Iron-Catalysed Remote C(sp 3 )-H Azidation of O-Acyl Oximes and N-Acyloxy Imidates Enabled by 1,5-Hydrogen Atom Transfer of Iminyl and Imidate Radicals: Synthesis of γ-Azido Ketones and β-Azido Alcohols.

In the presence of a catalytic amount of iron(III) acetylacetonate [Fe(acac)(3)], the reaction of structurally diverse ketoxime esters with trimethylsilyl azide (TMSN3) afforded gamma-azido ketones in good to excellent yields. This unprecedented distal gamma-C(sp(3))-H bond azidation reaction went through a sequence of reductive generation of an iminyl radical, 1,5-hydrogen atom transfer (1,5-HAT) and iron-mediated redox azido transfer to the translocated carbon radical. TMSN3 served not only as a nitrogen source to functionalise the unactivated C(sp(3))-H bond, but also as a reductant to generate the catalytically active Fe-II species in situ. Based on the same principle, a novel beta-C(sp(3))-H functionalisation of alcohols via N-acyloxy imidates was subsequently realised, leading, after hydrolysis of the resulting ester, to beta-azido alcohols, which are important building blocks in organic and medicinal chemistry.