Characterization of electrochemical reactions hidden in the background discharge the redox catalyzed reduction of fluorobenzene

Metal‐Free Photoredox‐Catalyzed Hydrodefluorination of Fluoroarenes Utilizing Amide Solvent as Reductant

“…From these results, the oxidation potential of the lowest singlet excited state (S 1 ) of 1 is estimated to be −2.94 V vs. SCE in DMF, which is slightly higher than the reported value of 1* (−3.25 V vs. SCE in MeCN) [16,22] . This value is almost equal to oxidation potentials of highly reducing alkali metals, [9c] and is close to the reported value of the reduction potential of fluorobenzene 2 a (−2.97 V vs. SCE in DMF) [3a] . In order to prove the SET step from 1* to fluoroarenes 2 , Stern‐Volmer fluorescence quenching experiments were conducted between 1 and arenes 2 a , 2 x , and 3 a in DMF (Figure 1b).…”

Photoinduced C−F Bond Cleavage in Some Fluorinated 7-Amino-4-quinolone-3-carboxylic Acids

“…This species fragments to the corresponding σ aryl radical ( 8 or 9 , see Scheme ) with structure-dependent efficiency. The fluorobenzene radical anion has been characterized, and there are few known defluorinations via the radical anion, although in polysubstituted aromatics other substituents are as a rule lost in preference to fluorine. , Thus, defluorination from the radical anion is expected to occur inefficiently, even though it is facilitated with the present substrates by the substituent stabilization of the resulting aryl radicals. Indeed, electron-transfer quenching of the excited states by sulfite mainly leads to physical decay via back-electron transfer rather than to chemical reaction.…”

Electrosynthetic C–F bond cleavage

“…Electroanalytical studies of C-F bond cleavage in fluorobenzenes were first reported more than 50 years ago, 21,22 establishing that the standard reduction potential for fluorobenzene was close to -3 V vs SCE. 23,24 One of the first synthetic protocols for hydrodefluorination of fluoroarenes was reported by Kariv-Miller et al 25 Using a Hg pool cathode in the presence of dimethylpyrrolidinium tetrafluoroborate ((DMP)BF 4 ), selective monodefluorination of 1,3difluorobenzene to fluorobenzene was achieved in 85% yield using a divided cell setup (Figure 2, top). A constant current of 1.25 mA/cm 2 at 2 o C and 2 F/mol was found optimal for the monodefluorination, whereas higher current densities resulted in over-reduction to benzene.…”

“…SCE. 23,24 One of the first synthetic protocols for hydrodefluorination of fluoroarenes was reported by Kariv-Miller et al 25 Using a Hg pool cathode in the presence of dimethylpyrrolidinium tetrafluoroborate ((DMP)BF 4 ), selective monodefluorination of 1,3-difluorobenzene to fluorobenzene was achieved in 85% yield using a divided cell setup (Fig. 2, top).…”