Significant amounts of metal phosphate impurities have been detected by NMR spectroscopy and ICPOES analysis of synthetic, as well as purchased, samples of VAPOL hydrogen phosphate purified on silica gel. The previously reported VAPOL hydrogen phosphate-catalyzed desymmetrization of meso-aziridines with different silylated compounds, has been re-examined. While metal-free phosphoric acid exhibited low activity and enantioselectivity, calcium and magnesium phosphate salts proved to be the true catalysts in these related processes. Reproducible high enantioselectivities were obtained in the ring-opening of cyclic meso-aziridines with Me3SiX (X¼SPh, SePh, N3) employing a 1:1 mixture of calcium and magnesium VAPOL phosphates. The reaction has been successfully extended to Me3SiSBn, Me3SiSMe and Me3SiNCS, giving ring-opened products in high yield and unprecedented moderate to good enantioselectivities.

Studies on the true catalyst in the phosphate-promoted desymmetrization of meso-aziridines with silylated nucleophiles

DELLA SALA, Giorgio
2013-01-01

Abstract

Significant amounts of metal phosphate impurities have been detected by NMR spectroscopy and ICPOES analysis of synthetic, as well as purchased, samples of VAPOL hydrogen phosphate purified on silica gel. The previously reported VAPOL hydrogen phosphate-catalyzed desymmetrization of meso-aziridines with different silylated compounds, has been re-examined. While metal-free phosphoric acid exhibited low activity and enantioselectivity, calcium and magnesium phosphate salts proved to be the true catalysts in these related processes. Reproducible high enantioselectivities were obtained in the ring-opening of cyclic meso-aziridines with Me3SiX (X¼SPh, SePh, N3) employing a 1:1 mixture of calcium and magnesium VAPOL phosphates. The reaction has been successfully extended to Me3SiSBn, Me3SiSMe and Me3SiNCS, giving ring-opened products in high yield and unprecedented moderate to good enantioselectivities.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11386/3886971
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 34
  • ???jsp.display-item.citation.isi??? 24
social impact