Anbazhagan V, Kathiravan A, Jhonsi MA, Renganathan R. Fluorescence Quenching Study on Electron Transfer from Certain Amines to Excited State Triphenylpyrylium Ion (TPP+). ACTA ACUST UNITED AC 2009. [DOI: 10.1524/zpch.2007.221.7.929] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The fluorescence quenching of excited singlet state of 2,4,6-triphenylpyrylium tetrafluoroborate (TPPBF4 or TPP+), a very good electron acceptor by amines were investigated in a acetonitrile solution using steady state technique. The bimolecular quenching rate constants lie in the range 2.11–10.26 × 1010 M-1 s-1. The driving force (ΔGet) for electron transfer process was calculated from the oxidation potential of amines and the reduction potential of TPP+. The observed k
q values correlated well with the driving force for the electron transfer reactions. Aromatic amines show higher k
q than aliphatic amines. From the oxidation potential of amines and the quenching rate constant values, a mechanism involving photoinduced electron transfer from amines to excited state TPP is suggested.
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Goez M, Henbest KB, Windham EG, Maeda K, Timmel CR. Quenching mechanisms and diffusional pathways in micellar systems unravelled by time-resolved magnetic-field effects. Chemistry 2009; 15:6058-64. [PMID: 19405051 DOI: 10.1002/chem.200802502] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Magnetic-field effects (MFEs) are used to investigate the photoreaction of xanthone (A) and DABCO (D) in anionic (SDS) or cationic (DTAC) micelles at high pH (DABCO = 1,4-diazabicyclo[2.2.2]octane, SDS = sodium dodecyl sulfate, DTAC = dodecyl trimethyl ammonium chloride). From MFE experiments with nanosecond time resolution, the radical anion A(.)(-) can be observed without any interference from the much more strongly absorbing triplet (3)A*, the different quenching processes can be separated and their rates can be measured. Triplet (3)A* is quenched dynamically both by the SDS micelle (k(1) = 5.0x10(5) s(-1)) and by DABCO approaching from the aqueous phase (k(2) = 2.0x10(9) M(-1) s(-1)). Static quenching by solubilised DABCO (association constant with the SDS micelles, 1.5 M(-1)) also participates at high DABCO concentrations, but is chemically nonproductive and does not lead to MFE generation. The MFEs stemming from the radical ion pairs A(.)(-) D(.)(+) are about 40 times larger in the anionic micelles than in the cationic ones despite a higher yield of free radicals in the latter case. This can be rationalised by different diffusional dynamics: Because of the location of their precursors, A(.)(-) and D(.)(+) are formed at opposite sides of the micelle boundary. Subsequently, the negatively charged Stern layer of the SDS micelle traps the radical cation, which then undergoes surface diffusion, so both the recombination probability and the spin mixing are high; in contrast, the positive surface charge of the DTAC micelle forces the radical cation into the bulk of the solution, thus efficiently blocking a recombination.
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Affiliation(s)
- Martin Goez
- Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, Kurt-Mothes-Str. 2, 06120 Halle/Saale, Germany.
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Kim D, Stansbury JW. A photo-oxidizable kinetic pathway of three-component photoinitiator systems containing porphrin dye (Zn-tpp), an electron donor and diphenyl iodonium salt. ACTA ACUST UNITED AC 2009. [DOI: 10.1002/pola.23401] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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38
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Yang M, Albrecht-Schmitt T, Cammarata V, Livant P, Makhanu DS, Sykora R, Zhu W. Trialkylamines More Planar at Nitrogen Than Triisopropylamine in the Solid State. J Org Chem 2009; 74:2671-8. [DOI: 10.1021/jo802086h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Minmin Yang
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, and Department of Chemistry, University of South Alabama, Mobile, Alabama 36688-0002
| | - Thomas Albrecht-Schmitt
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, and Department of Chemistry, University of South Alabama, Mobile, Alabama 36688-0002
| | - Vince Cammarata
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, and Department of Chemistry, University of South Alabama, Mobile, Alabama 36688-0002
| | - Peter Livant
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, and Department of Chemistry, University of South Alabama, Mobile, Alabama 36688-0002
| | - David S. Makhanu
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, and Department of Chemistry, University of South Alabama, Mobile, Alabama 36688-0002
| | - Richard Sykora
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, and Department of Chemistry, University of South Alabama, Mobile, Alabama 36688-0002
| | - Wei Zhu
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, and Department of Chemistry, University of South Alabama, Mobile, Alabama 36688-0002
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Prashanthi S, Bangal PR. Reductive quenching of pyridine linked porphyrins by phenol: a case of proton coupled electron transfer. Chem Commun (Camb) 2009:1757-9. [DOI: 10.1039/b818892k] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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40
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Investigations on the fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene by certain flavonoids. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2008; 91:143-50. [DOI: 10.1016/j.jphotobiol.2008.03.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2007] [Revised: 03/08/2008] [Accepted: 03/11/2008] [Indexed: 11/22/2022]
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41
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Pischel U, Heller B. Molecular logic devices (half-subtractor, comparator, complementary output circuit) by controlling photoinduced charge transfer processes. NEW J CHEM 2008. [DOI: 10.1039/b710216j] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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42
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Anbazhagan V, Kandavelu V, Kathiravan A, Renganathan R. Investigation on the fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by certain estrogens and catechols. J Photochem Photobiol A Chem 2008. [DOI: 10.1016/j.jphotochem.2007.06.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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43
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Broglia MF, Bertolotti SG, Previtali CM. Proton and Electron Transfer in the Excited State Quenching of Phenosafranine by Aliphatic Amines†. Photochem Photobiol 2007; 83:535-41. [PMID: 17576369 DOI: 10.1562/2006-07-31-ra-989] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The quenching of the excited singlet and triplet states of phenosafranine by aliphatic amines was investigated in acetonitrile and methanol. The rate constants for the quenching of the excited singlet state depend on the one-electron redox potential of the amine suggesting a charge transfer process. However, for the triplet state, quenching dependence on the redox potential either is opposite to the expectation or there is not dependence at all. Moreover, in MeOH the first-order rate constant for the decay of the triplet state, k(obs) presents a downward curvature as a function of the amine concentration. This behavior was interpreted in terms of the reversible formation of an intermediate excited complex, and from a kinetic analysis the equilibrium constant K(exc) could be extracted. The log K(exc) shows a linear relationship with the pKb of the amine. On the other hand, for the triplet state quenching in acetonitrile k(obs) varies linearly with the amine concentration. Nevertheless, the quenching rate constants correlate satisfactorily with pKb and not with the redox potential. The results were interpreted in terms of a proton transfer quenching, reversible in the case of MeOH and irreversible in MeCN. This was further confirmed by the transient absorption spectra obtained by laser flash photolysis. The transient absorption immediately after the triplet state quenching could be assigned to the unprotonated form of the dye. At later times the spectrum matches the semireduced form of the dye. The overall process corresponds to a one-electron reduction of the dye mediated by the deprotonated triplet state.
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Affiliation(s)
- Martín F Broglia
- Departamento de Química, Universidad Nacional de Río Cuarto, Río Cuarto, Argentina
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Abad S, Bosca F, Domingo LR, Gil S, Pischel U, Miranda MA. Triplet Reactivity and Regio-/Stereoselectivity in the Macrocyclization of Diastereomeric Ketoprofen−Quencher Conjugates via Remote Hydrogen Abstractions. J Am Chem Soc 2007; 129:7407-20. [PMID: 17508750 DOI: 10.1021/ja0712827] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Intramolecular excited triplet state interactions in diastereomeric compounds composed of a benzophenone chromophore (ketoprofen) and various hydrogen donor moieties (tetrahydrofuran, isopropylbenzene) have been investigated by laser flash photolysis. The rate constants for hydrogen abstraction by excited triplet benzophenone are in the order of 10(4)-10(5) s(-1), with the highest reactivity for the tetrahydrofuran residue. A remarkable diastereodifferentiation, expressed in the triplet lifetimes of the carbonyl chromophore (e.g., 1.6 versus 2.7 micros), has been found for these compounds. With an alkylaromatic moiety as donor, related effects have been observed, albeit strongly dependent on the length of the spacer. The reactivity trend for the initial hydrogen transfer step is paralleled by the quantum yields of the overall photoreaction. The biradicals, formed via remote hydrogen abstraction, undergo intramolecular recombination to macrocyclic ring systems. The new photoproducts have been isolated and characterized by NMR spectroscopy. The stereochemistry of the macrocycles, which contain up to four asymmetric carbons, has been unambiguously assigned on the basis of single-crystal structures and/or NOE effects. Interestingly, a highly regio- and stereoselective macrocyclization has been found for the ketoprofen-tetrahydrofuran conjugates, where hydrogen abstraction from the less substituted carbon is exclusive; cisoid ring junction is always preferred over the transoid junction. The photoreaction is less regioselective for compounds with an isopropylbenzene residue. The reactivity and selectivity trends have been rationalized by DFT (B3LYP/6-31G*) calculations.
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Affiliation(s)
- Sergio Abad
- Instituto de Tecnología Química, UPV-CSIC, Universidad Politécnica de Valencia, Av. de los Naranjos s/n, E-46022 Valencia, Spain
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Shikhova E, Danilov EO, Kinayyigit S, Pomestchenko IE, Tregubov AD, Camerel F, Retailleau P, Ziessel R, Castellano FN. Excited-State Absorption Properties of Platinum(II) Terpyridyl Acetylides. Inorg Chem 2007; 46:3038-48. [PMID: 17378551 DOI: 10.1021/ic0618652] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A comprehensive photophysical study is presented which compares the ground- and excited-state properties of four platinum(II) terpyridyl acetylide compounds of the general formula [Pt(tBu3tpy)(CCR)]+, where tBu3tpy is 4,4',4' '-tri-tert-butyl-2,2':6',2' '-terpyridine and R is an alkyl or aryl group. [Ru(tBu3tpy)3]2+ and the pivotal synthetic precursor [Pt(tBu3tpy)Cl]+ were also investigated in the current work. The latter two complexes possess short excited-state lifetimes and were investigated using ultrafast spectrometry while the other four compounds were evaluated using conventional nanosecond transient-absorption spectroscopy. The original intention of this study was to comprehend the nature of the impressive excited-state absorptions that emanate from this class of transition-metal chromophores. Transient-absorbance-difference spectra across the series contain the same salient features, which are modulated only slightly in wavelength and markedly in intensity as a function of the appended acetylide ligand. More intense absorption transients are observed in the arylacetylide structures relative to those bearing an alkylacetylide, consistent with transitions coupled to the pi system of the ancillary ligand. Reductive spectroelectrochemical measurements successfully generated the electronic spectrum of the tBu3tpy radical anion in all six complexes at room temperature. These measurements confirm that electronic absorptions associated with the tBu3tpy radical anion simply do not account for the intense optical transitions observed in the excited state of the Pt(II) chromophores. Transient-trapping experiments using the spectroscopically silent reductive quencher DABCO clearly demonstrate the loss of most transient-absorption features in the acetylide complexes throughout the UV, visible, and near-IR regions following bimolecular excited-state electron transfer, suggesting that these features are strongly tied to the photogenerated hole which is delocalized across the Pt center and the ancillary acetylide ligand.
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Affiliation(s)
- Elena Shikhova
- Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA
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46
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Wang HW, Cheng YJ, Chen CH, Lim TS, Fann W, Lin CL, Chang YP, Lin KC, Luh TY. Photoinduced Electron Transfer in Silylene-Spaced Copolymers Having Alternating Donor−Acceptor Chromophores. Macromolecules 2007. [DOI: 10.1021/ma070119t] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hsian-Wen Wang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106; Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115; and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106
| | - Yen-Ju Cheng
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106; Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115; and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106
| | - Chih-Hsien Chen
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106; Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115; and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106
| | - Tsong-Shin Lim
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106; Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115; and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106
| | - Wunshain Fann
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106; Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115; and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106
| | - Cheng-Lan Lin
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106; Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115; and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106
| | - Yuan-Pin Chang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106; Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115; and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106
| | - Kin-Chuan Lin
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106; Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115; and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106
| | - Tien-Yau Luh
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 106; Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115; and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106
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47
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Hennig A, Florea M, Roth D, Enderle T, Nau WM. Design of peptide substrates for nanosecond time-resolved fluorescence assays of proteases: 2,3-Diazabicyclo[2.2.2]oct-2-ene as a noninvasive fluorophore. Anal Biochem 2007; 360:255-65. [PMID: 17134673 DOI: 10.1016/j.ab.2006.09.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Revised: 09/15/2006] [Accepted: 09/17/2006] [Indexed: 11/26/2022]
Abstract
Fluorescence protease assays were investigated with peptide substrates containing a 2,3-diazabicyclo[2.2.2]oct-2-ene-labeled asparagine (Dbo) as a fluorescent amino acid. The special characteristic of the fluorophore Dbo is its exceedingly long fluorescence lifetime (ca. 300 ns in water under air), which allows the use of nanosecond time-resolved fluorescence (Nano-TRF) detection to efficiently suppress shorter-lived background emission. In addition, the natural amino acids tryptophan and tyrosine can be employed as intramolecular fluorescence quenchers, which facilitates substrate design. Fourteen synthetic peptide substrates (composed of 2-19 amino acids) and five enzymes (trypsin, pepsin, carboxypeptidase A, leucine aminopeptidase, and chymotrypsin) were investigated and, in all 28 examined combinations, enzymatic activity was detected by monitoring the increase in steady state fluorescence with time and determining the reaction rates as kcat/Km values, which ranged from 0.2 to 80x10(6) M-1 min-1. The results suggest an excellent compatibility of the very small and hydrophilic fluorescent probe Dbo with solid-phase peptide synthesis and the investigated proteases. For all 14 peptides the fluorescence lifetimes before and after enzymatic cleavage were measured and Nano-TRF measurements were performed in 384-well microplates. The fluorescence lifetimes of the different peptides provide the basis for the rational design of Dbo-based fluorescent substrates for protease assays. Measurements in Nano-TRF mode revealed, in addition to efficient suppression of background fluorescence, an increased differentiation between cleaved and uncleaved substrate. The Dbo-based assays can be adapted for high-throughput screening.
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Affiliation(s)
- Andreas Hennig
- School of Engineering and Science, International University Bremen, Campus Ring 1, D-28759 Bremen, Germany
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48
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Thanasekaran P, Liao RT, Manimaran B, Liu YH, Chou PT, Rajagopal S, Lu KL. Photoluminescence Electron-Transfer Quenching of Rhenium(I) Rectangles with Amines. J Phys Chem A 2006; 110:10683-9. [PMID: 16970357 DOI: 10.1021/jp060391p] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electron-transfer (ET) reactions from aromatic amines to excited states of rhenium(I)-based molecular rectangles [{Re(CO)3(mu-bpy)Br}{Re(CO)3(mu-L)Br}]2 (bpy = 4,4'-bipyridine, L = 4,4'-dipyridylacetylene (dpa), I; L = 4,4'-dipyridylbutadiyne (dpb), II; and L = 1,4-bis(4'-pyridylethynyl)benzene (bpeb), III) were investigated in a dichloromethane solution using luminescence quenching techniques. Direct evidence for the ET reaction was obtained from the detection of the amine cation radical in this system using time-resolved transient absorption spectroscopy. The values of the luminescence quenching rate constants, kq, of the 3MLCT excited state of Re(I) rectangles with amines were found to be higher than those for the monomeric Re(I) complexes and other Re(I)-based metallacyclophanes. The observed kq values were correlated well with the driving force (Delta G degrees) for the ET reactions. In addition, a semiclassical theory of ET was successfully applied to the photoluminescence quenching of Re(I) rectangles with amines.
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Affiliation(s)
- P Thanasekaran
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
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Pischel U, Patra D, Koner AL, Nau WM. Investigation of Polar and Stereoelectronic Effects on Pure Excited-state Hydrogen Atom Abstractions from Phenols and Alkylbenzenes†. Photochem Photobiol 2006; 82:310-7. [PMID: 15882091 DOI: 10.1562/2005-02-07-ra-434] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The fluorescence quenching of singlet-excited 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by 22 phenols and 12 alkylbenzenes has been investigated. Quenching rate constants in acetonitrile are in the range of 10(8)-10(9) M(-1)s(-1) for phenols and 10(5)-10(6) M(-1)s(-1) for alkylbenzenes. In contrast to the quenching of triplet-excited benzophenone, no exciplexes are involved, so that a pure hydrogen atom transfer is proposed as quenching mechanism. This is supported by (1) pronounced deuterium isotope effects (kH/kD ca 4-6), which were observed for phenols and alkylbenzenes, and (2) a strongly endergonic thermodynamics for charge transfer processes (electron transfer, exciplex formation). In the case of phenols, linear free energy relationships applied, which led to a reaction constant of rho = -0.40, suggesting a lower electrophilicity of singlet-excited DBO than that of triplet-excited ketones and alkoxyl radicals. The reactivity of singlet-excited DBO exposes statistical, steric, polar and stereoelectronic effects on the hydrogen atom abstraction process in the absence of complications because of competitive exciplex formation.
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Affiliation(s)
- Uwe Pischel
- REQUIMTE/Department of Chemistry, University of Porto, Porto, Portugal.
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Chen H, Li S. Theoretical Study on the Photolysis Mechanism of 2,3-Diazabicyclo[2.2.2]oct-2-ene. J Am Chem Soc 2005; 127:13190-9. [PMID: 16173746 DOI: 10.1021/ja050002p] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A CASPT2/CASSCF study has been carried out to investigate the mechanism of the photolysis of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) under direct and triplet-sensitized irradiation. By exploring the detailed potential energy surfaces including intermediates, transition states, conical intersections, and singlet/triplet crossing points, for the first excited singlet (S(1)) and the low-lying triplet states (T(1), T(2), and T(3)), we provide satisfactory explanations of many experimental findings associated with the photophysical and photochemical processes of DBO. A key finding of this work is the existence of a significantly twisted S(1) minimum, which can satisfactorily explain the envelope of the broad emission band of DBO. It is demonstrated that the S(1) (n-pi*) intermediate can decay to the T(1) (n-pi*) state by undergoing intersystem crossing (rather inefficient) to the T(2) (pi-pi*) state followed by internal conversion to the T(1) state. The high fluorescence yield and the extraordinarily long lifetime of the singlet excited DBO are due to the presence of relatively high barriers, both for intersystem crossing and for C-N cleavage. The short lifetime of the triplet DBO is caused by fast radiationless decay to the ground state.
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Affiliation(s)
- Hui Chen
- Lab of Mesoscopic Chemistry, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing 210093, People's Republic of China
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