5,11-Ditosyl-5H,11H-dibenzo[b,f][1,5]diazocine-6,12-dione acetic acid hemisolvate

The molecular structure of the title compound, C28H22N2O6S2·0.5CH3COOH, is built up from three fused rings, two six and one eight membered. The eight-membered ring shows a boat conformation and the dihedral angle between the two benzene groups attached thereto is 66.43 (11)°, resulting in a V-shaped geometry. Two tosyl substituents are bound to the N atoms. The planes through the tolyl rings are roughly perpendicular, as indicated by the dihedral angle of 82.44 (12)°. In the crystal, the molecule and its inversion-related symmetry-equivalent are linked to the acetic acid solvent molecule by non-classical O—H⋯O and C—H⋯O hydrogen bonds. Two half-occupied acetic acid solvent molecules are disordered at the same site and linked by a center of symmetry.

Two half acetic acid solvent molecules are disordered at the same site of the crystal structure and linked by a center of symmetry.

Experimental
A mixture of 2-nitrobenzaldehyde (1.22 mmol) and anhydrous SnCl 2 (1.1 g, 6.1 mmol) in 25 mL of absolute ethanol was stirred for 1 h. After reduction, the starting material disappeared, and the solution was allowed to cool down. The pH was adjusted to 7-8 by addition of 5% aqueous potassium bicarbonate before extraction with ethyl acetate. The organic phase was washed with brine and dried over magnesium sulfate. The solvent was removed to afford the amine, which was immediately dissolved in pyridine (5 ml) and then reacted with 4-methylbenzenesulfonyl chloride (0.26 g, 1.25 mmol) at room temperature for 24 h. After the reaction mixture was concentrated in vacuo, the resulting residue was purified by flash chromatography (eluted with ethyl acetate : hexane 3:7). Colourless prisms of the title compound suitable for X-ray structure determination were collected after recrystallization from ethyl acetate : hexane (3:7 v/v) by slow evaporation of the solvent at room temperature after some days.

Refinement
H atoms were located from a difference Fourier map and treated as riding with C-H = 0.96 and C-H = 0.93 Å for methyl and aromatic CH, respectively. Thermal parameters of hydrogen atoms were refined with U iso (H) = 1.2 U eq for aromatic supplementary materials sup-2 Acta Cryst. (2013). E69, o614-o615 and U iso (H) = 1.5 U eq for methyl hydrogen atoms. The refinement of the two half molecule acetic acid required the use of some constraints. Indeed, C29 and O8 occupy the same position with equal share and their atomic displacments are coupled. All sites of the atoms forming the acetic acid molecule are half filled except the one containing C29 and O8. The two half acetic acid molecule are linked by a center of symmetry.

Figure 1
Molecular structure of the title compound with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented as small circles.  Refinement. Refinement of F 2 against all reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on all data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ.