5-Fluoro-1-(4-methoxybenzyl)indoline-2,3-dione

In the title compound, C16H12FNO3, the dihedral angle between the benzene ring and the plane of the indole ring system is 71.60 (6)°. In the crystal, molecules stack along the b axis through π–π interactions between the adjacent indole-2,3-dione units with a centroid–centroid distance of 3.649 (3) Å. Intermolecular C—H⋯O=C and C—H⋯π interactions further stabilize the structure, forming a three-dimensional framework.

In the title compound, C 16 H 12 FNO 3 , the dihedral angle between the benzene ring and the plane of the indole ring system is 71.60 (6) . In the crystal, molecules stack along the b axis throughinteractions between the adjacent indole-2,3dione units with a centroid-centroid distance of 3.649 (3) Å . Intermolecular C-HÁ Á ÁO C and C-HÁ Á Á interactions further stabilize the structure, forming a three-dimensional framework.   Table 1 Hydrogen-bond geometry (Å , ).

Related literature
Cg1 is the centroid of the C1-C6 benzene ring.

Experimental
To an ice-bath cooled solution of 5-fluoroindoline-2,3-dione (0.33 g, 2 mmol) in N,N-dimethylformamide (20 ml) was added potassium carbonate (0.33 g, 2.4 mmol) and potassium iodide (0.07 g, 0.4 mmol) followed by 4-methoxybenzyl chloride (0.32 ml, 2.2 mmol). The reaction mixture was stirred at 110 °C for 3 h. After cooling to room temperature, the reaction mixture was poured into ice water (80 ml). The resulting precipitate was filtered and subsequently purified by column chromatography on silica gel with dichloromethane as an eluent to give the title compound (Rf = 0.81, dichloromethane; m.p. 138-139 °C; yield 78%). Yellow crystals of the title compound were obtained by slow evaporation from the solution of dichloromethane/ethanol 8:2 (v/v) at room temperature after a week.

Refinement
All the H atoms were discernible in the difference electron density maps. Nevertheless, the hydrogen atoms were placed into idealized positions and allowed to ride on the carrier atoms, with C-H = 0.93 and 0.97 Å for aryl and methylene hydrogens, respectively. U iso (H) = 1.2U eq (C) aryl / methylene . Fig. 1. The title molecule with the atomic numbering scheme. The displacement ellipsoids are shown at the 30% probability level, while the hydrogen atoms are shown as spheres of arbitrary radius.

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.