The reaction of active zinc with organic bromides

The oxidative addition of highly reactive zinc to organic bromides shows a pronounced structure-reactivity dependence, in contrast to that shown by other metals. The kinetic and LEER studies suggest a mechanism in which electron transfer (ET) is the rate-determining step of the reaction. Experiments carried out with radical clocks as well as the stereochemical outcome of the reaction support the presence of radicals. The reactivity profiles suggest that the ET has an important component of inner-sphere process in the reaction with alkyl bromides. In the case of aryl halides, Hammet plots are consistent with the participation of aryl halide radical anions as intermediates. The reaction contemplated here can be ascribed as another example of radical-mediated selective reaction, and it has straightforward synthetic applications. Some synthetic work was done in this direction, to demonstrate how this structure-reactivity dependence can be used to obtain selective organozinc formation in unsymmetrical dibromides.