Tandem Neat Synthesis of Substituted Pyrano[3,2-c]chromen-5-ones: Unraveling the Camphor-10-sulfonic Acid Catalysis

Camphor-10-sulfonic acid (CSA) is valued for its wide range of solubility, user friendliness, cost effectiveness, and catalytic activity. This work presents a catalytic approach using a minimal amount of CSA to promote a one-pot reaction between aromatic aldehydes, acetophenones, and 4-hydroxycoumarin. This tandem neat strategy delivers the desired 2,4-diarylpyrano[3,2-c]chromen-5-one derivatives in excellent yields (65–92%). The product identity was confirmed by 1H and 13C NMR and LCMS characterization. The scalability of the method is demonstrated by achieving consistent yields in gram-scale reactions, highlighting its potential for industrial applications. Mechanistic insights were gained through controlled experiments, providing a valu­able understanding of the role of CSA in catalyzing the formation of the target compounds.