Search results for: Hans-Achim Wagenknecht

Items from 1 to 20 out of 77 results

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N‐Arylphenothiazines and N,N‐Diarylphenazines as Tailored Organophotoredox Catalysts for the Reductive Activation of Alkenes

Madeleine Giraud, Mathis Robin Mitha, Sven Klehenz, Hans‐Achim Wagenknecht

European Journal of Organic Chemistry > 27 > 40 > n/a - n/a

A small library of N‐arylphenothiazines, N‐arylbenzo[b]phenothiazines and N,N‐diarylphenazines has been synthesized as strongly reducing organophotocatalysts without the need for sacrificial reagents or electrochemistry. Their opto‐electronic properties and their suitability as organophotoredox catalysts for the efficient activation of olefins was investigated using the addition of methanol to α‐methylstyrene...

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Front Cover: N‐Arylphenothiazines and N,N‐Diarylphenazines as Tailored Organophotoredox Catalysts for the Reductive Activation of Alkenes (Eur. J. Org. Chem. 40/2024)

Madeleine Giraud, Mathis Robin Mitha, Sven Klehenz, Hans‐Achim Wagenknecht

European Journal of Organic Chemistry > 27 > 40 > n/a - n/a

The Front Cover features an abstract representation of two novel, highly reducing organophotocatalysts derived from N‐arylphenothiazines and N,N‐diarylphenazines, compounds widely recognized as versatile and effective photoredox catalysts. The catalysts shown are the most efficient from a library of 17 catalysts synthesized. They show remarkable performance in the addition of methanol to α‐methylstyrene,...

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Nucleic Acid‐Templated Synthesis of Cationic Styryl Dyes in Vitro and in Living Cells

Kriangsak Faikhruea, Kotchakorn Supabowornsathit, Kitipong Angsujinda, Chanat Aonbangkhen, more

Chemistry – A European Journal > 30 > 31 > n/a - n/a

A novel method for synthesizing cationic styryl dyes through a nucleic acid‐templated reaction has been developed. This approach overcomes issues associated with traditional synthesis methods, such as harsh conditions, low throughput, and wasteful chemicals. The presence of a nucleic acid template accelerated the styryl dye formation from quaternized heteroaromatic and cationic aldehyde substrates...

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Cyclopropene als Chemische Reporter für die Duale Bioorthogonale und Orthogonale Metabolische Markierung von DNA

Nicola Seul, Dennis Lamade, Petko Stoychev, Michaela Mijic, more

Angewandte Chemie > 136 > 22 > n/a - n/a

Die duale bioorthogonale Markierung ermöglicht die Untersuchung und das Verständnis von Wechselwirkungen in der biologischen Umgebung, die mit einer einzigen Markierung nicht zugänglich sind. Eine Herausforderung bleibt jedoch die Anwendung von zwei bioorthogonalen Reaktionen in der gleichen Umgebung aufgrund von Kreuzreaktivität. Um dieses Problem für die duale und orthogonale Markierung von DNA...

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Cyclopropenes as Chemical Reporters for Dual Bioorthogonal and Orthogonal Metabolic Labeling of DNA

Nicola Seul, Dennis Lamade, Petko Stoychev, Michaela Mijic, more

Angewandte Chemie International Edition > 63 > 22 > n/a - n/a

Dual bioorthogonal labeling enables the investigation and understanding of interactions in the biological environment that are not accessible by a single label. However, applying two bioorthogonal reactions in the same environment remains challenging due to cross‐reactivity. We developed a pair of differently modified 2′‐deoxynucleosides that solved this issue for dual and orthogonal labeling of DNA...

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Photoredox Catalytic Access to N,O‐Acetals from Enamides by Means of Electron‐Poor Perylene Bisimides

Desirée Steuernagel, David Rombach, Hans‐Achim Wagenknecht

Chemistry – A European Journal > 30 > 26 > n/a - n/a

N,O‐acetals are found as structural motifs in natural products and are important synthetic precursors for N‐acylimines as building blocks in organic synthesis for C−C‐bond formation and amines. For the synthesis of N,O‐acetals, an acid‐, base‐ and metal‐free catalytic method is reported applying N,N‐di‐(2,6‐diisopropyl)‐1,7‐dicyano‐perylen‐3,4,9,10‐tetracarboxylic acid imide and N,N‐di‐(2,6‐diisopropyl)‐1,6,7,12‐tetrabromo‐2,5,8,11‐tetracyano‐perylen‐3,4,9,10‐tetracarboxylic...

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Front Cover: Photocatalytic Synthesis of Acetals and Ketals from Aldehydes and Silylenolethers without the Use of Acids (Chem. Eur. J. 13/2023)

Desirée Steuernagel, Hans‐Achim Wagenknecht

Chemistry – A European Journal > 29 > 13 > n/a - n/a

The photoredox catalytic cycle with an electron‐deficient perylene bisimide (PBI) runs as long as green light is provided. The substrate silylenolethers and aldehydes enter the cycle, are oxidized to their radical cations and converted to acetals and ketals, which leave the cycle as products. Acid catalysts are not needed. Ketal and acetal groups protect the carbonyl compounds like helmets. More information...

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Photocatalytic Synthesis of Acetals and Ketals from Aldehydes and Silylenolethers without the Use of Acids

Desirée Steuernagel, Hans‐Achim Wagenknecht

Chemistry – A European Journal > 29 > 13 > n/a - n/a

Acetals and ketals are among the most important protecting groups for carbonyl compounds. A new method for acetalization and ketalization by means of photoredox catalysis has been developed. A biscyanolated perylene bisimide is used as an electron‐poor photocatalyst, together with green light (525 nm LED). Silylenolethers derived from aldehydes react efficiently to give acetals in good to excellent...

article

Photocatalytic Synthesis of Acetals and Ketals from Aldehydes and Silylenolethers without the Use of Acids

Desirée Steuernagel, Hans‐Achim Wagenknecht

Chemistry – A European Journal > 29 > 13 > n/a - n/a

Invited for the cover of this issue are Desirée Steuernagel and Hans‐Achim Wagenknecht at the Karlsruhe Institute of Technology. The image depicts a traffic roundabout, which symbolizes the photocatalytic cycle for the conversion of aldehydes and silylenolethers as starting materials into their acetals. Read the full text of the article at 10.1002/chem.202203767.

article

Two‐Factor Fluorogenicity of Tetrazine‐Modified Cyanine‐Styryl Dyes for Bioorthogonal Labelling of DNA

Philipp Geng, Eileen List, Franziska Rönicke, Hans‐Achim Wagenknecht

Chemistry – A European Journal > 29 > 8 > n/a - n/a

Two green fluorescent tetrazine‐modified cyanine‐styryl dyes were synthesized for bioorthogonal labelling of DNA by means of the Diels‐Alder reaction with inverse electron demand. With DNA as target biopolymer the fluorescence of these dyes is released by two factors: (i) sterically by their interaction with DNA, and (ii) structurally via the conjugated tetrazine as quencher moiety. As a result, the...

article

The Concept of Photozymes: Short Peptides with Photoredox Catalytic Activity for Nucleophilic Additions to α‐Phenyl Styrenes

Daniel Sack, Hans‐Achim Wagenknecht

European Journal of Organic Chemistry > 2021 > 46 > 6400 - 6407

Conventional photoredox catalytic additions of alcohols to olefins require additives, like thiophenol, to promote back electron transfer. The concept of “photozymes” assumes that forward and backward electron transfer steps in a photoredox catalytic cycle are controllable by substrate binding to photocatalytically active peptides. Accordingly, we synthesized a short tripeptide modified with 1,7‐dicyano‐perylene‐3,4...

article

Fast and Efficient Postsynthetic DNA Labeling in Cells by Means of Strain‐Promoted Sydnone‐Alkyne Cycloadditions

Katja Krell, Bastian Pfeuffer, Franziska Rönicke, Zoeisha S. Chinoy, more

Chemistry – A European Journal > 27 > 65 > 16093 - 16097

Sydnones are highly stable mesoionic 1,3‐dipoles that react with cyclooctynes through strain‐promoted sydnone‐alkyne cycloaddition (SPSAC). Although sydnones have been shown to be valuable bioorthogonal chemical reporters for the labeling of proteins and complex glycans, nucleic acids have not yet been tagged by SPSAC. Evaluation of SPSAC kinetics with model substrates showed fast reactions with cyclooctyne...

article

Cover Feature: Fast and Efficient Postsynthetic DNA Labeling in Cells by Means of Strain‐Promoted Sydnone‐Alkyne Cycloadditions (Chem. Eur. J. 65/2021)

Katja Krell, Bastian Pfeuffer, Franziska Rönicke, Zoeisha S. Chinoy, more

Chemistry – A European Journal > 27 > 65 > 16058 - 16058

DNA strands, modified with the novel bioorthogonal reporter sydnone, undergo fast and efficient labeling with cyclooctyne–dye conjugates, both in vitro and in HeLa cells. These results show that sydnones are versatile bioorthogonal tags and have the premise to become essential tools for tracking DNA and potentially RNA in living cells. More information can be found in the Communication by F. Friscourt,...

article

Cover Feature: Photoredox Catalytic Pentafluorosulfanylative Domino Cyclization of α‐Substituted Alkenes to Oxaheterocycles by Using SF₆ (Chem. Eur. J. 31/2021)

David Rombach, Bernhard Birenheide, Hans‐Achim Wagenknecht

Chemistry – A European Journal > 27 > 31 > 8059 - 8059

Let's play dominoes with SF₆: The photoredox catalytic activation of SF₆ in the presence of a‐substituted styrenes and alkynols initiates a reaction sequence that consecutively forms a C−O bond, a C−C bond and a C−SF₅ bond, one after another. Finally, this domino reaction yields pentafluorosulfanylated oxygen‐containing heterocycles in a single step. These new compounds bear a complex structure and...

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Photoredox Catalytic Pentafluorosulfanylative Domino Cyclization of α‐Substituted Alkenes to Oxaheterocycles by Using SF₆

David Rombach, Bernhard Birenheide, Hans‐Achim Wagenknecht

Chemistry – A European Journal > 27 > 31 > 8088 - 8093

Virtually inert sulfur hexafluoride becomes a precious pentafluorosulfanylation agent, if properly activated by photoredox catalysis, to access α‐fluoro and α‐alkoxy SF₅‐compounds. This advanced protocol converts SF₆ in the presence of alkynols as bifunctional C−C‐ and C−O‐bond forming reagents directly into pentafluorosulfanylated oxygen‐containing heterocycles in a single step from α‐substituted...

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Nucleophilic Alkoxylations of Unactivated Alkyl Olefins and α‐Methyl Styrene by Photoredox Catalysis

Fabienne Seyfert, Mathis Mitha, Hans‐Achim Wagenknecht

European Journal of Organic Chemistry > 2021 > 5 > 773 - 776

N,N‐diisobutylaminophenyl‐phenothiazine is a strongly reducing catalyst that allows – for the first time – the photoredox catalytic addition of alcohols to alkyl olefins as non‐activated substrates to products with Markovnikov orientation. The irradiation at 365 nm does not require any additional reagent. Using α‐methyl styrene as activated substrate we additionally show that this photoredox catalytic...

article

Front Cover: Nucleophilic Alkoxylations of Unactivated Alkyl Olefins and α‐Methyl Styrene by Photoredox Catalysis (Eur. J. Org. Chem. 5/2021)

Fabienne Seyfert, Mathis Mitha, Hans‐Achim Wagenknecht

European Journal of Organic Chemistry > 2021 > 5 > 709 - 709

The Front Cover shows an illustration how N‐phenylphenothiazines can be used as photoredox catalysts for the photoreduction of alkylated olefins and subsequent nucleophilic addition by alcohols. Compared to conventional photoredox catalyst, such as [Ru(bpy)3]2+ and eosin Y, N‐phenylphenothiazine have significantly more reducing power that is crucial for the photoinduced electron transfer to alkylated...

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Wie weit wandert Energie in der DNA und verursacht Schäden? Nachweis des langreichweitigen Photoschadens in DNA

Arthur Kuhlmann, Larissa Bihr, Hans‐Achim Wagenknecht

Angewandte Chemie > 132 > 40 > 17530 - 17535

Eine neue DNA‐Architektur ermöglicht zu untersuchen, wie weit Energie in DNA wandert und Cyclobutanpyrimidindimere (CPD) als Photoschäden, die Hautkrebs verursachen, bildet. Das Nucleosid des 3‐Methoxyxanthons erlaubt die ortsselektive Injektion von Lichtenergie in die DNA. Die designierte CPD‐Stelle, der die Phosphodiesterbindung fehlt, kann in definierten Distanzen platziert werden. Die CPD‐Bildung...

article

Frontispiz: Wie weit wandert Energie in der DNA und verursacht Schäden? Nachweis des langreichweitigen Photoschadens in DNA

Arthur Kuhlmann, Larissa Bihr, Hans‐Achim Wagenknecht

Angewandte Chemie > 132 > 40 > n/a - n/a

DNA‐Läsionen In der Zuschrift auf S. 17530 berichten H.‐A. Wagenknecht et al. über eine neue DNA‐Architektur, mit der die Frage untersucht wird, wie weit Energie in DNA migriert und Cyclobutanpyrimidin‐Dimere als Hautkrebs verursachende Photoschäden bildet.

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How Far Does Energy Migrate in DNA and Cause Damage? Evidence for Long‐Range Photodamage to DNA

Arthur Kuhlmann, Larissa Bihr, Hans‐Achim Wagenknecht

Angewandte Chemie International Edition > 59 > 40 > 17378 - 17382

A new DNA architecture addresses the question, how far energy migrates in DNA and forms cyclobutane pyrimidine dimers (CPDs) as photodamages causing skin cancer. The 3‐methoxyxanthone nucleoside allows site‐selective photoenergy injection into DNA. The designated CPD site lacks the phosphodiester bond and can be placed in defined distances. The CPD formation links two oligonucleotides together and...

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Search results for: Hans-Achim Wagenknecht

N‐Arylphenothiazines and N,N‐Diarylphenazines as Tailored Organophotoredox Catalysts for the Reductive Activation of Alkenes

Front Cover: N‐Arylphenothiazines and N,N‐Diarylphenazines as Tailored Organophotoredox Catalysts for the Reductive Activation of Alkenes (Eur. J. Org. Chem. 40/2024)

Nucleic Acid‐Templated Synthesis of Cationic Styryl Dyes in Vitro and in Living Cells

Cyclopropene als Chemische Reporter für die Duale Bioorthogonale und Orthogonale Metabolische Markierung von DNA

Cyclopropenes as Chemical Reporters for Dual Bioorthogonal and Orthogonal Metabolic Labeling of DNA

Photoredox Catalytic Access to N,O‐Acetals from Enamides by Means of Electron‐Poor Perylene Bisimides

Front Cover: Photocatalytic Synthesis of Acetals and Ketals from Aldehydes and Silylenolethers without the Use of Acids (Chem. Eur. J. 13/2023)

Photocatalytic Synthesis of Acetals and Ketals from Aldehydes and Silylenolethers without the Use of Acids

Photocatalytic Synthesis of Acetals and Ketals from Aldehydes and Silylenolethers without the Use of Acids

Two‐Factor Fluorogenicity of Tetrazine‐Modified Cyanine‐Styryl Dyes for Bioorthogonal Labelling of DNA

The Concept of Photozymes: Short Peptides with Photoredox Catalytic Activity for Nucleophilic Additions to α‐Phenyl Styrenes

Fast and Efficient Postsynthetic DNA Labeling in Cells by Means of Strain‐Promoted Sydnone‐Alkyne Cycloadditions

Cover Feature: Fast and Efficient Postsynthetic DNA Labeling in Cells by Means of Strain‐Promoted Sydnone‐Alkyne Cycloadditions (Chem. Eur. J. 65/2021)

Cover Feature: Photoredox Catalytic Pentafluorosulfanylative Domino Cyclization of α‐Substituted Alkenes to Oxaheterocycles by Using SF₆ (Chem. Eur. J. 31/2021)

Photoredox Catalytic Pentafluorosulfanylative Domino Cyclization of α‐Substituted Alkenes to Oxaheterocycles by Using SF₆

Nucleophilic Alkoxylations of Unactivated Alkyl Olefins and α‐Methyl Styrene by Photoredox Catalysis

Front Cover: Nucleophilic Alkoxylations of Unactivated Alkyl Olefins and α‐Methyl Styrene by Photoredox Catalysis (Eur. J. Org. Chem. 5/2021)

Wie weit wandert Energie in der DNA und verursacht Schäden? Nachweis des langreichweitigen Photoschadens in DNA

Frontispiz: Wie weit wandert Energie in der DNA und verursacht Schäden? Nachweis des langreichweitigen Photoschadens in DNA

How Far Does Energy Migrate in DNA and Cause Damage? Evidence for Long‐Range Photodamage to DNA

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