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

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, (C 21 H 23 F 2 NO 4 ), ( I ), crystallizes in the monoclinic space group C 2/ 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, (C 23 H 27 F 2 NO 4 ), ( II ) and tert -butyl 4-[4-(difluoromethoxy)phenyl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, (C 24 H 29 F 2 NO 4 ), ( 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.