Cooperative Hydrogen Atom Transfer: From Theory to Applications

Synlett ◽  
2021 ◽  
Author(s):  
Padmanabha Venkatesh ◽  
Julian G West
Keyword(s):  
Organic Chemistry ◽  
Hydrogen Atom ◽  
Closed Shell ◽  
Reaction Scheme ◽  
Hydrogen Atom Transfer ◽  
Radical Center ◽  
Atom Transfer ◽  
Hydrogen Atoms ◽  
Strength Differential ◽  
Radical Reduction

Hydrogen atom transfer (HAT) is one of the fundamental transformations of organic chemistry, allowing for the interconversion of open and closed shell species through the concerted movement of a proton an electron. While the value of this transformation is well-appreciated in isolation, allowing for homolytic C–H activation via abstractive HAT and radical reduction via donative HAT, cooperative HAT (cHAT) reactions, where two hydrogen atoms are removed or donated to vicinal reaction centers in succession proceeding through radical intermediates, are comparatively unknown outside of the mechanism of desaturase enzymes. This tandem reaction scheme has important ramifications in the thermochemistry of each HAT, with the bond dissociation energy of the C–H bond adjacent to the radical center being significantly lowered compared to that of the parent alkane, allowing for each HAT to be performed by different species. Here we discuss the thermodynamic basis of this bond strength differential in cHAT and demonstrate its use as a design principle in organic chemistry for both dehydrogenative (application 1) and hydrogenative (application 2) reactions. Together, we hope that this overview will highlight the exciting reactivity possible with cHAT and inspire further development using this mechanistic approach.

ChemInform Abstract: Catalytic Hydrogen Atom Transfer (HAT) for Sustainable and Diastereoselective Radical Reduction.

ChemInform ◽  
2013 ◽  
Vol 44 (2) ◽  
pp. no-no
Author(s):  
Andreas Gansaeuer ◽  
Max Klatte ◽  
Gerhard M. Braendle ◽  
Joachim Friedrich
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Radical Reduction ◽  
Catalytic Hydrogen

Effect of the Kerogen Molecular Structure on the Formation of Methane During Kerogen Pyrolysis

2019 ◽  
Vol 72 (3) ◽  
pp. 174 ◽  
Author(s):  
Qing Wang ◽  
Xinmin Wang ◽  
Shuo Pan
Keyword(s):  
Hydrogen Atom ◽  
Energy Barrier ◽  
Density Functional ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Reaction Energy ◽  
Hydrogen Atoms ◽  
Energy Barriers ◽  
Kerogen Pyrolysis ◽  
Intramolecular Hydrogen

In this study, density functional theory (DFT) at the GGA/RPBE level was employed to examine the effects of the kerogen microstructure on the formation mechanism of methane during the pyrolysis of kerogen. The calculations prove that the evolution of CH4 during kerogen pyrolysis corresponds to demethylation, and the process of forming methane involves the interaction of intramolecular hydrogen atom transfer and assistant hydrogen atom transfer. In all reaction paths, the energy barrier of path 5 is the smallest at 260.56kJmol−1. The energy barrier of path 6 is the largest at 554.36kJmol−1. The results indicate that CO is favourable for demethylation, and CO2 is not conducive to demethylation. Path 1 is the formation of methane by the transfer of assistant hydrogen atoms, and the required energy barrier is 379.45kJmol−1. The side chain structure of the aromatic hydrocarbon structure is liable to demethylation to form methane. A comparison of the reaction energy barriers follows the order: path 1<path 15<path 14<path 10, which indicates the that difference in the demethylation reaction is based on the microstructure. In the same reaction process, the benzene ring and the aliphatic hydrocarbon structure are more susceptible to demethylation to form methane. In the heterocyclic bicyclic structures containing O and S, a comparison of the reaction energy barriers follows the order: path 11 ≈ path 12<path 13, so paths 11 and 12 are close, but path 13 is more difficult to occur, indicating that it is more difficult to demethylate with heteroatoms in the same ring. From a thermodynamic point of view, in the process of assisting the formation of methane by hydrogen atoms, the demethylation reaction is mainly an endothermic reaction. During the transfer of intramolecular hydrogen atoms, the demethylation reaction is mainly an exothermic reaction, and most reactions are spontaneous.

scholarly journals Triarylamine-based porous coordination polymers performing both hydrogen atom transfer and photoredox catalysis for regioselective α-amino C(sp3)–H arylation

2021 ◽  
Author(s):  
Hanning Li ◽  
Yang Yang ◽  
Jing Xu ◽  
Cheng He ◽  
Chunying Duan
Keyword(s):  
Organic Chemistry ◽  
Hydrogen Atom ◽  
Coordination Polymer ◽  
Coordination Polymers ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Photoredox Catalysis ◽  
Porous Coordination Polymers ◽  
Direct Functionalization

Direct functionalization of C(sp3)–H bonds in a predictable, selective and recyclable manner has become a central challenge in modern organic chemistry. Through incorporating different triarylamine-containing ligands into one coordination polymer,...

scholarly journals Remote C–H Functionalization via Selective Hydrogen Atom Transfer

Synthesis ◽  
2018 ◽  
Vol 50 (08) ◽  
pp. 1569-1586 ◽  
Author(s):  
David Nagib ◽  
Leah Stateman ◽  
Kohki Nakafuku
Keyword(s):  
Hydrogen Atom ◽  
Closed Shell ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Alkoxy Radical ◽  
Radical Initiation ◽  
Selective Functionalization ◽  
Modern Methods ◽  
Intramolecular Hydrogen ◽  
New Strategies

The selective functionalization of remote C–H bonds via intramolecular hydrogen atom transfer (HAT) is transformative for organic synthesis. This radical-mediated strategy provides access to novel reactivity that is complementary to closed-shell pathways. As modern methods for mild generation of radicals are continually developed, inherent selectivity paradigms of HAT mechanisms offer unparalleled opportunities for developing new strategies for C–H functionalization. This review outlines the history, recent advances, and mechanistic underpinnings of intramolecular HAT as a guide to addressing ongoing challenges in this arena.1 Introduction2 Nitrogen-Centered Radicals2.1 sp3 N-Radical Initiation2.2 sp2 N-Radical Initiation3 Oxygen-Centered Radicals3.1 Carbonyl Diradical Initiation3.2 Alkoxy Radical Initiation3.3 Non-alkoxy Radical Initiation4 Carbon-Centered Radicals4.1 sp2 C-Radical Initiation4.2 sp3 C-Radical Initiation5 Conclusion

Sustainable Radical Reduction through Catalytic Hydrogen Atom Transfer

2008 ◽  
Vol 130 (22) ◽  
pp. 6916-6917 ◽  
Author(s):  
Andreas Gansäuer ◽  
Chun-An Fan ◽  
Frederik Piestert
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Radical Reduction ◽  
Catalytic Hydrogen
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