To easily obtain in a high yield the subject high purity compound by carrying out a reaction of methoxybromonaphthalene and ethylenedioxybutene in the presence of a specific catalyst and a co-catalyst, followed by catalytic hydrogenation, acid-hydrolysis.

6-Methoxy-2-(3-ethylenedioxybutene-1-yl)naphthalene is obtained by carrying out the reaction of 6-methoxy-2-bromonaphthalene and 3- ethylenedioxybutene in the presence of a divalent palladium salt (e.g. PdCl2) as the catalyst and phosphine (e.g. triphenylphosphine) as the co-catalyst, in the polar aprotic solvent (e.g. N,N-dimethylacetamide) at 140-150°C. Catalytic hydrogenation of the obtained compound is carried out in the presence of Raney nickel then acid hydrolyzed using aqueous hydrogen chloride to afford 4-(6- methoxynaphthalene-2-yl)-2-butanone(nabumetone).