Recyclable and reusable n-Bu4NBF4/PEG-400/H2O system for electrochemical C-3 formylation of indoles with Me3N as a carbonyl source

Abstract

A safe, practical and eco-friendly electrochemical methodology for the synthesis of 3-formylated indoles has been developed by the utilization of Me₃N as a novel formylating reagent. Stoichiometric oxidants, metal catalysts, and activating agents were avoided in this method, and an aqueous biphasic system of n-Bu₄NBF₄/PEG-400/H₂O was used as a recyclable and reusable reaction medium, which made this electrosynthesis approach more sustainable and environmentally friendly. This process expanded the substrate scope and functional group tolerance for both N-EDG and N-EWG indoles. Furthermore, late-stage functionalization and total/formal synthesis of drugs and natural products were realized by means of this route.