Reaction of Secondary Aromatic Amines with Manganese(III) Acetate

The reaction of 2-(methylamino)benzophenone with manganese(III) acetate afforded 5-[(o-benzoylanilino)methyl]-2-(methylamino)benzophenone, 2-aminobenzophenone, 5-formyl-2-(methylamino)benzophenone, 2-amino-5-[(o-benzoylanilino)methyl]benzophenone, 2-formamidobenzophenone, 2-amino-5-formylbenzophenone, and 2-(N-methylformamido)benzophenone. It was found that the reaction did not cause oxidative cyclization, but dimerization and conversion of N-methyl into N-formyl groups. Characterization of the products, the detailed oxidation mechanism, and the effects of the additives are discussed.