Facile access to methoxylated 2-phenylnaphthalenes and epoxydibenzocyclooctenes

Methoxylated phenylethanals were treated with concentrated hydrochloric acid in 1,4-dioxane to give methoxylated 2-phenylnaphthalenes or 1,2,9,10-tetrahydro-1,9-epoxydibenzo[a,e]cyclooctenes. Yields in 2-phenylnaphthalenes were quite good and 1,2,9,10-tetrahydro-1,9-epoxydibenzo[a,e]cyclooctenes could be easily isolated. 2-Phenylnaphthalenes were obtained by a tandem aldol condensation-intramolecular Friedel–Crafts cyclisation and 1,2,9,10-tetrahydro-1,9-epoxydibenzo[a,e]cyclooctenes by a O-condensation followed by a double intramolecular Friedel–Crafts alkylation.