Room Temperature One-Pot Green Synthesis of Coumarin-3-carboxylic Acids in Water: A Practical Method for the Large-Scale Synthesis

A simple, facile, and convenient practical method for the room temperature one-pot synthesis of a series of potentially biologically active coumarin-3-carboxylic acids has been developed in water from the Knoevenagel condensation and intramolecular cyclization of diverse 2-hydroxybenzaldehydes with Meldrum's acid using either potassium carbonate or sodium azide as a commercially available, cheap, and eco-friendly catalyst. The salient features of the present protocol are mild reaction conditions, good to excellent yields, high atom-economy, environmentally benignity, easy isolation of products, without column chromatography, clean reaction profiles, and applicability toward large-scale synthesis.