Synthesis and in vitro antimicrobial activity evaluation of coumarin-3-carboxylic acids obtained via cascade reaction using chitosan as a recyclable catalyst

Abstract

In this work, commercial chitosan was used as a recyclable and biodegradable catalyst for efficient one-pot synthesis of coumarin-3-carboxylic acids in water or ethanol:water (3 : 7, v/v) at 75 °C via Knoevenagel-intramolecular cyclization cascade reaction. Coumarin-3-carboxylic acids (3a–i) were obtained from different substituted salicylaldehydes and Meldrum's acid under mild conditions in short times (10–45 min) and good isolated yields (77–88%) without requiring laborious purifications. The proposed method combined the advantages of homogeneous catalysis with recovery and recyclability of four times catalyst without compromising its catalytic activity and structural integrity. In the evaluation of in vitro antimicrobial activity against 4 bacterial and 8 fungal strains, the tested coumarin-3-carboxylic acids 3c–e, 3h, and 3i showed an inhibitory effect on the growth of the microorganisms (1024–256 μg mL⁻¹). Product 3d showed the lowest MIC against fungal and bacterial strains (256 μg mL⁻¹), suggesting a bactericidal and fungicidal nature.