A new, efficient method for the preparation of β-chloro, β-bromo, and β-iodo α, β-unsaturated ketones is described. The method involves the reaction of β-diketones or α- hydroxymethylenecycloalkanones with triphenylphosphine dihalides in the presence of triethylamine. With the dichloride and dibromide reagents, the reactions are conveniently carried out in benzene at room temperature, while with triphenylphosphine diiodide the ...