PURPOSE: To produce the subject compound in high hyield industrially by subjecting 2-methyl-1,4-naphthoquinone and 6-methyl-1,4-naphthoquinone and a conjugated diene to Diels-Alder reaction, acetylating the resulting substance under a reducing condition, then isolating.

CONSTITUTION: A mixture of 2-methyl-1,4-naphthoquinone of formula I obtained by oxidizing 2-methylnaphthalene and 6-methyl-1,4-naphthoquinone of formula II is subjected to Diels-Alder reaction with a conjugated diene (e.g. cyclopentadiene) to give a mixture of the compound of formula I and 6- methyl-1,4,4a,9a-tetrahydro-1,4-methanoanthraquinone of formula IV. Then, this mixture is acetylated under a reducing condition and then isolated to give the objective 1,4-diacetoxy-2-methylnaphthalene of formula III. The compound of formula III is vitamin K1 useful as a hemostatic vitamin and is suitable as an intermediate for manatetrenone (vitamin K2) useful as a therapeutic agent for hypoprothrombinemia of newborn infant, intrapartum hemorrhage and hypoprothrombinemia occurring during administration of antibiotic.