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-center dot radicals are the initiating species in organic reactions mediated by RnM/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(mu(3)-OOtBu)(3)-(mu(4)-O)(O2CEt)(3)](2), as well as the novel octanuclear zinc oxo(alkoxide) aggregate with entrapped O-THF species, [Zn-4(mu(4)-O)(mu(3)-2-O-THF)(O2CEt)(5)](2), provide clear mechanistic signatures for the mode of function of the RZn(O2CR')/air system.