1-Dodecylindoline-2,3-dione

The structure of the title compound, C20H29NO2, is isotypic to that of its homologue 1-octylindoline-2,3-dione. The indoline ring and the two carbonyl-group O atoms are approximately coplanar, the largest deviation from the mean plane being 0.0760 (10) Å. The mean plane through the fused-ring system is nearly perpendicular to the mean plane passing through the 1-dodecyl chain [dihedral angle = 77.69 (5)°]. All C atoms of the dodecyl group are in an antiperiplanar arrangement. In the crystal, molecules are linked by C—H⋯O hydrogen bonds, forming a three-dimensional network.

The structure of the title compound, C 20 H 29 NO 2 , is isotypic to that of its homologue 1-octylindoline-2,3-dione. The indoline ring and the two carbonyl-group O atoms are approximately coplanar, the largest deviation from the mean plane being 0.0760 (10) Å . The mean plane through the fused-ring system is nearly perpendicular to the mean plane passing through the 1-dodecyl chain [dihedral angle = 77.69 (5) ]. All C atoms of the dodecyl group are in an antiperiplanar arrangement. In the crystal, molecules are linked by C-HÁ Á ÁO hydrogen bonds, forming a three-dimensional network. Cu K radiation = 0.58 mm À1 T = 123 K 0.12 Â 0.11 Â 0.04 mm
Supporting information for this paper is available from the IUCr electronic archives (Reference: RZ5103).

Comment
Isatin (1H-indoline-2,3-dione) and derivatives possess a broad range of biological and pharmacological properties and are widely used as starting materials for the synthesis of heterocyclic compounds and as substrates for drug synthesis relevant to application as insecticides and fungicides. These compounds find applications also in a broad range of therapies as anticancer drugs, antibiotics and antidepressants (Bhrigu et al., 2010;Malhotra et al., 2011;Da Silva et al., 2001;Ramachandran, 2011;Smitha et al., 2008). In our work, we are interested in developing a new isatin derivative with the addition of an alkyl halide to explore other potential applications.
The molecule of title compound is build up from a fused five-and six-membered ring system linked to a 1-dodecyl chain and to two ketone O atoms as shown in Fig. 1. The indoline ring and the two carbonyl-group O atoms are nearly coplanar, the largest deviation from the mean plane being 0.0760 (10) Å for atom O1. The plane of the fused ring system is nearly perpendicular to the mean plane passing through the 1-dodecyl chain as indicated by the dihedral angle of 77.69 (5)°. The dodecyl substituent has all carbon atoms in an antiperiplanar conformation. The structure of the title compound is similar to that of its homologue 1-octylindoline-2,3-dione (Qachchachi et al., 2013).

Experimental
To a solution of isatin (0.5 g, 3.4 mmol) dissolved in DMF (30 ml) was added potassium carbonate (0.61 g, 4.4 mmol), a catalytic quantity of tetra-n-butylammonium bromide (0.1 g, 0.4 mmol) and 1-bromododecane (0.9 ml, 3.7 mmol). The mixture was stirred for 48 h and the reaction monitored by thin layer chromatography. The mixture was filtered and the solvent removed under vacuum. The solid obtained was recrystallized from ethanol to afford the title compound as orange crystals in 86% yield (m. p. 321 K).

Refinement
All H atoms could be located in a difference Fourier map. However, they were placed in calculated positions with C-H = 0.95 Å (aromatic), C-H = 0.99 Å (methylene) and C-H = 0.97 Å (methyl) and refined as riding on their parent atoms with U iso (H) = 1.2 U eq (C) or U iso (H) = 1.5 U eq (C) for methyl H atoms.   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.