PURPOSE: To produce the subject compound having high purity and free from isomers on an industrial scale at a low cost from starting raw materials consisting of an alkyIbenzene, n-butene and carbon monoxide using 3-4 steps via a p-alkylphenyl-sec-butyl ketone.

CONSTITUTION: The objective 2-(2-3C alkyl or alkenyl)-6-methylnaphthalene useful as a raw material for a high-performance polyester is produced in high purity at a low cost using inexpensive raw materials and catalysts by (1) an acylation step to selectively synthesize p-(2-3C alkyl)phenyl-sec-butyl ketone from an alkylbenzene having one 2-3C alkyl group, n-butene and carbon monoxide, (2) a hydrogenation step to hydrogenate the carbonyl group of the ketone and (3) a cyclizing dehydrogenation step or dehydration and cyclizing dehydrogenation steps to perform the cyclizing dehydrogenation of the p-alkylphenyl-sec- butyl carbinol synthesized by the step 2 optionally after dehydration.