3-(3-Nitrobenzyl)-4H-chromen-4-one

In the title compound, C16H11NO4, the dihedral angle between the 10-membered coplanar chromone ring system and the benzene ring is 77.83 (3)°. In the crystal, weak C—H⋯O hydrogen bonds link the molecules into a three-dimensional network.

homoisoflavoinoids involves the condensation of chroman-4-one with an aromatic aldehyde in the presence of either an acidic or basic catalyst (Shaikh et al., 2011).

Experimental
A mixture of chroman-4-one (1.00 g, 6.75 mmol), 3-nitrobenzaldehyde (1.25 g, 8.10 mmol) and 10-15 drops of piperidine was heated at 80°C for 10 hrs. The reaction mixture was monitored for completion by thin layer chromatography. Upon completion, the reaction mixture was cooled, diluted with water and neutralized using 10% HCl.
To the viscous reaction mixture, 15 ml of ethyl acetate was added. The homoisoflavonoid precipitated out upon the addition of hexane to the reaction mixture. The powdered product was filtered, washed with hexane and dried under vacuum. Upon slow evaporation of chloroform, the crystals of the homoisoflavonoid were obtained with a m.p. of 129-130 °C.

Refinement
All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in idealized positions and refined with geometrical constraints, and with U iso (H) = 1.2U eq (C).

3-(3-Nitrobenzyl)-4H-chromen-4-one
Crystal data 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.