Clean synthesis of coumarin-3-carboxylic acids using water extract of rice straw husk

Here, the authors report a novel methodology for the synthesis of coumarin-3-carboxylic acids by using water extract of rice straw ash, which is a simple method for obtaining the final product. Coumarin-3-carboxylic acids have been synthesized from several substituted salicylaldehydes and Meldrum's acid as starting materials in outstanding yields (72-94%) in 220-320 min at room temperature.