Conformational studies on some 3-chloro-2,6-diaryl-piperidin-4-ones by H-1 NMR spectra

A series of 2,6-diarylpiperidin-4-ones 1-10 with a chloro substitution at C3 and dichloro substitutions at C3 and C5 have been prepared. Based on the H-1 NMR data, the compounds are assigned the chair conformation in which aryl and chloro substituents are equatorially disposed. The presence of chloro group(s) on the piperidinone ring does not affect the nature of ring conformation. However, the coupling constant data of the compounds reveal that in few cases there is a flattening of the piperidinone ring. The H-1 NMR data of the compounds are substantiated by the dihedral angles estimated by the DAERM method.