Conformational study of some N-Nitroso-2r, 6c-diphenylpiperidin-4-one oximes using NMR spectra.

Abstract Stereochemistry of N-nitroso-2r,6c-diphenylpiperidin-4-one oxime (1) , N nitroso -3t-methyl-2r,6c-diphenylpiperidin-4-one oxime (2) , N nitroso-3t-isopropyl -2r,6c-diphenylpiperidin-4-one oxime (3) , N nitroso-3t-ethyl-2r,6c-diphenylpiperidin-4-one oxime (4) has been studied using 1H, 13C and two-dimensional NMR spectra. Analysis of the spectral data shows that in 2, 3 and 4 the NOH group is anti to the alkyl group at C-3. All the four compounds seem to exist largely in boat conformations with one phenyl group in the flagpole position. Analysis on the reported spectral data on N nitroso -2r,6c-diphenylpiperidin-4-ones suggests that these compounds also largely exist in boat conformations with one phenyl group in the flagpole position. Chair conformation with axial phenyl groups may contribute to some extent. The relative populations of the boat and chair conformations have been supported by the observed NOEs in their NOESY spectra. Graphical abstract Image 1 Highlights • N-nitroso-2r,6c-diphenylpiperidin-4-one oxime (1) , ans some N nitroso -3t- alkyl-2r,6c-diphenylpiperidin-4-one oximes (2–4) , has been synthesized and its stereo chemistry has been studied. • The assignment of signal and conformations has been studied for compound 1–4 using COSY, coupling constant and NOESY spectra. • The compounds 1 &2 seem to exist largely in boat conformations. • The compounds 3&4 seem to exist as an equilibrium mixture of both chair and boat conformations. • The relative populations of the boat and chair conformations have been supported by the observed NOEs. [ABSTRACT FROM AUTHOR]