Two-step metal-mediated transformation of isoxazolidine-5-spirocyclopropanes into pyridone derivatives

The two-step metal-catalyzed overall transformation of isoxazolidine-5-spirocyclopropanes into the corresponding dihydro- and tetrahydropyridones is described. The first step is the chemoselective reduction of the N-O bond of the isoxazolidine ring preserving the fragile cyclopropanol moiety while the second transformation is the Pd(II) or Pd(O) conversion of the beta-aminocyclopropanol derivatives into the final compounds. The scope and limitations of this strategy are described.