Development of zinc alkyl/air systems as radical initiators for organic reactions

This paper reports a series of comparative experiments on the activity of carbon- and oxygen-centred radical species in a model reaction of the radical addition of THF to imines mediated by a series of zinc alkyl/air reaction systems. The study strongly contradicts the notion that generally R˙ radicals are the initiating species in organic reactions mediated by R(n)M/air systems, and simultaneously demonstrates that oxygen-centred radical species are the key intermediates responsible for the initiation process. In addition, a new efficient RZn(L)/air initiating system for radical organic reactions exampled by a model reaction of radical addition of THF to imines is developed. Moreover, the isolation and structural characterization of the first zinc alkylperoxide supported by a carboxylate ligand, [Zn(4)(μ(3)-OOtBu)(3)(μ(4)-O)(O(2)CEt)(3)](2), as well as the novel octanuclear zinc oxo(alkoxide) aggregate with entrapped O–THF species, [Zn(4)(μ(4)-O)(μ(3)-2-O–THF)(O(2)CEt)(5)](2), provide clear mechanistic signatures for the mode of function of the RZn(O(2)CR′)/air system.