The photocyclisation of 1,2-Ciarylpyridinium cations and the photobiscyclisation of 1,2,6-triarylpyridinium cations

Abstract

Photocyclisation of 1-(2-pyridyl)-2-arylpyridiniums yields benzo[c]pyrido[1,2-a]-1,8-naphthyridinylinium cations. Photobiscyclisation of 1,2,6-triarylpyridiniums gives benzo[8,9]quinolizino[4,5,6,7-fed]phenanthridinylium cations and their 9-aza-derivatives. Electron donor substituents tend to lower the yields which are otherwise high. The structures are supported by X-ray crystallographic analysis and by ultraviolet and n.m.r. spectra.