Crystal structures of three 3-chloro-3-methyl-2,6-di-aryl-piperidin-4-ones.

The syntheses and crystal structure of 3-chloro-3-methyl-r-2,c-6-di-phenyl-piperidin-4-one, C18H18ClNO, (I), 3-chloro-3-methyl-r-2,c-6-di-p-tolyl-piperidin-4-one, C20H22ClNO, (II), and 3-chloro-3-methyl-r-2,c-6-bis-(4-chloro-phen-yl)piperidin-4-one, C18H16Cl3NO, (III), are described. In each structure, the piperidine ring adopts a chair conformation and dihedral angles between the mean planes of the phenyl rings are 58.4 (2), 73.5 (5) and 78.6 (2)° in (I), (II) and (III), respectively. In the crystals, mol-ecules are linked into C(6) chains by weak N-H⋯O hydrogen bonds and C-H⋯π inter-actions are also observed.