WE HAVE recently illustrated the synthesis of some a-substituted 2-and 4-styrylpyridines and some aspects of their photoreactions of geometrical isomerization and phenanthrenic cyclization [ 11.We have now extended the study to a-phenyl-3-styrylpyridine. The photochemistry of this compound appears to be very interesting; by U.V. irradiation, besides the cistrans photoisomerization, the formation of three different photocyclization products is expected, as illustrated in Fig. 1.The a-phenyl-3-styrylpyridine cannot be prepared by the method adopted for the corresponding 2-and 4-styrylpyridines, i.e., by the Shaw [21 condensation of benzylpyridine and benzaldehyde, as the greater charge density in the meta than in the orrho and para position in the pyridine ring makes the proton detachment from the reactive (I 1 ( 111) It Fig. I . Photoreactions of a-phenyl-3-styrylpyridine. Cis a-phenyl-3-styrylpyndine(I); fruns a-phenyl-3-styrylpyridine(lI); IO-phenyl-4-azaphenanthrene(III); IO-phenyl-2azaphenanthrene(1V); l0-(3-pyridyl) phenanthrene(V).