Aqueous glyoxal: a versatile synthon in heterocyclic synthesis

Abstract

Glyoxal is a versatile, non-volatile compound with a wide range of applications, attracting significant interest from both researchers and various industries. It can be synthesized by numerous methods and is potentially derivable from natural sources. Moreover, glyoxal forms various hydrates and oligomers (e.g., dimers and trimers). Its high reactivity allows it to undergo addition, condensation, and crosslinking reactions with a wide range of compounds, including alcohols, amines, aldehydes, carboxylic acids, cellulose, polyvinyl alcohol, and urea. This review discusses the applications of aqueous glyoxal as a versatile reagent in organic synthesis, with a focus on protocols for generating diverse molecular frameworks, including five- and six-membered heterocycles, aromatic compounds, fused heterocycles, polyaza polycyclic compounds, polyoxa polycyclic compounds and polyaza–polyoxa polycyclic compounds. The employed strategies include one-pot, multicomponent reactions and sequential methods, which use different catalysts under various conditions.