Reactions Leading to 1,2-Dibenzoylethanes: The Dehalogenation of Phenacyl Bromide and the Photolysis of Methyl Phenacyl Sulfoxide

The dehalogenation of phenacyl bromide by means of lower-oxidation-state metallic ions complexed by DMSO gives 1,2-dibenzoylethane. The by-products are 2,4-diphenylfuran and phenacyl chloride in the presence of Cu(I) chloride, whereas acetophenone and ω-acetoxyacetophenone are produced in the reaction with Cr(II) acetate. Treatment with K3Co(CN)5/DMSO gives 1,2-dibenzoylethane and acetophenone. The second title reaction consists of the photolysis of methyl phenacyl sulfoxides, the isolated by-products being acetophenones and methyl methanethiolsulfonate. The product distribution is strongly affected by the pH of the reaction mixture and also by the benzene-ring substituents.