1,4-Dicarbonyl-1,4-dihydronaphthalene (1)was synthesized by the dehydrochlorination reaction of 1,4-dihydronaphthalene-1,4-dicarbonyl chloride with triethylamine and obtained as its very dilute solution, but it easily polymerized in the concentration as high as 0.1 mol/L to give its polymer. 1 generated in situ by the dehydrochlorination reaction of 1,4-dihydronaphthalene-1,4-dicarbonyl chloride in a deoxygenated toluene polymerized alternatingly with benzoquinones such as 2-dodecylthio-p-benzoquinone, 2,5-di(tert-butyl)-p-benzoquinone, p-benzoquinone, and 2,3-dichloro-5,6-dicyano-p-benzoquinone, and with benzoquinone diimines such as N,N＇-diethoxycarbonyl-p -benzoquinone diimine, N,N＇-dibenzoyl-p-benzoquinone diimine, and N,N ＇-diphenyl-p-benzoquinone diimine to give aromatic polyesters and polyamides, respectively.