Synthesis of spiro polycyclic aromatic hydrocarbons by intramolecular palladium-catalyzed arylation

The palladium-catalyzed intramolecular arylation reaction has been applied to the synthesis of the spiro polycyclic aromatic hydrocarbons and planar polycyclic aromatic hydrocarbons by formation of a six-membered ring. The reaction proceeds more readily with aryl bromides substituted with electron-withdrawing groups by using palladium acetate in N,N-dimethylformamide as the solvent. For the less reactive-p-methoxyaryl derivatives the use of LiI as an additive was shown to give the best results. The results obtained in the cyclization of nitro derivatives 21 and 23 suggest that the second step of the cyclization reaction is not an electrophilic substitution reaction.