(Z)-1-Acetyl-3-[2-oxo-1-phenyl-2-(3-pyridyl)ethylidene]indolin-2-one

The title compound, C23H16N2O3, exists in a Z configuration with respect to the acyclic C=C bond. The pyridine and phenyl rings are oriented at dihedral angles of 72.97 (4) and 45.05 (4)°, respectively, with respect to the almost planar indoline ring system [maximum deviation 0.080 (1) Å]. The pyridine and phenyl rings are oriented almost perpendicular to each other [dihedral angle 88.93 (5)°]. In the crystal, molecules are interconnected into a three-dimensional framework via intermolecular C—H⋯O and C—H⋯N hydrogen bonds and weak π–π interactions [centroid–centroid distance = 3.681 (1) Å].

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009). Fun, J. H. Goh, H. Yu and Y. Zhang Comment Indole derivatives have a variety of biological activities and are synthetic precursors for many naturally occuring alkaloids (Aanandhi et al., 2008;Muthukumar et al., 2008;Lawrence et al., 2008). The C3 carbonyl group is the common reactive group in isatin (1H-indole-2,3-dione) for further derivation in either thermal reactions or photoreactions (Zhang et al., 2004b;. Photoreactions of N-acetylisatin and alkenes or alkynes have provided a facile way to build various heterocyclic frameworks containing indole moieties (Wang et al., 2005;Zhang et al., 2004a;Xue et al., 2000). Azaaryl substituted acetylenes have been used to react with carbonyl groups which may lead to formation of various heterocyclic polycycles (Yu et al., 2010). In view of the importance of the title compound, (I), as a typical quinone methide product in photoreaction between carbonyl and acetylenes, this paper reports its crystal structure.

Experimental
The title compound was obtained in the reaction between N-acetylisatin and 3-pyridinyl phenyl acetylene under photo-irradiation with light of wavelength > 400 nm. The compound was purified by flash column chromatography with ethyl acetate-petroleum ether (1:5) as eluents. X-ray quality single crystals of (I) were obtained by slow evaporation of a acetone-petroleum ether (1:2) solution (m.p. 568-571 K).

Refinement
H atoms were placed in their calculated positions, with C-H = 0.93 or 0.96 Å, and refined using a riding model, with U iso (H) = 1.2 or 1.5U eq (C). The rotating group model was applied to the methyl group.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.
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.