Crystal structure of methyl (E)-2-(1-methyl-2-oxoindolin-3-ylidene)acetate

The title compound, C12H11NO3, is essentially planar, with the mean plane of the acetate side chain [–C—C(=O)—O—C] being inclined to the mean plane of the indole ring system by 12.49 (7)°. The five- and six-membered rings of the indole group are almost coplanar, making a dihedral angle of 1.76 (8)°. The conformation about the C=C bond is E and there is an intramolecular C—H⋯O hydrogen bond present. In the crystal, molecules are linked by pairs of C—H⋯O hydrogen bonds forming inversion dimers, with an R 2 2(16) ring motif. The dimers are linked by a second pair of C—H⋯O hydrogen bonds, enclosing R 2 2(16) ring motifs, forming ribbons lying parallel to (-114). The ribbons are linked via C—H⋯π interactions, forming a three-dimensional structure.


S1. Comment
The indole skeleton is a key component of many biologically active compounds and 3-substituted indole derivatives have been evaluated as precursors of potent anti-inflammatory and analgesic agents (Radwan et al., 2007). Herein, we report on the synthesis and crystal structure of the title compound.
In the title compound ( Fig. 1), all bond lengths and angles are normal and comparable with those reported for similar structures (Bhella et al., 2009;Hou & Li, 2011). The five-membered ring (N1/C4-C7) and the six-membered ring (C6-C11) of the the indole group are almost co-planar, with a dihedral angle of 1.76 (8)°.
In the crystal, molecules are linked by pairs of C-H···O hydrogen bonds forming inversion dimers, with an R 2 2 (16) ring motif (Table 1 and Fig. 2). The dimers are linked by a second pair of C-H···O hydrogen bonds, enclosing R 2 2 (16) ring motifs, forming ribbons lying parallel to (114); see Table 1 and Fig. 2. The ribbons are linked via C-H···π interactions (Table 1 and Fig. 3) forming a three-dimensional structure.

S2. Experimental
A mixture of isatin and 1.5 eq of methylbromoacetate were dissolved in DMF with potassium tert-butoxide as catalyst.
Th reaction mixture was refluxed at 353 K for 2 h. On completion of the reaction, monitored by thin layer chromatography, the mixture was extracted with ethyl acetate and water. The product was dried and purified by column chromatography using ethyl acetate and hexane (1:9) as an elutent to afford the title compound (yield: 90 %). Colourless block-like crystals were obtained by slow evaporation of a solution in ethyl acetate at room temperature.

S3. Refinement
All the H atoms were fixed geometrically and allowed to ride on their parent C atoms: C-H = 0.93 -0.98 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and = 1.2U eq (C) for other H atoms.  The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.   Table 1 for details; H atoms not involved in hydrogen bonding have been omitted for clarity).  The crystal packing of the title compound viewed along the b axis. The hydrogen bonds are shown as dashed lines (see Table 1 for details; H atoms not involved in hydrogen bonding have been omitted for clarity).