Studies in photochemistry. Part VIII. The ultraviolet, proton magnetic resonance, and mass spectra, and photocyclisation of some styrylnaphthalenes to some benzo[c]phenanthrenes and chrysenes

Abstract

Kinetic data for the first-order ring opening of the dihydro-intermediates, formed on the photocyclisation of several styrylnaphthalene analogues, are presented and some aspects of their electronic spectra are discussed. The photocyclodehydrogenation of 1,2-di-(2-naphthyl)ethylene to benzo[g,h,i]perylene proceeded via dibenzo[c,g]-phenanthrene. Photocyclodehydrogenation of 2-methyl-1-(2,4,6-trimethylstyryl)naphthalene, 2-methyl-1-styrylnaphthalene, 1-(2,4,6-trimethylstyryl)naphthalene, and 1-(2,6-dichlorostyryl)naphthalene yielded the expected chrysene derivatives. 1-Bromo-2-styrylnaphthalene and 2-(2,4,6-trimethylstyryl)naphthalene photocyclised to benzo[c]phenanthrene and 2,4-dimethylbenzo[c]phenanthrene respectively. No migration of substituents was observed. The effect of electron impact on these styrylnaphthalenes correlates with their photochemical behaviour. The u.v. and ¹H n.m.r. spectra of the styrylnaphthalenes are discussed.