Trifluoromethanesulfonic-carboxylic anhydrides, highly active acylating agents

Abstract

The trifluoromethanesulfonate anion has proved the best leaving group so far in solvolytic displacement reactions. For acylation with carboxylic acid derivatives, however, a straightforward estimate of the influence of the leaving group on the reaction rate is impossible; depending on substrate and reaction conditions, there are several mechanistic pathways with a varying dependance on the nature of the leaving group. Recent investigations have shown though, that the acylation potential is higher for sulfoniccarboxylic than for carboxylic anhydrides. So, further increased reactivity may be expected with trifluoromethane-sulfonic-carboxylic anhydrides.