(E)-3-(1-Phenylethylidene)indolin-2-one

In the title molecule, C16H13NO, the indoline-2-one ring system is nearly planar [maximum atomic deviation = 0.082 (2) Å] and is oriented at a dihedral angle of 66.60 (12)° with respect to the phenyl ring. In the crystal, intermolecular N—H⋯O hydrogen bonds link the molecules into supramolecular dimers.

In the title molecule, C 16 H 13 NO, the indoline-2-one ring system is nearly planar [maximum atomic deviation = 0.082 (2) Å ] and is oriented at a dihedral angle of 66.60 (12) with respect to the phenyl ring. In the crystal, intermolecular N-HÁ Á ÁO hydrogen bonds link the molecules into supramolecular dimers.

Related literature
For applications of indoline-2-one and its derivatives as precursors in the synthesis of pharmaceuticals, see: Stephen et al. (1996).  Table 1 Hydrogen-bond geometry (Å , ).   Indoline-2-one and its derivatives have been used as precursors to synthesis pharmaceuticals (Stephen et al., 1996). Rooting from its perfect conformation, indoline-2-one were tried to built electro-optic compounds recently. In the course of synthesis, we obtained the intermediate compound C 16 H 13 NO, (I), and the synthesis and structure are reported here.

D-HÁ
In the title molecule, the indole system lies approximately in a plane and the maximum displacement from the least-square plane defined by all the 9 atoms of the indole framework is 0.082 (2) Å for C2 atom. The interplanar angle between the benzene plane and that of the indole moiety is 66.60 (12)°.
The title compound has three substituent ring systems, an indoline-2-one ring and two benzene rings which are arranged in a propeller-like fashion around the central atom C9 (Fig. 1). The interplanar dihedral angle between the two benzene rings defined by C10-C15 and C16-C21 is 73.41 (14)°. The interplanar angles between these benzene planes and that of the indoline moiety are 76.61 (12)° and 67.68 (12)°, respectively.
In the crystal structure there is an intermolecular N-H···O hydrogen-bonding interaction (Table 1) linking the molecules into dimers (Fig. 2).

Experimental
Indolin-2-one (0.50 g, 3.76 mmol) was dissolved in THF (20 mL) and KOH (0.80 g, 14.3 mmol) was slowly added. After heating the stirred mixture at reflux temperature for 30 min, a solution of acetophenone (1.00 g, 8.33 mmol) in THF was slowly added and the refluxing continued for 2 h. The mixture was then cooled to 333 K and poured into water (200 mL) and was extracted with chloroform and dried over Na 2 SO 4 . After removing the solvent, the crude product was purified by column chromatography on silica gel, affording the title compound (yield: 0.15 g, 17%). The compound was then dissolved in THF, and yellow crystals were formed on slow evaporation at room temperature over one week.

Refinement
All H atoms were placed in geometrically calculated positions with C-H = 0.93 (aromatic), 0.96 (methyl) and N-H = 0.86 Å, and refined using a riding model with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C,N).
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

Data collection
Bruker SMART 1000 CCD area-detector diffractometer 1599 reflections with I > 2σ(I)

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.