Stereoselective synergystic organo photoredox catalysis with enamines and iminiums

Visible light photoredox catalysis has recently emerged as a powerful tool for the development of new and valuable chemical transformations under mild conditions. Visible-light promoted enantioselective radical transformations of imines and iminium intermediates provide new opportunities for the asymmetric synthesis of amines and asymmetric β-functionalization of unsaturated carbonyl compounds. In this review, the advance in the catalytic asymmetric radical functionalization of imines, as well as iminium intermediates, are summarized. 1 Introduction 2 The enantioselective radical functionalization of imines 2.1 Asymmetric reduction 2.2 Asymmetric cyclization 2.3 Asymmetric addition 2.4 Asymmetric radical coupling 3 The enantioselective radical functionalization of iminium ions 3.1 Asymmetric radical alkylation 3.2 Asymmetric radical acylation 4 Conclusion

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The chemistry of amine radical cations produced by visible light photoredox catalysis

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.9.234 ◽

2013 ◽

Vol 9 ◽

pp. 1977-2001 ◽

Cited By ~ 238

Author(s):

Jie Hu ◽

Jiang Wang ◽

Theresa H Nguyen ◽

Nan Zheng

Keyword(s):

Visible Light ◽

Radical Cations ◽

Reactive Intermediates ◽

Visible Light Photocatalysis ◽

Photoredox Catalysis ◽

Iminium Ions ◽

Distonic Ions ◽

Synthetic Intermediates

Amine radical cations are highly useful reactive intermediates in amine synthesis. They have displayed several modes of reactivity leading to some highly sought-after synthetic intermediates including iminium ions, α-amino radicals, and distonic ions. One appealing method to access amine radical cations is through one-electron oxidation of the corresponding amines under visible light photoredox conditions. This approach and subsequent chemistries are emerging as a powerful tool in amine synthesis. This article reviews synthetic applications of amine radical cations produced by visible light photocatalysis.

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Hole-Mediated PhotoRedox Catalysis: Tris(p-Substituted)biarylaminium Radical Cations as Tunable, Precomplexing and Potent Photooxidants

10.26434/chemrxiv.13140053.v1 ◽

2020 ◽

Author(s):

Shangze Wu ◽

Jonas Zurauskas ◽

Michal Domanski ◽

Patrick Hitzfeld ◽

Valeria Butera ◽

...

Keyword(s):

Cyclic Voltammetry ◽

Excited State ◽

Excited States ◽

Organic Molecules ◽

Radical Cations ◽

Single Electron Transfer ◽

Photoredox Catalysis ◽

Small Organic Molecules ◽

Fundamental Limitations ◽

Ion Species

Electrochemically-mediated Photoredox Catalysis emerged as a powerful synthetic technique in recent years, overcoming fundamental limitations of electrochemistry and photoredox catalysis in the single electron transfer activation of small organic molecules. However, the mechanism of how photoexcited radical ion species with ultrashort (picosecond-order) lifetimes could ever undergo productive photochemistry has eluded synthetic chemists. We report tri(para-substituted)biarylamines as a tunable class of electroactivated photocatalysts that become superoxidants in their photoexcited states, even able to oxidize molecules (such as dichlorobenzene and trifluorotoluene) beyond the solvent window limits of cyclic voltammetry. Furthermore, we demonstrate that precomplexation not only permits the excited state photochemistry of tris(para-substituted)biarylaminium cations, but enables and rationalizes the surprising photochemistry of their higher-order doublet (Dn) excited states.

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Visible Light Promoted Functionalisation of Carbon-Carbon Sigma Bonds

10.26434/chemrxiv.7958765.v1 ◽

2019 ◽

Author(s):

Jeremy Nugent ◽

Carlos Arroniz ◽

Bethany Shire ◽

Alistair J. Sterling ◽

Helena D. Pickford ◽

...

Keyword(s):

Visible Light ◽

Organic Molecules ◽

Functional Group ◽

Single Step ◽

Transition Metal Catalysts ◽

Organic Radicals ◽

Photoredox Catalysis ◽

Halogen Bonds ◽

Organic Halides ◽

Pi Bonds

The use of visible light to activate transition metal catalysts towards redox processes has transformed the way organic molecules can be constructed. Promotion of an electron to an excited state enables the generation of organic radicals through electron transfer to or from the metal complex, with the resulting radicals primed for reactions such as addition to carbon–carbon pi bonds. Despite advances in photoredox catalysis which have led to the discovery of numerous such methods for bond construction, this mild approach to the generation of free radicals has not been applied to the functionalisation of carbon–carbon sigmabonds. Here we report the first such use of photoredox catalysis to promote the addition of organic halides to the caged carbocycle [1.1.1]propellane; the products of this process are bicyclo[1.1.1]pentanes (BCPs), motifs that are of high importance as bioisosteres in the pharmaceutical industry, and in materials applications. The methodology shows broad substrate scope and functional group tolerance, and is applicable to both sp2and sp3carbon–halogen bonds, while the use of substrates containing alkene acceptors enables the single-step construction of polycyclic bicyclopentane products through cyclisation cascades. Finally, the potential to accelerate drug discovery is demonstrated through examples of late-stage bicyclopentylation to access natural product- and drug-like molecules.

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Visible Light Promoted Functionalisation of Carbon-Carbon Sigma Bonds

10.26434/chemrxiv.7958765 ◽

2019 ◽

Author(s):

Jeremy Nugent ◽

Carlos Arroniz ◽

Bethany Shire ◽

Alistair J. Sterling ◽

Helena D. Pickford ◽

...

Keyword(s):

Visible Light ◽

Organic Molecules ◽

Functional Group ◽

Single Step ◽

Transition Metal Catalysts ◽

Organic Radicals ◽

Photoredox Catalysis ◽

Halogen Bonds ◽

Organic Halides ◽

Pi Bonds

The use of visible light to activate transition metal catalysts towards redox processes has transformed the way organic molecules can be constructed. Promotion of an electron to an excited state enables the generation of organic radicals through electron transfer to or from the metal complex, with the resulting radicals primed for reactions such as addition to carbon–carbon pi bonds. Despite advances in photoredox catalysis which have led to the discovery of numerous such methods for bond construction, this mild approach to the generation of free radicals has not been applied to the functionalisation of carbon–carbon sigmabonds. Here we report the first such use of photoredox catalysis to promote the addition of organic halides to the caged carbocycle [1.1.1]propellane; the products of this process are bicyclo[1.1.1]pentanes (BCPs), motifs that are of high importance as bioisosteres in the pharmaceutical industry, and in materials applications. The methodology shows broad substrate scope and functional group tolerance, and is applicable to both sp2and sp3carbon–halogen bonds, while the use of substrates containing alkene acceptors enables the single-step construction of polycyclic bicyclopentane products through cyclisation cascades. Finally, the potential to accelerate drug discovery is demonstrated through examples of late-stage bicyclopentylation to access natural product- and drug-like molecules.

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Photoredox catalysis by [Ru(bpy)3]2+ to trigger transformations of organic molecules. Organic synthesis using visible-light photocatalysis and its 20th century roots

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc2011078 ◽

2011 ◽

Vol 76 (7) ◽

pp. 859-917 ◽

Cited By ~ 411

Author(s):

Filip Teplý

Keyword(s):

Visible Light ◽

Organic Synthesis ◽

Organic Molecules ◽

Recent Literature ◽

Synthetic Methods ◽

Bond Breaking ◽

Materials Chemistry ◽

Photoredox Catalysis ◽

Contemporary Work ◽

Developing Area

Reactions triggered by light constitute a treasure trove of unique synthetic methods that are available to chemists. Photoinduced redox processes using visible light in conjunction with sensitizing dyes offer a great variety of catalytic transformations useful in the realm of organic synthesis. The recent literature amply shows that this preparative toolbox is expanding substantially. This review discusses historical and contemporary work in the area of photoredox catalysis with [Ru(bpy)3]2+. Elegant examples from the most recent literature document the importance of this fast developing area of research. The photoredox chemistry has also emerged as a promising bond-making and bond-breaking tool for chemical biology and materials chemistry. A review with 96 references.

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Benzylic C−H acylation by cooperative NHC and photoredox catalysis

Nature Communications ◽

10.1038/s41467-021-22292-z ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Qing-Yuan Meng ◽

Lena Lezius ◽

Armido Studer

Keyword(s):

Organic Molecules ◽

Functional Group ◽

Photoredox Catalysis ◽

Diverse Range ◽

Site Selectivity ◽

Aryl Ketones ◽

Direct Acylation ◽

Selective Acylation ◽

Site Selective ◽

Complex Organic

AbstractMethods that enable site selective acylation of sp3 C-H bonds in complex organic molecules are not well explored, particularly if compared with analogous transformations of aromatic and vinylic sp2 C-H bonds. We report herein a direct acylation of benzylic C-H bonds by merging N-heterocyclic carbene (NHC) and photoredox catalysis. The method allows the preparation of a diverse range of benzylic ketones with good functional group tolerance under mild conditions. The reaction can be used to install acyl groups on highly functionalized natural product derived compounds and the C-H functionalization works with excellent site selectivity. The combination of NHC and photoredox catalysis offers options in preparing benzyl aryl ketones.

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Recent Advances in Visible-Light-Mediated Amide Synthesis

Molecules ◽

10.3390/molecules27020517 ◽

2022 ◽

Vol 27 (2) ◽

pp. 517

Author(s):

Bin Lu ◽

Wen-Jing Xiao ◽

Jia-Rong Chen

Keyword(s):

Visible Light ◽

Organic Molecules ◽

Structural Motif ◽

Radical Reactions ◽

Photoredox Catalysis ◽

Mild Conditions ◽

Amide Synthesis ◽

Functionalized Materials ◽

Activating Agent ◽

Ubiquitous Presence

Visible-light photoredox catalysis has attracted tremendous interest within the synthetic community. As such, the activation mode potentially provides a more sustainable and efficient platform for the activation of organic molecules, enabling the invention of many controlled radical-involved reactions under mild conditions. In this context, amide synthesis via the strategy of photoredox catalysis has received growing interest due to the ubiquitous presence of this structural motif in numerous natural products, pharmaceuticals and functionalized materials. Employing this strategy, a wide variety of amides can be prepared effectively from halides, arenes and even alkanes under irradiation of visible light. These methods provide a robust alternative to well-established strategies for amide synthesis that involve condensation between a carboxylic acid and amine mediated by a stoichiometric activating agent. In this review, the representative progresses made on the synthesis of amides through visible light-mediated radical reactions are summarized.

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Hole-Mediated PhotoRedox Catalysis: Tris(p-Substituted)biarylaminium Radical Cations as Tunable, Precomplexing and Potent Photooxidants

10.26434/chemrxiv.13140053 ◽

2020 ◽

Author(s):

Shangze Wu ◽

Jonas Zurauskas ◽

Michal Domanski ◽

Patrick Hitzfeld ◽

Valeria Butera ◽

...

Keyword(s):

Cyclic Voltammetry ◽

Excited State ◽

Excited States ◽

Organic Molecules ◽

Radical Cations ◽

Single Electron Transfer ◽

Photoredox Catalysis ◽

Small Organic Molecules ◽

Fundamental Limitations ◽

Ion Species

Electrochemically-mediated Photoredox Catalysis emerged as a powerful synthetic technique in recent years, overcoming fundamental limitations of electrochemistry and photoredox catalysis in the single electron transfer activation of small organic molecules. However, the mechanism of how photoexcited radical ion species with ultrashort (picosecond-order) lifetimes could ever undergo productive photochemistry has eluded synthetic chemists. We report tri(para-substituted)biarylamines as a tunable class of electroactivated photocatalysts that become superoxidants in their photoexcited states, even able to oxidize molecules (such as dichlorobenzene and trifluorotoluene) beyond the solvent window limits of cyclic voltammetry. Furthermore, we demonstrate that precomplexation not only permits the excited state photochemistry of tris(para-substituted)biarylaminium cations, but enables and rationalizes the surprising photochemistry of their higher-order doublet (Dn) excited states.

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High Resolution Replication of Organoclay Surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055126 ◽

1982 ◽

Vol 40 ◽

pp. 576-577

Author(s):

W. W. Barker ◽

W. E. Rigsby ◽

V. J. Hurst ◽

W. J. Humphreys

Keyword(s):

Clay Mineral ◽

Organic Molecule ◽

Organic Molecules ◽

X Ray Diffraction ◽

Xrd Pattern ◽

X Ray ◽

Naturally Occurring ◽

Silicate Layers ◽

Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

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