Application of α-Amino Radicals as the Reaction Activators

Synthesis ◽  
2021 ◽  
Author(s):  
Yong-liang Su ◽  
Michael P. Doyle
Keyword(s):  
Halogen Atom ◽  
Building Blocks ◽  
Short Review ◽  
Single Electron ◽  
Radical Species ◽  
Sulfonium Salts ◽  
Radical Intermediates ◽  
Organic Halides

α-Aminoalkyl radicals are easily accessible through multiple pathways from various precursors. Apart from their utilization as N-containing building blocks, they have recently been used as halogen atom abstraction reagents or single-electron reductants to transform organic halides or sulfonium salts to their corresponding highly reactive radical species. Benefiting from the richness of various halides and the diverse reactivity of radical intermediates, new transformations of halides and sulfonium salts have been developed. This short review summarizes this emerging chemistry that uses α-amino radicals as the reaction activators.

scholarly journals Aminoalkyl radicals as halogen-atom transfer agents for activation of alkyl and aryl halides

Science ◽  
2020 ◽  
Vol 367 (6481) ◽  
pp. 1021-1026 ◽  
Author(s):  
Timothée Constantin ◽  
Margherita Zanini ◽  
Alessio Regni ◽  
Nadeem S. Sheikh ◽  
Fabio Juliá ◽  
...  
Keyword(s):  
Halogen Atom ◽  
Building Blocks ◽  
Aryl Halides ◽  
Atom Transfer ◽  
Reduction Potentials ◽  
Tributyltin Hydride ◽  
Organic Halides ◽  
Wide Range ◽  
Carbon Carbon Bonds ◽  
Radical Processes

Organic halides are important building blocks in synthesis, but their use in (photo)redox chemistry is limited by their low reduction potentials. Halogen-atom transfer remains the most reliable approach to exploit these substrates in radical processes despite its requirement for hazardous reagents and initiators such as tributyltin hydride. In this study, we demonstrate that α-aminoalkyl radicals, easily accessible from simple amines, promote the homolytic activation of carbon-halogen bonds with a reactivity profile mirroring that of classical tin radicals. This strategy conveniently engages alkyl and aryl halides in a wide range of redox transformations to construct sp3-sp3, sp3-sp2, and sp2-sp2 carbon-carbon bonds under mild conditions with high chemoselectivity.

scholarly journals α-Functionalization of Imines via Visible Light Photoredox Catalysis

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 562 ◽  
Author(s):  
Alberto F. Garrido-Castro ◽  
M. Carmen Maestro ◽  
José Alemán
Keyword(s):  
Visible Light ◽  
Building Blocks ◽  
Single Electron ◽  
Synthetic Chemistry ◽  
Photoredox Catalysis ◽  
Reaction Conditions ◽  
Radical Intermediates ◽  
Research Programs ◽  
Electron Reduction

The innate electrophilicity of imine building blocks has been exploited in organic synthetic chemistry for decades. Inspired by the resurgence in photocatalysis, imine reactivity has now been redesigned through the generation of unconventional and versatile radical intermediates under mild reaction conditions. While novel photocatalytic approaches have broadened the range and applicability of conventional radical additions to imine acceptors, the possibility to use these imines as latent nucleophiles via single-electron reduction has also been uncovered. Thus, multiple research programs have converged on this issue, delivering creative and practical strategies to achieve racemic and asymmetric α-functionalizations of imines under visible light photoredox catalysis.

scholarly journals Core-Substituted Naphthalene-diimides (cNDI) and Related Derivatives: Versatile Scaffold for Supramolecular Assembly and Functional Materials

2021 ◽  
Author(s):  
Anurag Mukherjee ◽  
Suhrit Ghosh
Keyword(s):  
Photophysical Properties ◽  
Supramolecular Assembly ◽  
Functional Materials ◽  
Building Blocks ◽  
Short Review ◽  
Molecular Engineering ◽  
Organic Optoelectronics ◽  
Naphthalene Diimide ◽  
Naphthalene Diimides ◽  
Derivatives Of

Naphthalene-diimide (NDI) derived building blocks have been explored extensively for supramolecular assembly as they exhibit attractive photophysical properties, suitable for applications in organic optoelectronics. Core-substituted derivatives of the NDI chromophore (cNDI) differ significantly from the parent NDI dye in terms of optical and redox properties. Adequate molecular engineering opportunities and substitution-dependent tunable optoelectronic properties make cNDI derivatives highly promising candidates for supramolecular assembly and functional material. This short review discusses recent development in the area of functional supramolecular assemblies based on cNDIs and related molecules.

scholarly journals Oxidative Generation of Boron-Centered Radicals in Carboranes

2019 ◽  
Author(s):  
Harrison A. Mills ◽  
Joshua Martin ◽  
Arnold L. Rheingold ◽  
Alexander Spokoyny
Keyword(s):  
Direct Oxidation ◽  
Radical Species ◽  
Boron Cluster ◽  
Radical Intermediates ◽  
Substitution Chemistry ◽  
Indirect Observation ◽  
Electronic Environments ◽  
Oxidative Generation

<div><div><div><p>We report the first indirect observation and use of boron vertex-centered carboranyl radicals generated by the oxidation of modified carboranyl precursors. These radical intermediates are formed by the direct oxidation of a B−B bond between a boron cluster cage and an exopolyhedral boron-based substituent (e.g., −BF3K, −B(OH)2). The in situ generated radical species are shown to be competent substrates in reactions with oxygen-based radicals, dichalcogenides, and N-heterocycles, yielding the corresponding substituted carboranes containing B−O, B−S, B−Se, B−Te, and B−C bonds. Remarkably, this chemistry tolerates various electronic environments, providing access to facile substitution chemistry at both electron-rich and electron-poor B−H vertices in carboranes.</p></div></div></div>

Enantioselective Intermolecular Murai-Type Alkene Hydroarylation Reactions

Synthesis ◽  
2021 ◽  
Author(s):  
John F. Bower ◽  
Timothy P. Aldhous ◽  
Raymond W. M. Chung ◽  
Andrew G. Dalling
Keyword(s):  
Building Blocks ◽  
Short Review ◽  
Synthetic Chemistry ◽  
Complex Building

AbstractStrategies that enable the efficient assembly of complex building blocks from feedstock chemicals are of paramount importance to synthetic chemistry. Building upon the pioneering work of Murai and co-workers in 1993, C–H-activation-based enantioselective hydroarylations of alkenes offer a particularly promising framework for the step- and atom-economical installation of benzylic stereocenters. This short review presents recent intermolecular enantioselective Murai-type alkene hydroarylation methodologies and the mechanisms by which they proceed.1 Introduction2 Enantioselective Hydroarylation Reactions of Strained Bicyclic Alkenes3 Enantioselective Hydroarylation Reactions of Electron-Rich Acyclic Alkenes4 Enantioselective Hydroarylation Reactions of Electron-Poor Acyclic Alkenes5 Enantioselective Hydroarylation Reactions of Minimally Polarized Acyclic Alkenes6 Conclusion and Outlook

Ascending of Cycloaddition Strategy for N-O Heterocycles

Synthesis ◽  
2021 ◽  
Author(s):  
Prasanjit Ghosh ◽  
Swati Lekha Mondal ◽  
Mahiuddin Baidya
Keyword(s):  
Organic Synthesis ◽  
Building Blocks ◽  
Short Review ◽  
Biologically Relevant

The N–O heterocycles are biologically relevant scaffolds and versatile building blocks in contemporary organic synthesis. In this short review, we effort to showcase the involvement and elevation of various cycloaddition strategies towards the production of N–O heterocycles 1,2-oxazines, 1,2-oxazepanes, and 1,2-oxazetidines. A blueprint of advantages and challenges associated with these synthetic endeavors is provided.

scholarly journals Radical Biocatalysis: Using Non-Natural Single Electron Transfer Mechanisms to Access New Enzymatic Functions

Synlett ◽  
2019 ◽  
Vol 31 (03) ◽  
pp. 248-254 ◽  
Author(s):  
Todd K. Hyster
Keyword(s):  
Electron Transfer ◽  
Active Sites ◽  
Hydrogen Atom Transfer ◽  
Single Electron ◽  
Great Promise ◽  
Single Electron Transfer ◽  
Radical Intermediates ◽  
Redox Activation ◽  
Transfer Mechanisms ◽  
Ground State Electron

Exploiting non-natural reaction mechanisms within native enzymes is an emerging strategy for expanding the synthetic capabilities of biocatalysts. When coupled with modern protein engineering techniques, this approach holds great promise for biocatalysis to address long-standing selectivity and reactivity challenges in chemical synthesis. Controlling the stereochemical outcome of reactions involving radical intermediates, for instance, could benefit from biocatalytic solutions because these reactions are often difficult to control by using existing small molecule catalysts. General strategies for catalyzing non-natural radical reactions within enzyme active sites are, however, undeveloped. In this account, we highlight three distinct strategies developed in our group that exploit non-natural single electron transfer mechanisms to unveil previously unknown radical biocatalytic functions. These strategies allow common oxidoreductases to be used to address the enduring synthetic challenge of asymmetric hydrogen atom transfer.1 Introduction2 Photoinduced Electron Transfer from NADPH3 Ground State Electron Transfer from Flavin Hydroquinone4 Enzymatic Redox Activation in NADPH-Dependent Oxidoreductases5 Conclusion

scholarly journals Alcohol-Initiated Dediazoniation of Aryldiazonium Ions to Aryl Radicals: A Simple and Efficient Route to Arylboronates

2018 ◽  
Vol 42 (9) ◽  
pp. 481-485
Author(s):  
Xiulian Zhang ◽  
Zhicheng Zhang ◽  
Yongbin Xie ◽  
Yujie Jiang ◽  
Ruibo Xu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Bond Formation ◽  
Single Electron ◽  
Single Electron Transfer ◽  
Aryl Radical ◽  
Radical Species ◽  
Aryl Radicals ◽  
Efficient Access ◽  
Efficient Route ◽  
Operational Simplicity

A simple and efficient access to arylboronates was achieved with methanol-initiated borylation of aryldiazonium salts. Reduction of aryldiazonium ions by single electron transfer from methanol affords aryl radical species, which undergo a subsequent C–B bond formation with bis(pinacolato)diboron. This highly practical borylation process, which can be carried out on the gram-scale, enjoys operational simplicity as well as mild and catalyst-free conditions.

scholarly journals Mixed-Oxide Catalysts with Spinel Structure for the Valorization of Biomass: The Chemical-Loop Reforming of Bioethanol

Catalysts ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 332 ◽  
Author(s):  
Olena Vozniuk ◽  
Tommaso Tabanelli ◽  
Nathalie Tanchoux ◽  
Jean-Marc Millet ◽  
Stefania Albonetti ◽  
...  
Keyword(s):  
Solid State ◽  
Spinel Structure ◽  
Mixed Oxides ◽  
Building Blocks ◽  
Short Review ◽  
Solid State Chemistry ◽  
Spinel Type ◽  
Mixed Oxide Catalysts ◽  
Versatile Tool ◽  
Review Reports

This short review reports on spinel-type mixed oxides as catalysts for the transformation of biomass-derived building blocks into chemicals and fuel additives. After an overview of the various methods reported in the literature for the synthesis of mixed oxides with spinel structure, the use of this class of materials for the chemical-loop reforming of bioalcohols is reviewed in detail. This reaction is aimed at the production of H2 with intrinsic separation of C-containing products, but also is a very versatile tool for investigating the solid-state chemistry of spinels.

Recent Advances in the Synthesis of Enantiomerically Enriched Diaryl, Aryl Heteroaryl, and Diheteroaryl Alcohols through Addition of Organometallic Reagents to Carbonyl Compounds

Synthesis ◽  
2020 ◽  
Vol 52 (13) ◽  
pp. 1855-1873
Author(s):  
Senthil Narayanaperumal ◽  
Ricardo S. Schwab ◽  
Wystan K. O. Teixeira ◽  
Danilo Yano de Albuquerque
Keyword(s):  
Carbonyl Compounds ◽  
Building Blocks ◽  
Short Review ◽  
Biological Properties ◽  
Enantioselective Synthesis ◽  
Grignard Reagents ◽  
Organometallic Reagents ◽  
Important Family ◽  
Organolithium Reagents ◽  
Organozinc Reagents

Enantiomerically enriched diaryl, aryl heteroaryl, and dihetero­aryl alcohols are an important family of compounds known for their biological properties. Moreover, these molecules are highly privileged scaffolds used as building blocks for the synthesis of pharmaceutically relevant products. This short review provides background on the enantioselective arylation and heteroarylation of carbonyl compounds, as well as, the most significant improvements in this field with special emphasis on the application of organometallic reagents.1 Introduction2 Background on the Enantioselective Synthesis of Diaryl, Aryl Heteroaryl, and Diheteroaryl Alcohols3 Organozinc Reagents4 Organolithium Reagents5 Grignard Reagents6 Organoaluminum Reagents7 Organotitanium Reagents8 Organobismuth Reagents9 Miscellaneous10 Conclusion

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