Synthesis, spectral and computational studies of some N-acyl-t(3)-isopropyl-r(2),c(6)-bis-2 '-furylpiperidin-4-one oximes

Four N-acyl-t(3)-isopropyl-r(2),c(6)-bis-2'-furylpiperidin-4-one oximes 1-4 were synthesized and the high resolution H-1 and C-13 NMR spectra have been recorded at Various temperatures and analyzed. The spectra reveal the presence of two rotameric forms (syn and anti) in solution. H-1-H-1 COSY and H-1-C-13 COSY spectra have been recorded to assist the assignment of the signals for the syn and anti isomers of 1-4. Coupling constants predict an equilibrium mixture of boat form B-1 and alternate chair form CA for 1-4. The effect of varying the substituents at nitrogen and at C(4) on the H-1 and C-13 chemical shifts has been analyzed in detail. The molecular structures of the N-acyl derivatives 1-4 were also determined using AM I Hamiltonian and the results have been compared to the results derived from spectral Studies. Mass spectra have also been recorded for 1-4. (C) 2009 Elsevier B.V. All rights reserved.