Comparative study of crystal structures of N-benzenesulfonyl derivatives of tetrahydroquinolines

KOMROVSKY F; SPERANDEO NR; VERA DMA; CRUICKSHANK DL; CAIRA MR; MAZZIERI MR

Congreso; I Reunión Latinoamericana de Cristalografía - IX Reunión Anual de la AACr; 2013

We have studied comparatively the crystal structures of five derivatives from a library of N-benzenesulfonyl tetrahydroquinolines (THQ) [1,2], to identify their conformational preferences that may be related to their biological activities. We evaluated the molecular conformations and the relationship between intermolecular interactions and melting points (mps). Also, we compared the structures calculated in vacuo by the DFT/B3LYP/6-311+G(2d,p) method with the ones obtained from X-ray analysis. Single crystals of four derivatives were prepared and their crystal structures were resolved: N-(benzenesulfonyl)-1,2,3,4-THQ (1), N-(benzenesulfonyl)-2-methyl-1,2,3,4-THQ (2), N-(4-nitrobenzenesulfonyl)-1,2,3,4-THQ (3) and N-(2,3,5,6-tetramethylbenzenesulfonyl)-1,2,3,4-THQ (4). The X-ray structure of N-(4-fluoro-benzenesulfonyl)-2-methyl-1,2,3,4-THQ (5), was reported previously [3]. Compounds 1-3 and 5 showed typical butterfly-like conformations as the energetically most favorable, as already described for sulfonamides [4]. Compound 4 presented a different conformation, because of the steric hindrance originating from its ortho substituents, as a result of which, it adopts a more extended arrangement in space. In the crystals, molecules of 1-5 are held together primarily by van der Waals forces. Compound 5 had two interaction hydrogen bonds (IHB) and mp = 121°C. Compound 3 had an IHB and a  stacking interaction, which could explain a mp = 115ºC. Compounds 1, 2 and 4 had a unique IHB, which would explain the fact that their mps were lower than those of 3 and 5 (< 100ºC). The comparison of the conformations of 1-5 in the solid state and in vacuo, showed root-mean-square deviations of 0.34, 0.09, 0.16, 0.2 and 0.73 Å, respectively. These small differences could originate from the intermolecular forces in the crystal structure.