The Thermal Reaction of Sterically Hindered Nitroxyl Radicals with Allylic and Benzylic Substrates:  Experimental and Computational Evidence for Divergent Mechanisms

The reaction of stable sterically hindered nitroxyl radicals with benzylic and allylic substrates was investigated. An allyloxyamine derivative was obtained by the reaction of 2 molar equiv of a nitroxyl radical with an unactivated alkene. Experimental and computational evidence is consistent with a low-energy pathway involving addition of the nitroxyl radical to the double bond followed by H-atom abstraction from the intermediate by another equivalent of nitroxyl radical.