N-methyl imidazole as an efficient catalyst for Knoevenagel condensation

Carbon-carbon bond formation reaction is one of the most important reaction in organic synthesis[1]. Knoevenagel condensation is one of the most useful and widely employed reactions for carbon-carbon bond formation in organic synthesis[2]. Generally, Knoevenagel reactions are carried out by the condensation of active methylene compounds with aldehydes using some catalysts such as some bases, their salts, Lewis acids and ionic liquids in the presence or solvent free synthesis. Also the condensation products are the key intermediates for the synthesis of natural and therapeutic drugs, polymer, cosmetics and perfumes[3]. However, many of those procedures require the use of long reaction time, harsh reaction conditions and have difficulties in the reuse of catalysts, which prompt chemical researchers to further develop more efficient, cheap, operationally simple Knoevenagel protocols. Herein, we report the synthesis of arylmethylidenes from aromatic aldehydes and active compounds catalyzed by catalytic amount of N-methyl imidazole as an efficient catalyst in 50/50 ratio of Ethanol/ H2O. The reactions go to completion within 3 min and give products in excellent yields at room temperature. The effect of reaction time, amount of catalyst, solvent, different aromatic aldehydes and acidic methylene reagents (malononitril and diethylmalonate) was investigated in this condensation.