Cobaloximes as Environmentally Advantageous Alternatives to Organotin Hydrides in Iodine Atom Abstraction Routes to Benzyl Radicals

Abstract

High yields of alkyl radicals derived from alkylcobaloximes have been achieved using tungsten light (or in some cases ultrasound) radiation in both organic and aqueous media. These improved yields are obtained when pyridine (the usual base ligand) is replaced by suitably bulky lone‐pair donors or water. The alkyl radicals so generated take part in iodine abstraction reactions with benzyl iodide giving benzyl radicals which may be trapped in near‐quantitative yield with 2,2,6,6‐tetramethylpiperidinyloxy (TEMPO) or in good yield with lepidinium (4‐methylquinolinium) trifluoroethanoate or lepidinium camphor‐10‐sulphonate. The usual drawbacks of cost and tedious work‐up procedures associated with the more commonly used organotin hydride reagents are avoided.