Variously substituted 2,6-diarylpiperidin-4-one O-benzyloximes were synthesized by the direct condensation of the corresponding 2,6- diarylpiperidin-4-ones with O-benzylhydroxylamine hydrochloride. In addition, the effect of NMe group on the 2,6-diarylpiperidin-4-one-O-benzyloximes was also studied.' Based on the NMR data, the effects of oximination on ring carbons and their associated protons and alkyl substituents are discussed. The observed chemical shifts and coupling constants suggest that the synthesized oxime ethers adopt chair conformation with equatorial orientation of all the substituents, whereas 1-methyl-3-isopropyl-2,6-diphenylpiperidin- 4-one-O-benzyloxime also exists in boat conformation. The conformational preference of the synthesized oxime ethers with/without alkyl and aryl substituents at C-3/C-5 and C-2/C-6 is discussed using the spectral data. All the synthesized compounds are characterized by IR, Mass and NMR (1H NMR, 13C NMR, 1H-1H COSY, 1H-13C COSY and HMBC) spectral studies. Among them, the direct conversion of 2,6-diarylpiperidin-4-ones into the corresponding oxime ethers (method A) was proved to be better than the other two methods in the sense of good yield, convenience, easy work-up and quick reaction time. 'Abstract A series of variously substituted N-methylpiperidin- 4-one-O-benzyloximes were synthesized by three different methods.
