Studies in photochemistry. Part VII. The photocyclisation of some nuclear-substituted stilbenes to substituted phenanthrenes

Abstract

Photocyclodehydrogenation of trans-9-styryl-1,2,3,4,5,6,7,8-octahydroanthracene in cyclohexane solution formed a mixture of 11-butyl- and 11-but-3-enyl-1,2,3,4-tetrahydrochrysene in very small yield, identified by their i.r., u.v., ¹H n.m.r., and mass spectra. 2,4,6-Trimethylstilbene photocyclised to 1,3-dimethylphenanthrene with the elimination of a methyl group. 3,3′,5,5′-Tetramethylstilbene formed 2,4,5,7-tetramethylphenanthrene when irradiated in cyclohexane solution. Similarly, 4,4′-dibromo- and 4,4′-dicyano-stilbene formed the corresponding 3,6-disubstituted phenanthrenes.