Nano Clinoptilolite: Highly Efficient Catalyst for the Synthesis of Chromene Derivatives Under Solvent-Free Conditions

An efficient and selective synthesis of substituted chromene derivatives via three-component reaction of 4-hydroxycoumarin or 1,3-dicarbonyl compounds, activated acetylenic compounds and N-nucleophiles is described. The reaction was conducted under solvent-free conditions at 70 degrees C using potassium fluoride impregnated on natural zeolite as a cheap and available solid base. The procedure has several advantages involving selectivity, excellent yields and a convenient work-up method.