Methyl 2,7,7-trimethyl-4-(3-nitrophenyl)-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3- carboxylate and 3-acetyl-2,7,7-trimethyl-4-phenyl-1,4,5,6,7,8-hexahydro-5-quinolone

Article abstract of DOI:10.1107/S0108270196004611

The 1,4-dihydropyridine (1,4-DHP) ring and the cyclohexanone ring adopt similar conformations in both the title compounds, methyl 2,7,7-trimethyl-4-(3-nitro-phenyl)-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3- carboxylate, C₂₀H₂₂N₂O₅, (I) and 3-acetyl-2,7,7-trimethyl-4-phenyl-1,4,5,6,7,8-hexahydro-5-quinolone, C₂₀H₂₃NO₂, (II). The 1,4-DHP rings have boat conformations with the aryl group occupying the pseudo-axial position and orthogonal to the plane through the 1,4-DHP ring. The cyclohexanone ring has an intermediate half-chair/sofa form. In both compounds, the carboxyl group is coplanar to the endocyclic double bond as a consequence of π conjugation. The molecules are linked by N-H...O hydrogen bonds but the packing is different in each case. In compound (I) a hydrogen bond is formed between the N-H and the carboxyl group while in compound (II), a hydrogen bond is formed between the N-H and the O atom of the cyclohexanone ring.