Tandem isomerization–lactonization of olefinic fatty acids using the Lewis acidic ionic liquid, choline chloride·2ZnCl2

The tandem isomerization–lactonization of unsaturated fatty acids to their corresponding γ-lactones was carried out for the first time in the presence of a Lewis acidic ionic liquid, choline chloride·2ZnCl2. The ionic liquid initially catalyzes the stepwise migration of the double bond along the carbon chain toward the carboxyl group at the Δ4 position, which subsequently undergoes lactonization resulting in the formation of γ-lactones. This one step process allows the formation of γ-lactone in good yield with little or no formation of δ-lactones. The studied ionic liquid plays the dual role of solvent as well as catalyst.