4-Acetyl-2,3,4,5-tetrahydro-1H-1,4-benzodiazepine

The title compound, C11H14N2O·H2O, crystallizes with one formula unit in the asymmetric unit. The seven-membered ring has a chair conformation with the C=O group turned away from the benzene ring. N—H⋯O and O—H⋯O hydrogen bonds are present in the crystal structure.

The title compound, C 11 H 14 N 2 OÁH 2 O, crystallizes with one formula unit in the asymmetric unit. The seven-membered ring has a chair conformation with the C O group turned away from the benzene ring. N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds are present in the crystal structure.

Comment
The title molecule ( Fig. 1) is an important imtermediate used to synthesize a variety of pharmaceuticals, such as inhibitors of phenylethanolamine N-methyltransferase (Grunewald et al., 1996) and inhibitors of Farnesyltransferase (Ding et al., 1999).
A view of the molecular structure of title compound is depicted in Fig.1. The central seven-membered ring has an chair conformation, which is consistent with reported exo conformational form with the C=O group turns away from benzene ring (Kim et al., 1976). All bond lengths and angles are normal (Allen et al., 1987). Molecules related by an c-axis translation are stacked over each other and stabilized by van de waals (Fig. 2). The stacked columns are linked together via an intermolecular hydrogen bond, in which the amine H1 act as a donor to H 2 O O1w atom and H 2 O H1A as a donor to H 2 O O1w atom ( Fig. 2 and Table 1).

Experimental
Acetyl chloride (6 ml) was added dropwise to CH 2 Cl 2 solution (80 ml) containing 2,3,4,5-tetrahydro-1H-1,4-benzodiazepine (14.8 g, 0.1 mol) at ice-water bath. After addition, the reaction temperature was raised to room temperature. The resulting mixture was crashed to ice-water bath after stirring for 5 hrs. The organic layer was separated and dried over MgSO 4 . After filtration, the filtrate was evaporated to give an oil which can be crystallized from acetone to give title compound in 96% yield. Single crystals suitable for X-ray analysis (m.p. 358 K) were obtained by slow evaporation of a ethyl acetate/n-hexane/H 2 O solution at 298 K.

Refinement
The water H atoms and imine H atom were located from Fourier difference maps and refined subject to an O-H restraint of 0.85Å and N-H 0.88 Å. Other H atoms were introduced at calculated positions (C-H = 0.93-0.97 Å) and refined using a riding model. The isotropic displacement parameters of all H atoms were set to 1.2 times U eq of the parent atoms.
supplementary materials sup-2 Figures Fig. 1. View of the molecule of (I) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.