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

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.

Automated summary

This electrochemical methodology for the synthesis of 3-formylated indoles utilizes Me3N as a formylating reagent, eliminates the need for stoichiometric oxidants, metal catalysts, and activating agents, and uses a recyclable aqueous biphasic system as the reaction medium, expanding substrate scope and enhancing functional group tolerance. Late-stage functionalization and total/formal synthesis of drugs and natural products can be achieved through this sustainable and environmentally friendly approach.