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(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 PhINTs 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 RuNTs species to form a carboradical intermediate. The amidation with PhI(OAc)₂/TsNH₂ gave results comparable to those obtained with PhINTs. 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.