4-Methyl-2,3-dihydro-1H-1,5-benzodiazepin-2-one monohydrate

The seven-membered fused-ring in the title compound, C10H10N2O·H2O, adopts a boat conformation (with the two phenylene C atoms representing the stern and the methylene C atom the prow). In the crystal, two benzodiazepinone molecules are linked about a center of inversion by diazepine–carbonyl N—H⋯O hydrogen bonds. The dimers are further linked by water–diazepine O—H⋯N hydrogen bonds, forming a linear chain.

The seven-membered fused-ring in the title compound, C 10 H 10 N 2 OÁH 2 O, adopts a boat conformation (with the two phenylene C atoms representing the stern and the methylene C atom the prow). In the crystal, two benzodiazepinone molecules are linked about a center of inversion by diazepinecarbonyl N-HÁ Á ÁO hydrogen bonds. The dimers are further linked by water-diazepine O-HÁ Á ÁN hydrogen bonds, forming a linear chain.

Comment
The compound is belongs to the class of benzodiazepine drugs; the compound is synthesized by condensing o-phenylenediamine with ethyl acetoacetate, two readily-available commerically chemicals. The chemical background of this class of precusor compounds is presented in an earlier report (Ahabchane et al., 1999). A more recent study reports the microwaveassisted synthesis of the title compound (Koizumi, 2006), which is presumably anhydrous. However, the compound crystallizes as a monohydrate (Scheme I, Fig. 1), as shown from the crystal structure analysis.
One of the two hydrogen atoms of the water molecule is disordered over two positions in a 1:1 ratio. That hydrogen atom near the center-of-inversion is hydrogen bonded to the inversion-related oxygen atom. As the benzodiazepinone molecule is N-H···O hydrogen bonded into a dimer, the water molecule then links adjacent dimers into a linear chain (Table 1).
When the heating time is lengthened to 6 hours, the product is N-isopropenyl 1,3-benzimidazol-2-one; details are given in another report (Saber et al., 2010).

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.95-0.98 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2-1.5U eq (C).
One of the two hydrogen atoms of the water molecule is disordered over two positions. The hydrogen atom near the center-of-inversion should have only half occupancy; this is linked to the inversion-related water molecule. The O-H distances were restrained to 0.84±0.01 Å and the H···H distances to 1.37±0.01 Å; the isotropic temperature factors of the hydrogen atoms were freely refined.
The amino H-atom was located in a difference Fourier map, and was refined with a distance restraint of N-H 0.86±0.01 Å; its temperature factor was also freely refined. Fig. 1. Thermal ellipsoid plot (Barbour, 2001) of the molecule of C 10 H 10 N 2 O . H 2 O at the 70% probability level; hydrogen atoms are drawn as spheres of arbitrary radius. The disorder in one of the two the hydrogen atoms of the water molecule is not shown.