The direct polycondensations of cubane-1,4-dicarboxylic acid with 1,4-phenylenediamine (2a), 4,4’-oxydianiline (2b), 4,4’-sulfonyldianiline (2c), and 9,9’-bis(4-aminophenyl)florene (2d) were carried out in N-methyl-2-pyrrolidone/pyridine containing triphenylphosphite and lithium chloride at 110 degrees C for 9 h. Polyamide 3a obtained from 2a was scarcely soluble in organic solvent even during heating, and was soluble only in conc-H2SO4, whereas 3c and 3d derived from 2c and 2d, respectively, were readily soluble in N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethylsulfoxide. After treating polyamide 3d with the rhodium complex catalyst in NMP, cubane units were quantitatively converted into cyclooctatetraenes.