Efficient iron catalyzed ligand-free access to acridines and acridinium ions

Abstract

Acridines and acridinium ions are one of the important classes of compounds in terms of their usefulness in pharmaceuticals, materials, dyes and photo-catalysis. Here we present an unconventional FeCl₃-alcohol catalysed one-pot method for their synthesis directly from aldehydes, 1,3-cyclohexanedione and amines. This method efficiently merged high atom-economy and diversity of multicomponent reaction with novel iron catalyzed dehydrogenation, using aerobic oxygen as the terminal oxidant, in alcoholic solvent to produce water as the only by-product. Easy scaling up of the method has been successfully demonstrated.