Abstract The Mg-mediated conjugate addition of bromoform to enones followed by alcoholysis of the resulting keto tribromides proceeds through an unusual course, affording cyclic orthoester (dihydrofuran) intermediates under neutral workup conditions. However, acid workup of the reaction mixture or treatment of the isolated dihydrofurans with acid provides the expected but synthetically useful γ-keto esters. The intermediacy of ...
