An Investigation of the Reactivity of MCPBA and (alpha)-Bromoalkenes under Traditional or MicrowaveAssisted Conditions: Selective Formation of Epoxides or Allylic Bromides

The reaction of (alpha)-bromo-(beta),(gamma)-unsaturated lactams and esters with m-chloroperbenzoic acid has been studied to find experimental conditions that could afford exclusively epoxide formation or bromide 1,3-shift. The results show a strong dependence of reactivity on the dilution and on the amount of peracid used, suggesting a radical mechanism for the bromine rearrangement. This last reaction is also strongly favored by microwave-assisted conditions.