Homolytic Aromatic Substitution by Iminyl Radicals. Photolysis of Aromatic Ketone O-Acyloximes in Aromatic Solvents

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Abstract
Irradiation of benzophenone O-acetyloxime, O-phenylacetyloxime, O-benzoyloxime, and O-(p-chlorobenzoyl)oxime in benzene, toluene, chlorobenzene, or o-xylene effected aromatic substitution on the solvent molecules by diphenylmethaniminyl radicals to give N-diphenylmethylenearylamines only when benzoxyl or p-chlorobenzoxyl radicals were generated concurrently. A mechanism involving a participation of the sufficiently long-lived acyloxyl radicals is proposed for the iminylation reaction on the basis of the reactivity patterns in this substitution reaction. o-Phenylbenzophenone O-benzoyloxime was also photolyzed in benzene to give 9-phenylphenanthridine, the intramolecular cyclization product of 2-biphenylylphenylmethaniminyl radicals.