13C NMR chemical shifts, in some N-chloro-2,6-diarylpiperidin-4-ones

The 13C shifts in several N‐chloro‐2,6‐diarylpiperidin‐4‐ones have been measured and compared with previously reported sifts in the corresponding 2,6‐diarylpiperidones. The shifts of the α‐carbons in these compounds move downfield by 12–13 ppm, which can be attributed to the increased electronegativity of the nitrogen atoms. The changes in the chemical shifts of the β‐carbons are minimal. Surprisingly, the absorptions of the carbonyl carbons move upfield by as much as 4.0 ppm. The magnitude of the shift in the resonance of the carbonyl carbon indicates the possibility of a transannular interaction between the nitrogen and the carbonyl group, which has not previously been observed in these systems. A preferred conformation for the aryl group in these compounds is also proposed.