1
|
Ulmann N, Hioe J, Touraud D, Horinek D, Kunz W. Self-association as a solubility limiting factor of riboflavin in aqueous media. Phys Chem Chem Phys 2024; 26:18930-18942. [PMID: 38952212 DOI: 10.1039/d4cp02074j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/03/2024]
Abstract
Single crystal X-ray diffraction analysis of needle shaped riboflavin (RF) crystals revealed π-stacking of RF's isoalloxazine units (distance: 3.643-3.313 Å) with syn-orientated ribityl chains. In line with this, classical molecular dynamics (MD) (400 ns) using an isobaric-isothermal (NPT) ensemble of eight RF in a water box (〈V〉 ∼ 508.62 nm3, 〈p〉 = 1.11 bar) revealed anti-aligned aggregation of RF in water (COM-distance: 4 Å). Comparing umbrella sampling for the separation of two RF molecules to the separation of two lumichrome molecules, the similar mean potential force for the separation of RF and lumichrome (22.8 kJ mol-1; 24.4 kJ mol-1) proved dispersive interactions as the origin of RF's aggregation. Though stacking of RF is the major water-solubility limiting factor, the conformation of RF's ribityl chain may alter the solubility in water. Both, MD (in water) and COSMO-RS (in water continuum) predicted that conformations of RF with an extended ribityl chain are thermodynamically preferred over any conformations with internal hydrogen bonds between hydroxyl groups and nitrogen/oxygen atoms of the pyrimidine moiety of the flavin ring. Interestingly, COSMO-RS predicted the solubility of the extended conformation to be significantly lower than the latter leading to the very low average solubility of RF. Nuclear Overhauser effect measurements (NOESY) of the structurally related sodium riboflavin 5'-monophosphate (RF-PO4) in deuterium oxide confirmed π-stacking of the isoalloxazine rings. In conformity with the 350 times higher water-solubility of RF-PO4, NOESY also indicated a contorted conformation of the ribityl phosphate chain, whereas, for RF, indications for a contorted chain were not observed.
Collapse
Affiliation(s)
- Nadja Ulmann
- Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
| | - Johnny Hioe
- Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
| | - Didier Touraud
- Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
| | - Dominik Horinek
- Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
| | - Werner Kunz
- Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
| |
Collapse
|
2
|
Valera JS, López-Acosta Á, Hermans TM. Photoinitiated Transient Self-Assembly in a Catalytically Driven Chemical Reaction Cycle. Angew Chem Int Ed Engl 2024:e202406931. [PMID: 38770670 DOI: 10.1002/anie.202406931] [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: 04/11/2024] [Revised: 05/10/2024] [Accepted: 05/20/2024] [Indexed: 05/22/2024]
Abstract
Chemically fueled chemical reaction networks (CRNs) are essential in controlling dissipative self-assembly. A key challenge in the field is to store chemical fuel-precursors or "pre-fuels" in the system that are converted into activating or deactivating fuels in a catalytically controlled CRN. In addition, real-time control over catalysis in a CRN by light is highly desirable, but so far not yet achieved. Here we show a catalytically driven CRN that is photoinitiated with 450 nm light, producing activated monomers that go on to perform transient self-assembly. Monomer activation proceeds via photoredox catalysis, converting the monomer alcohol groups into the corresponding aldehydes that self-assemble into large supramolecular fibers. Monomer deactivation is achieved by organometallic catalysis that relies on pre-fuel hydrolysis to release formate (i.e. the deactivating fuel). Additionally, irradiation with 305 nm light accelerates the release of formate by photo-uncaging the pre-fuel, leading to a factor of ca. 2 faster deactivation of the monomer. Overall, we show transient self-assembly upon visible light photoactivation, and tunable life-times by ultraviolet light.
Collapse
Affiliation(s)
- Jorge S Valera
- IMDEA Nanociencia, C/ Faraday 9, 28049, Madrid, Spain
- Université de Strasbourg, CNRS, UMR7140, 4 Rue Blaise Pascal, 67081, Strasbourg, France
| | | | - Thomas M Hermans
- IMDEA Nanociencia, C/ Faraday 9, 28049, Madrid, Spain
- Université de Strasbourg, CNRS, UMR7140, 4 Rue Blaise Pascal, 67081, Strasbourg, France
| |
Collapse
|
3
|
Guo H, Qiu Y, Liu S, Zhang X, Zhao J. Tailoring flavin-based photosensitizers for efficient photooxidative coupling of benzylic amines. Phys Chem Chem Phys 2023; 26:161-173. [PMID: 38086643 DOI: 10.1039/d3cp04579j] [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
Photooxidative coupling of benzylic amines using naturally abundant O2 as an oxidant under visible light irradiation is an alternative green approach to synthesis imines and is of both fundamental and practical significance. We investigated the photophysical properties of flavin (FL) that is a naturally available sensitizer and its derivatives, i.e. 9-bromoflavin (MB-FL), 7,8-dibromoflavin (DB-FL) and 10-phenylflavin (Ph-FL), as well as the performance of these FL-based sensitizers (FLPSs) in the photooxidative coupling of benzylic amines to imines combining experimental and theoretical efforts. We showed that chemical functionalization with Br and phenyl effectively improves the photophysical properties of these FLPSs, in terms of absorption in the visible light range, singlet oxygen quantum yields, triplet lifetime, etc. Apart from nearly quantitative selectivity for the production of imines, the performance of DB-FL is superior to those of other FLPSs, and it is among the best photocatalysts for imine synthesis. Specifically, 0.5 mol% DB-FL is capable of converting 91% of 0.2 mmol benzylamine and more than 80% of 0.2 mmol fluorobenzylic amine derivatives into their corresponding imines in 5 h batch runs. Mechanistic investigation finely explained the observed photophysical properties of FLPSs and highlighted the dominant role of electron transfer in FLPS sensitized coupling of benzylic amines to imines. This work not only helps to understand the pathways for photocatalysis with FLPSs but also paves the way for the design of novel and efficient PSs to promote organic synthesis.
Collapse
Affiliation(s)
- Huimin Guo
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| | - Yang Qiu
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| | - Siyu Liu
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| | - Xiangyu Zhang
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| | - Jianzhang Zhao
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| |
Collapse
|
4
|
Kawamorita S, Li Z, Okamoto K, Naota T. Multistimuli-Responsive Chromism of Vinylene-Linked Bisflavin Based on the Aggregation and Redox Properties. Chemistry 2023; 29:e202202257. [PMID: 36380653 DOI: 10.1002/chem.202202257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 11/11/2022] [Accepted: 11/11/2022] [Indexed: 11/17/2022]
Abstract
Multistimuli-responsive chromism was observed for vinylene-linked bisflavin 1 a with an extended π-conjugated platform. The yellow emission of a dilute solution of 1 a in CHCl3 (0.2 mM) observed at 298 K under UV excitation was changed to orange or red emission upon (1) an increase of concentration, (2) a decrease of temperature, and (3) variation of the solvent. This is in contrast to the almost non stimuli-responsive chromism of the N-methylated bisflavin analogue 1 b and monoflavin 2 a. Mechanistic investigation by 1 H NMR analysis under various conditions revealed that the extended π-conjugation platform and imide moiety of 1 a generate controllability in the formation of lower- and higher-ordered aggregates, which induce variation of the emission color upon change. Bisflavin 1 a also exhibited redox-induced chromism, where the orange emission of 1 a was quenched by the addition of hydrazine under anaerobic conditions, and changed back to the original emission upon subsequent bubbling of O2 gas.
Collapse
Affiliation(s)
- Soichiro Kawamorita
- Department of Chemistry, Graduate School of Engineering Science, Osaka University Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
| | - Zimeng Li
- Department of Chemistry, Graduate School of Engineering Science, Osaka University Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
| | - Koyo Okamoto
- Department of Chemistry, Graduate School of Engineering Science, Osaka University Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
| | - Takeshi Naota
- Department of Chemistry, Graduate School of Engineering Science, Osaka University Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
| |
Collapse
|
5
|
Burlingham SJ, Guijarro D, Bosque I, Chinchilla R, Gonzalez-Gomez JC. Visible-light-mediated decarboxylative ( E)-alkenylation of aliphatic carboxylic acids with aryl styryl sulfones under metal-free conditions. Org Biomol Chem 2022; 20:7923-7928. [PMID: 36178275 DOI: 10.1039/d2ob01360f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The decarboxylative alkenylation of aliphatic carboxylic acids with aryl styryl sulfones is efficiently catalyzed by riboflavin tetraacetate under visible light irradiation at room temperature. This metal-free protocol is cost-efficient, environmentally friendly and provides the corresponding olefins with excellent (E)-diastereocontrol. The methodology can also be used to prepare internal alkynes regioselectively by using alkynyl sulfones as radical acceptors. The suitability as building blocks of the olefins obtained was demonstrated by performing an (E)- to (Z) photoisomerization, an iron-catalyzed allylic substitution of the phenoxy group derived from the 2-phenoxycarboxylic acid substrates, as well as syn-epoxidations, and diastereoselective intramolecular iodoarylations. Based on control experiments and DFT calculations, we proposed a reaction mechanism that accounts for the regio- and diastereo-selectivity observed.
Collapse
Affiliation(s)
- Sarah-Jayne Burlingham
- Instituto de Síntesis Orgánica (ISO) and Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain.
| | - David Guijarro
- Instituto de Síntesis Orgánica (ISO) and Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain.
| | - Irene Bosque
- Instituto de Síntesis Orgánica (ISO) and Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain.
| | - Rafael Chinchilla
- Instituto de Síntesis Orgánica (ISO) and Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain.
| | - Jose C Gonzalez-Gomez
- Instituto de Síntesis Orgánica (ISO) and Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain.
| |
Collapse
|
6
|
Guo H, Lei Z, Ma X, Liu S, Qiu Y, Zhao J. Boosting Sulfides Photooxidation by Fusing Naphthalimide and Flavin together. Phys Chem Chem Phys 2022; 24:15255-15264. [DOI: 10.1039/d2cp01368a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Efficient and selective photocatalytic conversion of chemicals with visible light and naturally abundant resources has long been desired, but this requires finely designed sensitizers that are capable to convert light...
Collapse
|
7
|
Trenker S, Grunenberg L, Banerjee T, Savasci G, Poller LM, Muggli KIM, Haase F, Ochsenfeld C, Lotsch BV. A flavin-inspired covalent organic framework for photocatalytic alcohol oxidation. Chem Sci 2021; 12:15143-15150. [PMID: 34909156 PMCID: PMC8612393 DOI: 10.1039/d1sc04143f] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 11/02/2021] [Indexed: 12/02/2022] Open
Abstract
Covalent organic frameworks (COFs) offer a number of key properties that predestine them to be used as heterogeneous photocatalysts, including intrinsic porosity, long-range order, and light absorption. Since COFs can be constructed from a practically unlimited library of organic building blocks, these properties can be precisely tuned by choosing suitable linkers. Herein, we report the construction and use of a novel COF (FEAx-COF) photocatalyst, inspired by natural flavin cofactors. We show that the functionality of the alloxazine chromophore incorporated into the COF backbone is retained and study the effects of this heterogenization approach by comparison with similar molecular photocatalysts. We find that the integration of alloxazine chromophores into the framework significantly extends the absorption spectrum into the visible range, allowing for photocatalytic oxidation of benzylic alcohols to aldehydes even with low-energy visible light. In addition, the activity of the heterogeneous COF photocatalyst is less dependent on the chosen solvent, making it more versatile compared to molecular alloxazines. Finally, the use of oxygen as the terminal oxidant renders FEAx-COF a promising and “green” heterogeneous photocatalyst. In this manuscript, we report the development of a novel alloxazine COF inspired by naturally occurring flavin cofactors for photoredox catalysis.![]()
Collapse
Affiliation(s)
- Stefan Trenker
- Max Planck Institute for Solid State Research Heisenbergstr. 1 70569 Stuttgart Germany .,Department of Chemistry, University of Munich (LMU) Butenandtstr. 5-13 81377 Munich Germany.,Center for Nanoscience Schellingstr. 4 80799 Munich Germany
| | - Lars Grunenberg
- Max Planck Institute for Solid State Research Heisenbergstr. 1 70569 Stuttgart Germany .,Department of Chemistry, University of Munich (LMU) Butenandtstr. 5-13 81377 Munich Germany
| | - Tanmay Banerjee
- Department of Chemistry, Birla Institute of Technology and Science Pilani, Pilani Campus Rajasthan 333031 India
| | - Gökcen Savasci
- Max Planck Institute for Solid State Research Heisenbergstr. 1 70569 Stuttgart Germany .,Department of Chemistry, University of Munich (LMU) Butenandtstr. 5-13 81377 Munich Germany.,Center for Nanoscience Schellingstr. 4 80799 Munich Germany.,Karlsruhe Institute of Technology (KIT), IFG - Institute for Functional Interfaces Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen Germany
| | - Laura M Poller
- Department of Chemistry, University of Munich (LMU) Butenandtstr. 5-13 81377 Munich Germany
| | - Katharina I M Muggli
- Department of Chemistry, University of Munich (LMU) Butenandtstr. 5-13 81377 Munich Germany
| | - Frederik Haase
- Karlsruhe Institute of Technology (KIT), IFG - Institute for Functional Interfaces Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen Germany
| | - Christian Ochsenfeld
- Max Planck Institute for Solid State Research Heisenbergstr. 1 70569 Stuttgart Germany .,Department of Chemistry, University of Munich (LMU) Butenandtstr. 5-13 81377 Munich Germany.,Center for Nanoscience Schellingstr. 4 80799 Munich Germany.,e-conversion Cluster of Excellence Lichtenbergstr. 4a, 85748 Garching Germany
| | - Bettina V Lotsch
- Max Planck Institute for Solid State Research Heisenbergstr. 1 70569 Stuttgart Germany .,Department of Chemistry, University of Munich (LMU) Butenandtstr. 5-13 81377 Munich Germany.,Center for Nanoscience Schellingstr. 4 80799 Munich Germany.,e-conversion Cluster of Excellence Lichtenbergstr. 4a, 85748 Garching Germany
| |
Collapse
|
8
|
Rehpenn A, Walter A, Storch G. Molecular Editing of Flavins for Catalysis. SYNTHESIS-STUTTGART 2021. [DOI: 10.1055/a-1458-2419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
AbstractThe diverse activity of flavoenzymes in organic transformations has fascinated researchers for a long time. However, when applied outside an enzyme environment, the isolated flavin cofactor only shows largely reduced activity. This highlights the importance of embedding the reactive isoalloxazine core of flavins in defined surroundings. The latter include crucial non-covalent interactions with amino acid side chains or backbone as well as controlled access to reactants such as molecular oxygen. Nevertheless, molecular flavins are increasingly applied in the organic laboratory as valuable organocatalysts. Chemical modification of the parent isoalloxazine structure is of particular interest in this context in order to achieve reactivity and selectivity in transformations, which are so far only known with flavoenzymes or even unprecedented. This review aims to give a systematic overview of the reported designed flavin catalysts and highlights the impact of each structural alteration. It is intended to serve as a source of information when comparing the performance of known catalysts, but also when designing new flavins. Over the last few decades, molecular flavin catalysis has emerged from proof-of-concept reactions to increasingly sophisticated transformations. This stimulates anticipating new flavin catalyst designs for solving contemporary challenges in organic synthesis.1 Introduction2 N1-Modification3 N3-Modification4 N5-Modification5 C6–C9-Modification6 N10-Modification7 Conclusion
Collapse
|
9
|
Liu J, Han S, Hu Y, Pao CW. Fabrication and characterization of a novel PMO containing riboflavin-5'-phosphate sodium salt for sensitive detection of pesticide ferbam. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.126375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
10
|
Berg N, Bergwinkl S, Nuernberger P, Horinek D, Gschwind RM. Extended Hydrogen Bond Networks for Effective Proton-Coupled Electron Transfer (PCET) Reactions: The Unexpected Role of Thiophenol and Its Acidic Channel in Photocatalytic Hydroamidations. J Am Chem Soc 2021; 143:724-735. [DOI: 10.1021/jacs.0c08673] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Nele Berg
- Institute of Organic Chemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Sebastian Bergwinkl
- Institute of Physical and Theoretical Chemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Patrick Nuernberger
- Institute of Physical and Theoretical Chemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Dominik Horinek
- Institute of Physical and Theoretical Chemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Ruth M. Gschwind
- Institute of Organic Chemistry, University of Regensburg, D-93053 Regensburg, Germany
| |
Collapse
|
11
|
Oka Y. Cesium Cation Complexation by a Flavin Receptor via Self-Assembly and Deprotonation. ACS OMEGA 2020; 5:21226-21230. [PMID: 32875259 PMCID: PMC7450633 DOI: 10.1021/acsomega.0c03006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 07/30/2020] [Indexed: 06/11/2023]
Abstract
This study focuses on the self-assembly of a new flavin compound and its scaffolding function for a Cs+ ion. 7,8-Dimethyl-10-[4'-(methoxycarbonyl)phenyl]-isoalloxazine (FlH-MB) displays self-assembly in a DMSO solution and has strong dependence on the solvent. In the DMSO solution, both the resulting scaffold and the deprotonation of FlH-MB were demonstrated to induce complex formation with a Cs+ ion, which was investigated by UV-vis, 1H NMR, and fluorescence titrations. This complex formation involves both Coulombic and cation-π interactions through the Fl- site in an Fl--MB dimer.
Collapse
Affiliation(s)
- Yoshimi Oka
- Research Promotion Institute, Oita University, 700 Dannoharu, Oita 870-1192, Japan
| |
Collapse
|
12
|
Guo H, Xia H, Ma X, Chen K, Dang C, Zhao J, Dick B. Efficient Photooxidation of Sulfides with Amidated Alloxazines as Heavy-atom-free Photosensitizers. ACS OMEGA 2020; 5:10586-10595. [PMID: 32426617 PMCID: PMC7227068 DOI: 10.1021/acsomega.0c01087] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 04/16/2020] [Indexed: 06/11/2023]
Abstract
Photooxidation utilizing visible light, especially with naturally abundant O2 as the oxygen source, has been well-accepted as a sustainable and efficient procedure in organic synthesis. To ensure the intersystem crossing and triplet quantum yield for efficient photosensitization, we prepared amidated alloxazines (AAs) and investigated their photophysical properties and performance as heavy-atom-free triplet photosensitizers and compared with those of flavin (FL) and riboflavin tetraacetate (RFTA). Because of the difference in the framework structure of AAs and FL and the introduction of carbonyl moiety, the absorption of FL at ∼450 nm is blue-shifted to ∼380 nm and weakened (ε = 8.7 × 103 for FL to ∼6.8 × 103 M-1 cm-1), but the absorption at ∼340 nm is red-shifted to ∼350 nm and enhanced by ∼50% (from ε = 6.4 × 103 for FL to ∼9.9 × 103 M-1 cm-1) in AAs. The intersystem crossing rates from the S1 to T1 are also enhanced in these AAs derivatives, while the fluorescence quantum yield decreases from ∼30 to ∼7% for FL and AAs, respectively, making the triplet excited state lifetime and the singlet oxygen quantum yield of AAs at least comparable to those of FL and RFTA. We examined the performance of these heave-atom-free chromophores in the photooxidation of sulfides to afford sulfoxides. In accordance with the prolonged triplet excited state lifetime and enhanced triplet quantum yield, 2-5-fold performance enhancements were observed for AAs in the photooxidation of sulfides with respect to FL. We proposed that the key reactive oxygen species of AA-sensitized photooxidation are singlet oxygen and superoxide radical anion based on mechanistic investigations. The research highlights the superior performance of AAs in photocatalysis and would be helpful to rationalize the design of efficient heavy-atom-free organic photocatalysts.
Collapse
Affiliation(s)
- Huimin Guo
- State
Key Laboratory of Fine Chemicals, Department of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, P. R. China
| | - Hongyu Xia
- State
Key Laboratory of Fine Chemicals, Department of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, P. R. China
| | - Xiaolin Ma
- State
Key Laboratory of Fine Chemicals, Department of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, P. R. China
| | - Kepeng Chen
- State
Key Laboratory of Fine Chemicals, Department of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, P. R. China
| | - Can Dang
- State
Key Laboratory of Fine Chemicals, Department of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, P. R. China
| | - Jianzhang Zhao
- State
Key Laboratory of Fine Chemicals, Department of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, P. R. China
| | - Bernhard Dick
- Institut
für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstr. 31, Regensburg 93053, Germany
| |
Collapse
|
13
|
Tolba AH, Vávra F, Chudoba J, Cibulka R. Tuning Flavin-Based Photocatalytic Systems for Application in the Mild Chemoselective Aerobic Oxidation of Benzylic Substrates. European J Org Chem 2019. [DOI: 10.1002/ejoc.201901628] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Amal Hassan Tolba
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 166 28 Prague Czech Republic
| | - František Vávra
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 166 28 Prague Czech Republic
| | - Josef Chudoba
- Central Laboratories; University of Chemistry and Technology Prague; Technická 5 166 28 Prague Czech Republic
| | - Radek Cibulka
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 166 28 Prague Czech Republic
| |
Collapse
|
14
|
Nitschke P, Lokesh N, Gschwind RM. Combination of illumination and high resolution NMR spectroscopy: Key features and practical aspects, photochemical applications, and new concepts. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2019; 114-115:86-134. [PMID: 31779887 DOI: 10.1016/j.pnmrs.2019.06.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 06/04/2019] [Accepted: 06/04/2019] [Indexed: 06/10/2023]
Abstract
In the last decade, photochemical and photocatalytic applications have developed into one of the dominant research fields in chemistry. However, mechanistic investigations to sustain this enormous progress are still relatively sparse and in high demand by the photochemistry community. UV/Vis spectroscopy and EPR spectroscopy have been the main spectroscopic tools to study the mechanisms of photoreactions due to their higher time resolution and sensitivity. On the other hand, application of NMR in photosystems has been mainly restricted to photo-CIDNP, since the initial photoexcitation was thought to be the single key to understand photoinduced reactions. In 2015 the Gschwind group showcased the possibility that different reaction pathways could occur from the same photoexcited state depending on the reaction conditions by using in situ LED illumination NMR. This was the starting point to push the active participation of NMR in photosystems to its full potential, including reaction profiling, structure determination of intermediates, downstream mechanistic studies, dark pathways, intermediate sequencing with CEST etc. Following this, multiple studies using in situ illumination NMR have been reported focusing on mechanistic investigations in photocatalysis, photoswitches, and polymerizations. The recent increased popularity of this technique can be attributed to the simplicity of the experimental setup and the availability of low cost, high power LEDs. Here, we review the development of experimental design, applications and new concepts of illuminated NMR. In the first part, we describe the development of different designs of NMR illumination apparatus, illuminating from the bottom/side/top/inside, and discuss their pros and cons for specific applications. Furthermore, we address LASERs and LEDs as different light sources as well as special cases such as UVNMR(-illumination), FlowNMR, NMR on a Chip etc. To complete the discussion on experimental apparatus, the advantages and disadvantages of in situ LED illumination NMR versus ex situ illumination NMR are described. The second part of this review discusses different facets of applications of inside illumination experiments. It highlights newly revealed mechanistic and structural information and ideas in the fields of photocatalyis, photoswitches and photopolymerization. Finally, we present new concepts and methods based on the combination of NMR and illumination such as sensitivity enhancement, chemical pump probes, experimental access to transition state combinations and NMR actinometry. Overall this review presents NMR spectroscopy as a complementary tool to UV/Vis spectroscopy in mechanistic and structural investigations of photochemical processes. The review is presented in a way that is intended to assist the photochemistry and photocatalysis community in adopting and understanding this astonishingly powerful in situ LED illumination NMR method for their investigations on a daily basis.
Collapse
Affiliation(s)
- Philipp Nitschke
- Organic Chemistry, University of Regensburg, 93040 Regensburg, Germany
| | | | - Ruth M Gschwind
- Organic Chemistry, University of Regensburg, 93040 Regensburg, Germany.
| |
Collapse
|
15
|
Yang S, McCormick J, Mamone S, Bouchard L, Glöggler S. Nuclear Spin Singlet States in Photoactive Molecules: From Fluorescence/NMR Bimodality to a Bimolecular Switch for Spin Singlet States. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201814198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Shengjun Yang
- Research Group for NMR Signal Enhancement, Max Planck Institute for Biophysical Chemistry Am Fassberg 11 37077 Göttingen Germany
- Center for Biostructural Imaging of Neurodegeneration Von-Siebold-Str. 3A 37075 Göttingen Germany
| | - Jeffrey McCormick
- Department of Chemistry and Biochemistry University of California at Los Angeles Los Angeles CA 90095-1569 USA
| | - Salvatore Mamone
- Research Group for NMR Signal Enhancement, Max Planck Institute for Biophysical Chemistry Am Fassberg 11 37077 Göttingen Germany
- Center for Biostructural Imaging of Neurodegeneration Von-Siebold-Str. 3A 37075 Göttingen Germany
| | - Louis‐S. Bouchard
- Department of Chemistry and Biochemistry University of California at Los Angeles Los Angeles CA 90095-1569 USA
| | - Stefan Glöggler
- Research Group for NMR Signal Enhancement, Max Planck Institute for Biophysical Chemistry Am Fassberg 11 37077 Göttingen Germany
- Center for Biostructural Imaging of Neurodegeneration Von-Siebold-Str. 3A 37075 Göttingen Germany
| |
Collapse
|
16
|
Yang S, McCormick J, Mamone S, Bouchard L, Glöggler S. Nuclear Spin Singlet States in Photoactive Molecules: From Fluorescence/NMR Bimodality to a Bimolecular Switch for Spin Singlet States. Angew Chem Int Ed Engl 2019; 58:2879-2883. [DOI: 10.1002/anie.201814198] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 12/27/2018] [Indexed: 11/07/2022]
Affiliation(s)
- Shengjun Yang
- Research Group for NMR Signal Enhancement, Max Planck Institute for Biophysical Chemistry Am Fassberg 11 37077 Göttingen Germany
- Center for Biostructural Imaging of Neurodegeneration Von-Siebold-Str. 3A 37075 Göttingen Germany
| | - Jeffrey McCormick
- Department of Chemistry and Biochemistry University of California at Los Angeles Los Angeles CA 90095-1569 USA
| | - Salvatore Mamone
- Research Group for NMR Signal Enhancement, Max Planck Institute for Biophysical Chemistry Am Fassberg 11 37077 Göttingen Germany
- Center for Biostructural Imaging of Neurodegeneration Von-Siebold-Str. 3A 37075 Göttingen Germany
| | - Louis‐S. Bouchard
- Department of Chemistry and Biochemistry University of California at Los Angeles Los Angeles CA 90095-1569 USA
| | - Stefan Glöggler
- Research Group for NMR Signal Enhancement, Max Planck Institute for Biophysical Chemistry Am Fassberg 11 37077 Göttingen Germany
- Center for Biostructural Imaging of Neurodegeneration Von-Siebold-Str. 3A 37075 Göttingen Germany
| |
Collapse
|
17
|
Zelenka J, Svobodová E, Tarábek J, Hoskovcová I, Boguschová V, Bailly S, Sikorski M, Roithová J, Cibulka R. Combining Flavin Photocatalysis and Organocatalysis: Metal-Free Aerobic Oxidation of Unactivated Benzylic Substrates. Org Lett 2018; 21:114-119. [PMID: 30582822 DOI: 10.1021/acs.orglett.8b03547] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We report a system with ethylene-bridged flavinium salt 2b which catalyzes the aerobic oxidation of toluenes and benzyl alcohols with high oxidation potential ( Eox > +2.5 V vs SCE) to give the corresponding benzoic acids under visible light irradiation. This is caused by the high oxidizing power of excited 2b ( E(2b*) = +2.67 V vs SCE) involved in photooxidation and by the accompanying dark organocatalytic oxygenation provided by the in situ formed flavin hydroperoxide 2b-OOH.
Collapse
Affiliation(s)
- Jan Zelenka
- Institute for Molecules and Materials , Radboud University , Heyendaalseweg 135 , 6525 AJ Nijmegen , The Netherlands
| | | | - Ján Tarábek
- Institute of Organic Chemistry and Biochemistry , Academy of Science of the Czech Republic , Flemingovo náměstí 542/2 , 16610 Prague , Czech Republic
| | | | | | | | - Marek Sikorski
- Faculty of Chemistry ; Adam Mickiewicz University in Poznan , Umultowska 89b , 61614 Poznan , Poland
| | - Jana Roithová
- Institute for Molecules and Materials , Radboud University , Heyendaalseweg 135 , 6525 AJ Nijmegen , The Netherlands
| | | |
Collapse
|
18
|
Abstract
Abstract
Thanks to rapid development in the last decades, flavins have been recognized as promising photoactive compounds to design new valuable synthetic methodologies based on photoredox catalysis. The review summarizes general photochemical properties of flavins as well as their early applications in transformations mediated by visible light. Special attention has been paid to the catalyst design for benzylic oxidations as well as to recent flavin applications, for example in E/Z-isomerization, [2+2] cycloaddition, cycloelimination, electrophilic chlorination and sulfide oxidation.
Collapse
|
19
|
Seegerer A, Nitschke P, Gschwind RM. Combined In Situ Illumination-NMR-UV/Vis Spectroscopy: A New Mechanistic Tool in Photochemistry. Angew Chem Int Ed Engl 2018; 57:7493-7497. [PMID: 29573313 PMCID: PMC6033024 DOI: 10.1002/anie.201801250] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Indexed: 12/22/2022]
Abstract
Synthetic applications in photochemistry are booming. Despite great progress in the development of new reactions, mechanistic investigations are still challenging. Therefore, we present a fully automated in situ combination of NMR spectroscopy, UV/Vis spectroscopy, and illumination to allow simultaneous and time-resolved detection of paramagnetic and diamagnetic species. This optical fiber-based setup enables the first acquisition of combined UV/Vis and NMR spectra in photocatalysis, as demonstrated on a conPET process. Furthermore, the broad applicability of combined UVNMR spectroscopy for light-induced processes is demonstrated on a structural and quantitative analysis of a photoswitch, including rate modulation and stabilization of transient species by temperature variation. Owing to the flexibility regarding the NMR hardware, temperature, and light sources, we expect wide-ranging applications of this setup in various research fields.
Collapse
Affiliation(s)
- Andreas Seegerer
- Institute of Organic ChemistryUniversity of RegensburgUniversitätsstrasse 3193053RegensburgGermany
| | - Philipp Nitschke
- Institute of Organic ChemistryUniversity of RegensburgUniversitätsstrasse 3193053RegensburgGermany
| | - Ruth M. Gschwind
- Institute of Organic ChemistryUniversity of RegensburgUniversitätsstrasse 3193053RegensburgGermany
| |
Collapse
|
20
|
Seegerer A, Nitschke P, Gschwind RM. Combined In Situ Illumination-NMR-UV/Vis Spectroscopy: A New Mechanistic Tool in Photochemistry. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201801250] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Andreas Seegerer
- Institute of Organic Chemistry; University of Regensburg; Universitätsstrasse 31 93053 Regensburg Germany
| | - Philipp Nitschke
- Institute of Organic Chemistry; University of Regensburg; Universitätsstrasse 31 93053 Regensburg Germany
| | - Ruth M. Gschwind
- Institute of Organic Chemistry; University of Regensburg; Universitätsstrasse 31 93053 Regensburg Germany
| |
Collapse
|
21
|
Visible light mediated aerobic photocatalytic activation of C H bond by riboflavin tetraacetate and N -hydroxysuccinimide. Tetrahedron Lett 2018. [DOI: 10.1016/j.tetlet.2018.01.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
22
|
Mojr V, Pitrová G, Straková K, Prukała D, Brazevic S, Svobodová E, Hoskovcová I, Burdziński G, Slanina T, Sikorski M, Cibulka R. Flavin Photocatalysts for Visible-Light [2+2] Cycloadditions: Structure, Reactivity and Reaction Mechanism. ChemCatChem 2018. [DOI: 10.1002/cctc.201701490] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Viktor Mojr
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 16628 Prague Czech Republic
| | - Gabriela Pitrová
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 16628 Prague Czech Republic
| | - Karolína Straková
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 16628 Prague Czech Republic
| | - Dorota Prukała
- Faculty of Chemistry; Adam Mickiewicz University in Poznan; Umultowska 89b 61-614 Poznan Poland
| | - Sabina Brazevic
- Quantum Electronics Laboratory, Faculty of Physics; Adam Mickiewicz University in Poznan; Umultowska 85 61-614 Poznan Poland
| | - Eva Svobodová
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 16628 Prague Czech Republic
| | - Irena Hoskovcová
- Department of Inorganic; Chemistry; University of Chemistry and Technology; Prague
| | - Gotard Burdziński
- Quantum Electronics Laboratory, Faculty of Physics; Adam Mickiewicz University in Poznan; Umultowska 85 61-614 Poznan Poland
| | - Tomáš Slanina
- Department of Chemistry and RECETOX, Faculty of Science; Masaryk University; Kamenice 5 62500 Brno Czech Republic
- Institute of Organic Chemistry and Chemical Biology; Goethe University Frankfurt; Frankfurt am Main Germany
| | - Marek Sikorski
- Faculty of Chemistry; Adam Mickiewicz University in Poznan; Umultowska 89b 61-614 Poznan Poland
| | - Radek Cibulka
- Department of Organic Chemistry; University of Chemistry and Technology, Prague; Technická 5 16628 Prague Czech Republic
| |
Collapse
|
23
|
März M, Chudoba J, Kohout M, Cibulka R. Photocatalytic esterification under Mitsunobu reaction conditions mediated by flavin and visible light. Org Biomol Chem 2017; 15:1970-1975. [DOI: 10.1039/c6ob02770a] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Excited flavin facilitates stereoselective coupling of alcohols and acids to esters in the presence of triphenylphosphine and catalytic amount of dialkyl hydrazinedicarboxylate.
Collapse
Affiliation(s)
- M. März
- Department of Organic Chemistry
- University of Chemistry and Technology
- Prague
- 166 28 Prague
- Czech Republic
| | - J. Chudoba
- Central Laboratories
- University of Chemistry and Technology
- Prague
- 166 28 Prague
- Czech Republic
| | - M. Kohout
- Department of Organic Chemistry
- University of Chemistry and Technology
- Prague
- 166 28 Prague
- Czech Republic
| | - R. Cibulka
- Department of Organic Chemistry
- University of Chemistry and Technology
- Prague
- 166 28 Prague
- Czech Republic
| |
Collapse
|
24
|
Neveselý T, Svobodová E, Chudoba J, Sikorski M, Cibulka R. Efficient Metal-Free Aerobic Photooxidation of Sulfides to Sulfoxides Mediated by a Vitamin B2Derivative and Visible Light. Adv Synth Catal 2016. [DOI: 10.1002/adsc.201501123] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
25
|
Metternich JB, Gilmour R. One Photocatalyst, n Activation Modes Strategy for Cascade Catalysis: Emulating Coumarin Biosynthesis with (-)-Riboflavin. J Am Chem Soc 2016; 138:1040-5. [PMID: 26714650 DOI: 10.1021/jacs.5b12081] [Citation(s) in RCA: 184] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Generating molecular complexity using a single catalyst, where the requisite activation modes are sequentially exploited as the reaction proceeds, is an attractive guiding principle in synthesis. This requires that each substrate transposition exposes a catalyst activation mode (AM) to which all preceding or future intermediates are resistant. While this concept is exemplified by MacMillan's beautiful merger of enamine and iminium ion activation, examples in other fields of contemporary catalysis remain elusive. Herein, we extend this tactic to organic photochemistry. By harnessing the two discrete photochemical activation modes of (-)-riboflavin, it is possible to sequentially induce isomerization and cyclization by energy transfer (ET) and single-electron transfer (SET) activation pathways, respectively. This catalytic approach has been utilized to emulate the coumarin biosynthesis pathway, which features a key photochemical E → Z isomerization step. Since the ensuing SET-based cyclization eliminates the need for a prefunctionalized aryl ring, this constitutes a novel disconnection of a pharmaceutically important scaffold.
Collapse
Affiliation(s)
- Jan B Metternich
- Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster , Corrensstrasse 40, 48149 Münster, Germany
| | - Ryan Gilmour
- Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster , Corrensstrasse 40, 48149 Münster, Germany
| |
Collapse
|
26
|
Mataranga-Popa LN, Torje I, Ghosh T, Leitl MJ, Späth A, Novianti ML, Webster RD, König B. Synthesis and electronic properties of π-extended flavins. Org Biomol Chem 2015; 13:10198-204. [PMID: 26303394 DOI: 10.1039/c5ob01418b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Flavin derivatives with an extended π-conjugation were synthesized in moderate to good yields from aryl bromides via a Buchwald-Hartwig palladium catalyzed amination protocol, followed by condensation of the corresponding aromatic amines with violuric acid. The electronic properties of the new compounds were investigated by absorption and emission spectroscopy, cyclic voltammetry, density functional theory (DFT) and time dependent density functional theory (TDDFT). The compounds absorb up to 550 nm and show strong luminescence. The photoluminescence quantum yields ϕPL measured in dichloromethane reach 80% and in PMMA (poly(methyl methacrylate)) 77%, respectively, at ambient temperature. The electrochemical redox behaviour of π-extended flavins follows the mechanism previously described for the parent flavin.
Collapse
Affiliation(s)
- L N Mataranga-Popa
- University of Regensburg, Universitatsstraße 31, 93053 Regensburg, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Mojr V, Svobodová E, Straková K, Neveselý T, Chudoba J, Dvořáková H, Cibulka R. Tailoring flavins for visible light photocatalysis: organocatalytic [2+2] cycloadditions mediated by a flavin derivative and visible light. Chem Commun (Camb) 2015; 51:12036-9. [PMID: 26121238 DOI: 10.1039/c5cc01344e] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A new application of flavin derivatives in visible light photocatalysis was found. 1-Butyl-7,8-dimethoxy-3-methylalloxazine, when irradiated by visible light, was shown to allow an efficient cyclobutane ring formation via an intramolecular [2+2] cycloaddition of both styrene dienes, considered as electron-rich substrates, and electron-poor bis(arylenones), presumably proceeding via an energy transfer mechanism.
Collapse
Affiliation(s)
- Viktor Mojr
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague, Czech Republic.
| | | | | | | | | | | | | |
Collapse
|
28
|
Metternich JB, Gilmour R. A Bio-Inspired, Catalytic E → Z Isomerization of Activated Olefins. J Am Chem Soc 2015; 137:11254-7. [PMID: 26310905 DOI: 10.1021/jacs.5b07136] [Citation(s) in RCA: 234] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Herein, Nature's flavin-mediated activation of complex (poly)enes has been translated to a small molecule paradigm culminating in a highly (Z)-selective, catalytic isomerization of activated olefins using (-)-riboflavin (up to 99:1 Z/E). In contrast to the prominent Z → E isomerization of the natural system, it was possible to invert the directionality of the isomerization (E → Z) by simultaneously truncating the retinal scaffold, and introducing a third olefin substituent to augment A1,3-strain upon isomerization. Consequently, conjugation is reduced in the product chromophore leading to a substrate/product combination with discrete photophysical signatures. The operationally simple isomerization protocol has been applied to a variety of enone-derived substrates and showcased in the preparation of the medically relevant 4-substituted coumarin scaffold. A correlation of sensitizer triplet energy (ET) and reaction efficiency, together with the study of additive effects and mechanistic probes, is consistent with a triplet energy transfer mechanism.
Collapse
Affiliation(s)
- Jan B Metternich
- Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster , Corrensstrasse 40, 48149 Münster, Germany
| | - Ryan Gilmour
- Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster , Corrensstrasse 40, 48149 Münster, Germany
| |
Collapse
|
29
|
Angnes RA, Li Z, Correia CRD, Hammond GB. Recent synthetic additions to the visible light photoredox catalysis toolbox. Org Biomol Chem 2015; 13:9152-67. [PMID: 26242759 DOI: 10.1039/c5ob01349f] [Citation(s) in RCA: 171] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The boom in visible light photoredox catalysis (VLPC) research has demonstrated that this novel synthetic approach is here to stay. VLPC enables reactive radical intermediates to be catalytically generated at ambient temperature, a feat not generally allowed through traditional pyrolysis- or radical initiator-based methodologies. VLPC has vastly extended the range of substrates and reaction schemes that have been traditionally the domain of radical reactions. In this review the photophysics background of VLPC will be briefly discussed, followed by a report on recent inroads of VLPC into decarboxylative couplings and radical C-H functionalization of aromatic compounds. The bulk of the review will be dedicated to advances in synergistic catalysis involving VLPC, namely the combination of photoredox catalysis with organocatalysis, including β-functionalization of carbonyl groups, functionalization of weak aliphatic C-H bonds, and anti-Markovnikov hydrofunctionalization of alkenes; dual catalysis with gold or with nickel, photoredox catalysis as an oxidation promoter in transition metal catalysis, and acid-catalyzed enantioselective radical addition to π systems.
Collapse
Affiliation(s)
- Ricardo A Angnes
- Chemistry Institute, State University of Campinas - Unicamp C.P. 6154, CEP. 13083-970, Campinas, São Paulo, Brazil
| | | | | | | |
Collapse
|
30
|
Suzuki H, Inoue R, Kawamorita S, Komiya N, Imada Y, Naota T. Highly fluorescent flavins: rational molecular design for quenching protection based on repulsive and attractive control of molecular alignment. Chemistry 2015; 21:9171-8. [PMID: 25962532 DOI: 10.1002/chem.201406346] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Indexed: 11/05/2022]
Abstract
Unprecedented intense fluorescent emission was observed for a variety of flavin compounds bearing a perpendicular cyclic imide moiety at the C7 position of an isoalloxazine platform. A series of alloxan-substituted flavins was prepared selectively by reduction of the corresponding N-aryl-2-nitro-5-alkoxyanilines with zinc dust and subsequent reaction with alloxan monohydrate in the presence of boric acid. Analogues bearing oxazolidine-2,4-dione functionality were obtained on methylation of the alloxan-substituted flavins with methyl iodide and subsequent rearrangement in the presence of an inorganic base. The flavin compounds exhibit intense white-green fluorescent emission in the solution state under UV excitation at 298 K, with emission efficiencies Φ298 K greater than 0.55 in CH3 CN, which are higher than the values for all reported flavin compounds under similar conditions. The highest Φ298 K value of 0.70 was obtained in CH3 CN for isoalloxazine bearing C7-alloxan and N10-2,6-diisopropylphenyl groups. The temperature dependence of the emission intensities indicates that the pronounced emission properties at 298 K are attributable to the highly heat resistant properties towards emission decay with increasing temperature. Mechanistic studies, including X-ray diffraction analysis, revealed that the good emission properties and high heat resistance of the alloxan-substituted flavins are due to a synergetic effect of the associative nature of the C7-alloxan unit and the repulsive nature of the perpendicular bulky substituents at the C7 and N10 positions.
Collapse
Affiliation(s)
- Haruka Suzuki
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)
| | - Ryo Inoue
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)
| | - Soichiro Kawamorita
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)
| | - Naruyoshi Komiya
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)
| | - Yasushi Imada
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-8531 (Japan).,Present address: Department of Chemical Science and Technology, Institute of Technology and Science, Tokushima University, Minamijosanjima, Tokushima 770-8506 (Japan)
| | - Takeshi Naota
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-8531 (Japan).
| |
Collapse
|
31
|
Iida H, Imada Y, Murahashi SI. Biomimetic flavin-catalysed reactions for organic synthesis. Org Biomol Chem 2015; 13:7599-613. [DOI: 10.1039/c5ob00854a] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Using simple riboflavin related compounds as biomimetic catalysts, catalytic oxidation of various substrates with hydrogen peroxide or molecular oxygen can be performed selectively under mild conditions. The principle of these reactions is fundamental and will provide a wide scope for environmentally benign future practical methods.
Collapse
Affiliation(s)
- H. Iida
- Department of Chemistry
- Interdisciplinary Graduate School of Science and Engineering
- Shimane University
- Matsue 690-8504
- Japan
| | - Y. Imada
- Department of Chemical Science and Technology
- Tokushima University
- Tokushima 770-8506
- Japan
| | - S.-I. Murahashi
- Department of Chemistry
- Okayama University of Science
- Okayama 700-0005
- Japan
| |
Collapse
|
32
|
Feldmeier C, Bartling H, Magerl K, Gschwind RM. LED-beleuchtete NMR-Spektroskopie Flavin-katalysierter Photooxidationen zeigt Lösungsmittelkontrolle des Elektronentransfermechanismus. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201409146] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
33
|
Feldmeier C, Bartling H, Magerl K, Gschwind RM. LED-Illuminated NMR Studies of Flavin-Catalyzed Photooxidations Reveal Solvent Control of the Electron-Transfer Mechanism. Angew Chem Int Ed Engl 2014; 54:1347-51. [DOI: 10.1002/anie.201409146] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Indexed: 11/11/2022]
|
34
|
Atmaca U, Usanmaz HK, Çelik M. Oxidations of alkenes with hypervalent iodine reagents: an alternative ozonolysis of phenyl substituted alkenes and allylic oxidation of unsubstituted cyclic alkenes. Tetrahedron Lett 2014. [DOI: 10.1016/j.tetlet.2014.02.076] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
35
|
Jurok R, Hodačová J, Eigner V, Dvořáková H, Setnička V, Cibulka R. Planar Chiral Flavinium Salts: Synthesis and Evaluation of the Effect of Substituents on the Catalytic Efficiency in Enantioselective Sulfoxidation Reactions. European J Org Chem 2013. [DOI: 10.1002/ejoc.201300847] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
36
|
Feldmeier C, Bartling H, Riedle E, Gschwind RM. LED based NMR illumination device for mechanistic studies on photochemical reactions--versatile and simple, yet surprisingly powerful. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 232:39-44. [PMID: 23685874 DOI: 10.1016/j.jmr.2013.04.011] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 04/17/2013] [Indexed: 06/02/2023]
Abstract
An LED based illumination device for mechanistic studies on photochemical reactions by means of NMR spectroscopy is presented. The LEDs are directly switched by the NMR spectrometer with the help of a one-stage electronic circuit. This allows for continuous or alternatively pulsed operation of the LEDs. Continuous operation provides direct comparability with conditions in synthetic chemistry, in pulsed operation the short time light power can be enhanced ninefold. The LEDs are efficiently coupled to a 1000 μm core optical fiber guiding the light into the spectrometer by simply bringing it in close contact to the fiber. The tip of the fiber is roughened by sandblasting and thus emits light in a uniform and efficient way over the full length of the receiver coil. The combination of these techniques tremendously increases the amount of light brought into the NMR sample and makes LEDs an easy, versatile and handy light source for the in situ illumination of NMR samples allowing even for single millisecond time resolved Photo-CIDNP spectroscopy.
Collapse
Affiliation(s)
- C Feldmeier
- Department of Organic Chemistry, University of Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany.
| | | | | | | |
Collapse
|