ABSTRACT
The crystal of 6-(3-nitro-phen-yl)-7-phenyl-5-thia-7-aza-spiro-[2.6]nonan-8-one (1), C19H18N2O3S, has monoclinic (P21/n) symmetry while that of its isomer 6-(4-nitro-phen-yl)-7-phenyl-5-thia-7-aza-spiro-[2.6]nonan-8-one (2), has ortho-rhom-bic (Pca21) symmetry: compound 1 has two mol-ecules, A and B, in the asymmetric unit while 2 has one. In all three mol-ecules, the seven-membered thia-zepan ring exhibits a chair conformation with Q2 and Q3 values (Å) of 0.521â (3), 0.735â (3) and 0.485â (3), 0.749â (3) in 1 and 0.517â (5), 0.699â (5) in 2. In each structure, the phenyl rings attached to adjacent atoms of the thia-zepan ring have inter-planar angles ranging between 41 and 47°. Except for the nitro groups, the three mol-ecules have similar conformations when overlayed in pairs. Both crystal structures are consolidated by C-Hâ¯O hydrogen bonds.