Abd.Ura&: Am&M, edpeciaeey inkiazoik, wet~e dound to be e..~evu%L in the memo-teakaphenyl-po~p&nato~on(llIJ pkomoted demtihytion 06 N,N-din&hyLanXine N-oxide though the PoLonounki ape heU&Ofl and in the cumene hy&opehoxidc dependeti oxidtive demeXhyLuZion 06 N, N-c&methyLaWne in ckchX.o~omtihane. #hen benzen&kioL wan wed ititead 06 than am&en, deoxygetion 06 N,N-dimethylk~LL&e N-oxide tooh #ace ue~y hbldiey. Earlier, Terayama reported that incubation of 4-dimethylaminoazobenzene N-oxide with myoglobin or hemin afforded a mixture of N-demethylated and deoxygenated products. 1) Meanwhile, Ziegler et al. found that a hepatic microsomal hemoprotein catalyzes the demethylation of N,N-dimethylaniline N-oxide (DMAO).') Actually the purified liver microsomal cytochrome P-450 catalyzes the demethylation of DMAO. 394) Recently, the reaction of DMAO with metalloporphyrins have been proposed to be good models of cytochrome P-450 reaction. 3,596) We have shown that the meso-tetraphenylporphinatoiron(III) chloride (TPPFeIIICl) promoted oxygenation of sulfides in which imidazole is an essential component. 7) This paper deals with that amines, especially imidazole, play an essential role in the TPPFe ID promoted cleavage of N-O bond in DMAO and that of O-O bond of cumene hydroperoxide. When DMAO was treated with TPPFe=Cl in dichloromethane at room temperature, no measurable reaction took place.