DBU-promoted regioselective HBr-elimination of vicinal dibromides: effects of the adjacent oxygen and/or other heterofunctional groups

DBU-promoted HBr-eliminations of a variety of vicinal dibromides having an adjacent heteroatom (F, O, or N) under mild basic conditions and relevant theoretical calculations were carried out. These HBr-eliminations proceeded more or less regioselectively, and all associated calculation results agreed with the experimental facts. This work suggests that the HBr-elimination selectivity is an effect of the electronegativity of the neighboring heteroatoms themselves rather than the electron-withdrawing effects of the entire heterofunctional group.