Electrochemical Cross‐Coupling of C(sp²)−H with Aryldiazonium Salts via a Paired Electrolysis: an Alternative to Visible Light Photoredox‐Based Approach

Abstract

Photoredox‐based C−H bond functionalization constitutes one of the most powerful and atom‐economical approaches to organic syntheses. During this type of reaction, single electron transfer takes place between the photocatalyst (PC) and redox‐ active substrates. Electrosynthesis also involves electron transfer between substrates and electrodes. In this paper, we focus upon electrochemical cross‐coupling of C(sp2)−H with aryldiazonium salts and have developed an efficient electrochemical approach to the Minisci‐type arylation reaction. The constant current paired electrosynthesis proceeds in a simple undivided cell without external supporting electrolyte, features a wide range of substrates and is easy to scale‐up. These results demonstrate that photoredox‐based cross‐coupling of C(sp2)−H with aryldiazonium salts can also proceed successfully under paired electrolysis conditions, thereby contributing to understanding of the parallels between photosynthesis and electrosynthesis.magnified image

Recent Advances in Paired Electrosynthesis

“…For example, an electrochemical Minisci‐type arylation has been reported (as an alternative to visible light photoredox processes) based on a diazonium starting material (Figure 18). This C(sp 2 )−H arylation process using aryldiazonium salts via a paired electrolysis has been reported by Jiang et al [66] . for a range of substrates and for a range of diazonium salts.…”

Mechanochemical Synthesis of 2‐Arylquinoxalines and 3‐Arylquinoxalin‐2(1H)‐ones via Aryldiazonium Salts

“…In 2019, Lei and Zhang's team [8] developed a electrochemical arylation method for the synthesis of 2‐arylquinoxaline and other electron‐deficient arenes utilizing acetonitrile (CH 3 CN) and trifluoroacetic acid (TFA) as the co‐solvent (Figure 1). Almost at the same time, Zeng and co‐workers [9] developed electrochemical cross‐coupling of C(sp 2 )−H with aryldiazonium salts in DMSO, affording the product of 2‐arylquinoxaline and 3‐arylquinoxalin‐2(1 H )‐one (Figure 1).…”

Green Chemistry: Electrochemical Organic Transformations via Paired Electrolysis

“…More recently, Zeng and co-workers reported efficient linear C­(sp 2 )–H electrochemical cross-coupling reactions . Different types of quinoxalin-2­(1 H )-one 84 and phenyldiazonuim salt 85 could afford a wide range of desired compound 86 in moderate to good yields (Scheme ).…”