9-Ethyl-2,3-dihydro-9H-carbazol-4(1H)-one

In the title compound, C28H30N2O2, the cyclohexene ring system adopts a sofa conformation. The crystal structure is stabilized by C—H⋯O interactions between methyl H atoms of the ethyl substituents and the O atoms of carbonyl groups of adjacent molecules, and by an intermolecular carbonyl–carbonyl interactions [3.207 (2) Å]

In the title compound, C 28 H 30 N 2 O 2 , the cyclohexene ring system adopts a sofa conformation. The crystal structure is stabilized by C-HÁ Á ÁO interactions between methyl H atoms of the ethyl substituents and the O atoms of carbonyl groups of adjacent molecules, and by an intermolecular carbonylcarbonyl interactions [3.207 (2) Å ]

Comment
Carbazole derivatives exhibit good charge transfer and hole transporting properties, which are being explored for a multitude of optoelectronic and photocatalytic applications, including organic light emitting diodes (OLEDs) (Mi et al., 2003). In carbazole derivatives, the preliminary study shows that the presence of oxygenated substituents increases their biological activity (Hewlins, Oliveira-Campos & Shannon, 1984). The 2,3-disubstituted indoles have been used as bidentate synthons for the synthesis of various medicinally important carbazole alkaloids (Mohanakrishnan & Srinivasan, 1995). Intercalation between the base pairs in DNA has been implicated for their anticancer activity. It was conceived that the benzo[b] carbazoles as isosteric analogs of pyrido[4,3-b]carbazoles, with oxygenated D-ring could mimic the anti-cancer activity of ellipticine.
So it was of interest to study the anticancer activity of D-ring oxygenated benzo[b]carbazoles as it is believed that these molecules could form a stable intercalation complex with DNA (Kansal & Potier, 1986). Tetrahydrocarbazole derivatives are present in the framework of indole-type alkaloids of biological interest (Phillipson & Zenk, 1980;Saxton, 1983;Abraham, 1975). Here we report the crystal and molecular structure of the title compound, 9-ethyl-1,2,3-trihydrocarbazol-4(2H)-one ( Fig. 1).

Experimental
A mixture of (0.5 g, 1.0 mol), ethyl bromide (0.18 g, 1.0 mol) and potassium carbonate (2.0 g) in 1,4-dioxane (10 ml) was refluxed for ca. 5.0 h. Then the reaction mixture was poured in water and then the crude solid was filtered. Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the title compound in ethanol at room temperature.

Refinement
All H atoms were fixed geometrically and allowed to ride on their parent C atoms, with C-H distances fixed in the range 0.93-0.98 Å with U iso (H) = 1.5U eq (C) for methyl H 1.2U eq (C) for other H atoms. 9-Ethyl-2,3-dihydro-9H-carbazol-4(1H)-one

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.