(E)-3-(2-Chloro-6-methyl-3-quinolyl)-1-(2,3-dihydro-1,4-benzodioxin-6-yl)prop-2-en-1-one

In the title molecule, C21H16ClNO3, the quinoline and benzene rings are inclined at 56.96 (6)° with respect to each other and the dioxine ring is in a twist-chair conformation. The structure is devoid of any classical hydrogen bonds. Rather weak intermolecular hydrogen-bonding interactions of the types C—H⋯N and C—H⋯O are present, consolidating the crystal structure.

In the title molecule, C 21 H 16 ClNO 3 , the quinoline and benzene rings are inclined at 56.96 (6) with respect to each other and the dioxine ring is in a twist-chair conformation. The structure is devoid of any classical hydrogen bonds. Rather weak intermolecular hydrogen-bonding interactions of the types C-HÁ Á ÁN and C-HÁ Á ÁO are present, consolidating the crystal structure.
The title molecule is presented in Fig. 1. The bond distances (Allen et al., 1987) and angles are as expected and agree with the corresponding bond distances and angles reported in a closely related compound (Rizvi et al., 2010). The least-square planes of the quinoline and phenyl rings defined by atoms N1/C1-C9 and C14-C19, respectively, are inclined at 56.95 (6)°w ith respect to each other. The dioxine ring is in a twist-chair conformation with C20 and C21 atoms 0.425 (3) and 0.307 (3) Å on the opposite sides of the plane formed by the remining ring atoms. The structure is devoid of any classical hydrogen bonds. However, short intramolecular interactions involving Cl1 and O1 and rather weak hydrogen bonding inter-molecular interactions of the types C-H···N and C-H···O are present consolidating the crystal packing; details have been provided in Table 1.
The precipitates were collected by filtration, washed with cold water followed by cold MeOH. The resulting chalcone was recrystallised from CHCl 3 to obtain the title compound as yellow crystalline product, (yield 2.76 g, 7.55 mmol, 75.5%), (m.p. 458-460 K).

Refinement
Though all the H atoms could be distinguished in the difference Fourier map the H-atoms were included at geometrically idealized positions and refined in riding-model approximation with the following constraints: C-H distances were set to 0.95, 0.98 and 0.99 Å for aromatic, methyl and methylene H-atoms, respectively, and U iso (H) = 1.2U eq (C). The final difference map was essentially featurless. Fig. 1. ORTEP-3 (Farrugia, 1997) drawing of (I) with displacement ellipsoids plotted at 50% probability level.

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