Ru-bentonite catalyzed green Knoevenagel condensation of substituted benzaldehydes with ethyl cyanoacetate

Abstract

The full-text of the article will be published in the English version of the journal "Catalysis in Industry" No. 1, 2024.To develop Ru-incorporated bentonite clay as a heterogeneous base catalyst for use in Knoevenagel condensation as an alternative to hazardous base catalysts like pyridine, piperidine, etc., we purify the naturally occurring bentonite clay and Ru3+ cation incorporated into its interlayers of bentonite clay to improve its porosity and to increase the surface area of bentonite clay. Purified bentonite and Ru-bentonite were characterized by FTIR, PXRD, HRTEM, SEM & EDS, BET surface area analysis, and TGA. Base activation was done to these clays and a comparative study of these clays as recyclable heterogeneous catalysts for Knoevenagel Condensation was undertaken in water as a solvent for the chemical transformation of 2,4-dichlorobenzaldehyde and 4-hydroxybenzaldehyde with ethyl cyanoacetate into their corresponding α,β-unsaturated acids. The products were characterized by FTIR, 1H NMR, and 13C NMR analyses. The essential key points of this reaction are mild reaction conditions, absence of hazardous chemicals as used in classical Knoevenagel condensation, reusability of the catalyst, and high yield percentage of the products.