Acta Crystallographica Section B

Structural Science

Volume 64, Part 1 (February 2008)

research papers

Acta Cryst. (2008). B64, 72-83 [ doi:10.1107/S0108768107065743 ]

Structural comparisons of isomeric series of 7-aryl-benzo[h]pyrazolo[3,4-b]quinolines and 11-aryl-benzo[f]pyrazolo[3,4-b]quinolines

J. Portilla, J. Quiroga, M. Nogueras, J. M. de la Torre, J. Cobo, J. N. Low and C. Glidewell

Abstract: The structures of three new 7-aryl-benzo[h]pyrazolo[3,4-b]quinolines, 8-methyl-7-(4-chlorophenyl)-10-phenyl-6,10-dihydro-5H-benzo[h]pyrazolo[3,4-b]quinoline, C₂₇H₂₀ClN₃, 8-methyl-7-(3-pyridinyl)-10-phenyl-6,10-dihydro-5H-benzo[b]pyrazolo[3,4-b]quinoline, C₂₆H₂₀N₄, and 8-methyl-7-(4-pyridinyl)-10-phenyl-10H-benzo[h]pyrazolo[3,4-b]quinoline, C₂₆H₁₈N₄, which is an unexpected oxidation product isolated from the attempted synthesis of 8-methyl-7-(4-pyridinyl)-10-phenyl-6,10-dihydro-5H-benzo[h]pyrazolo[3,4-b]quinoline, and those of three new 11-aryl-benzo[f]pyrazolo[3,4-b]quinolines, 11-(4-methylphenyl)-10-methyl-8-phenyl-6,8-dihydro-5H-benzo[f]pyrazolo[3,4-b]quinoline, C₂₈H₂₃N₃ ( $P\bar 1$ , Z' = 2), 11-(4-methoxyphenyl)-10-methyl-8-phenyl-6,8-dihydro-5H-benzo[f]pyrazolo[3,4-b]quinoline, C₂₈H₂₃N₃O (P2₁/c, Z' = 4), and 11-(3,4,5-trimethoxyphenyl)-10-methyl-8-phenyl-6,8-dihydro-5H-benzo[f]pyrazolo[3,4-b]quinoline, C₃₀H₂₇N₃O₃, are reported. The crystal structures are compared with those of a number of analogues reported in the recent literature; in particular, structural comparisons are drawn within each series as the substituted pendent aryl group is varied, and between several pairs of strictly isomeric 7-aryl-benzo[h]pyrazolo[3,4-b]quinolines and 11-aryl-benzo[f]pyrazolo[3,4-b]quinolines containing the same aryl substituents within each pair. Intermolecular interactions of the C-H [pi] type are found in the crystal structures of both series, but [pi] [pi] stacking interactions are found only in the 7-aryl-benzo[h]pyrazolo[3,4-b]quinoline series.

Keywords: structural comparisons; anti-viral and anti-malarial agents; cyclocondensation reactions.