1-(2,6-Dichlorophenyl)indolin-2-one

In the molecule of the title compound, C14H9Cl2NO, the planar indole ring system [with a maximum deviation of 0.020 (2) Å for the N atom] is oriented at a dihedral angle of 72.17 (3)° with respect to the phenyl ring. In the crystal structure, weak intermolecular C—H⋯O hydrogen bonds link the molecules. A weak C—H⋯π interaction may further stabilize the structure.

In the molecule of the title compound, C 14 H 9 Cl 2 NO, the planar indole ring system [with a maximum deviation of 0.020 (2) Å for the N atom] is oriented at a dihedral angle of 72.17 (3) with respect to the phenyl ring. In the crystal structure, weak intermolecular C-HÁ Á ÁO hydrogen bonds link the molecules. A weak C-HÁ Á Á interaction may further stabilize the structure.

Comment
Indolinones are a class of heterocyclic compounds found in many natural products and in a number of marketed drugs (Hibino & Choshi, 2002;Somei & Yamada, 2003). They have diverse chemical structures and complex physiological and pharmacological actions. The search for potential drugs and their mechanism of action has been difficult because of their complexity. These compounds contain both oxoindole and dioxolane moieties which have independently been seen in other anticonvulsants (Popp, 1977(Popp, , 1984. The title compound, a chloro analogue, was found to be most potent in the MES test.
Since no common target site has yet been established, X-ray analysis was undertaken to search its crystal structure, which may help to understand the mechanism of action at the molecular level.
In the crystal structure, weak intermolecular C-H···O hydrogen bonds (Table 1) link the molecules (Fig. 2), in which they may be effective in the stabilization of the structure. The weak C-H···π interaction (Table 1) may further stabilize the structure.

Experimental
For the preparation of the title compound, sodium salt of 2-(2-(2,6-dichloro-phenylamino)phenyl)acetate (3.18 g, 10 mmol) was dissolved in distilled water (50 ml) and heated on a hot plate, until a homogeneous solution obtained, and then filtered to remove the undissolved product. It was poured into concentrated hydrochloric acid (5 ml) diluted with ice water (25 ml) in an Erlenmeyer flask to obtain 2-(2-(2,6-dichlorophenylamino)phenyl)acetic acid. Then, it was stand for 15 min in an ice bath. The crude product was separated and recrystallized in ethanol. 2-(2-(2,6-dichlorophenylamino)phenyl)acetic acid (2.96 g, 10 mmol) was refluxed in methanol (50 ml) in catalytic amount of sulfuric acid. As soon as a methyl ester is formed, it is cyclized to form the title compound, which was recrystallized in ethanol (yield; 79%; m.p. 420-421 K).

Refinement
H atoms were positioned geometrically, with C-H = 0.95 and 0.99 Å for aromatic, and methylene H, respectively, and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme.   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.