An Electrocatalytic Strategy for Dehydrogenative [4 + 2] Cycloaddition over a Cobalt‐Based Catalyst

Abstract

Exploring the anodic reaction to substitute conventional oxygen evolution reaction (OER) for the synthesis of complex pharmaceutical molecules is highly attractive. Here, we report an electrocatalytic strategy for dehydrogenative [4+2] cycloaddition of N,N-dialkylanilines with maleimides via dual functionalization of both C(sp 3 )-H and C(sp 2 )-H bonds, by using an electrochemically activated cobalt carbonate hydroxide hydrate supported on carbon cloth (CCHH-A/CC), affording various tetrahydroquinolines with high yields. This electrochemical transformation proceeds with high activity and stability, as well as good substrate compatibility. Mechanism study shows that α-aminoalkyl radical exists in the electrooxidation reaction. This strategy shows significant potential for the synthesis of valuable chemicals by using an electrocatalytic strategy.

Recent advances in radical-mediated intermolecular (4 + 2) cycloaddition

“…31 Later, in 2022, Ma, Duan and coworkers also reported a novel electrocatalytic strategy for dehydrogenative (4 + 2) cycloaddition of N , N -dimethylanilines with maleimides (Scheme 18c). 32 This strategy affords a variety of tetrahydroquinolines with high yields via dual functionalization of both C(sp 3 )–H and C(sp 2 )–H bonds with the use of electrochemically activated cobalt carbonate hydroxide hydrate supported on carbon cloth (CCHH-A/CC).…”

Ferrocene as a Redox Catalyst for Organic Electrosynthesis

“…[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). Simultaneously, some of the α-amino C-radicals (70) add to quinoxalinones to yield diamine (73) following a single electron reduction and protonation.…”

“…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).…”