Sulfonic acid supported silica coated magnetic nanoparticles (Fe3O4@SiO2@PrSO3H), was prepared by using low cost precursors and a facile immobilization technique. The final catalyst, which was characterized by XRD, FT‐IR, vibrating sample magnetometer (VSM), TEM, and TGA techniques, was found to be an efficient and environmentally benign solid acid for the Pechmann condensation of substituted phenols with ethyl acetoacetate leading to the formation of coumarin derivatives. After the reaction, the catalyst could be effortlessly separated by external magnet and reused for 22 consecutive runs, without any significant loss in catalytic efficiency. The catalytic system presented offers a reusable strategy for the efficient synthesis of coumarin, simplicity in operation, and a green reaction profile by avoiding toxic conventional catalysts and solvents.

A new system for decarboxylation of aromatic carboxylic acids under amine‐free conditions has been developed. In situ generated copper nanoparticles (Cu NPs) stabilized by tetrabutylammonium hydrogen sulfate (TBAHS) were found to catalyze the decarboxylation of aromatic carboxylic acids under amine‐free conditions. Ortho‐substituted benzoic acids bearing electron‐deficient and electron‐rich groups were effectively decarboxylated under these conditions whereas meta‐ and para‐substituted benzoic acids were less reactive and gave moderate yields of desired decarboxylated products.