Cobalt-catalyzed asymmetric hydrogenation of enamides enabled by single-electron reduction

Science ◽  
2018 ◽  
Vol 360 (6391) ◽  
pp. 888-893 ◽  
Author(s):  
Max R. Friedfeld ◽  
Hongyu Zhong ◽  
Rebecca T. Ruck ◽  
Michael Shevlin ◽  
Paul J. Chirik
Keyword(s):  
Asymmetric Hydrogenation ◽  
Single Electron ◽  
Electron Reduction

scholarly journals An electron transfer driven magnetic switch: ferromagnetic exchange and spin delocalization in iron verdazyl complexes

2018 ◽  
Vol 47 (18) ◽  
pp. 6351-6360 ◽  
Author(s):  
David J. R. Brook ◽  
Connor Fleming ◽  
Dorothy Chung ◽  
Cardius Richardson ◽  
Servando Ponce ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Spin Crossover ◽  
Large Change ◽  
Single Electron ◽  
Spin Multiplicity ◽  
Magnetic Switch ◽  
Ferromagnetic Exchange ◽  
Spin Delocalization ◽  
Electron Reduction

A single electron reduction of an iron bis(verdazyl) complex results in a large change in spin multiplicity resulting from a combination of spin crossover and exceptionally strong ferromagnetic exchange.

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 Enzymatic single-electron reduction and aerobic cytotoxicity of tirapazamine and its 1-oxide and nor-oxide metabolites

Chemija ◽  
2018 ◽  
Vol 29 (4) ◽  
Author(s):  
Jonas Šarlauskas ◽  
Aušra Nemeikaitė-Čėnienė ◽  
Audronė Marozienė ◽  
Lina Misevičienė ◽  
Mindaugas Lesanavičius ◽  
...  
Keyword(s):  
Side Effects ◽  
Anticancer Agent ◽  
Redox Cycling ◽  
Nitroaromatic Compounds ◽  
Single Electron ◽  
Reductive Activation ◽  
Cell Nuclei ◽  
Electron Reduction ◽  
Phenylene Diamine

Aerobic cytotoxicity of 3-amino-1,2,4-benzotriazine-1,4-dioxide (tirapazamine, TPZ), a bioreductively activated hypoxia-specific anticancer agent, is responsible for TPZ side effects in chemotherapy. In order to clarify its mechanisms, we examined the aerobic cytotoxicity of TPZ and its main metabolites, 3-amino-1,2,4-benzotriazine-1-oxide and 3-amino-1,2,4-benzotriazine in murine hepatoma MH22a cells, and their reduction by NADPH:cytochrome P-450 reductase (P-450R) and ferredoxin:NADP+ reductase (FNR). Analogous studies of several quinones and nitroaromatic compounds with similar values of single-electron reduction midpoint potentials (E17) were carried out. In single-electron reduction by P-450R and FNR, the reactivity of TPZ and its monoxide was similar to that of quinones and nitroaromatics, and increased with an increase in their E17. The cytotoxicity of TPZ and its metabolites possessed a prooxidant character, because it was partly prevented by an antioxidant N,N’-diphenyl-p-phenylene diamine and desferrioxamine, and potentiated by 1,3-bis(2-chloroethyl)-1-nitrosourea. Importantly, the cytotoxicity of TPZ and, possibly, its 1-N-oxide, was much higher than that of quinones and nitroaromatics with similar values of E17 and redox cycling activities. A possible additional factor in the aerobic cytotoxicity of TPZ is its reductive activation in oxygen-poor cell nuclei, leading to the formation of DNA-damaging species similar to those forming under hypoxia.

ChemInform Abstract: PREPARATION OF β-(P′-NITROAZOXY)BENZENE AND ITS SINGLE-ELECTRON REDUCTION

1977 ◽  
Vol 8 (38) ◽  
pp. no-no
Author(s):  
V. S. SMOLYAKOV ◽  
Z. V. TODRES ◽  
A. N. USHAKOV ◽  
L. A. NEIMAN
Keyword(s):  
Single Electron ◽  
Electron Reduction

α-Amino Radicals via Photocatalytic Single-Electron Reduction of Imine Derivatives

ACS Catalysis ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 2009-2025 ◽  
Author(s):  
Jamie A. Leitch ◽  
Thomas Rossolini ◽  
Tatiana Rogova ◽  
J. Andrew P. Maitland ◽  
Darren J. Dixon
Keyword(s):  
Single Electron ◽  
Electron Reduction

Rate of single electron reduction of Togni’s reagent

2017 ◽  
Vol 203 ◽  
pp. 218-222 ◽  
Author(s):  
Nico Santschi ◽  
Thomas Nauser
Keyword(s):  
Single Electron ◽  
Electron Reduction

scholarly journals Mechanistic Insights on Hypervalent Iodine-Mediated Styrene Hetero- and Homodimerization

2020 ◽  
Author(s):  
Aqeel A. Hussein ◽  
Ahmed Al-Yasari ◽  
Yumiao Ma
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Single Electron ◽  
Hypervalent Iodine ◽  
Functional Theory ◽  
Rate Determining Step ◽  
Before And After ◽  
Electron Reduction ◽  
Dynamics Simulations ◽  
Insight Into

A mechanistic insight into the hetero- and homodimerizations (HETD and HOMD) of styrenes promoted by hypervalent iodine reagents (HVIRs; DMP and PIDA) and facilitated by HFIP to yield all trans cyclobutanes is reported using density functional theory (DFT) calculations. The HFIP molecules lower the energy of the single electron oxidation (SEO) or initiation as a result of strong hydrogen bonding interactions that substantially stabilize the frontier orbitals before and after electron addition. The HETD or HOMD is a radically-characterized π-π stacked head-to-head stepwise [2+2] cycloaddition initiated via SEO by DMP or PIDA, respectively. DFT results supported by quasiclassical molecular dynamics simulations show that HOMD is a competing pathway to HETD although the latter is relatively faster, in accordance with experimental observations. The initiation is a rate-determining step as a thermodynamically endergonic and propagation is accomplished by radically-cationic hetero- and homodimerized intermediate as propagation is faster than single electron reduction (SER) or termination by radically-anionic HVIRs. Initiation by DMP found to be faster and less endergonic than by PIDA due to (1) the energy gap of electron transfer in a SEO step by I(V) is lower than I(III) and (2) the SOMO energy of the radical anion I(V) is lower than I(III). Furthermore, the presence of p-methoxy group is essential to underpin the SEO by which the more thermodynamically favorable SEO leads to a successful cycloaddition as the thermodynamic term represents a major contribution in the initiative barrier.

scholarly journals Thermodynamics Control Reactivity of Hypervalent Iodine-Mediated Styrene Hetero- and Homodimerization: Mechanistic Insights

2020 ◽  
Author(s):  
Aqeel A. Hussein ◽  
Ahmed Al-Yasari ◽  
Yumiao Ma
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Single Electron ◽  
Hypervalent Iodine ◽  
Functional Theory ◽  
Rate Determining Step ◽  
Before And After ◽  
Electron Reduction ◽  
Dynamics Simulations ◽  
Insight Into

A mechanistic insight into the hetero- and homodimerizations (HETD and HOMD) of styrenes promoted by hypervalent iodine reagents (HVIRs; DMP and PIDA) and facilitated by HFIP to yield all trans cyclobutanes is reported using density functional theory (DFT) calculations. The HFIP molecules lower the energy of the single electron oxidation (SEO) or initiation as a result of strong hydrogen bonding interactions that substantially stabilize the frontier orbitals before and after electron addition. The HETD or HOMD is a radically-characterized π-π stacked head-to-head stepwise [2+2] cycloaddition initiated via SEO by DMP or PIDA, respectively. DFT results supported by quasiclassical molecular dynamics simulations show that HOMD is a competing pathway to HETD although the latter is relatively faster, in accordance with experimental observations. The initiation is a rate-determining step as a thermodynamically endergonic and propagation is accomplished by radically-cationic hetero- and homodimerized intermediate as propagation is faster than single electron reduction (SER) or termination by radically-anionic HVIRs. Initiation by DMP found to be faster and less endergonic than by PIDA due to (1) the energy gap of electron transfer in a SEO step by I(V) is lower than I(III) and (2) the SOMO energy of the radical anion I(V) is lower than I(III). Furthermore, the presence of p-methoxy group is essential to underpin the SEO by which the more thermodynamically favorable SEO leads to a successful cycloaddition as the thermodynamic term represents a major contribution in the initiative barrier.

The electron that breaks the catalyst’s back – excited state dynamics in intermediates of molecular photocatalysts

2021 ◽  
Author(s):  
Carolin Müller ◽  
Ilse Friedländer ◽  
Benedikt Bagemihl ◽  
Sven Rau ◽  
Benjamin Dietzek
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Single Electron ◽  
Intramolecular Electron Transfer ◽  
Excited State Dynamics ◽  
Transfer Processes ◽  
Electron Reduction ◽  
Electron Transfer Processes ◽  
Franck Condon

In situ spectroelectrochemical studies focussing on the Franck-Condon region and sub-ns electron transfer processes in Ru(II)-tpphz-Pt(II) based photocatalysts reveal that single-electron reduction effectively hinders intramolecular electron transfer between the photoexcited...

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