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 ot her metals. The kinetic and LEER studies suggest a mechanism in which elect ron transfer (ET) is the rate-determining step of the reaction. Experiments carried out with radical clocks as well as the stereochemical outcome of t he reaction support the presence of radicals. The reactivity profiles sugge st that the ET has an important component of inner-sphere process in the re action with alkyl bromides. In the case of aryl halides, Hammet plots are c onsistent with the participation of aryl halide radical anions as intermedi ates. The reaction contemplated here can be ascribed as another example of radical-mediated selective reaction, and it has straightforward synthetic a pplications. Some synthetic work was done in this direction, to demonstrate how this structure-reactivity dependence can be used to obtain selective o rganozinc formation in unsymmetrical dibromides.