Diethyl 2-[(5-methoxy-2-methyl-1-phenylsulfonyl-1H-indol-3-yl)methylene]malonate

In the title compound, C24H25NO7S, the sulfonyl-bound phenyl ring is approximately perpendicular to the indole ring system [dihedral angle = 87.72 (5)°]. The methyl group of one of the ester units is disordered over two positions with occupancies of 0.527 (13) and 0.473 (13). An intramolecular C—H⋯O hydrogen bond is observed. In the crystal structure, molecules are linked into a ribbon structure running along the c axis by intermolecular C—H⋯O hydrogen bonds and C—H⋯π interactions involving the pyrrole ring.

In the title compound, C 24 H 25 NO 7 S, the sulfonyl-bound phenyl ring is approximately perpendicular to the indole ring system [dihedral angle = 87.72 (5) ]. The methyl group of one of the ester units is disordered over two positions with occupancies of 0.527 (13) and 0.473 (13). An intramolecular C-HÁ Á ÁO hydrogen bond is observed. In the crystal structure, molecules are linked into a ribbon structure running along the c axis by intermolecular C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions involving the pyrrole ring.

Comment
Indoles form an integral part of many natural products and possess potentially reactive sites to perform variety of chemical reactions to generate molecular diversity (Farhanullah et al., 2004). Many of the indole derivatives are found to possess antibacterial (Okabe & Adachi, 1998), antitumour (Schollmeyer et al., 1995 and antimicrobial (El-Sayed et al., 1986) activities.
In the crystal structure, the molecules are linked into a zigzag C(12) chain running along the c axis by intermolecular C-H···O hydrogen bonds involving atoms C14 and O5 (Table 1). The inversion-related molecules of adjacent chains are linked via weak C-H···π interactions involving the N1/C2-C5 ring (centroid Cg1) to form a ribbon structure (Fig. 2).

Experimental
A solution of TiCl 4 (0.37 ml, 3.34 mmol) in dry dichloromethane (DCM; 20 ml) was added drop by drop into dry DCM (10 ml) kept at 273 K and stirred at the same temperature for 45 min. To this, a solution of 5-methoxy-2-methyl-1-(phenylsulfonyl)-1H-indole-3-carbaldehyde (0.5 g, 1.52 mmol) and diethylmalonate (0.24 ml, 1.60 mmol) in dry DCM (20 ml) was slowly added. After the addition was completed, the reaction mixture was stirred at 273 K for 1 h. A solution of pyridine (0.6 ml, 6.08 mmol) in dry DCM (20 ml) was then added dropwise for 30 min. The content was stirred at 273 K for 12 h and then at room temperature for 48 h. The reaction mass was quenched with water and extracted with CHCl 3 (2 × 10 ml). The organic layer was washed with 0.5 M HCl (2 × 20 ml) followed by brine solution (2 × 20 ml). Removal of solvent followed by flash column chromatographic purification (n-hexane-ethyl acetate 97:3) afforded the title compound as a yellow solid.

Refinement
The methyl group at the end of one of ethyl carboxylate chains is disordered over two positions (C24 and C24') with refined occupancies of 0.527 (13) and 0.473 (13). The C23-C24 and C23-C24'bond distances were restrained to be 1.50 (5) Å.
The components of the anisotropic displacement parameters of atoms C13, C14, C23 and O6 in the direction of the bond supplementary materials sup-2 between them were restrained to be equal within an effective standard deviation of 0.001. The U ij parameters of atoms C24 and C24' were restrained to an approximate isotropic behaviour. H atoms were positioned geometrically and refined using riding model with C-H = 0.93-0.97 Å and U iso (H) = 1.2U eq (C) and 1.5U eq (C methyl ).

Special details
Geometry. All e.s. 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 Rfactors(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. supplementary materials sup-9