Iron oligopyridine complexes as efficient catalysts for practical oxidation of arenes, alkanes, tertiary amines and N-acyl cyclic amines with Oxone

Abstract

The iron complexes [Fe(qpy)](ClO 4) 2 (1) (qpy = 2, 2′:6′, 2′′:6′′, 2′′′: 6′′′, 2′′′′-quinquepyridine), [Fe 2(spy) 2](ClO 4) 4 (2) (spy = 2, 2′:6′, 2′′:6′′, 2′′′: 6′′′, 2′′′′: 6′′′ ′, 2′′′′′-sexipyridine), [Fe 2(septipy) 2](ClO 4) 4 (3) (septipy = 2, 2′:6′, 2′′:6′′, 2′′′: 6′′′, 2′′′′: 6′′′′, 2′′′′′: 6′′′′′, 2′′′′′ ′-septipyridine) and SBA-15-supported iron terpyridine complex (4) are efficient catalysts for the practical oxidation of alkenes, arenes, alkanes, tertiary amines and N-acyl cyclic amines using Oxone as the oxidant. With 1, 2, 3 or 4 as the catalyst, a variety of electron-rich and electron-deficient alkenes were oxidized to the corresponding epoxides in high isolated yields (up to 99%). The reaction of arenes with Oxone afforded quinones in up to 91% isolated yields. Selective C-H bond oxidation of saturated alkanes to alcohols/ketones and demethylation of tertiary amines to secondary amines were achieved in good product yields. For the oxidation of N-acyl cyclic amines, the ring-opened products were obtained in up to 75% isolated yield with up to 96% substrate conversion. All of these iron complexes can efficiently catalyse the oxidative C-C bond cross-coupling reaction of tertiary amines with NaCN in up to 86% isolated yield using ( tBuO) 2 as the terminal oxidant. The oligopyridine ligands were oxidatively robust and could be re-used by the addition of iron(ii) salt to generate the iron catalysts in situ. The active SBA-15-supported terpy ligand could be re-used for the oxidative catalysis for five consecutive runs without significant loss of catalytic activity. © The Royal Society of Chemistry 2011.