An easy-to-use heterogeneous catalyst for the Knoevenagel condensation

Abstract

Physical mixtures of alkali and earth alkali metal carbonates and commercially available zeolites were investigated as solid catalysts for the Knoevenagel condensation. Best results for the model reaction between benzaldehyde and ethyl cyanoacetate were obtained for a 1:4 mixture of Na2CO3 with 4 Å molecular sieves (MS). The effects of the following parameters were investigated: structure of substrate, type and basicity of metal carbonate and zeolite, and temperature. Between 50 and 90°C chemical yields up to >90% were obtained without continuous removal of water and with reasonable catalyst activities and reaction times. Na2CO3 – MS 4 Å proved to be active for the condensation of several aldehydes and ketones with a variety of active methylene components.Key words: Knoevenagel condensation, solid basic catalysts, zeolite – sodium carbonate mixtures.