Acid-catalyzed Reactions of 1,2-Dicarbonylethanes with Benzene. Ethylene Dication Electrophiles.

Article abstract of DOI:10.1016/0040-4039(95)01075-S

1,2-dicarbonyl compounds reacted with benzene in the presence of a strong acid, trifluoromethanesulfonic acid, to give gem-diphenylated ketones in high yields.The reaction was accelerated when the acidity of the medium was increased, supporting involvement of O,O-diprotonated 1,2-dicarbonyl species (i.e., 1,2-dihydroxyethylene dications) as the active electrophiles.