GEOMETRICAL ISOMERISM AND PHOTOCHEMICAL BEHAVIOUR OF ALPHA-SUBSTITUTED 2 AND 4-STYRYLPYRIDINES

α‐Methyl and α‐phenyl substituted 2 and 4‐styrylpyridines were prepared by classical routes. The geometrical isomers were separated and characterized on the basis of their U.V. absorption spectra and/or of their behaviour under U.V. irradiation which led to photoisomerization and photocyclization products. The last photoreaction, in the case of α‐phenyl derivatives, gave pyridyl‐substituted phenanthrenes and phenyl‐substituted azaphenanthrenes which were isolated and characterized. Spectral, chromatographic and physical properties of trans and cis derivatives and related photocyclization products are given as well as some kinetic data for the photochemical reactions. Copyright © 1969 Journal of Heterocyclic Chemistry