Synthesis of 2-phenylnaphthalenes from styrene oxides using a recyclable Bronsted acidic [HNMP]+HSO4- ionic liquid

This work reports a novel and efficient protocol for the synthesis of 2-phenylnaphthalenes from styrene oxides using a recyclable ionic liquid. The ionic liquid N-methyl-2-pyrrolidone hydrogensulfate [HNMP]+HSO4- played the dual role of a catalyst and a solvent. It efficiently constructs 2-phenylnaphthalene and its derivatives in excellent yields with much simplicity in the operation. The present protocol has higher atom efficiency and wider substrate applicability. The [HNMP]+HSO4- has been effectively recycled for up to five consecutive cycles without appreciable loss in its activity.