5-(Prop-2-ynyl)-5H-dibenzo[b,f]azepine

The asymmetric unit of the title compound, C17H13N, contains two independent butterfly-shaped molecules. The seven-membered azepine rings both adopt a boat conformation. The dihedral angles between the benzene rings in the two molecules are 46.95 (11) and 52.21 (11)°.

The asymmetric unit of the title compound, C 17 H 13 N, contains two independent butterfly-shaped molecules. The sevenmembered azepine rings both adopt a boat conformation. The dihedral angles between the benzene rings in the two molecules are 46.95 (11) and 52.21 (11) .

Experimental
The structure of the title compound contains two independent molecules in the asymmetric unit ( Fig. 1). Each molecule is consists of two phenyl rings fused to a seven-membered azepine ring adopting a boat conformation. The overall shape of each molecule is butterfly-like. The dihedral angles between the phenyl rings are 46.95 (11) and 52.21 (11)° for C1-C5/C14, C6-C11 and C18-C22/C31, C23-C28, respectively. The bond lengths and angles are found to be similar to those observed in other structurally related compounds (Jayasankar et al., 2009;Nagaraj et al., 2005;Sadashiva et al., 2005). The crystal packing (Fig. 2) is enforced only by van der Waals forces.

Experimental
To the stirred solution of iminostilbene (0.2921 g, 1.5 mmol) in DMF (3.0 mL), propargyl bromide (0.41 ml, 4.5 mmol) and potassium carbonate (0.418 ml, 3.02 mmol) were added and refluxed for 15 h at 90°C. After completion of the reaction reaction as judged by TLC, the crude mixture was adsorbed on silica and purified by column chromatography (eluent: n-hexane:ethyl acetate, 9.5:0.5 v/v) to obtain the title compound in 77% yield. Recrystallization by slow evaporation of a methanol solution afforded yellow crystals suitable for single-crystal X-ray diffraction studies. Iminostilbene and propargyl bromide were purchased from Alfa Acer and Aldrich, respectively.

Refinement
Aromatic, methine and methylene H atoms were positioned geometrically with C-H = 0.93-0.97 Å, and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (CH). The hydrogen of the acetylene groups (C-H= 0.91 (2) and 0.92 (3) Å) were located in difference Fourier maps and refined isotropically.

Figure 2
The crystal packing of the title compound viewed along the a axis.   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.