Mechanism for synthesis of Meldrum's Acid I have a little bit of problem trying to figure out the mechanism for the synthesis of Meldrum Acid. Meldrum acid is synthesis by a condensation reaction of acetone with malonic acid in acetic anhydride.



First, the carboxyl OH will be acetylated by acetic anhydride. But I can't figure out how the two ester bonds are being formed subsequently. I'm thinking that there's an acid-catalysed aldol condensation somewhere that results in the removing of water. Perhaps by attack of the enol (from acetone) to the acetylated carbon. But I'm not really sure about it either.

Any thoughts?
The first step (reaction with acetic anhydride) creates a mixed anhydride, this is a good electrophile with acetate as a leaving group. This is nucleophilically attacked by the oxygen of acetone (drawn as its enol in the scheme, but it is easier to visualise it as acetone) to give a cationic intermediate which is immediately attacked by the -OH of the neighbouring carboxyl group to give the product.