Annulation Reaction of Quinoxalin-2(1H)-ones Initiated by Electrochemical Decarboxylation of N-Arylglycines

Abstract

A new methodology for the synthesis of tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones has been accomplished through annulation of quinoxalin-2(1H)-ones initiated by electrochemical decarboxylation of N-arylglycines catalyzed by ferrocene. With a pair of oxidative and reductive processes occurring among the substrates and intermediates instead of on the electrodes, the electricity consumption was decreased.

Electrochemical Decarboxylative Addition of N‐Aryl Glycines to Enaminones: Access to C3‐Aminomethyl Chromones

“…With inspiration from literature reports [16a,b,d] and mechanistic studies, a plausible reaction mechanism was proposed (Scheme 6). The N ‐phenyl glycine 2 a undergoes sequential anodic oxidation and deprotonation to form a carboxyl radical A , which then discharges carbon dioxide to generate the primary carbon radical B .…”

Paraformaldehyde as C1 Synthon: Electrochemical Three‐Component Synthesis of Tetrahydroimidazo[1,5‐a]quinoxalin‐4(5H)‐ones in Aqueous Ethanol

“…According to the above-mentioned investigation and literature reports, [10][11][12] a plausible mechanism was postulated in Scheme 5. At first, the cathodic reduction of EtOH produced an ethoxide (EtŌ), [17] , which deprotonated N-arylglycines (2) to form a carboxylic ion.…”

“…[9] Chen and Yu's group [10] , and Cui and Pi's group [11] have achieved the synthesis of imidazo [1,5-a]quinoxalinones through visible light-induced cascade decarboxylation/annulation of quinoxalin-2(1H)-ones and N-arylglycines (Scheme 1a). Very recently, the electrochemical synthesis of imidazo [1,5-a]quinoxalinones from quinoxalin-2(1H)-ones and N-arylglycines has been independently realized by Huang's group [12] and our group. [13] .…”

Ferrocene as a Redox Catalyst for Organic Electrosynthesis

“…Huang's team has recently presented a method utilizing Fc as a catalyst for the decarboxylative annulation of N-aryl glycines with quinoxalinones (Figure 15B). [96] They proposed that N-aryl glycines 68 were oxidized electrocatalytically to generate α-amino C-radicals (70). [97] A portion of these electron-rich radicals are further oxidized to form iminium (71), which reacts with H 2 O, resulting in the production of aniline and formaldehyde (HCHO).…”