(Z)-3-[(E)-3-Phenylallylidene]indolin-2-one

The title compound, C17H13NO, synthesized to be tested for neuroprotective activities, consists of an indoline and a phenylallylidene unit with a dihedral angle of 9.0 (1)° between the two ring systems. There are two independent molecules in the asymmetric unit which are connected into a dimer by intermolecular N—H⋯O hydrogen bonds.


Experimental
Crystal data

Comment
It is known that some 3-substituted indoline-2-ones compounds exhibit a variety of pharmacologically important properties such as protein kinase inhibitors (Sun et al., 2003), anti-tumor agents (Andreani et al., 2006) and neuroprotecting agents (Johnson et al., 2005). For studying the biological properties, a series of 3-substituted indoline-2-one derivatives have been synthesized in our lab and their neuroprotective activities have been tested (Balderamos et al., 2008). The results are very promising. To expand our research, a few known compounds were made for test purpose. The title compound was first made by Elliott & Rivers (1964), and modified synthetic methods were reported later (Tacconi & Marinone, 1968;Villemin & Martin, 1998). As a part of our studies on the relationship between the biological activities and solid structures a couple of crystal structures of the derivatives have been carried out (Zhang, et al., 2008(Zhang, et al., , 2009). The title compound consists an indoline and a phenylallylidene unit. The two aromatic rings are slightly twisted with a dihedral angle of 9.0 (1)° (Fig 1).
In the crystal the molecules are connected by intermolecular H-bonds between the two independent molecules to form a dimer (Table 1, Fig. 2).

Experimental
The title compound was synthesized by the condensation of trans-cinnamaldehyde (1 mmol) with 2-oxindole (1 mmol) in ethanol (10 ml) in the presence of catalytic amount of piperidine (0.1 mmol). After refluxing for 3 h, the reaction mixture was left to stand for overnight. The resulting crude solid was filtered, washed with cold ethanol (10 ml) and dried. Orange colored single crystals of the compound suitable for x-ray structure determination were recrystallized from ethanol.

Refinement
All H atoms were placed in calculated positions and included in the final cycles of refinement using a riding model, with distances N-H = 0.86 Å and C-H = 0.93 Å, and displacement parameters U iso (H) = 1.2U eq (N,C). Friedel pairs have been merged prior to refinement.

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 Rfactors(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.