Organocatalyzed Multicomponent Synthesis of Isoxazolidin-5-ones

An unprecedented multicomponent organocatalyzed Knoevenagel-aza-Michael cydocondensation reaction between Meldrum's acid, hydroxylamines, and aldehydes afforded a straightforward entry to a large array of racemic and syn-diastereoenriched isoxazolidinones as synthetically useful scaffolds. This process revealed a markedly facile aza-Michael-cyclocondensation sequence as a key domino reaction between RCO2NHOH and transient alkylidene Meldrum's acid upon Bronsted base catalysis.