3,3′-Ethylenebis(3,4-dihydro-6-chloro-2H-1,3-benzoxazine)

The asymmetric unit of the title compound, C18H18Cl2N2O2, contains one half of an independent molecule, the other half being generated via a centre of inversion at the molecular centroid. In the crystal structure, molecular chains are formed through non-classical C—H⋯ O hydrogen bonds between an axial H atom of the oxazine ring and the O atom of a neighbouring molecule.

The asymmetric unit of the title compound, C 18 H 18 Cl 2 N 2 O 2 , contains one half of an independent molecule, the other half being generated via a centre of inversion at the molecular centroid. In the crystal structure, molecular chains are formed through non-classical C-HÁ Á Á O hydrogen bonds between an axial H atom of the oxazine ring and the O atom of a neighbouring molecule.
Data collection: CrysAlis CCD (Oxford Diffraction, 2009); cell refinement: CrysAlis RED (Oxford Diffraction, 2009); data reduction: CrysAlis RED; program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: JANA2006 (Petříček et al., 2006); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: JANA2006.   (2007); Ranjith et al. (2009). During our investigations, a series of bis-benzoxazines were prepared by reaction of phenols, formaldehyde and ethylenediamine (Rivera et al., 1986). However, the crystallization of these compounds was difficult and led to crystals of bad quality. In the present work, the single crystals of the title compound were finally successfully prepared and its crystal structure has been determined herein.

Structure Reports Online
The molecule contains two 1,3-benzoxazine units linked by an ethylene bridge. The asymmetric unit of the title compound There is also possibility for very weak intermolecular interaction between the hydrogen H2A and the aromatic ring C3,C4,C6, C7, C8, C9, with the distance between H2A and the centre of the ring of 2.99 Å.

Experimental
Under vigorous stirring a mixture of ethylenediamine (0.34 ml, 5 mmol) and p-chlorophenol (1.3 g 10 mmol) was dissolved in dioxane (10 ml) and (1.5 ml, 20 mmol) was slowly added. Stirring was continued for 4 h at rt until a precipitate appeared.
The solid was filtered off and washed with water (1.83 g, 92%). Recrystallization from ethanol gave a white solid.

Refinement
All hydrogen atoms were discernible in difference Fourier maps and could be refined to reasonable geometry. According to common practice H atoms attached to C atoms were nevertheless kept in ideal positions during the refinement. The isotropic atomic displacement parameters of hydrogen atoms were evaluated as 1.2*U eq of the parent atom.
supplementary materials sup-2 Figures   Fig. 1. The molecular structure of title compound, showing the atomic numbering scheme with atomic displacement ellipsoids drawn at the 50%. Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F 2 for refinement carried out on F and F 2 , respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement.
The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )