Electrochemical oxidative annulation of amines and aldehydes or ketones to synthesize polysubstituted pyrroles

Abstract

A general and practical protocol to synthesize polysubstituted pyrroles has been established by electrooxidative annulation of amines and aldehydes or ketones.

Electrochemical Oxidative Cyclization: Synthesis of Polysubstituted Pyrrole from Enamines

“…Considering the experimental results above and previous literature reports, [6a,12] a possible mechanism was proposed for the synthesis of polysubstituted pyrroles (Scheme 4). Firstly, enamino ester 1 a could isomerize to afford the imine A, which single‐electron‐transfer (SET) oxidation form a C‐radical intermediate B at the anode.…”

Recent Advances on Pyrrole Synthesis through Different Annulation Modes

“…In 2019, during their pursuit of a more environmentally friendly strategy to construct pyrrole skeleton, the same team also developed a practical protocol to synthesize polysubstituted pyrroles via electrooxidative annulation between amines and aldehydes or ketones (Scheme 77). [112] Although corresponding imine intermediates should be prepared before the key annulation, this protocol presents good functional group tolerance and scalability under mild conditions.…”

Electrifying green synthesis: recent advances in electrochemical annulation reactions

“…77 Recently, Lei and co-workers described an annulation reaction for the preparation of indolines 78 and polysubstituted pyrroles. 79 Likewise, the author proposed an electrooxidative [3 + 2] annulation using activated phenols 67 with N-acetylindoles 68 under undivided electrolytic conditions with no external oxidant and catalyst, providing the respective benzofuro [3,2]indolines 69 in up to 99% yield (Scheme 19). 80 Both 3-substituted N-acetylindoles and 2-substituted N-acetylindoles were suitable for this transformation.…”