Crystal structures of two solvated 2-aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones

The synthesis and crystal structures of two solvated 2-aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones are reported. Both are racemic mixtures (centrosymmetric crystal structures) of the individual compounds and incorporate solvent molecules in their structures.


Structural commentary
The asymmetric unit of 1 (Fig. 1) comprises the title molecule along with the solvent molecule (toluene) straddling an inversion center. The 1,3-thiazine ring is in an envelope pucker conformation according to the puckering parameters [Q = 0.6016 (16) Å , = 115.35 (16) , and ' = 220.50 (18) ] calculated by PLATON (Spek, 2009), with atom C1 displaced from the other atoms. The phenyl rings on the 2 and 3 positions of the thiazine ring are close to orthogonal, forming a dihedral angle of 77.65 (10) ; their dihedral angles with respect to the N2 pyridine ring are 81.45 (11) and 79.22 (9) , respectively. Atom C1 is a stereogenic center; in the arbitrarily chosen asymmetric unit, it has an S configuration, but crystal symmetry generates a racemic mixture.
In 2, the configurations of the stereogenic centers in the four arbitrarily chosen independent thiazine molecules A, B, C, and D (Fig. 2) are R at C1 and C39, and S at C20 and C58. A solvent molecule of 2-propanol and a water molecule with partial (0.25) occupancy complete the asymmetric unit. The puckering of the thiazine ring in each case is an envelope (Q $ 55 Å , $ 65 , and ' $ 41 , considering chirality tranformations), which is very similar to that in 1. The four molecules within this structure are all very similar in their threedimensional dispositions, as can be seen in the overlay figure (Fig. 3). For the X (pyridine C3-C7/N2), Y (phenyl C8-C13), and Z (para-nitrophenyl C14-C19) rings in molecule A, the  The asymmetric unit of 2 with solvent 2-propanol and water (0.25 occupancy) molecules. The displacement ellipsoids are drawn at the 50% probability level.

Figure 1
The asymmetric unit of 1 with the solvent toluene molecule straddling the inversion center. The displacement ellipsoids are drawn at the 50% probability level.

Supramolecular features
The asymmetric unit of 1 has the chiral C atom (C1) participating in a C-HÁ Á Á-type interaction with the toluene ring [C-HÁ Á Á = 3.735 (3) Å , 142 ]. The O atom on the fused thiazine ring system accepts a C-HÁ Á ÁO hydrogen bond from a symmetry-related pyridine ring in a parallel-reciprocal fashion (Table 1 and Fig. 5). Some other weak C-HÁ Á Á interactions may help to consolidate the structure. The aryl and pyridyl rings of symmetry-related molecules exhibit a T-type interaction. Noparallel stacking is observed in this structure.

Figure 4
Overlay image showing the similarity of the structures of 1 and 2.

Figure 6
Packing diagram for 2, showing the aromatic ring stacking interactions along with the C-HÁ Á ÁN() and C-HÁ Á ÁO hydrogen bonds.

Database survey
Along with the previously mentioned structure (Yennawar et al., 2014), we have published a structure of the sulfoxide derivative (Yennawar et al. 2017). No other similar structures were found.

Special details
Experimental. The data collection nominally covered a full sphere of reciprocal space by a combination of 4 sets of ω scans each set at different φ and/or 2θ angles and each scan (10 s exposure) covering -0.300° degrees in ω. The crystal to detector distance was 5.82 cm. 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. 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 > 2sigma(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.