3,3′-(p-Phenylene)bis(3,4-dihydro-2H-1,3-benzoxazine)

Molecules of the title compound, C22H20N2O2, are situated on crystallographic centres of symmetry. The oxazinane ring adopts a sofa conformation. Molecules are linked into cyclic centrosymmetric dimers via C—H⋯O hydrogen bonds with the motif R 2 2(6). In addition to the C—H⋯O interactions, the crystal structure is also stabilized by C—H⋯π interactions.

Molecules of the title compound, C 22 H 20 N 2 O 2 , are situated on crystallographic centres of symmetry. The oxazinane ring adopts a sofa conformation. Molecules are linked into cyclic centrosymmetric dimers via C-HÁ Á ÁO hydrogen bonds with the motif R 2 2 (6). In addition to the C-HÁ Á ÁO interactions, the crystal structure is also stabilized by C-HÁ Á Á interactions.
The oxazinane ring of the benzoxazine moiety adopts the sofa conformation, with the puckering parameters q 2 and φ (Cremer & Pople, 1975) and the smallest displacement asymmetric parameters, Δ s (Nardelli et al., 1983) as follows: In addition to the van der Waals interactions, the crystal packing is stabilized by C-H···O and C-H···π hydrogen bonds (Tab. 1) as well as by π-π-electron interactions. The atom C8 acts as a donor to the atom O1 of the neighbour molecule.
This hydrogen bond is involved in a motif C 1 1 (10) forming an infinite chain along b axis. C 1 1 (10) projected on the axis b corresponds to the translational period along this axis. Simultaneously a pair of C8-H8A···O1 hydrogen bonds form a cyclic centrosymmetric dimer [R 2 2 (6)]. The π-π-electron interactions between the rings (C1\C2···C6) at x, y, z and 1-x, -y, -z with the centroid-centroid distances equal to 3.780 (2) Å are observed in the crystal structure.

Experimental
A mixture of 2-(4-[(2-hydroxybenzyl)amino]anilinomethyl)benzenol (0.005 mole) and methanal (0.010 mole) was irradiated under microwaves generated by IFB Microwave Oven (Frequency = 2450 MHz ~λ=122 mm; 480 W) for 4 to 6 minutes; the distance from the source to the sample was 15 cm. The progress of the reaction was monitored by a thin layer chromatography. After completion of reaction, ice-cold water (50 ml) was added to the reaction mixture and stirred. The title compound was extracted with chloroform, the combined organic layers were dried over anhydrous sodium sulfate and then the solvent was evaporated. The crude product was recrystallized in ethylacetate at room temperature. The elongated single cystals of the title compound of average length of 2 mm were grown.

Refinement
All the H atoms could be clearly discerned in the difference electron density map. Nevertheless the atoms were situated into the idealized positions and refined in the riding model approximation. The constraints: C aryl -H = 0.93 and C methylene -H = 0.97 Å. U iso H=1.2U eq (C aryl / methylene ). Fig. 1. View of the title molecule with the atom labelling scheme. The displacement ellipsoids are drawn at the 30% probability level while the H atoms are shown as small spheres of arbitrary radii.   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 Rfactors(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.