SYNTHESIS OF POLYCYCLIC AZONIA-AROMATIC COMPOUNDS BY PHOTOINDUCED INTRAMOLECULAR QUATERNIZATION - AZONIA DERIVATIVES OF BENZO[C]PHENANTHRENE, [5]HELICENE AND [6]HELICENE

A series of new polycyclic azonia-aromatic compounds incorporating a b enzo[c]quinolizinium ring have been synthesized by photo-induced intra molecular quaternization. Acetonitrile solutions of 2-[2-(2-chlorophen yl)vinyl]quinoline 8 and 2-[2-(1-chloro-2-naphthyl)vinyl]pyridine 9 ha ve been irradiated with a high-pressure mercury lamp through a Pyrex f ilter to afford the azonia derivatives of benzo[c]phenanthrene, viz di benzo[cf]quinolizinium salt 15 and naphtho[2,1-c]quinolizinium salt 18 , respectively, On photoreaction of 2-[2-(1-chloro-2-naphthyl)vinyl]qu inoline 10 and 2-[2-(2-chlorophenyl)vinyl]benzo[h]quinoline 11 two suc cessive cyclizations occur: the first converting substrates 10 and 11 into 10b-azonia[5]helicene salt 19 by photo-induced intramolecular qua ternization and the second converting the salt 19 into 4c-azoniabenzo[ ghi]perylene salt 20 by oxidative photocyclodehydrogenation. The photo induced intramolecular quaternization of 2-[2-(2-chlorophenyl)vinyl]-1 ,10-phenanthroline 12 gives 10-aza-10c-azonia[5]helicene salt 21. The 12c-azonia[6]helicene salts 30 and 31, in which a carbon atom of the i nner helix skeleton of [6]helicene is replaced by a quaternary nitroge n atom, have been synthesized by photo-induced quaternization of the c orresponding olefins 13 and 14, respectively.