Knoevenagel reaction[kə′nē·və‚näg·əl rē‚ak·shən]
the condensation of aldehydes or ketones with compounds containing an active methylene group in the presence of bases, resulting in the formation of ethylene derivatives. For example, a derivative of cinnamic acid (III) is obtained during the condensation of benzaldehyde (I) with the diethyl ester of malonic acid (II) in the presence of piperidine:
The Knoevenagel reaction is widely used in the laboratory for organic synthesis and in the chemical-pharmaceutical and perfume industries. The German scientist E. Knoevenagel discovered the reaction in 1896.