Cα Hydrogen Atom Transfer in Post-Cleavage Radical-Cation Complexes: Short and Steep versus Long Winding Road

2014 ◽  
Vol 118 (45) ◽  
pp. 10797-10803 ◽  
Author(s):  
Benjamin J. Bythell
Keyword(s):  
Hydrogen Atom ◽  
Radical Cation ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Cation Complexes

Selected-ion flow tube studies of reactions of the radical cation (HC3N)+• in the interstellar chemical synthesis of cyanoacetylene

1986 ◽  
Vol 64 (2) ◽  
pp. 399-403 ◽  
Author(s):  
A. Fox ◽  
A. B. Raksit ◽  
S. Dheandhanoo ◽  
D. K. Bohme
Keyword(s):  
Hydrogen Atom ◽  
Proton Transfer ◽  
Radical Cation ◽  
Covalent Bond ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Flow Tube ◽  
Ion Flow ◽  
Wide Range ◽  
Selected Ion Flow Tube

The radical cation (HC3N)+• was produced in a Selected-Ion Flow Tube (SIFT) apparatus from cyanoacetylene by electron impact and reacted at room temperature in helium buffer gas with a selection of molecules including H2, CO, HCN, CH4, H2O, O2, HC3N, C2H2, OCS, C2H4, and C4H2. The observed reactions exhibited a wide range of reactivity and a variety of pathways including charge transfer, hydrogen atom transfer, proton transfer, and association. Association reactions were observed with CO, O2, HCN, and HC3N. With the latter two molecules association was observed to proceed close to the collision limit, which is suggestive of covalent bond formation perhaps involving azine-like N—N bonds. For HC3N an equally rapid association has been observed by Buckley etal. with ICR (Ion Cyclotron Resonance) measurements at low pressures and this is suggestive of radiative association. The hydrogen atom transfer reaction of ionized cyanoacetylene with H2 is slow while similar reactions with CH4 and H2O are fast. The reaction with CO fails to transfer a proton. These results have implications for synthetic schemes for cyanoacetylene as proposed in recent models of the chemistry of interstellar gas clouds. Proton transfer was also observed to be curiously unfavourable with all other molecules having a proton affinity higher than (C3N)•. Also, hydrogen-atom transfer was inefficient with the polar molecules HCN and HC3N. These results suggest that interactions at close separations may lead to preferential alignment of the reacting ion and molecule which is not suited for proton transfer or hydrogen atom transfer.

Acid-promoted hydride transfer from an NADH analogue to a Cr(iii)–superoxo complex via a proton-coupled hydrogen atom transfer

2021 ◽  
Author(s):  
Tarali Devi ◽  
Yong-Min Lee ◽  
Shunichi Fukuzumi ◽  
Wonwoo Nam
Keyword(s):  
Hydrogen Atom ◽  
Radical Cation ◽  
Hydride Transfer ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Acid Proceeds

Acid-promoted hydride transfer from an NADH analogue to a Cr(iii)–superoxo complex in the presence of acid proceeds via the full formation of the NADH analogue radical cation, followed by the decay of the radical, and accompanied then by the formation of NAD+.

Efficient Reduction of Electron-Deficient Alkenes Enabled by a Photoinduced Hydrogen Atom Transfer

2020 ◽  
Author(s):  
Xacobe Cambeiro ◽  
Natalia A. Larionova ◽  
Jun Miyatake Ondozabal
Keyword(s):  
Hydrogen Atom ◽  
Aromatic Ring ◽  
Radical Cation ◽  
Electron Affinity ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Computational Studies ◽  
Atom Transfer ◽  
Efficient Reduction

Direct hydrogen atom transfer from a photoredox-generated Hantzsch ester radical cation to electron-deficient alkenes has enabled the<br>development of an efficient formal hydrogenation under mild, operationally simple conditions. The HAT-driven mechanism, key to circumvent<br>the problems associated with the low electron affinity of alkenes, is supported by experimental and computational studies. The reaction is applied<br>to a variety of cinnamate derivatives and related structures, irrespective of the presence of electron-donating or electron-withdrawing<br>substituents in the aromatic ring and with good functional group compatibility.

scholarly journals Efficient Reduction of Electron-Deficient Alkenes Enabled by a Photoinduced Hydrogen Atom Transfer

2020 ◽  
Author(s):  
Xacobe Cambeiro ◽  
Natalia A. Larionova ◽  
Jun Miyatake Ondozabal
Keyword(s):  
Hydrogen Atom ◽  
Aromatic Ring ◽  
Radical Cation ◽  
Electron Affinity ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Computational Studies ◽  
Atom Transfer ◽  
Efficient Reduction

Direct hydrogen atom transfer from a photoredox-generated Hantzsch ester radical cation to electron-deficient alkenes has enabled the<br>development of an efficient formal hydrogenation under mild, operationally simple conditions. The HAT-driven mechanism, key to circumvent<br>the problems associated with the low electron affinity of alkenes, is supported by experimental and computational studies. The reaction is applied<br>to a variety of cinnamate derivatives and related structures, irrespective of the presence of electron-donating or electron-withdrawing<br>substituents in the aromatic ring and with good functional group compatibility.

scholarly journals Efficient Reduction of Electron-Deficient Alkenes Enabled by a Photoinduced Hydrogen Atom Transfer

2020 ◽  
Author(s):  
Xacobe Cambeiro ◽  
Natalia A. Larionova ◽  
Jun Miyatake Ondozabal
Keyword(s):  
Hydrogen Atom ◽  
Aromatic Ring ◽  
Radical Cation ◽  
Electron Affinity ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Computational Studies ◽  
Atom Transfer ◽  
Efficient Reduction

Direct hydrogen atom transfer from a photoredox-generated Hantzsch ester radical cation to electron-deficient alkenes has enabled the<br>development of an efficient formal hydrogenation under mild, operationally simple conditions. The HAT-driven mechanism, key to circumvent<br>the problems associated with the low electron affinity of alkenes, is supported by experimental and computational studies. The reaction is applied<br>to a variety of cinnamate derivatives and related structures, irrespective of the presence of electron-donating or electron-withdrawing<br>substituents in the aromatic ring and with good functional group compatibility.

Direct Cyclization of Alkenyl Thioester via Transition Metal‐hydrogen Atom Transfer/radical‐polar Crossover Mechanism

2019 ◽  
Author(s):  
Shiori Date ◽  
Kensei Hamasaki ◽  
Karen Sunagawa ◽  
Hiroki Koyama ◽  
Chikayoshi Sebe ◽  
...  
Keyword(s):  
Natural Products ◽  
Hydrogen Atom ◽  
Transition Metal ◽  
Hydrogen Atom Transfer ◽  
Synthetic Method ◽  
Atom Transfer ◽  
Reaction Conditions ◽  
Hydride Hydrogen ◽  
Sulfur Heterocycles ◽  
One Step

<div>We report here a catalytic, Markovnikov selective, and scalable synthetic method for the synthesis of saturated sulfur heterocycles, which are found in the structures of pharmaceuticals and natural products, in one step from an alkenyl thioester. Unlike a potentially labile alkenyl thiol, an alkenyl thioester is stable and easy to prepare. The powerful Co catalysis via a cobalt hydride hydrogen atom transfer and radical-polar crossover mechanism enabled simultaneous cyclization and deprotection. The substrate scope was expanded by the extensive optimization of the reaction conditions and tuning of the thioester unit.</div>

Catalytic Synthesis of Cyclic Guanidines via Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Shunya Ohuchi ◽  
Hiroki Koyama ◽  
Hiroki Shigehisa
Keyword(s):  
Hydrogen Atom ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Catalytic Synthesis ◽  
Membered Ring ◽  
Biologically Active ◽  
Atom Transfer ◽  
Powerful Method ◽  
Protective Groups ◽  
The Common

A catalytic synthesis of cyclic guanidines, which are found in many biologically active compounds and natu-ral products, was developed, wherein transition-metal hydrogen atom transfer and radical-polar crossover were employed. This mild and functional-group tolerant process enabled the cyclization of alkenyl guanidines bearing common protective groups, such as Cbz and Boc. This powerful method not only provided the common 5- and 6-membered rings but also an unusual 7-membered ring. The derivatization of the products afforded various heterocycles. We also investigated the se-lective cyclization of mono-protected or hetero-protected (TFA and Boc) alkenyl guanidines and their further derivatiza-tions.

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