2-Oxoindolin-3-yl acetate

In the title compound, C10H9NO3, the mean plane through the acetate group forms a dihedral angle of 83.39 (5)° with the plane of the indole ring system. In the crystal, pairs of centrosymmetrically related molecules are linked into dimers by N—H⋯O hydrogen bonds. The dimers are further connected into layers parallel to the bc plane by C—H⋯O hydrogen bonds.

In the title compound, C 10 H 9 NO 3 , the mean plane through the acetate group forms a dihedral angle of 83.39 (5) with the plane of the indole ring system. In the crystal, pairs of centrosymmetrically related molecules are linked into dimers by N-HÁ Á ÁO hydrogen bonds. The dimers are further connected into layers parallel to the bc plane by C-HÁ Á ÁO hydrogen bonds.   Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) Àx þ 2; Ày; Àz; (ii) x; Ày þ 1 2 ; z þ 1 2 ; (iii) x; y; z þ 1.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: RZ2559). Indole-2,3-dione derivatives have driven much attention for their anti-bacterial, anti-virus and neuroprotective activities Chen, Wang et al., 2009;Chen, Tang et al., 2010). The title compound, whose structure is reported herein, has been synthesized by reduction of isatin with sodium borohydride followed by acylation. The X-ray structural analysis of the title compound revealed the molecular structure as depicted in Fig. 1. Geometric parameters are in the usual ranges. In the molecule, the mean plane through the ester group (O2/O3/C9/C10) is almost perpendicular to the plane of the indole ring system, forming a dihedral angle of 83.39 (5)°. In the crystal structure, centrosymmetrically related molecules are linked into dimers by N-H···O hydrogen bonds ( Fig. 2; Table 1). The dimers are further connected into a layers parallel to the bc plane by weak C-H···O hydrogen bonds.

Experimental
To a solution of isatin (1.0 mmol) in methanol (20 ml), sodium borohydride (1.0 mmol) in methanol (10 ml) was added dropwise until the disappearance of isatin, as evidenced by thin-layer chromatography, then diluted hydrochloric acid (0.1 M) was added dropwise to eliminate the excess sodium borohydride. The solvent was removed in vacuo, and the residue was dissolved in 10 ml pyridine. Acetic anhydride (1.0 mmol) was then added, and the mixture was refluxed for 1 h. On completion of the reaction, the solvent was removed in vacuo, and the residue was separated by column chromatography (silica gel; petroleum ether/ethyl acetate 5:1 v/v), giving the title compound. 30 mg of the title compound was dissolved in 30 ml me thanol and the solution was kept at room temperature for 7 d, to give colourless single crystals suitable for X-ray analysis on slow evaporation of the solvent.

Refinement
All H atoms were placed at calculated positions and refined as riding, with C-H = 0.93-0.98 Å, N-H = 0.86 Å, and with U iso (H) = 1.2 U eq (C, N) or 1.5 U eq (C) for methyl H atoms.
supplementary materials sup-2 Figures   Fig. 1. The molecular structure of the title compound, with 30% probability displacement ellipsoids.