Electroreduction of quinones under aprotic conditions

A study of glassy carbon electrodes modified with azobenzene derivatives

“…But to a certain extent, the native quinone groups are still blocked by the AB, GBC and FBK films. Recently, it has been proposed that the aryl radical formed by diazonium reduction can react with carbonyl groups [58]. This might be an alternative explanation for a decrease in the O 2 reduction current at pre-wave potentials, besides steric hindrance caused by an aryl layer.…”

Electrosynthesis of Oxazol‐2(3H)‐Ones and Diaroylhydrazines from 1,2‐Dicarbonyl Compounds and Arenediazonium Salts

“…The coupling reaction of the N ‐methylaminocarbonyl radical and the radical anion of diketone 1 produces the alkoxide anion ( I ) that, due to the absence of steric hindrance (present however when DMF was used as the solvent), attacks the amidic carbonyl group, as showed in Scheme . Simultaneous migration of methylamine (as leaving group) to the adjacent carbonyl moiety, affords N ‐methyl 4,5‐disubstituted oxazol‐2‐ones 2 ( a , b ) after further protonation of II , followed by dehydration and final cyclization.…”

“…The former, that evolves to an aryl radical, can further abstract the hydrogen atom at the formyl position of N-methylformamide, which is converted to the Nmethyl aminocarbonyl radical, as it was already reported. [6] The coupling reaction of the N-methylaminocarbonyl radical and the radical anion of diketone 1 produces the alkoxide anion (I) that, due to the absence of steric hindrance (present however when DMF was used as the solvent [4] ), attacks the amidic carbonyl group, as showed in Scheme 2. Simultaneous migration of methylamine (as leaving group) to the adjacent carbonyl moiety, affords N-methyl 4,5-disubstituted oxazol-2-ones 2(a,b) after further protonation of II, followed by dehydration and final cyclization.…”

“…[3] The electroreduction of quinones in DMF, acetonitrile or 1,2dichloroethane, under controlled potential conditions and in the presence/absence of benzenediazonium tetrafluoroborate, was described to be an interesting entry to new hydroxy carboxamides, dioxins, cyanomethylated derivatives and other useful compounds. [4] Similarly concomitant electrochemical reduction of a representative o-quinone scaffold, 9,10-phenanthrenequinone, and benzenediazonium tetrafluoroborate, using other organic solvents such as chloroform, dichloromethane or chloroacetonitrile led to new coupling products [5] by electro-chemically promoted radical pathways that offered wide scope to solvents with labile C-H bonds. When N-methylformamide (NMF) was used as the solvent in the simultaneous reduction of 9,10-phenanthrenequinone (or 1,10-phenanthroline-5,6-dione) and a diazonium salt, 1,3,4-oxadiazol-2(3H)-ones and dibenzo [c,e]azepines were surprisingly obtained ( Figure 1a).…”

Preparation of ursodeoxycholic acid from 7-ketone lithocholic acid by stereoselective electroreduction

“…A number of methods for creating a chiral environment have been reported using electrochemical stereoselective synthesis, such as the use of chiral solvents [16][17][18], chiral supporting electrolytes [17][18][19][20], intrinsic optical substrate conformation [19], chiral electrodes [21][22][23], and chiral catalytic systems [24,25]. In the previous work [26], our group synthesized 7-ketolithocholic acid, which is an important intermediate in ursodeoxycholic acid synthesis, by indirect electrooxidation.…”