(E)-2-(4-Bromobenzylidene)indan-1-one

In the title compound, C16H11BrO, the dihydroindene ring system is approximately planar, with a maximum deviation of 0.008 (2) Å. The mean plane of this ring system forms a dihedral angle of 3.73 (11)°, with the bromo-substituted benzene ring. In the crystal, weak intermolecular C—H⋯O hydrogen bonds link the molecules into sheets parallel to the ab plane and further stabilization is provided by weak C—H⋯π interactions involving the bromo-substituted benzene rings.

In the title compound, C 16 H 11 BrO, the dihydroindene ring system is approximately planar, with a maximum deviation of 0.008 (2) Å . The mean plane of this ring system forms a dihedral angle of 3.73 (11) , with the bromo-substituted benzene ring. In the crystal, weak intermolecular C-HÁ Á ÁO hydrogen bonds link the molecules into sheets parallel to the ab plane and further stabilization is provided by weak C-HÁ Á Á interactions involving the bromo-substituted benzene rings.
Cg1 is the centroid of the C10-C15 ring.
Another indanone analogue donepezil hydrochloride has been approved by US-FDA for the treatment of mild to moderate alzheimer's disease. This drug acts as an AChE (Acetylcholinesterase) inhibitor and some other indanones have been isolated from natural products. Being such a useful moiety, several synthetic strategies have also been developed for their synthesis (Leoni et al., 2000;Sugimoto, 1999;Beukes et al., 1998). They are very useful intermediates for the synthesis of five and six membered heterocyclic compounds. Dihydroindene derivatives exhibit diverse pharmacological activities. Chemistry of dihydroindene has been recognized as a significant field of study.
In the title compound ( Fig. 1), the dihydroindene ring system (C8-C16) is approximately planar, with a maximum deviation of 0.008 (2) Å for atom C15. This ring system is almost coplanar with the benzene ring (C1-C6), with a dihedral angle of 3.73 (11)°. Bond lengths and angles are within the normal ranges and are comparable to those in the related crystal structures (Ali et al., 2010(Ali et al., , 2011. In the crystal (Fig. 2), intermolecular C4-H4A···O1 i and C9-H9B···O1 ii hydrogen bonds (Table 1) link the molecules into sheets parallel to the ab plane ( Fig. 2) and further stabilization is provided by C-H···π iii interactions, involving the centroids of benzene rings (C10-C15; Cg1).

Experimental
A mixture of 2,3-dihydro-1H-indene-1-one (0.001 mmol) and 4-bromobenzaldehyde (0.001 mmol) was dissolved in methanol (10 mL) and to this mixture was added 30% sodium hydroxide solution (5ml). The mixture was stirred for 5 h. After completion of the reaction, as evident from TLC, the mixture was poured into crushed ice, then neutralized with concentrated HCl. The precipitated solid was filtered, washed with water and recrystallised from ethanol to yield the title compound as light yellow crystals.

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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Br1 1.082380 (