Selective functionalization of C(sp3)–H bonds: catalytic chlorination and bromination by IronIII-acacen-halide under ambient condition

Abstract

The oxidative catalytic halogenations of the C(sp³)–H bond of alkanes promoted by Fe^III(acacen)Cl (1^III-Cl) and Fe^III(acacen)Br (1^III-Br) in the presence of trifluoroacetic acid (TFA) were investigated. Four major steps were involved: (i) formation of [Fe^V(acacen)(oxo)X] species (X = Cl or Br), (ii) hydrogen-atom transfer, (iii) halogen atom rebound, and (iv) regeneration of 1^III-Cl or 1^III-Br. TFA played a significant role in (i) forming the high-valent iron-oxo intermediate and (ii) generating the reaction selectivity.