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

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-nitrophenyl)-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 comformations with the aryl group occupying the pseudoaxial position and orthogonal to the plane of 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.

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