Photochemical reactions of 1-naphthylamines and haloforms: formation of bis(4-amino-1-naphthyl)methylium salts with remarkably long-wave electronic absorption

Abstract

The photochemical colour change from colourless to green of N-substituted 1-naphthylamines 1a–c in CH₂Cl₂ containing a haloform was found to be irreversible, although optically active 3-(1-naphthylamino)camphor 1a had been reported to exhibit reversible photochromism in CHCl₃. Irradiation of N-(cis-4-tert-butylcyclohexyl)-1-naphthylamine 1b with CHI₃ in hexane gave bis-1,1′-[4,4′(N-cis-4-tert-butylcyclohexyl)aminonaphthyl]methylium triiodide as green needles and N-(cis-4-tert-butylcyclohexyl)-1-naphthylamine hydroiodide as colourless crystals. A plausible pathway for the photochemical reaction of the N-substituted 1-naphthylamines with a haloform, which is initiated by electron-transfer from the nitrogen in the amines to the haloform followed by radical reactions which liberate hydrogen halide, is proposed.