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

Abstract

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.