13C and 1H NMR spectral studies of some piperidin‐4‐one oximes

Abstract 13 C NMR spectra have been recorded for eleven piperidin‐4‐one oximes and for seven of them 1 H NMR spectra have been recorded at 270 MHz. The effect of oximation on the NMR chemical shitts is discussed. The conformations of the oximes are also discussed, based on the observed chemical shifts. Although several oximes appear to adopt a chair conformation, in the same manner as the corresponding ketones, the oximes of 3,5‐dimethyl‐2,6‐diarylpiperidin‐4‐ones with cis ‐methyl groups seem to adopt an asymmetric non‐chair conformation. Analysis of the chemical shifts of cis ‐2,6‐dimethylcyclohexanone oxime suggests that this compound also exists in a non‐chair conformation, and not in a chair conformation with two axial methyl groups as suggested previously.