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I. Structure-reactivity relationships in the oxidative addition of active zinc and nickel metal into carbon -halide bonds. II. Addition of organozinc halides across carbon -nitrogen double bonds
The oxidative addition of highly reactive zinc (Zn*) to organic bromides shows pronounced structure-reactivity dependence, in contrast to that shown by magnesium. The kinetic and LFER studies conducted suggest a mechanism in which electron transfer is the rate-determining step of the reaction. Experiments carried out with radical clocks and stereochemical investigations support the presence of radicals. The reactivity profiles suggest that the electron transfer occurs in the normal Marcus region. In the case of aryl bromides, Hammett plots are consistent with participation of aryl halide radical anions as intermediates and again show a qualitative adherence to Marcus theory. The reaction proposed here can be described as another example of radical mediated selective reaction, and it has straightforward synthetic applications. ^ While there are other examples in the literature of the addition of dialkyl zinc reagents, organozinc cuprates, and allylic organozinc halides to imines, to our knowledge we report here the first addition of a non-allylic organozinc halide across a carbon-nitrogen double bond. Addition of organozinc halides to N-benzyl bensensulfonimine with a copper catalyst under mild conditions gives the corresponding sulfonamide. Alkyl, ester, cyclic, vinylic, and heterocyclic organozincs give moderate to good yields, but best results are obtained with benzylic organozinc species. This type of reaction is currently limited to sulfonimines and is not successful with other carbon-nitrogen double bonds. ^ The oxidative addition of highly reactive nickel to organic bromides shows only slight structure-reactivity dependence. This is in contrast to the behavior shown by oxidative addition of nickel (0) complexes and is counter to what Marcus theory predicts comparative to zinc. The Hammett relationship is determined for the addition of active nickel and the anomalous behavior is attributed to surface effects involving precursor complex formation, the activated complex, and temperature. ^
Rosenberg, David Michael, "I. Structure-reactivity relationships in the oxidative addition of active zinc and nickel metal into carbon -halide bonds. II. Addition of organozinc halides across carbon -nitrogen double bonds" (2001). ETD collection for University of Nebraska - Lincoln. AAI3022658.