Crystal structure of 2,2,4-trimethyl-2,3,4,5-tetrahydro-1H-benzo[b][1,4]diazepine hemihydrate

The title compound, C12H18N2·0.5H2O, crystallizes with two independent organic molecules (A and B) in the asymmetric unit, together with a water molecule of crystallization. The diazepine rings in each molecule have a chair conformation. The dihedral angle between benzene ring and the mean plane of the diazepine ring is 21.15 (12)° in molecule A and 17.42 (11)° in molecule B. In the crystal, molecules are linked by N—H⋯O and O—H⋯N hydrogen bonds, forming zigzag chains propagating along [001].


S2. Structural commentary
The title compound, crystallized with two independent organic molecules (A and B) in the asymmetric unit (Fig. 1). The C-C and C-N bond distances are normal and in good agreement with those reported for similar structures (Lamkaddem et al., 2015;Ponnuswamy et al., 2006;Thiruselvam et al., 2013).
The diazepine rings each have a chair conformation. The dihedral angle between benzene ring and the mean plane of the diazepine ring is 21.15 (11)° in molecule A and and 17.42 (1)° in molecule B.
In the crystal of the title compound, molecules are linked through N-H···O and O-H···N hydrogen bonds, involving the water molecule, forming zigzag chains propagating along the c axis direction (Table 1 and Fig. 2).
Methanol was evaporated partially and the reaction mass was poured into water and extracted with chloroform several times. The organic extractions were combined, dried with anhydrous sulphate and then evaporated. The yellow oil obtained was purified by recrystallization from aqueous ethanol and afforded colourless crystals of the title compound (M.p.: 329-330 K).

S4. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The NH and water H atoms were located in difference Fourier maps. The water H atoms were freely refined and the NH H atoms were refined with distance restraints; N-H = 0.86 (2) Å. The C-bound H atoms were positioned geometrically and treated as riding: C-H = 0.93-0.97 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms.
supporting information

Figure 1
The molecular structure of the two independent molecules (A and B) of the title compound, with atom labelling.
Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
The crystal packing of the title compound, viewed along the a axis. The dashed lines indicate the hydrogen bonds (see Table 1 for details; molecule A red, molecule B blue). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.48 e Å −3 Δρ min = −0.20 e Å −3 Extinction correction: SHELXL, Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0040 (10) Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.