Reactions of acid anhydrides—II : Reactions of ketones with mixed sulphonic-carboxylic anhydride, isopropenyl acetate, and acetic anhydride

Abstract

The reactions of unsymmetrically substituted ketones with trichloroacetyl p-toluenesulphonate, isopropenyl acetate and acetic anhydride were investigated. Trichloroacetyl p-toluenesulphonate converted the saturated ketone 2 to the enol tosylate 5 but testosterone acetate 6 to the corresponding dienol trichloroacetate 7b. Reaction of the ketones 1,2 and 10 with isopropenyl acetate or acetic anhydride in the presence of acid led to isomeric enol acetates 3,4 and 11. The ratio of the isomeric enol acetates differed according to the acid used, when isopropenyl acetate was employed, but was independent of the acid, when acetic anhydride was used. It is suggested that the formation of enol acetates involves addition of either acetic anhydride (when acetic anhydride is used) or mixed anhydride (when isopropenyl acetate or the mixed anhydride is used) to give a gem disubstituted intermediate.