Electrophilic Thallation of Aniline Derivatives and Nitrogen Heterocycles with Phenylthallium(III) 18-Crown-6 Diperchlorate

Electrophilic thallation of diphenylamine, diphenylmethylamine, triphenylamine, pyrrole, N-methylpyrrole, and pyrazole with [PhTl^III(18-crown-6)] (ClO₄) (1) gives compounds of the type [PhArTl^III(18-crown-6)](ClO₄) (Ar = aryl = 4′-(phenylamino)phenyl, 4′-(methylphenylamino)phenyl, 4′-(diphenylamino)phenyl, 2′-pyrrolyl, 2′-N-methylpyrrolyl, and 4′-pyrazolyl, respectively). On the other hand, the reaction of 1 with imidazole resulted in coordination of imidazole nitrogen to the thallium ion without substitution at the ring. The character of Tl-C bonds formed by the thallation is discussed on the basis of spin-spin coupling constants between thallium nucleus and ortho protons of the phenyl group, ³J_TlH2.