3-Methyl-1-tosyl-1H-indole-2-carbaldehyde

The title indole derivative, C17H15NO3S, crystallizes with two independent molecules in the asymmetric unit. The benzene ring of the tosyl group is almost perpedicular to the indole ring in both molecules, with interplanar angles of 82.60 (5)° and 81.82 (6)°. The two molecules are, as a consequence, able to form an almost centrosymmetric non-bonded dimer, in which the molecules are linked by pairs of C—H⋯π interactions. The crystal structure displays a three-dimensional network of C—H⋯O interactions. A π–π interaction occurs between inversion-related indole rings with a centroid–centroid distance of 3.6774 (16) Å and an interplanar angle of 1.53 (15)°. This interaction leads to a stacking of molecules along the a axis.

The title indole derivative, C 17 H 15 NO 3 S, crystallizes with two independent molecules in the asymmetric unit. The benzene ring of the tosyl group is almost perpedicular to the indole ring in both molecules, with interplanar angles of 82.60 (5) and 81.82 (6) . The two molecules are, as a consequence, able to form an almost centrosymmetric non-bonded dimer, in which the molecules are linked by pairs of C-HÁ Á Á interactions. The crystal structure displays a three-dimensional network of C-HÁ Á ÁO interactions. Ainteraction occurs between inversion-related indole rings with a centroid-centroid distance of 3.6774 (16) Å and an interplanar angle of 1.53 (15) . This interaction leads to a stacking of molecules along the a axis.  Table 1 Hydrogen-bond geometry (Å , ).
The structure contains several C-H···π interactions which are shown in Fig. 2. A layer of A and B molecules along the (001) plane is given in Fig. 3 showing the relative orientation of the A and B molecules in the layer. Geometrical details for the C-H···π and C-H···O interactions are given in Table 1.

Experimental
The title compound was synthesized by reaction of iodine (942 mg, 3.70 mmol) with N-(2-(2-hydroxybut-3-yn-2yl)phenyl-4-methyl)benzenesulfonamide (584.9 mg,1.854 mmol) in the presence of methanol (20 ml) as a solvent. The resulting mixture was stirred for 6 h at 60°C. The reaction was then quenched by adding a saturated aq. solution of Na 2 S 2 O 3 and extracted with ethyl acetate (3×20 mL). The combined organics were then washed with aq. NaHCO 3 and brine, and dried over anhydrous Na 2 SO 4 . After removal of solvent, the left over residue was purified by flash column chromatography, with silica gel using a mixture of hexane and ethyl acetate (20:1) to give 3-methyl-1-tosyl-1H-indole-2carbaldehyde (329 mg, 86%). Single crystals were grown by slow evaporation from dichloromethane.

Refinement
All H atoms attached to carbon were positioned geometrically, and allowed to ride on their parent atoms, with C-H bond lengths of 0.95 Å (CH) or 0.98 Å (CH 3 ), and isotropic displacement parameters set to 1.2 (CH) or 1.5 times (CH 3 ) the U eq of the parent atom.

Figure 1
The molecular structure of the title compound, showing the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.   Also shown are the interactions between the molecules which result in molecules A and B forming almost centrosymmetric C-H···π stabilized dimers.

3-Methyl-1-tosyl-1H-indole-2-carbaldehyde
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.   (11)  120.6 (2) C16B-C11B-C12B 120.6 (3) C12A-C11A-S1A 120.00 (19) C16B-C11B-S1B 119.2 (2) C16A-C11A-S1A 119.4 (2) C12B-C11B-S1B 120.2 (2) C13A-C12A-