Spiro[cyclopropane-1,3′-indolin]-2′-one

In the title molecule, C10H9NO, the dihedral angle between the mean plane of the cyclopropane ring and the essentially planar [maximum deviation = 0.032 (2) Å] indole ring system is 87.65 (17)°. In the crystal, intermolecular N—H⋯O hydrogen bonds link molecules into one-dimensional chains along [100].

In the title molecule, C 10 H 9 NO, the dihedral angle between the mean plane of the cyclopropane ring and the essentially planar [maximum deviation = 0.032 (2) Å ] indole ring system is 87.65 (17) . In the crystal, intermolecular N-HÁ Á ÁO hydrogen bonds link molecules into one-dimensional chains along [100].
Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXTL.  Indoline-2-one and its derivatives have been widely explored as materials for the synthesis of antitumor agents (Wang et al., 2011). Indoline-2-one may also be used as a precursor for synthesizing organic luminescent molecules because of its perfect conformation (Ji et al., 2010). In the course of exploring new electro-optic compounds, we obtained the title compound compound and the crystal structure is reported herein.

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 1,2-dibromoethane (1.00 g, 5.35 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: 0.18 g, 30%). The compound was then dissolved in THF, and colorless crystals were formed on slow evaporation at room temperature over one week.

Refinement
All H atoms were placed in geometrically calculated positions and refined using a riding model with C-H = 0.93-0.97 Å and N-H = 0.86 Å and with U iso (H) = 1.2U eq (C, N). Fig. 1. The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

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.