Sodium Sulfide Catalyzed Isomerization of Itaconic Anhydride to Citraconic Anhydride

In the study of thioanhydrides, a fast, simple, and cost effective means of producing thioanhydrides is necessary being that commercially available thioanhydrides are limited. A simple method of converting an anhydride into a thioanhydride involves the use of sodium sulfide. In general, this method of thioanhydride synthesis is effective in producing a substantial yield of thioanhydride from the conjugate anhydride. However, in the case of itaconic anhydride, this method seems to fail. By monitoring the reaction of itaconic anhydride with sodium sulfide using 1H NMR spectrometry, Raman spectrometry, and IR spectrometry, it is clear that the resulting product is not the expected itaconic thioanhydride, but is instead citraconic anhydride, an isomer of itaconic anhydride. While this isomerization reaction has been recorded using nitrogen-based compounds, this is the first instance in which sodium sulfide has been recorded as a catalyst in the isomerization of itaconic anhydride to citraconic anhydride.