K2S2O8-Mediated C-3 Formylation of Imidazopyridines Using Glyoxylic Acid

Abstract

A metal-free formylation of imidazopyridines by direct decarboxylative cross-coupling of glyoxylic acid in presence of K2S2O8 as oxidant under mild and neutral conditions is described. This reaction features a broad substrate scope, good functional group tolerance, and generates products in good yields between 68–85 %. The translational capacity of the reaction from a laboratory methodology to gram-scale synthesis has also been ensured. The involvement of a radical pathway has been demonstrated by radical trapping experiments with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and 2,6-di-tert-butyl-4-methylphenol (BHT). © 2023 Wiley-VCH GmbH.