Saturated amine oxides: part 10. hydroacridines: part 32. linear ¹⁷O/¹³C and ¹³C/¹³C chemical shift correlations between saturated azaheterocyclic N-methylamine N-oxides, and the methiodides of their parent amines.
Two kinds of good linear correlations were found between the chemical shifts of saturated six-membered azaheterocyclic N-methylamine N-oxides and the chemical shifts of the methiodides of their parent amines. One of the correlations occurs between the (17)O chemical shift of the N(+)-O(-) oxygen in the N-oxides and the (13)C chemical shift of the N(+)-CH3 methyl group analogously situated in the appropriate methiodide (r = 0.9778). This correlation enables unambiguous configuration assignment of the N(+)-O(-) bond, even if the experimentally observed (17)O chemical shift of only one N-epimer is available, provided the (13)C chemical shifts of both N(+)-CH3 groups in the methiodide are known and assigned; furthermore, it can be used also for the estimation of (17)O chemical shifts of the N(+)-O(-) oxygens in N-epimeric pairs of N-oxides, for which observed (17)O data hardly become available. The second correlation is observed between the (13)C chemical shift of the N(+)-CH3 methyl group in the N-oxides and the (13)C chemical shift of the N(+)-CH3 methyl group analogously situated in the appropriate methiodide (r = 0.9785). It can be used for safe configuration assignment of the N(+)-CH3 group and, indirectly, also of the N(+)-O(-) bond in an amine N-oxide, even if no (17)O NMR data, and the (13)C chemical shift of only one N-epimer is available.
Department of Organic Chemistry, Biochemistry and Catalysis, University of Bucharest, Bulev. Regina Elisabeta 4-12, RO-030018, Bucharest-1, Romania.
Francisc
F
Potmischil
13C NMR; 17O NMR; NMR; linear correlations; piperidines; quaternary ammonium salts; saturated amine oxides; tetradecahydroacridines; tropane alkaloids