(E)-2-[4-(Piperidin-1-yl)benzylidene]-2,3-dihydro-1H-inden-1-one

In the title compound, C21H21NO, the indene ring system is essentially planar with a maximum deviation of 0.066 (1) Å and makes dihedral angles of 7.93 (6) and 2.43 (6)°, respectively, with the benzene plane and the mean plane of the piperidine ring. These latter two planes make a dihedral angle of 7.61 (7)°. In the crystal, molecules are linked by C—H⋯O interactions, forming infinite chains along the b axis.

In the title compound, C 21 H 21 NO, the indene ring system is essentially planar with a maximum deviation of 0.066 (1) Å and makes dihedral angles of 7.93 (6) and 2.43 (6) , respectively, with the benzene plane and the mean plane of the piperidine ring. These latter two planes make a dihedral angle of 7.61 (7) . In the crystal, molecules are linked by C-HÁ Á ÁO interactions, forming infinite chains along the b axis.

Comment
Chalcones are well known intermediates for synthesizing various heterocyclic compounds. The compounds with the backbone of chalcones have been reported to possess various biological activities. The presence of a reactive unsaturated keto function in chalcones is found to be responsible for their various biological activities. Chalcone derivatives are very versatile as physiologically active compounds and substrates for the evaluation of various organic syntheses. Chalcones belong to one of the major classes of natural products with widespread distribution in spices, tea, beer, fruits and vegetables. Chalcones also have been recently the subject of great interests for their pharmacological activities (Di Carlo et al., 1999). Prostate cancer is one of the most commonly diagnosed cancers in men, and the second leading cause of cancer deaths in the European Union and United States of America (Heidenreich et al., 2008). Many antitumor drugs have been developed for prostate cancer patients, but their intolerable systemic toxicity often limits their clinical use. Chemoprevention is one of the most promising approaches in prostate cancer research, in which natural or synthetic agents are used to prevent this malignant disease (Heidenreich et al., 2008;Syed et al., 2008).
In the crystal structure, the molecules are linked by C8-H8A···O1 i (Table 1) interactions to form infinite chains along the b-axis.

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

Refinement
All H atoms were positioned geometrically and refined using a riding model [C-H = 0.93 Å for Csp 2 and 0.97 Å for methine C]; U iso (H) = 1.2U eq (C) for all H atoms. In the absence of significant anomalous dispersion,1848 Friedel pairs were merged in the final refinement.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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.