Free radical reactions in synthesis. Homolysis of alkylcobalt complexes in the presence of radical-trapping agents

Irradiations of the alkylcobalt salophen complexes (14), (21), (22), and (23) in the presence of radical-trapping agents, e.g. molecular oxygen, tetramethylpiperidine oxide, nitrogen monoxide, diphenyl disulphide, diphenyl diselenide, methanesulphonyl chloride, bromotrichloromethane, or iodine, leads to oxgen-[e.g., (18), (19), and (25)], nitrogen-[e.g., (27) and (28)], sulphur/selenium-[e.g., (30) and (31)] or halogen-(34) functionalised products. When these radical-trapping methodologies are combined with cobalt-mediated radical cyclisation reactions (Scheme 2) a powerful synthetic procedure, i.e. radical carbon-to-carbon bond formation with simultaneous functionalisation of the product radical centre, becomes available.