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(Me(3)tacn)(CF3CO2)(3).H2O] (2b, Me(3)tacn = N,N,N"-trimethyl-1,4,7-triazacyclononane) and cis-[Ru-II(6,6'-Cl(2)bpy)(2)Cl-2] (3, 6,6'-Cl(2)bpy = 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 parasubstituted 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)/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.