Crystal structure of 5-[4-(diethylamino)benzylidene]-2,2-dimethyl-1,3-dioxane-4,6-dione

The title compound, 5-[4-(diethylamino)phenylmethylidene]-2,2-dimethyl-1,3-dioxane-4,6-dione, have been synthesized and its crystal structure determined. Due to the absence of hydrogen-bond donors in the structure, the crystal packing is controlled by van der Waals forces and weak C—H⋯O interactions, which associate the molecules in dimers.

The title compound, C 17 H 21 NO 4 , consists of substituted Meldrum's acid with a [4-(diethylamino)phenyl]methylidene fragment attached to the fifth position. The heterocycle assumes a distorted boat conformation. The planar part of heterocycle is almost coplanar with the benzene ring due to the presence of a long conjugated system in the molecule. This leads to the formation of C-HÁ Á ÁO-type intramolecular contacts. As a result of the absence of hydrogenbond donors in the structure, the crystal packing is controlled by van der Waals forces and weak C-HÁ Á ÁO interactions, which associate the molecules into inversion dimers.

Structural commentary
The title compound, C 17 H 21 NO 4 , consists of substituted Meldrum's acid with a [4-(diethylamino)phenyl]methylidene fragment attached to fifth position (Fig. 1.). The heterocycle assumes a distorted boat conformation. Atoms C2 and C5 ISSN 2056-9890 deviate from the least-squares plane [maximum deviations AE0.013 (1) Å ] calculated for the other four atoms of the heterocycle by 0.549 (3) and 0.154 (3) Å , respectively. The planar part of heterocycle is nearly coplanar with the benzene ring [dihedral angle = 8.05 (10) ] due to the presence of a long conjugated system in the molecule. This leads to the formation of C-HÁ Á ÁO-type intramolecular contacts (Table 1).
stacking interactions are also observed between conjugated systems of the molecules. The distance between the corresponding least-square planes is 3.54 (su?) Å .

Supramolecular features
Because of the absence of hydrogen-bond donors in the structure, the crystal packing is controlled by van der Waals forces and weak C-HÁ Á ÁO interactions, which associate molecules into inversion dimers (Fig. 2

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The C-bound H atoms were positioned geometrically and refined as riding on their parent atoms: C-H = 0.93-0.98Å with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms. The molecular structure the title compound, showing 50% probability displacement ellipsoids and the atomic numbering Table 1 Hydrogen-bond geometry (Å , ). Symmetry code: (i) Àx; Ày þ 1; Àz þ 1.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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.