scholarly journals Potent Reductants via Electron-Primed Photoredox Catalysis: Unlocking Aryl Chlorides for Radical Coupling

2020 ◽  
Vol 142 (5) ◽  
pp. 2093-2099 ◽  
Author(s):  
Nicholas G. W. Cowper ◽  
Colleen P. Chernowsky ◽  
Oliver P. Williams ◽  
Zachary K. Wickens
Keyword(s):  
Photoredox Catalysis ◽  
Aryl Chlorides ◽  
Radical Coupling

Enantioselective Radical Functionalization of Imines and Iminium Intermediates via Visible Light Photoredox Catalysis

Synthesis ◽  
2020 ◽  
Author(s):  
Jia-Jia Zhao ◽  
Hong-Hao Zhang ◽  
Shouyun Yu
Keyword(s):  
Visible Light ◽  
Asymmetric Synthesis ◽  
Carbonyl Compounds ◽  
Asymmetric Reduction ◽  
Chemical Transformations ◽  
Photoredox Catalysis ◽  
Radical Coupling ◽  
Mild Conditions ◽  
Iminium Ions ◽  
Radical Functionalization

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

scholarly journals Combined Photoredox and Carbene Catalysis for the Synthesis of Ketones from Carboxylic Acids

2020 ◽  
Author(s):  
Anna Davies ◽  
keegan fitzpatrick ◽  
Rick Betori ◽  
Karl Scheidt
Keyword(s):  
Carboxylic Acids ◽  
Late Stage ◽  
Pharmaceutical Compounds ◽  
Single Electron ◽  
Photoredox Catalysis ◽  
Radical Coupling ◽  
Electron Reduction

Disclosed herein is the development of a novel single-electron reduction of acyl azoliums for the formation of ketones from carboxylic acids. Facile construction of the acyl azolium <i>in situ</i> followed by a radical-radical coupling was made possible using merged NHC-photoredox catalysis. The utility of this protocol in synthesis was demonstrated in the late-stage functionalization of a variety of pharmaceutical compounds.

scholarly journals Electro-mediated PhotoRedox Catalysis for Selective C(sp3)-O Cleavages of Phosphinates to Carbanions

2021 ◽  
Author(s):  
Xianhai Tian ◽  
Tobias Karl ◽  
Sebastian Reiter ◽  
Shahboz Yakubov ◽  
Regina de Vivie-Riedle ◽  
...  
Keyword(s):  
Radical Anion ◽  
Reductive Cleavage ◽  
Photoredox Catalysis ◽  
Structural Variations ◽  
Aryl Chlorides ◽  
Anion Form

We report a novel example of electro-mediated photoredox catalysis (e-PRC) in the reductive cleavage of C(sp<sup>3</sup>)-O bonds of phosphinates to alkyl carbanions. As well as deoxygenations, olefinations are reported which are <i>E</i>-selective and can be made <i>Z</i>-selective in a tandem reduction/photosensitization process where both steps are photoelectrochemically promoted. Spectroscopy, computation and catalyst structural variations reveal that our new naphthalene monoimide-type catalyst allows for a more intimate dispersive precomplexation of its radical anion form with the phosphinate substrate, facilitating a reactivity-determining C(sp<sup>3</sup>)-O cleavage. Surprisingly and in contrast to previously reported photoexcited radical anion chemistries, our conditions i) tolerate aryl chlorides/bromides and ii) do not give rise to Birch-type reductions.

Non-innocent Radical Ion Intermediates in Photoredox Catalysis: Parallel Reduction Modes Enable Coupling of Diverse Aryl Chlorides

2021 ◽  
Author(s):  
Alyah F. Chmiel ◽  
Oliver P. Williams ◽  
Colleen P. Chernowsky ◽  
Charles S. Yeung ◽  
Zachary K. Wickens
Keyword(s):  
Photoredox Catalysis ◽  
Aryl Chlorides ◽  
Parallel Reduction

scholarly journals Combined Photoredox and Carbene Catalysis for the Synthesis of Ketones from Carboxylic Acids

2020 ◽  
Author(s):  
Anna Davies ◽  
keegan fitzpatrick ◽  
Rick Betori ◽  
Karl Scheidt
Keyword(s):  
Carboxylic Acids ◽  
Late Stage ◽  
Pharmaceutical Compounds ◽  
Single Electron ◽  
Photoredox Catalysis ◽  
Radical Coupling ◽  
Electron Reduction

Disclosed herein is the development of a novel single-electron reduction of acyl azoliums for the formation of ketones from carboxylic acids. Facile construction of the acyl azolium <i>in situ</i> followed by a radical-radical coupling was made possible using merged NHC-photoredox catalysis. The utility of this protocol in synthesis was demonstrated in the late-stage functionalization of a variety of pharmaceutical compounds.

scholarly journals Non-Innocent Radical Ion Intermediates in Photoredox Catalysis: Parallel Reduction Modes Enable Coupling of Diverse Aryl Chlorides

2021 ◽  
Author(s):  
Alyah Chmiel ◽  
Oliver P. Williams ◽  
Colleen Chernowsky ◽  
Charles Yeung ◽  
Zachary Wickens
Keyword(s):  
Radical Anion ◽  
Sodium Formate ◽  
Coupling Reactions ◽  
Aryl Radical ◽  
Aryl Chloride ◽  
Aryl Chlorides ◽  
Radical Coupling ◽  
Substrate Reduction ◽  
Photocatalytic System

We describe a photocatalytic system that elicits potent photoreductant activity from conventional photocatalysts by leveraging radical anion intermediates generated <i>in situ</i>. The combination of isophthalonitrile and sodium formate promotes diverse aryl radical coupling reactions from abundant but difficult to reduce aryl chloride substrates. Mechanistic studies reveal two parallel pathways for substrate reduction both enabled by a key terminal reductant byproduct, carbon dioxide radical anion.

scholarly journals Pyridylphosphonium Salts as Alternatives to Cyanopyridines in Radical-Radical Coupling Reactions

2021 ◽  
Author(s):  
Jacob W. Greenwood ◽  
Andrew McNally
Keyword(s):  
Late Stage ◽  
Radical Anion ◽  
Cyano Group ◽  
Radical Anions ◽  
Coupling Reactions ◽  
Photoredox Catalysis ◽  
Phosphonium Salts ◽  
Radical Coupling

Radical couplings of cyanopyridine radical anions represent a valuable technology for functionalizing pyridines, which are prevalent throughout pharmaceuticals, agrochemicals, and materials. Installing the cyano group, necessary for radical anion stabilization, is challenging and limits the use of this chemistry to simple cyanopyridines. We discovered that pyridyl phosphonium salts, installed regioselectively from C-H precursors, are useful alternatives to cyanopyridines in radical-radical coupling reactions, expanding the scope of this reaction manifold to complex pyridines. Methods for both alkylation and amination of pyridines mediated by photoredox catalysis are described. Additionally, we demonstrate late-stage functionalization of pharmaceuticals, highlighting an advantage of pyridyl phosphonium salts over cyanopyridines.

scholarly journals Pyridylphosphonium Salts as Alternatives to Cyanopyridines in Radical-Radical Coupling Reactions

2021 ◽  
Author(s):  
Jacob W. Greenwood ◽  
Andrew McNally
Keyword(s):  
Late Stage ◽  
Radical Anion ◽  
Cyano Group ◽  
Radical Anions ◽  
Coupling Reactions ◽  
Photoredox Catalysis ◽  
Phosphonium Salts ◽  
Radical Coupling

Radical couplings of cyanopyridine radical anions represent a valuable technology for functionalizing pyridines, which are prevalent throughout pharmaceuticals, agrochemicals, and materials. Installing the cyano group, necessary for radical anion stabilization, is challenging and limits the use of this chemistry to simple cyanopyridines. We discovered that pyridyl phosphonium salts, installed regioselectively from C-H precursors, are useful alternatives to cyanopyridines in radical-radical coupling reactions, expanding the scope of this reaction manifold to complex pyridines. Methods for both alkylation and amination of pyridines mediated by photoredox catalysis are described. Additionally, we demonstrate late-stage functionalization of pharmaceuticals, highlighting an advantage of pyridyl phosphonium salts over cyanopyridines.

Synthesis of Chiral Amines by C–C Bond Formation with Photoredox Catalysis

Synthesis ◽  
2021 ◽  
Author(s):  
Gregory K. Friestad ◽  
Stephen T. J. Cullen
Keyword(s):  
Radical Addition ◽  
Biologically Active ◽  
Chiral Amines ◽  
Photoredox Catalysis ◽  
Conjugate Additions ◽  
Drug Candidates ◽  
Radical Intermediates ◽  
Radical Coupling ◽  
Amine Oxidation ◽  
Imine Reduction

AbstractChiral amines are key substructures of biologically active natural products and drug candidates. The advent of photoredox catalysis has changed the way synthetic chemists think about building these substructures, opening new pathways that were previously unavailable. New developments in this area are reviewed, with an emphasis on C–C bond constructions involving radical intermediates generated through photoredox processes.1 Introduction2 Radical–Radical Coupling of α-Amino Radicals2.1 Radical–Radical Coupling Involving Amine Oxidation2.2 Radical–Radical Coupling Involving Imine Reduction2.3 Couplings Involving both Amine Oxidation and Imine Reduction3 Addition Reactions of α-Amino Radicals3.1 Conjugate Additions of α-Amino Radicals3.2 Addition of α-Amino Radicals to Heteroaromatic Systems3.3 Cross Coupling via Additions to Transition Metal Complexes4 Radical Addition to C=N Bonds Using Photoredox Catalysis4.1 Intramolecular Radical Addition to C=N Bonds4.2 Intermolecular Radical Addition to C=N Bonds5 Conclusion

Sign in / Sign up

Export Citation Format

Share Document