Novel task-specific ionic liquid [Et2NH(CH2)2CO2H][AcO] as a robust catalyst for the efficient synthesis of some pyran-annulated scaffolds under solvent-free conditions

Abstract

A novel task-specific ionic liquid, 2-carboxy-N,N-diethylethanaminium acetate denoted as [Et2NH(CH2)2CO2H][AcO], is prepared in an easy process and fully characterized by using suitable methods such as FT-IR, 1H-NMR, 13C-NMR, and TG, DTG and DTA analyses. After preparation, the promoting ability of this catalyst for one-pot multicomponent synthesis of 2-amino-4H-chromenes, dihydropyrano[3,2-c]chromenes and dihydropyrano[2,3-c]pyrazoles using in situ-developed arylidenemalononitriles through Knoevenagel reaction under solvent-free conditions is described. The sustainable procedure, short reaction times (6–36 min), effortless work-up, non-chromatographic purification, good-to-excellent product yields (79–96%), ease of recovery and reusability of the catalyst up to six reaction runs without a decrease of activity are the notable features of the present protocol.