5-[(4-Methylphenyl)sulfonyl]-1-phenylthiopyrano[4,3-b]indole-3(5H)-thione dichloromethane monosolvate

Rhodium-catalyzed [2+2+2] cycloaddition of carbon disulfide to o,N-dialkynyltosylanilines gives two isomeric indolothiopyranthiones as violet and red isomers. This is the first crystal structure of a red isomer, which crystallizes with one molecule of dichloromethane in the asymmetric unit.


Structure description
Transition-metal-catalyzed [2+2+2] cycloadditions are an atom-economic route to aromatic rings (Reppe et al., 1948;Bö nnemann, 1978;Vollhardt, 1984). With tethered diynes, annulated systems are accessible, e.g. carbazoles and carbolines (Heller & Hapke;2007;Dassonneville et al., 2011). The first thiopyranthione was reported in 1973 (Wakatsuki & Yamazaki, 1973), followed by rare examples of this heterocycle. The [RhCl(C 8 H 14 ) 2 ] 2 -BINAP [BINAP is 2,2 0 -bis(diphenylphosphanyl)-1,1 0 -binaphthyl] (Tanaka et al., 2006) catalyzed [2+2+2] cycloaddition of carbon disulfide to o,N-dialkynyltosylamides gives mainly the violet indolothiopyranthiones with a [3,4-b] annulation, in some cases accompanied by their red isomers differing in the annulation pattern (Dassonneville et al., 2023). While the structure of the violet indolothiopyranthiones has been proven exemplarily in a single-crystal XRD study (Dassonneville et al., 2010), the structures of the red isomers were hitherto only based on spectroscopic data. This report gives the first crystal structure of a red isomer. The moderate stability of the red thiopyranthione allowed crystals to be grown by slow evaporation of a solution in dichloromethane/petroleum ether. The title compound (Fig. 1) crystallizes with one data reports molecule of the solvent. Centrosymmetric pairs with a distance of 3.5556 (13) Å between the centroids of the N1/C2/ C7/C8/C13 and C8-C13 -systems are arranged in strands along the a axis (Fig. 2). The solvent molecules fill the volume between the strands. The heterocyclic framework is essentially planar, the maximum deviation from the mean plane of thesystem is 0.043 (2) Å at the thiocarbonyl C4 atom. With a dihedral angle of 82.44 (8) , the phenyl ring is close to being orthogonal to the fused-ring system. The tolyl ring is also almost perpendicular [dihedral angle = 83.08 (8) ] to the plane of the three-membered ring system. The N-S-C angle of the sulfonyl group is 103.79 (9) . The C-N bonds in the pyrrole ring are significantly different, with the N-phenyl bond [1.436 (3) Å ] significantly longer than the N-thiopyrane bond [1.405 (3) Å ]. This and alternating bond lengths between the indole-N atom and the thiocarbonyl are an indication of an electronic coupling between the nitrogen thiocarbonyl group. Other structural features of the tricyclic core are similar to those of the isomeric system with a methyl instead of phenyl substitutuent. The two isomers differ in color and in the relative position of the indole-N atom to the thiocarbonyl group. In the violet isomer, these units are in perfect conjugation whereas the meta-conjunction in the red isomer restricts electronic interaction, thus shifting the absorption maximum about 60 nm to higher energies.

Synthesis and crystallization
The synthetic and spectroscopic details for the title compound have been reported previously (Dassonneville et al., 2023).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. H atoms were placed at calculated positions and refined in the riding-model approximation, with aromatic C-H = 0.95 Å , methylene C-H = 0.99 Å and methyl C-H = 0.98 Å , and with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) otherwise.

Figure 2
Part of the packing diagram, viewed along the a axis.

Figure 1
View of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

data-1
IUCrData ( 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.