The diacetyliminoxyl radical in oxidative functionalization of alkenes

The intermolecular oxime radical addition to C00000000000000000000000000000000111111110000000011111111000000000000000000000000C bonds was observed and studied for the first time. The diacetyliminoxyl radical was proposed as a model radical reagent for the study of oxime radical reactivity towards unsaturated substrates, which is important in the light of the active development of synthetic applications of oxime radicals. In the present work it was found that the diacetyliminoxyl radical reacts with vinylarenes and conjugated dienes to give radical addition products, whereas unconjugated alkenes can undergo radical addition or allylic hydrogen substitution by diacetyliminoxyl depending on the substrate structure. Remarkably, substituted alkenes give high yields of C-O coupling products despite the significant steric hindrance, whereas unsubstituted alkenes give lower yields of the C-O coupling products. The observed atypical C-O coupling yield dependence on the alkene structure was explained by the discovered ability of the diacetyliminoxyl radical to attack alkenes with the formation of a C-N bond instead of a C-O bond giving side products. This side process is not expected for sterically hindered alkenes due to lower steric availability of the N-atom in diacetyliminoxyl than that of the O-atom. The intermolecular oxime radical addition to CC bonds was discovered employing stable and reactive diacetyliminoxyl as a novel free-radical reagent.

Automated summary

The intermolecular oxime radical addition to C-C bonds was observed and studied for the first time. The diacetyliminoxyl radical was used as a model radical reagent to study the reactivity of oxime radicals towards unsaturated substrates. It was found that the diacetyliminoxyl radical can react with vinylarenes and conjugated dienes to form radical addition products, while unconjugated alkenes can undergo radical addition or allylic hydrogen substitution. Interestingly, substituted alkenes give high yields of C-O coupling products despite steric hindrance, while unsubstituted alkenes give lower yields. This can be explained by the diacetyliminoxyl radical's ability to attack alkenes with the formation of a C-N bond instead of a C-O bond.