Oxidation of amines in the presence of ruthenium complexes: molecular oxygen and iodosylbenzene as oxidants

Abstract

The intermediate formed during the oxidation of benzylamine with molecular oxygen at atmospheric pressure and 80 °C to yield the corresponding nitrile catalyzed by Ru(PPh 3) 2(RCH 2NH 2) 2Cl 2 ( I) (a reaction previously studied), has been shown to be Ru(PPh 3)(RCN)(RCH 2NH 2)Cl 2 (R = C 6H 5, p-CH 3OC 6H 4) ( II). A complex such as cis-Ru(bipy) 2Cl 2· 2H 2O (bipy = 2,2'-bipyridine) is inactive as catalyst in this reaction, the only product isolated being [Ru(bipy) 2(RCH 2NH 2)Cl] C1·2H 2O (R = C 6H 5) ( III). Dibenzylamine, (PhCH 2) 2NH, is oxidized to N-benzylidenebenzylamine, PhCHNCH 2Ph, by molecular oxygen at atmospheric pressure and 80 °C in the presence of Ru(PPh 3) 3Cl 2 and Ru(DMSO) 4Cl 2 as catalysts. Other secondary amines were not oxidized or gave intractable products, as in the case of N-benzylmethylamine. lodosylbenzene, PhIO, has been shown to be a very active and selective oxidant of primary and secondary amines at room temperature, its activity being negatively modified by the presence of Ru(PPh 3) 3Cl 2.