New Applications of Crown Ethers. II. Synthesis of 4′-Formylbenzocrown Ethers

Abstract 4′-Formylbenzo-15-crown-5, -18-crown-6, and bis(4′-formylbenzo)-18-crown-6 were conveniently synthesized in excellent yields by Smith modification of Duff reaction: formylation with hexamethylenetetramine and trifluoroacetic acid or methanesulfonic acid.