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13C GIAO DFT calculation as a tool for configuration prediction of N-O group in saturated heterocyclic N-oxides.

Authors
  • Pohl, Radek
  • Potmischil, Francisc
  • Dračínský, Martin
  • Vaněk, Václav
  • Slavětínská, Lenka
  • Buděšínský, Miloš
Type
Published Article
Journal
Organic Magnetic Resonance
Publisher
Wiley (John Wiley & Sons)
Publication Date
Jun 01, 2012
Volume
50
Issue
6
Pages
415–423
Identifiers
DOI: 10.1002/mrc.3810
PMID: 22539412
Source
Medline
License
Unknown

Abstract

Tropane, tropinone, pseudopelletierine and cocaine were oxidized in situ in a nuclear magnetic resonance (NMR) tube providing mixtures of exo/endo N-oxides. Observed (13)C chemical shifts were correlated with values calculated by gauge-including atomic orbitals density functional theory (DFT) OPBE/6-31G* method using DFT B3LYP/6-31G* optimized geometries. The same method of (13)C chemical shift calculation was applied on series of methyl-substituted 1-methylpiperidines and their epimeric N-oxides described in literature. The results show that using this undemanding calculation method enables assignment of configuration of N-O group in N-epimeric saturated heterocyclic N-oxides. The approach enables assigning of the configuration with high degree of certainty even if NMR data of only one isomer are available. An improved method of in situ oxidation of starting amines in an NMR tube is also described.

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