Brønsted acidic magnetic nano-Fe3O4-adorned calix[n]arene sulfonic acids: synthesis and application in the nucleophilic substitution of alcohols

Three magnetically recoverable Brønsted acidic calixn]arene derivatives were successfully constructed by immobilizing calixn]arene sulfonic acids onto silica-coated magnetic nanoparticles, a process, which allows calixn]arene derivatives to acquire magnetic properties. All of the magnetically recoverable Brønsted acidic calixn]arenes efficiently catalyze the coupling of electron-rich arenes with some alcohols in water. After separation and recovery from the reaction mixture by a simple magnet, these Brønsted acidic calixn]arenes can be recycled many times without losing their catalytic activity.