Synthesis, NMR Study and Antioxidant potency of 3,5-dimethyl-2,6-bis(2,4-dichlorophenyl) piperidin-4-one

Abstract

A new molecule, 3,5-dimethyl-2,6-bis(2,4-dichlorophenyl) piperidin-4-one was synthesized by a modified Mannich condensation of 2 moles of 2,4-dichlorobenzaldehyde, 1mole each of 3-pentanone and ammonium acetate (instead of amine in the typical procedure) in ethanol; recrystallized with ethanol to afford the pale yellow powder with 56% yield. The molecule was characterized by IR, 1H NMR,13C NMR and elemental analysis. Based on the NMR data, it is identified that the molecule exists in a chair conformation with equatorial orientation of all the substituents. Apart, few interesting NMR results are, (i) a broad singlet was observed for the active methine protons at C-3 and C-5, instead of a multiplet, (ii) significant deshielding of the protons at C-2 and C-6 due to the interaction of these protons with chlorine atoms at ortho positions (2’a and 6’a) of the phenyl groups; leads to restricted rotation of the phenyl groups as well, (iii) The ortho protons of 2,4-dichloro phenyl (2’e and 6’e) were also deshielded by nitrogen lone pair; about half of the deshielding magnitude is due to the protons at C-2 and C-6. Antioxidant efficacy of the molecule was verified with DPPH and ABTS methods.