2-Aryl-1,3-dimethylbenzimidazolines as Effective Electron and Hydrogen Donors in Photoinduced Electron-Transfer Reactions

2015 ◽  
Vol 68 (11) ◽  
pp. 1640 ◽  
Author(s):  
Eietsu Hasegawa ◽  
Shin-ya Takizawa
Keyword(s):  
Electron Transfer ◽  
Hydrogen Atom ◽  
Photoinduced Electron Transfer ◽  
Hydrogen Atom Transfer ◽  
Transfer Reactions ◽  
Organic Substrates ◽  
Iridium Complexes ◽  
Effective Electron ◽  
Hydrogen Donors ◽  
Wavelength Light

2-Aryl-1,3-dimethylbenzimidazolines (DMBIHs) have been applied to photoinduced electron-transfer reductions of various organic substrates. Either direct or indirect electron transfer between the substrates and DMBIHs is utilized to promote the desired transformations. Photoexcitation of the substrates using light above 280 nm was carried out in the former protocol whereas a photosensitization method using materials such as substituted pyrenes, ruthenium and iridium complexes that absorb longer-wavelength light was employed in the latter. In these reactions, DMBIHs undergo initial electron transfer and subsequent proton or hydrogen atom transfer.

2-Hydroxyphenyl-1,3-dimethylbenzimidazolines. Formal Two Hydrogen Atom-donors for Photoinduced Electron Transfer Reactions

2004 ◽  
Vol 33 (1) ◽  
pp. 18-19 ◽  
Author(s):  
Eietsu Hasegawa ◽  
Naoki Chiba ◽  
Tomoya Takahashi ◽  
Shinya Takizawa ◽  
Takashi Kitayama ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Hydrogen Atom ◽  
Photoinduced Electron Transfer ◽  
Transfer Reactions ◽  
Electron Transfer Reactions

The water–boryl radical as a proton-coupled electron transfer reagent for carbon dioxide, formic acid, and formaldehyde — Theoretical approach

2013 ◽  
Vol 91 (2) ◽  
pp. 155-168
Author(s):  
Waled Tantawy ◽  
Ahmed Hashem ◽  
Nabil Yousif ◽  
Eman Flefel
Keyword(s):  
Carbon Dioxide ◽  
Hydrogen Bond ◽  
Electron Transfer ◽  
Hydrogen Atom ◽  
Transfer Process ◽  
Carbonyl Compounds ◽  
Hydrogen Atom Transfer ◽  
Transfer Reactions ◽  
Atom Transfer ◽  
Proton Coupled Electron Transfer

The thermochemistry of the hydrogen atom transfer reactions from the H2O–BX2 radical system (X = H, CH3, NH2, OH, F) to carbon dioxide, formic acid, and (or) formaldehyde, which produce hydroxyformyl, dihydroxymethyl, and hydroxymethyl radicals, respectively, were investigated theoretically at ROMP2/6–311+G(3DF,2P)//UB3LYP/6–31G(D) and UG3(MP2)-RAD levels of theory. Surprisingly, in the cases of a strong Lewis acid (X = H, CH3, F), the spin transfer process from the water–boryl radical to the carbonyl compounds was barrier-free and associated with a dramatic reduction in the B–H bond dissociation energy (BDE) relative to that of isolated water–borane complexes. Examining the coordinates of these reactions revealed that the entire hydrogen atom transfer process is governed by the proton-coupled electron transfer (PCET) mechanism. Hence, the elucidated mechanism has been applied in the cases of weak Lewis acids (X = NH2, OH), and the variation in the accompanied activation energy was attributed to the stereoelectronic effect interplaying in CO2 and HCOOH compared with HCHO. We ascribed the overall mechanism as a SA-induced five-center cyclic PCET, in which the proton transfers across the so-called complexation-induced hydrogen bond (CIHB) channel, while the SOMOB–LUMOC=O′ interaction is responsible for the electron migration process. Owing to previous reports that interrelate the hydrogen-bonding and the rate of proton-coupled electron-transfer reactions, we postulated that “the rate of the PCET reaction is expected to be promoted by the covalency of the hydrogen bond, and any factor that enhances this covalency could be considered an activator of the PCET process.” This postulate could be considered a good rationale for the lack of a barrier associated with the hydrogen atom transfer from the water-boryl radical system to the carbonyl compounds. Light has been shed on the water–boryl radical reagent from the thermodynamic perspective.

2-Hydroxyphenyl-1,3-dimethylbenzimidazolines. Formal Two Hydrogen Atom-Donors for Photoinduced Electron Transfer Reactions.

ChemInform ◽  
2004 ◽  
Vol 35 (17) ◽  
Author(s):  
Eietsu Hasegawa ◽  
Naoki Chiba ◽  
Tomoya Takahashi ◽  
Shinya Takizawa ◽  
Takashi Kitayama ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Hydrogen Atom ◽  
Photoinduced Electron Transfer ◽  
Transfer Reactions ◽  
Electron Transfer Reactions

scholarly journals Photocatalytic Defluoroalkylation and Hydrodefluorination of Trifluoromethyls using o-Phosphinophenolate

2021 ◽  
Author(s):  
Can Liu ◽  
Ni Shen ◽  
Rui Shang
Keyword(s):  
Electron Transfer ◽  
Hydrogen Atom ◽  
Pharmaceutical Industry ◽  
Visible Light Irradiation ◽  
Aromatic Compounds ◽  
Photoinduced Electron Transfer ◽  
Essential Role ◽  
Hydrogen Atom Transfer ◽  
Facile Synthesis ◽  
Trifluoromethyl Groups

Abstract Under visible light irradiation, o-phosphinophenolate functions as an easily accessible photoredox catalyst to activate trifluoromethyl groups in trifluoroacetamides, trifluoroacetates, and trifluoromethyl (hetero)arenes to deliver corresponding difluoromethyl radicals. It works in relay with a thiol hydrogen atom transfer (HAT) catalyst to enable selective defluoroalkylation and hydrodefluorination. The reaction allows for the facile synthesis of a broad scope of difluoromethylene-incorporated carbonyl and (hetero)aromatic compounds, which are valuable fluorinated intermediates of interest in the pharmaceutical industry. The ortho-diphenylphosphino substituent, which is believed to facilitate photoinduced electron transfer, plays an essential role in the redox reactivity of phenolate. In addition to trifluoromethyl groups, pentafluoroethyl groups could also be selectively defluoroalkylated.

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