A Unique (3+2) Annulation Reaction between Meldrum's Acid and Nitrones: Mechanistic Insight by ESI-IMS-MS and DFT Studies

International audienceThe fragile intermediates of the domino process leading to an isoxazolidin‐5‐one, triggered by unique reactivity between Meldrum's acid and an N‐benzyl nitrone in the presence of a Brønsted base, were determined thanks to the softness and accuracy of electrospray ionization mass spectrometry coupled to ion mobility spectrometry (ESI‐IMS‐MS). The combined DFT study shed light on the overall organocatalytic sequence that starts with a stepwise (3+2) annulation reaction that is followed by a decarboxylative protonation sequence encompassing a stereoselective pathway issue