Photochemical syntheses. II. The photo-addition of diphenylacetylene to some substituted naphthalenes

Abstract

Twenty-one naphthalenes substituted with alkyl, fluoro, chloro, and cyano groups form photo-adducts with diphenylacetylene (dpa); eight naphthalenes with acyl, ammo, chloro, and bromo substituents do not react. ��� These adducts are derivatives of the adduct (1) as shown primarily by their p.m.r. and mass spectra. Except for 2-t-butylnaphthalene and possibly 1-cyano-naphthalene, two isomeric adducts are formed from naphthalene derivatives with non-equivalent rings, and addition to the more highly substituted ring is favoured with all substituents. The overall yields and the isomer ratios depend on the kind, number, and position of the substituents, and on experimental conditions, particularly the solvent. The results are discussed in terms of a mechanism previously considered for the addition of dpa to naphthalene.