Knoevenagel Condensation Reaction Catalyzed by Task Specific Ionic Liquid

The Knoevenagel condensation under solvent-free conditions was studied in order to develop an environmentally benign process for the preparation of compounds containing double bonds.It is found that the Knoevenagel condensation of aromatic aldehydes such as benzaldehyde,methylbenzaldehydes,methoxybenzaldehydes,chlorobenzaldehydes and furan-2-carbaldehyde with active methylene compounds,ethyl cyanoacetate or malononitrile,proceeds smoothly in the presence of catalytic amounts of a task specific ionic liquid,[H_3N~+CH_2CH_2OH][CH_3CH(OH)CO_2~-],at room temperature under solvent-free condition to afford the E-alkenes in 81%～98% yields.The products were easily separated from the reaction mixture by simple washing with aqueous alcohol and purified by recrystallzation from ethanol.The mechanism of the ionic liquid catalyzed Knoevenagel reaction was discussed.