(E)-3-Phenyl-2-(1-tosyl-1H-indol-3-ylcarbonyl)acrylonitrile

In the title compound, C25H18N2O3S, the indole moiety is planar and makes a dihedral angle of 89.95 (09)° with the phenyl ring of the sulfonyl substituent. The molecular conformation features a weak C—H⋯N short contact and the crystal packing reveals a weak C—H⋯O hydrogen bond.

In the title compound, C 25 H 18 N 2 O 3 S, the indole moiety is planar and makes a dihedral angle of 89.95 (09) with the phenyl ring of the sulfonyl substituent. The molecular conformation features a weak C-HÁ Á ÁN short contact and the crystal packing reveals a weak C-HÁ Á ÁO hydrogen bond.
The indole ring is planar and the sulfonyl bound phenyl ring is perpendicular to the nine membered indole moiety with a dihedral angle of 89.95 (09)°.
In the benzene ring of the indole system, the endo-cyclic angles at C2, C5 and C6 are contracted to 116.9 (3)°, 118.6 (3)° and 118.5 (3)° respectively, while those at C1, C3 and C4 expanded to 123.3 (3)°, 121.5 (3)° and 121.2 (3)° respectively. This may be due to a real effect caused by the fusion of the smaller pyrrole ring to the six membered benzene ring, and the strain is taken up by angular distortion rather than by bond length distortions (Allen, 1981). A similar effect has also been observed by Sankaranarayanan et al. (2000) and Seshadri et al. (2002).
The difference in C-N bond lengths may be due to the electron-withdrawing character of the phenyl sulfonyl group (Govindasamy et al., 1998;Seshadri et al., 2002). The molecular structure is stabilised by a weak C-H···N intramolecular interactions and the crystal packing reveals a weak C-H···O hydrogen bond.

Experimental
To the mixture of cyanoacetylindole(2 mmol) and benzaldehyde (2.1 mmol) sodium methoxide (10 mol %) was added in methanol. The mixture was allowed to reflux for 2 h. After completion of the reaction, which was washed with water and extracted with ethylacetate (10 × 2 = 20 ml), the filtrate was dried with sodium sulfate and concentrated. The crude was subjected to column chromatography to obtain pure condensed chalcone product. To the chalcone (1 mmol) which was suspended in 10 ml benzene add aqueous 30% NaOH (10 ml), containing tosyl chloride (1.1 mmol) and tetrabutylammonium bromide (0.10 mmol). After stirring vigorously for 30 min, the layers were separated and the water layer was extracted with benzene (10 ml). The combined organic layers were dried over Na 2 SO 4 and the solvent was removed under reduced pressure. The crude product was purified by recrystallisation from CH 2 Cl 2 /hexane to afford (E)-3-phenyl-2-(1- Refinement H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93-0.97 Å and U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2 U eq (C) for other H atoms.

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 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.