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

Selective amidation of simple hydrocarbons with pre-isolated and in-situ formed iminoiodanes catalyzed by ruthenium complexes [Ru(III)(Me3tacn)(CF3CO2)3·H2O] (2b, Me3tacn = N,N',N-trimethyl-1,4,7-triazacyclononane) and cis-[Ru(II)(6,6'-Cl2bpy)2Cl2] (3, 6,6'-Cl2bpy = 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-d10 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/TsNH2 gave results comparable to those obtained with PhI=NTs. Extension of the 'PhI(OAc)2/TsNH2 + catalyst 2b or 3' protocol to MeSO2NH2 and PhCONH2 with ethylbenzene as substrate produced the corresponding N-substituted amides in up to 89% yield.