Lactones and Epoxides to Succinic Anhydrides

The carbonylation of p-lactones to form succinic anhydrides also occurs with catalysts containing a combination of the salen-ligated aluminum Lewis acid and cobalt carbonyl anion (Equation 17.47). These reactions occur with lactones bearing alkyl, alkenyl, and ether substituents, as well as with the unsubstituted p-propiolactone. All of these substrates 

Direct synthesis of succinic anhydrides from epoxides has also been achieved by using the catalyst containing the aluminum Lewis acid and cobalt carbonyl anion (Equation 17.48). The carbonylations of epoxide and p-lactone in the presence of this catalyst were found to occur separately and sequentially, with p-lactone carbonylation occurring only after all of the epoxide had undergone carbonylation. p-Lactone carbonylation was slow in polar or donor solvents. Because epoxide and p-lactone carbonylation occur with opposing solvent dependences, the carbonylation of the epoxide to the anhydride in a single pot depended upon the identification of a solvent (1,4-dioxane) that is sufficiently donating to accelerate epoxide carbonylation, but sufficiently weak in polarity to allow rapid p-lactone carbonylation. 

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