Syntheses, characterizations, crystal structures and Hirshfeld surface analyses of methyl 4-[4-(difluoromethoxy)phenyl]-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, isopropyl 4-[4-(difluoromethoxy)phenyl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate and tert-butyl 4-[4-(difluoromethoxy)phenyl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate

Abstract

The crystal structures and Hirshfeld surface analyses of three similar compounds are reported. Methyl 4-[4-(difluoromethoxy)phenyl]-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, (C21H23F2NO4), (I), crystallizes in the monoclinic space group C2/c with Z = 8, while isopropyl 4-[4-(difluoromethoxy)phenyl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, (C23H27F2NO4), (II) and tert-butyl 4-[4-(difluoromethoxy)phenyl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, (C24H29F2NO4), (III) crystallize in the orthorhombic space group Pbca with Z = 8. In the crystal structure of (I), molecules are linked by N—H...O and C—H...O interactions, forming a tri-periodic network, while molecules of (II) and (III) are linked by N—H...O, C—H...F and C—H...π interactions, forming layers parallel to (002). The cohesion of the molecular packing is ensured by van der Waals forces between these layers. In (I), the atoms of the 4-difluoromethoxyphenyl group are disordered over two sets of sites in a 0.647 (3): 0.353 (3) ratio. In (III), the atoms of the dimethyl group attached to the cyclohexane ring, and the two carbon atoms of the cyclohexane ring are disordered over two sets of sites in a 0.646 (3):0.354 (3) ratio.

Keywords

• crystal structure
• 1,4-dihydropyridine ring
• cyclohexene ring
• quinoline ring system
• disorder
• van der waals interactions
• hirshfeld surface analysis