Mechanism of cyclization of aryl radicals containing unsaturated ortho-substituents

Abstract

Aryl radicals generated by interaction of tributylstannane with aryl iodides containing unsaturated ortho-substituents cyclize regiospecifically to afford products containing the newly formed-radical centre exocyclic to the newly-formed ring. The relative rates of cyclization of a number of related radicals have been determined. The results are consistent with the hypothesis that the transition state for homolytic addition to an olefin bond is formed by primary interaction of the semi-occupied orbital with one lobe of the π* orbital.