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Singlet Oxygen-Photooxygenation of Organic Compounds
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Singlet Oxygen-Photooxygenation of Organic Compounds

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 16224

Special Issue Editor

Prof. Dr. Axel G. Griesbeck

E-Mail Website
Guest Editor
Department of Chemistry, University of Cologne, Greinstr. 4, D-50939 Koeln, Germany
Interests: synthesis; medicinal chemistry; synthetic organic chemistry; medicinal and pharmaceutical chemistry; spectroscopy; natural product chemistry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

During the past decade, the field of photochemistry has been experiencing an unexpected upswing with respect to synthetic applications and mechanistic insights. This is mainly due to new catalysts that have been developed for energy and electron transfer steps to sophisticated spectroscopic techniques and increasingly improved computational methods.

Among the many different photochemical synthetic methods, photooxygenation with singlet oxygen occupies a superior position. Singlet oxygen is a remarkable electronically excited state: remarkably easy to generate, remarkably long-lived, and remarkably reactive—all in contrast to its triplet ground state. Thus, singlet oxygen is an inevitable part of biological processes where light, dye molecules, and cellular structures meet. Nature has developed a whole fire brigade to fight against oxidative stress, and singlet oxygen is a molecule that is also in its focus. Beside these biological aspects, the synthetic applicability of singlet oxygen is also appealing. Nearly all documented singlet oxygen reactions are defined pericyclic reactions without radical chain oxidation contribution. Thus, defined target molecules can be generated by singlet oxygenations and, on the other hand, singlet oxygen reactions can be exceedingly well investigated by spectroscopic methods or by oxygen consumption analyses. This Special Issue on “Singlet Oxygen-Photooxygenation of Organic Compounds” aims to collect submissions on new singlet oxygen reactions, new products from singlet photooxygenations, and new mechanistic insights into singlet oxygen chemistry.

Prof. Dr. Axel G. Griesbeck
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • oxygenation
  • photochemistry
  • sensitization
  • photocatalysis
  • singlet oxygen
  • natural antioxidants
  • peroxides

Related Special Issue

Published Papers (5 papers)

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Research

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10 pages, 2557 KiB  
Communication
A One-Pot Approach to Novel Pyridazine C-Nucleosides
by Flavio Cermola, Serena Vella, Marina DellaGreca, Angela Tuzi and Maria Rosaria Iesce
Molecules 2021, 26(8), 2341; https://doi.org/10.3390/molecules26082341 - 17 Apr 2021
Cited by 3 | Viewed by 2159
Abstract
The synthesis of glycosides and modified nucleosides represents a wide research field in organic chemistry. The classical methodology is based on coupling reactions between a glycosyl donor and an acceptor. An alternative strategy for new C-nucleosides is used in this approach, which [...] Read more.
The synthesis of glycosides and modified nucleosides represents a wide research field in organic chemistry. The classical methodology is based on coupling reactions between a glycosyl donor and an acceptor. An alternative strategy for new C-nucleosides is used in this approach, which consists of modifying a pre-existent furyl aglycone. This approach is applied to obtain novel pyridazine C-nucleosides starting with 2- and 3-(ribofuranosyl)furans. It is based on singlet oxygen [4+2] cycloaddition followed by reduction and hydrazine cyclization under neutral conditions. The mild three-step one-pot procedure leads stereoselectively to novel pyridazine C-nucleosides of pharmacological interest. The use of acetyls as protecting groups provides an elegant direct route to a deprotected new pyridazine C-nucleoside. Full article
(This article belongs to the Special Issue Singlet Oxygen-Photooxygenation of Organic Compounds)
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17 pages, 2073 KiB  
Article
Stereoselective [4+2] Cycloaddition of Singlet Oxygen to Naphthalenes Controlled by Carbohydrates
by Marcel Bauch, Werner Fudickar and Torsten Linker
Molecules 2021, 26(4), 804; https://doi.org/10.3390/molecules26040804 - 4 Feb 2021
Cited by 12 | Viewed by 3062
Abstract
Stereoselective reactions of singlet oxygen are of current interest. Since enantioselective photooxygenations have not been realized efficiently, auxiliary control is an attractive alternative. However, the obtained peroxides are often too labile for isolation or further transformations into enantiomerically pure products. Herein, we describe [...] Read more.
Stereoselective reactions of singlet oxygen are of current interest. Since enantioselective photooxygenations have not been realized efficiently, auxiliary control is an attractive alternative. However, the obtained peroxides are often too labile for isolation or further transformations into enantiomerically pure products. Herein, we describe the oxidation of naphthalenes by singlet oxygen, where the face selectivity is controlled by carbohydrates for the first time. The synthesis of the precursors is easily achieved starting from naphthoquinone and a protected glucose derivative in only two steps. Photooxygenations proceed smoothly at low temperature, and we detected the corresponding endoperoxides as sole products by NMR. They are labile and can thermally react back to the parent naphthalenes and singlet oxygen. However, we could isolate and characterize two enantiomerically pure peroxides, which are sufficiently stable at room temperature. An interesting influence of substituents on the stereoselectivities of the photooxygenations has been found, ranging from 51:49 to up to 91:9 dr (diastereomeric ratio). We explain this by a hindered rotation of the carbohydrate substituents, substantiated by a combination of NOESY measurements and theoretical calculations. Finally, we could transfer the chiral information from a pure endoperoxide to an epoxide, which was isolated after cleavage of the sugar chiral auxiliary in enantiomerically pure form. Full article
(This article belongs to the Special Issue Singlet Oxygen-Photooxygenation of Organic Compounds)
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12 pages, 3512 KiB  
Article
New Photochromic α-Methylchalcones Are Highly Photostable, Even under Singlet Oxygen Conditions: Breaking the α-Methyl Michael-System Reactivity by Reversible Peroxybiradical Formation
by Axel G. Griesbeck, Banu Öngel, Eric Brüllingen and Melissa Renner
Molecules 2021, 26(3), 642; https://doi.org/10.3390/molecules26030642 - 26 Jan 2021
Cited by 2 | Viewed by 2103
Abstract
The α-methylated chalcones 7a–7e behave as P-type photochromic substances with photo-stationary states (PSS) as high as 15:85 when irradiated at 350 nm. These compounds are easily accessible in pure E-configuration by aldol condensation or by oxidative coupling/elimination. The α-methyl groups make [...] Read more.
The α-methylated chalcones 7a–7e behave as P-type photochromic substances with photo-stationary states (PSS) as high as 15:85 when irradiated at 350 nm. These compounds are easily accessible in pure E-configuration by aldol condensation or by oxidative coupling/elimination. The α-methyl groups make these compounds potentially reactive with singlet oxygen following the gem-rule that predicts 1O2 regioselectivity. Even after long irradiations times in the presence of the singlet oxygen sensitizer tetraphenylporphyrin (TPP) and oxygen, however, no oxygenation products were detected. Under these conditions, all substrates were converted into 9:1 E/Z-mixtures despite the use of low-energy light that does not allow direct or sensitized excitation of the substrates 7. Additionally, chalcone 7a reduced the singlet oxygen reactivity of the tiglic ketone 3a by about a factor of two, indicating substantial physical quenching of singlet oxygen by the α-methylated chalcones 7a–7e. Thus, a singlet oxygen-induced E/Z-isomerization involving 1,2-dioxatetra-methylene biradicals that leads to triplet oxygen and thermodynamic E/Z-mixtures is postulated and supported by quantum chemical (DFT)-calculations. Full article
(This article belongs to the Special Issue Singlet Oxygen-Photooxygenation of Organic Compounds)
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Review

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42 pages, 6730 KiB  
Review
A Photosensitized Singlet Oxygen (1O2) Toolbox for Bio-Organic Applications: Tailoring 1O2 Generation for DNA and Protein Labelling, Targeting and Biosensing
by Dorien Aerssens, Enrico Cadoni, Laure Tack and Annemieke Madder
Molecules 2022, 27(3), 778; https://doi.org/10.3390/molecules27030778 - 25 Jan 2022
Cited by 20 | Viewed by 5101
Abstract
Singlet oxygen (1O2) is the excited state of ground, triplet state, molecular oxygen (O2). Photosensitized 1O2 has been extensively studied as one of the reactive oxygen species (ROS), responsible for damage of cellular components (protein, [...] Read more.
Singlet oxygen (1O2) is the excited state of ground, triplet state, molecular oxygen (O2). Photosensitized 1O2 has been extensively studied as one of the reactive oxygen species (ROS), responsible for damage of cellular components (protein, DNA, lipids). On the other hand, its generation has been exploited in organic synthesis, as well as in photodynamic therapy for the treatment of various forms of cancer. The aim of this review is to highlight the versatility of 1O2, discussing the main bioorganic applications reported over the past decades, which rely on its production. After a brief introduction on the photosensitized production of 1O2, we will describe the main aspects involving the biologically relevant damage that can accompany an uncontrolled, aspecific generation of this ROS. We then discuss in more detail a series of biological applications featuring 1O2 generation, including protein and DNA labelling, cross-linking and biosensing. Finally, we will highlight the methodologies available to tailor 1O2 generation, in order to accomplish the proposed bioorganic transformations while avoiding, at the same time, collateral damage related to an untamed production of this reactive species. Full article
(This article belongs to the Special Issue Singlet Oxygen-Photooxygenation of Organic Compounds)
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27 pages, 10276 KiB  
Review
Solar Photooxygenations for the Manufacturing of Fine Chemicals—Technologies and Applications
by Jayson S. Wau, Mark J. Robertson and Michael Oelgemöller
Molecules 2021, 26(6), 1685; https://doi.org/10.3390/molecules26061685 - 17 Mar 2021
Cited by 7 | Viewed by 3440
Abstract
Photooxygenation reactions involving singlet oxygen (1O2) are utilized industrially as a mild and sustainable access to oxygenated products. Due to the usage of organic dyes as photosensitizers, these transformations can be successfully conducted using natural sunlight. Modern solar chemical [...] Read more.
Photooxygenation reactions involving singlet oxygen (1O2) are utilized industrially as a mild and sustainable access to oxygenated products. Due to the usage of organic dyes as photosensitizers, these transformations can be successfully conducted using natural sunlight. Modern solar chemical reactors enable outdoor operations on the demonstration (multigram) to technical (multikilogram) scales and have subsequently been employed for the manufacturing of fine chemicals such as fragrances or biologically active compounds. This review will highlight examples of solar photooxygenations for the manufacturing of industrially relevant target compounds and will discuss current challenges and opportunities of this sustainable methodology. Full article
(This article belongs to the Special Issue Singlet Oxygen-Photooxygenation of Organic Compounds)
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