Coupling of amines, dialkyl acetylenedicarboxylates and formaldehyde promoted by [n-Bu4N][HSO4]: an efficient synthesis of highly functionalized dihydro-2-oxopyrroles and bis-dihydro-2-oxopyrroles

Tetrabutylammonium hydrogen sulfate [ n -Bu 4 N][HSO 4 ] is used as an efficient catalyst for the one-pot, multi-component synthesis of highly substituted dihydro-2-oxopyrroles and bis-dihydro-2-oxopyrroles by means of reaction between amines, dialkyl acetylenedicarboxylates and formaldehyde in methanol at ambient temperature. This homogeneous catalyst procedure includes some important aspects like the easy work-up, no need to column chromatography, simple and readily available precursors, relatively short reaction time, and high yields. Graphical abstract