Succinic anhydrides are valuable reactive intermediates that find use in an array of applications.

For example, their copolymerization with epoxides or diols yields biodegradable polyesters. Anhydrides are also useful intermediates in organic synthesis, since they can be readily ring opened to diacids or other succinate derivatives; some examples of which include biologically active natural products, pharmaceuticals, and metalloprotease inhibitors.
Substituted succinic anhydrides have previously been synthesized by a number of methods, most often by the dehydration of the corresponding diacid or from maleic anhydride via Diels-Alder or Ene reactions. They have also been made by metal catalyzed carbonylation of alkynes, alkenoic acids, and lactones; however, most of these catalytic reactions proceeded either in low yield, with significant side products, or without demonstrating substrate generality or product stereochemical purity. Thus, the development of more efficient and stereoselective syntheses remains an important goal.
As disclosed in U.S. Pat. No. 6,852,865 our group has developed a class of well-defined bimetallic catalysts of the general type [Lewis acid]+[M(CO)x]− for the ring-expanding carbonylation of strained heterocycles. We have found that related catalysts can carbonylate β-lactones to succinic anhydrides in high yields while preserving stereochemical purity. Given the many syntheses of enantiomerically pure epoxides and the recent advances in epoxide carbonylation to β-lactones, subsequent carbonylation of these lactones constitutes a versatile two-step method for the stereoselective synthesis of succinic anhydrides (Scheme 1).

This method would be far more synthetically useful if the two steps could be consolidated, eliminating the requirement for isolation and purification of potentially toxic lactone intermediates, saving time and catalyst, and increasing overall yield. The present invention provides such a methodology.