Et2Zn-mediated rearrangement of bromohydrins.

A simple and highly efficient method for the rearrangement of bromohydrins mediated by Et 2Zn to synthesize carbonyl compounds was described. Various beta-bromo alcohols were treated with 0.6 equiv of Et 2Zn to form a zinc complex in CH 2Cl 2 at room temperature for 2 h, followed by 1,2-migration to give the corresponding carbonyl compounds. This remarkable and clean rearrangement is general for acyclic and cyclic bromohydrins, and a variety of ring-expansive and -contractive carbonyl compounds were obtained in good to excellent yields according to the feature of the starting bromohydrins. The functional group tolerance of organozinc reagents in this reaction will be useful in organic synthesis. The scope and limitations of this rearrangement process were also investigated.