Halogenation with Copper(II). I. Saturated Ketones and Phenol

A procedure for halogenation of enolizable compounds using copper(II) chloride or bromide in dimethylformamide is described. Methyl ethyl ketone yields 55–70% 3-chlorobutanone, methyl cyclopropyl ketone yields both chloromethyl and dichloromethyl cyclopropyl ketones, propiophenone gives an excellent yield of α-chloropropiophenone, and phenol leads to o- and p-chlorophenols, in a ratio (1:6) substantially different from that of other chlorination methods, along with some 2,4-dichlorophenol. A convenient test for relative reactivities of enols and enolizable compounds is also included.