Oxidative N-Dealkylation of N,N-Dimethylanilines by Non-Heme Manganese Catalysts

Non-heme manganese(II) complexes [(IndH)MnIICl2] (1) and [(N4Py*)MnII(CH3CN)](ClO4)2 (2) with tridentate isoindoline pentadentate polypyridyl ligands (IndH = 1,3-bis(2′-pyridylimino)isoindoline; N4Py* N,N-bis(2-pyridylmethyl)-1,2- di(2-pyridyl)ethylamine) proved to be suitable catalyze the oxidative demethylation of N,N-dimethylaniline (DMA) various oxidants such as tert-butyl hydroperoxide (TBHP), peracetic acid (PAA), meta-chloroperoxybenzoic (mCPBA), resulting N-methylaniline (MA) a main product N-methylformanilide (MFA) result free-radical chain process under air. The effect electron-donating electron-withdrawing substituents on aromatic ring relative reactivity substrates composition (MA/MFA) was also studied showed significant impact catalytic N-demethylation reaction. Based Hammett correlation ρ −0.38 −0.45 −0.63 (TBHP) for 1 (PAA) −0.37 (mCPBA) 2, an electrophilic intermediate is suggested key oxidant. Furthermore, spectral investigation (UV-Vis) resulted in direct evidence formation high-valent oxomanganese(IV) transient radical cation intermediate, p-Me-DMA•+, suggesting that initial step manganese-catalyzed oxidations fast electron-transfer between amine high valent oxometal species. mechanisms subsequent steps are discussed.