Preparation of a novel, efficient, and recyclable magnetic catalyst,γ-Fe2O3@HAp-Ag nanoparticles, and a solvent- and halogen-free protocol for the synthesis of coumarin derivatives

In this protocol, Ag supported on the hydroxyapatite-core–shell magnetic γ-Fe2O3nanoparticles（γFe2O3@HAp-Ag NPs） as a novel, efficient, and magnetically recyclable catalyst is synthesized, and characterized by transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, Fourier transform infrared spectroscopy（FT-IR）, X-ray diffraction（XRD）, and vibrating sample magnetometry（VSM）. The use of the catalyst is described in the synthesis of coumarin derivatives by the Pechmann condensation of various phenols with β-ketoesters under solvent- and halogen-free conditions at 80℃.This novel and inexpensive method offers advantages, such as recyclability simple experimental protocol, short reaction time, minimal work-up procedure, and excellent yields of products, together with desirable, eco-friendly, green aspects by avoiding toxic elements and solvents, and ease of recovery from the reaction mixture using an external magnet.