Crystal structures of two 2,3-diaryl-2,3-dihydro-4H-1,3-benzothiazin-4-ones

Crystal structures of two benzothiazinones belonging to a class of compounds implicated in antimicrobial, antitumour, and HIV-RT inhibitory activity are reported.


Supramolecular features
In the two structures, C-HÁ Á ÁO interactions (Tables 1 and 2) in which the chiral carbon atom (C1 in 1; C1 and C23 in 2) donates its H atom to the oxygen atom of a symmetry related molecule in 1, or the independent enantiomer in 2. This results in infinite chains along the c-and b-axis directions, respec- The two independent molecules of 2 showing the C-HÁ Á ÁO interaction between the enantiomers. The displacement ellipsoids are drawn at the 50% probability level. Table 1 Hydrogen-bond geometry (Å , ) for 1. Symmetry codes: (i) x; Ày þ 3 2 ; z þ 1 2 ; (ii) x; y; z À 1.

Figure 1
The molecular structure of 1 with displacement ellipsoids drawn at the 50% probability level. Disorder in the CF 3 groups is not shown for clarity.

Database survey
Along with the structures we have previously published (Yennawar et al., 2013(Yennawar et al., , 2014(Yennawar et al., , 2015(Yennawar et al., , 2016, crystal structures of three other compounds with the same 2,3-dihydro-4H-1,3benzothiazin-4-one core have been reported (Krö ger et al. by Yin displays an envelope pucker with the 2-C atom as the flap for the thiazine ring that is sandwiched between two fused rings. CIFs were not available for the other two compounds.

Synthesis and crystallization
General: A two-necked 25 ml round-bottom flask was ovendried, cooled under N 2 , and charged with a stir bar and the imine (6 mmol). Thiosalicylic acid (0.93 g, 6 mmol) and then 2methyltetrahydrofuran (2.3 mL) were added and the solution was stirred. Pyridine (1.95 mL, 24 mmol) and, finally, 2,4,6tripropyl-1,3,5,2,4,6-trioxatriphosphorinane-2,4,6-trioxide (T3P) in 2-methyltetrahydrofuran (50 weight percent; 7.3 mL, 12 mmol) were added. The reaction was stirred at room temperature and followed by TLC. The mixture was poured into a separatory funnel with dichloromethane and distilled water. The layers were separated and the aqueous one was then extracted twice with dichloromethane. The organic layers    Packing diagram of 2 with red dotted lines representing C-HÁ Á ÁO contacts forming chains along the b-axis direction comprising of alternating enantiomers.
were combined and washed with saturated sodium bicarbonate and then saturated sodium chloride. The organic layer was dried over sodium sulfate and concentrated under vacuum. The crude product was chromatographed on 30 g flash silica gel and then recrystallized.

Refinement
Crystal data, data collection and structure refinement details for both compounds are summarized in Table 3

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 (30 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. The disorder in the two CF3 moieties were subject to SIMU and DELU Shelx restraints.

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.