Acylation of pyran-2,4,6-trione (acetonedicarboxylic anhydride)

The reaction of acetone-1,3-dicarboxylic acid with acetic anhydride at 40–50 °C gives 4-acetoxypyran-2,6(3H)-dione. This O-acetyl derivative can be converted into the C-acetyl derivative, 3-acetylpyran-2,4,6-trione. Pyran-2,4,6-trione reacts with benzoyl chloride to yield the O-benzoyl derivative, 4-benzoyloxypran-2,6(3H)-dione, whereas the reaction with ethoxycarbonylacetyl chloride gives the bis-C-acyl derivative, 3,5-bis(ethoxycarbonylacetyl)pyran-2,4,6-trione.