A novel synthetic approach to benzo[h]chromones via sequential intramolecular alkynoyl transfer followed by 6-endo ring closure

An intramolecular acyl transfer reaction took place on treatment of 1-methoxymethoxy-3-(2-alkynoyloxy)methyl-2-iodonaphthalenes with n-BuLi at −78°C to give 1-methoxymethoxy-2-alkynoyl-3-hydroxymethylnaphthalenes in high yields. After protection of the hydroxymethyl group as benzoates, formation of a γ-pyrone ring was easily achieved by deprotection of the MOM group followed by spontaneous 6-endo-digonal ring closure under mild acidic conditions.