5-Chloro-1-(4-methylphenylsulfonyl)-1H-indole

In the title compound, C15H12ClNO2S, the indole ring is essentially planar (r.m.s. deviation = 0.0107 Å) and makes a dihedral angle of 85.01 (6)° with the benzene ring. In the crystal, three C—H⋯O hydrogen bonds result in a hydrogen-bonded spiral running parallel to the c axis.


Experimental
MH thanks Professor Willem A. L. van Otterlo and Dr S. C. Pelly for their valuable input and research oversight. Stellenbosch University's Science Faculty is also acknowledged for providing laboratory space and financial research support (Subcommittee B). The South African National Research Foundation (NRF), Pretoria, is also acknowledged for providing some research funds.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: PV2597).

Mohammad Hassam and Vincent J. Smith
Comment 5-Chloroindole is frequently employed as a building block in the synthesis of various biologically active molecules (Hassam et al., 2012). For this communication, tosylation of 5-chloroindole was performed by deprotonation of the indole with sodium hydride, followed by the addition of tosyl chloride.
In the title molecule ( Fig. 1), the indole ring is essentially planar (rmsd = 0.0107 Å) with Cl1 lying in its plane (deviation 0.008 (2) Å). The dihedral angle between the mean planes of the indole and benzene rings is 85.01 (6)°. The bond distances and angles in the title compound agree very well with the corresponding bond distances and angles reported for 1-phenylsulfonyl-indole (Beddoes et al., 1986). There are three C-H···O hydrogen bonds which connect four symmetry related molecules into a hydrogen bonded spiral that runs parallel to the c-axis (Table 1 and Fig. 2).

Experimental
Sodium hydride (0.325 g, 14.1 mmol) was added to a solution of 5-chloroindole (1.00 g, 6.59 mmol) in dry THF (50 ml) at 273.15 K (ice bath). The reaction mixture was stirred at the same temperature for 10 min, followed by addition of tosyl chloride (4-methyl-benzene-1-sulfonyl chloride, 1.88 g, 9.86 mmol). The reaction mixture was then stirred at 273.15 K for 2 h. Water (25 ml) was added to the flask and the mixture was extracted with diethyl ether (2 x 25 ml). The organic layer was washed with brine (25 ml) and dried over anhydrous sodium sulfate. Solvent was removed under vacuum and the resulting residue was recrystallized from hexane and dichloromethane (4:1) to obtain the title compound as a colourless crystalline material (1.61 g, 80%).

Refinement
The H atoms were positioned geometrically and refined using a riding model, with C-H = 0.95 and 0.98 Å, for aryl and methyl H-atoms, respectively. The U iso (H) were allowed at 1.5U eq (methyl C) or 1.2U eq (aryl C).

Computing details
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001;Atwood & Barbour, 2003); software used to prepare material for publication: X-SEED (Barbour, 2001;Atwood & Barbour, 2003).    where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.31 e Å −3 Δρ min = −0.36 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > 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.