Crystal structure and theoretical study of N,N-bis[(5-chloro-2-oxo-2,3-dihydrobenzo[d]oxazol-3-yl)methyl]-2-phenylethanamine

One of the nine-membered 2,3-dihydro-1,3-benzoxazole rings and the phenyl ring are almost parallel to each other, making a dihedral angle of 5.30 (18)°. These rings are almost normal to the mean plane of the other nine-membered 2,3-dihydro-1,3-benzoxazole ring. The crystal structure features C—H⋯O hydrogen bonds and π–π stacking interactions.


Theoretical calculations
Semi-empirical molecular orbital (MO) calculations of the title molecule were carried out using the CNDO/2 method (Pople & Segal, 1966). It is based on the Complete Neglect of Differential Overlap integral approximation. The semiempirical CNDO/2 parameterization is widely used to derive bond lengths, bond angles, torsion angles, atom charges, HOMO and LUMO energy levels, dipole moments, polarizability, etc. The spatial view of the title compound calculated as a closed-shell in a vacuum at 0 K is shown in Fig. 3.
The calculated bond lengths and angles of the title molecule are consistent with those obtained by X-ray structure determination within error limits (Table 1). Looking at Figs. 1 and 3, the experimental and calculated conformations appear to be quite different. This is supported by the torsion angles N1- ]. The small differences between the theoretical and experimental results are due to the calculations being in a vacuum and at 0 K.

Synthesis and crystallization
4-Chloro-2-aminophenol (10 mmol), urea (50 mmol) and 37% wt HCl (2.5 ml) were irradiated (300 W, 413 K) for 15 min in a microwave oven. After completion of the reaction (monitored with TLC), water (10 ml) was added to the reaction mixture and stirred at room temperature for 1 h. The resulting precipitate was filtered and washed with water. After drying the precipitate, crystallization from ethanol-water (1:1 v/v) yielded 5-chloro-2(3H)-benzoxazolone. This compound (2 mmol) was dissolved in methanol (5 ml). Phenethylamine (2 mmol) and 37% wt formalin (2.5 mmol) were added to this solution. The mixture was then stirred vigorously for 1 h. The resulting precipitate was filtered and washed with cold methanol. The crude product was recrystallized from methanol, yield 40%; m.p. 427 K.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. All H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93 (aromatic) and 0.97 (methylene) Å and U iso = 1.2U eq (C).

Figure 3
The molecular structure of the title compound calculated using the CNDO/2 method.  N,N-bis[(5-chloro-2-oxo-2,3- SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: WinGX (Farrugia, 2012) and PLATON (Spek, 2009). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.13 e Å −3 Δρ min = −0.17 e Å −3 Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > 2sigma(F 2 ) is used only for calculating -R-factor-obs 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.