Two-Step Metal-Mediated Transformation of Isoxazolidine-5-spirocyclopropanes into Pyridone Derivatives
作者:Julia Revuelta、Stefano Cicchi、Alberto Brandi
DOI:10.1021/jo050640q
日期:2005.7.1
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.
Novel Prospects of the Acidic Thermal Rearrangement of Spiro[cyclopropane-1,5′-isoxazolidines] toβ-Lactams
作者:Franca M. Cordero、Maria Salvati、Federica Pisaneschi、Alberto Brandi
DOI:10.1002/ejoc.200300595
日期:2004.5
Monocyclic β-lactams were synthesized by a 1,3-cycloaddition/thermal rearrangement process in the presence of a protic acid, starting from methylenecyclopropane derivatives and acyclic nitrones. Five-membered cyclic nitrones failed to give carbapenam structures under the same conditions, affording exclusively the corresponding N-trifluoroacetyl β-amino acid derivatives in the presence of trifluoroacetic