Divergent coupling of ortho-alkynylnaphthols and p-quinone monoketals through a Michael addition/intramolecular annulation cascade to access benzofuryl β-naphthols

Abstract

A C₆F₅OH-catalysed tandem cyclization of ortho-alkynylnaphthols and p-quinone monoketals is disclosed. The C₆F₅OH catalyst activates alkynylnaphthol to generate an all-carbon tetrasubstituted VQM by nucleophilic addition to quinone monoketal (Michael addition). Furthermore, the C₆F₅OH catalyst triggers p-quinone monoketal to generate an electrophilic oxocarbenium cation to be captured by ortho-alkynylnaphthol regiospecifically, resulting in the formation of an all-carbon tetrasubstituted VQM, followed by an intramolecular cyclization to afford a series of 1-(3-arylbenzofuran-2-yl)naphthalen-2-ols.