Amidation of unfunctionalized hydrocarbons catalyzed by ruthenium cyclic amine or bipyridine complexes

Abstract

Selective amidation of simple hydrocarbons with pre-isolated and in-situ formed iminoiodanes catalyzed by ruthenium complexes [Ru(III)(Me 3tacn)(CF 3CO 2) 3·H 2O] (2b, Me 3tacn = N,N',N -trimethyl-1,4,7-triazacyclononane) and cis-[Ru(II)(6,6'-Cl 2bpy) 2Cl 2] (3, 6,6'-Cl 2bpy = 6,6'-dichloro-2,2'-bipyridine) was investigated. With PhI=NTs as nitrogen source, both catalysts efficiently promote the amidation of adamantane, cyclohexene, ethylbenzene, cumene, indan, tetralin, and diphenylmethane to afford N-substituted sulfonamides in 80-93% yields with high selectivity. Competitive amidations of para-substituted ethylbenzenes and kinetic isotope effect for the amidation of cyclohexene/cyclohexene-d 10 suggest that the amidation processes probably proceed via the hydrogen abstraction by a reactive Ru=NTs species to form a carboradical intermediate. The amidation with PhI(OAc) 2/TsNH 2 gave results comparable to those obtained with PhI=NTs. Extension of the 'PhI(OAc) 2/TsNH 2 + catalyst 2b or 3' protocol to MeSO 2NH 2 and PhCONH 2 with ethylbenzene as substrate produced the corresponding N-substituted amides in up to 89% yield.