Cross-dimerization reactions that employ nonequivalent 9-fluorenones have been accomplished. This cross-dimerization doesn't employ any additives such as metals and salts, that was unthinkable heretofore. Because the cross-couplings were achieved by phosphite solvent alone, they were not only operationally simple but also productively efficient owing to suppression of homo-dimerization. Significantly, the resulting single spiroketones were transformed into a hexacycle core of dibenzo[g,p]chrysene having twofold tert-butyl groups and twofold halogen atoms. The synthesis of solution-processable and multi-tunable hexacycle, coupled with the mechanistic aspects, enables general access to non-planar polyarenes from the viewpoint of diversity-oriented synthesis.