Meldrum’sacid has turned out to be a useful ketene equivalent when faced to nitrone dipoles to form various isoxazolidin‐5‐one derivatives under very mild Brønsted base organocatalytic conditions. The first asymmetric version of this original domino anionic formal [3+2] cycloaddition–decarboxylation reaction was demonstrated by means of quinine‐based organocatalysts.