Saturated amine oxides: part 10. hydroacridines: part 32. linear 17 O/ 13 C and 13 C/ 13 C 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 + ―CH 3 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 + ―CH 3 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 + ―CH 3 methyl group in the N ‐oxides and the 13 C chemical shift of the N + ―CH 3 methyl group analogously situated in the appropriate methiodide ( r  = 0.9785). It can be used for safe configuration assignment of the N + ―CH 3 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. Copyright © 2015 John Wiley & Sons, Ltd.