Hydrogen bonding in three anticonvulsant enaminones

Abstract

The crystal structures of three anticonvulsant enaminones: methyl 4-[( p-chlorophenyl)amino]-6-methyl-2-oxo-3-cyclohexen-1-carboxylate ( 1), methyl 4-[( p–ethylphenyl)amino]-6-methyl-2-oxo-3-cyclohexen-1-carboxylate ( 2), and methyl 4-[(4′-chloro-2′-pyridinyl)amino]-6-methyl-2-oxo-3-cyclohexen-1-carboxylate ( 3) have been determined. The cyclohexene rings adopt sofa conformations, with the methyl substituent at the out-of-plane carbon atom in equatorial position. The dihedral angle between the mean planes of cyclohexene and aromatic ring is significantly smaller for pyridinyl derivative as compared with phenyl ones; for the former an intramolecular C–H⋯N(pyridinyl) hydrogen bond closes nearly planar six-membered ring. For all compounds, the intermolecular N–H⋯OC hydrogen bonds form infinite chains of molecules. Both the graph-set notation and resonance-assisted hydrogen bond approach have been used for description of hydrogen bond networks. For 1 and 2, there is a significant disorder of the carbomethoxy groups, caused by a rotation of 180° around the C–C(OOC) single bond.