Molecular and crystal structure of 5,9-dimethyl-5H-pyrano[3,2-c:5,6-c′]bis[2,1-benzothiazin]-7(9H)-one 6,6,8,8-tetroxide dimethylformamide monosolvate

The benzothiazine skeleton is not planar, with a maximum deviation of 0.3154 (11) Å from the least-squares plane. The molecule was expected to adopt mirror symmetry but slightly different conformational characteristics of the condensed benzothiazine ring lead to point group symmetry 1.

The title molecule crystallizes as a dimethylformamide monosolvate, C 19 H 14 N 2 O 6 S 2 ÁC 3 H 7 NO. The molecule was expected to adopt mirror symmetry but slightly different conformational characteristics of the condensed benzothiazine ring lead to point group symmetry 1. In the crystal, molecules form two types of stacking dimers with distances of 3.464 (2) Å and 3.528 (2) Å between -systems. As a result, columns extending parallel to [100] are formed, which are connected to intermediate dimethylformamide solvent molecules by C-HÁ Á ÁO interactions.

Supramolecular features
In the crystal, molecules of (I) form columns extending parallel to [100] whereby centrosymmetric pairs of molecules within a column interact bystacking interactions (Fig. 2). The plane-to-plane distances between the -systems in the centrosymmetric dimers are 3.464 (2) and 3.528 (2) Å . The mean-square plane was calculated for O1 and all carbon atoms (with the exception of C19) of the polycyclic entity.

Database survey
A search of the Cambridge Structural Database (Version 5.38, update February 2019; Groom et al., 2016) for the benzothiazine skeleton revealed 34 hits. In all structures, the conformation of the benzothiazine fragment is similar.

Figure 2
Two types of stacking dimers in the crystal structure of (I).

Figure 3
The packing of the molecular entities in the crystal structure of (I) in a view along [100].

Figure 1
The structures of the molecular entities in solvated (I). Displacement ellipsoids are drawn at the 50% probability level.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Hydrogen atoms were located from difference-Fourier maps. They were included in calculated positions and treated as riding with C-H = 0.96 Å , U iso (H) = 1.5U eq (C) for methyl groups and with C-H = 0.93 Å , U iso (H) = 1.2U eq (C) for all other hydrogen atoms. Synthesis scheme for compound (I).