3-Spirocyclopropanedihydro- and tetrahydropyridin-4-ones from Nitrone Cycloadducts of Bicyclopropylidene via 1-(1'-Aminomethylcyclopropyl)cyclopropanol under Pd(II) Catalysis

A series of 3-spirocyclopropanedihydro- and -tetrahydropyrid- 4-ones have been synthesized by nitrone cycloaddition to 1,1-bicyclopropylidene (BCP), chemoselective reduction of the N–O bond of the isoxazolidine ring, and PdII-catalyzed cascade rearrangement of the β-aminocyclopropanol derivatives into the final products. The new tetrahydropyridone derivatives were also prepared by thermal rearrangement of the isoxazolidines.