3,9-Dimethyl-2,3-dihydrospiro[carbazole-1,2′-[1,3]dithiolan]-4(9H)-one

The title compound, C16H17NOS2, consists of a carbazole skeleton with methyl and dithiolane groups as substituents. In the indole ring system, the benzene and pyrrole rings are nearly coplanar, forming a dihedral angle of 1.02 (11)°. The cyclohexenone ring has a twisted conformation, while the dithiolane ring adopts an envelope conformation with one of the CH2 C atoms at the flap. In the crystal, weak C—H⋯O hydrogen bonds link the molecules into supramolecular chains nearly parallel to the c axis. These hydrogen bonds together with weak C—H⋯π interactions link the molecules into a three-dimensional supramolecular network.

The title compound, C 16 H 17 NOS 2 , consists of a carbazole skeleton with methyl and dithiolane groups as substituents. In the indole ring system, the benzene and pyrrole rings are nearly coplanar, forming a dihedral angle of 1.02 (11) . The cyclohexenone ring has a twisted conformation, while the dithiolane ring adopts an envelope conformation with one of the CH 2 C atoms at the flap. In the crystal, weak C-HÁ Á ÁO hydrogen bonds link the molecules into supramolecular chains nearly parallel to the c axis. These hydrogen bonds together with weak C-HÁ Á Á interactions link the molecules into a three-dimensional supramolecular network.
The molecule of the title compound, (I), (Fig. 1) consists of a carbazole skeleton with two methyl and a dithiolane groups at positions 3, N9 and 1, respectively, where the bond lengths are close to standard values (Allen et al., 1987) and generally agree with those in the previously reported compounds. In all structures atom N9 is substituted.
In the crystal, intermolecular weak C-H···O hydrogen bonds link the molecules into infinite chains nearly parallel to the c-axis (Table 1 and Fig. 2), in which they may be effective in the stabilization of the structure. There also exists a weak C-H···π interaction (Table 1).

Refinement
The C-bound H-atoms were positioned geometrically with C-H = 0.95, 1.00, 0.99 and 0.98 Å, for aromatic, methine, methylene and methyl H-atoms, respectively, and constrained to ride on their parent atoms, with U iso (H) = k × U eq (C), where k = 1.5 for methyl H-atoms and k = 1.2 for all other H-atoms. The highest residual electron density was found 0.96 Å from C2 and the deepest hole 0.65 Å from S2.

Figure 1
The molecular structure of the title molecule with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.73 e Å −3 Δρ min = −1.08 e Å −3 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.