SYNTHESIS OF AZONIA AROMATIC-COMPOUNDS BY PHOTOCYCLIZATION

Photocyclization provided a good route to prepare azonia derivatives of fused polycyclic aromatic compounds such as benzo[c]phenanthrene, benzo[ghi]perylene, benzo[a]coronene, picene, and [6]helicene. The photoreactions could be classified into four types; (A) photocyclization of 1-styrylpyridinium salts to benzo[a]quinolizinium derivatives, (B) photocyclizaiton of styrylquinolizinium salts to fused azonia compounds, (C) photocyclization of 2-styrylpyridine derivatives to benzo [c] quinolizinium salts, and (D) photocyclization of 1,2-diarylpyridinium salts. The photocyclization occurred when the bond order (P(rs)*) between atoms r and s, involved in the cyclization in the excited state, has a negative value.