Knoevenagel condensation reaction catalyzed by task-specific ionic liquid under solvent-free conditions

A task-specific ionic liquid, [H3N+–CH2–CH2–OH][CH3COO−] was synthesized and used as catalyst in the Knoevenagel condensation reaction of various kinds of aromatic aldehydes with ethyl cyanoacetate or malononitrile. α,β-Unsaturated carbonyl compounds were obtained in reasonable yields when the [H3N+–CH2–CH2–OH][CH3COO−] catalyzed Knoevenagel reaction was carried out at room temperature for several to 60 min under solvent-free conditions. Only E-isomers were detected. The task-specific ionic liquid after removed water could be recycled and reused for five times without noticeably decreasing the catalytic activity. The mechanism of the [H3N+–CH2–CH2–OH][CH3COO−] catalyzed Knoevenagel reaction was discussed.