Acid-base bifunctional SBA-15 as an active and selective catalyst for synthesis of ethyl α-cyanocinnamate via Knoevenagel condensation

Abstract

Alanine functionalized mesoporous SBA-15 (SBA-15-Alanine) as an active and selective catalyst for Knoevenagel condensation reaction of benzaldehyde and ethyl cyanoacetate is reported. The catalyst is prepared by 2-step grafting approach using (3-chloropropyl)triethoxysilane (CPTES) followed by dl-alanine. The XRD, TEM and N2 adsorption results reveal that the mesoporous characteristic of SBA-15-Alanine is retained upon modification. Furthermore, the IR, TG/DTG, CHN and TPD analyses indicate the successful functionalization of alanine, leading to the formation of bifunctional mesoporous catalyst bearing both acidic (-COOH) and basic (-NH) sites. This catalyst exhibits acid-base cooperative effect and good catalytic performance in the Knoevenagel condensation between benzaldehyde with ethyl cyanoacetate (96.7% conversion) with 100% selective to ethyl α-cyanocinnamate under novel non-microwave instant heating conditions. The SBA-15-Alanine also shows stable catalytic performance with high reusability where insignificant decline in catalytic reactivity is observed after five successive cycles, thus suggesting a promising replacement of base catalysts in condensation reactions.