6-Methyl-2,7-diphenyl-1,4-diazepan-5-one

The title compound, C18H20N2O, crystallizes with two molecules in the asymmetric unit. The seven-membered ring in both molecules adopts a distorted chair conformation. The dihedral angles between the phenyl rings are 43.2 (1) and 54.7 (1)° in the two molecules. The crystal packing features N—H⋯O and weak N—H⋯π and C—H⋯π interactions.

The title compound, C 18 H 20 N 2 O, crystallizes with two molecules in the asymmetric unit. The seven-membered ring in both molecules adopts a distorted chair conformation. The dihedral angles between the phenyl rings are 43.2 (1) and 54.7 (1) in the two molecules. The crystal packing features N-HÁ Á ÁO and weak N-HÁ Á Á and C-HÁ Á Á interactions.

Comment
In view of the biological activities of the heterocyclic compounds with 1,4-diazepan-5-one fragment that have widespread applications in pharmaceuticals (Wlodarczyk et al., 2006;Gopalakrishnan et al., 2007), we report the crystal structure of the title compound.
In the molecule A atoms C7, C8 and C9 show S-configuration whereas in the enatiomeric molecule B atoms C25, C26 and C27 show R-configuration. The phenyl ring C1-C6 forms the dihedral angle of 43.2 (1)° with the phenyl ring C13-C18 in molecule A and the phenyl ring C19-C24 forms the dihedral angle of 54.7 (1) ° with the phenyl ring C31-C36 in molecule B. Intermolecular N-H··· O interactions between the two symmetry independent molecules generates an eight-membered ring with graph-set motif R 2 2 (8) (Bernstein et al., 1995). The crystal packing is controlled by weak N-H··· O, N-H···π and C-H···π interactions (see Table 1 & Fig. 2).

Experimental
The title compound was prepared according to the general procedure reported by Thennarasu & Perumal (2002). 3-Methyl-2,6-diphenylpiperidin-4-one (1.82 g, 5 mmole) was added into the ice cold sulfuric acid and the mixture was allowed to reach the room temperature. Then, sodium azide (1.92 g, 30 mmole) was added in portions over a period of one hour. The solution was then poured into crushed ice. The pH of the solution was adjusted to approximately 8.0 using 2 N NaOH solution. The precipitated white solid was recrystallized from ethanol to yield colourless diffraction quality crystals.

Refinement
The H atoms from the N-H groups were located in difference Fourier maps and their positions and isotropic displacement parameters were freely refined. All other H atoms were positioned geometrically and refined using riding model with C-H = 0.93 Å and U iso (H) = 1.2U eq (C) for aromatic C-H, C-H = 0.98 Å and U iso (H) = 1.2U eq (C) for methine C-H, C-H = 0.97 Å and U iso (H) = 1.2U eq (C) for methylene C-H and C-H = 0.96 Å and U iso (H) = 1.5U eq (C) for methyl. The components of the anisotropic displacement parameters in direction of the bond of C33 and C34 were restrained to be equal within an effective standard deviation of 0.001 using the DELU command in SHELXL97 (Sheldrick, 2008 Fig. 1. The molecular structure of the title compound, with atom labels and 30% probability displacement ellipsoids for non-H atoms. A and B are the two molecules in the asymmetric unit. 6-Methyl-2,7-diphenyl-1,4-diazepan-5-one  (7)  0.0559 (11) 0.0503 (11) 0.0522 (10) 0.0020 (