Reductive Halogenation Reactions: Selective Synthesis of Unsymmetrical Α-Haloketones.

A method for the selective synthesis of unsymmetrical α-haloketones has been developed. The key transformation is a triphenylphosphine oxide catalyzed reductive halogenation of an α,β-unsaturated ketone in which trichlorosilane is the reducing reagent and an N-halosuccinimide is the electrophilic halogen source. This method allows for a halogen atom to be installed selectively at either of two very similarly substituted sites adjacent to a ketone group.