Crystal structures of three substituted 3-aryl-2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-ones

The crystal structures of three closely related benzothiazinone structures are reported. All three are conformationally similar having screw-boat puckering in the thiazine ring and C—H⋯π-type intermolecular interactions in the crystals.


Figure 2
The molecular conformation and atom-numbering scheme for (II), with non-H atoms shown as 50% probability displacement ellipsoids. The minor component of the disordered CF 3 group is not shown.

Figure 3
The molecular conformation and atom-numbering scheme for (III), with non-H atoms shown as 50% probability ellipsoids. The partial-occupancy disordered toluene solvent molecule has a site occupancy of 0.50. between the benzene ring of the benzothiazine system and the substituent benzene rings at the 2-position are 82.68 (6) in (I), 95.69 (5) and 78.10 (5) in (II), and 98.37 (1) in (III). Those with the benzene rings at the 3-position are 59.10 (6) in (I), 70.56 (5) and 72.26 (5) in (II), and 78.66 (1) in (III). The CF 3 substituent group in one of the molecules of (II) shows positional disorder, with an occupancy ratio of 0.57 (3):0.43 (3).

Figure 5
The crystal packing of (II) in the unit cell, viewed along b, showing C-HÁ Á ÁO hydrogen bonds as dashed lines.

Database survey
The three structures reported here and four previously reported analogous structures (Yennawar et al., 2013(Yennawar et al., , 2014(Yennawar et al., , 2015 have very similar screw-boat puckering for the thiazine ring. Among the seven crystal structures, the variation in the interplanar angles between the benzene ring of the benzothiazine moiety and the two substituent benzene rings at positions 2 and 3 lie within 26 and 30 , respectively. A structure for 2-(5-methylthiophen-2-yl)-3-phenyl-2,3-dihydroquinazolin-4(1H)-one has been reported in a patent application (Atwood et al., 2015).

Synthesis and crystallization
A two-necked 25 ml round-bottomed flask was oven-dried, cooled under N 2 and charged with a stir bar and an N-aryl-Cphenylimine (6 mmol). Tetrahydrofuran or 2-methyltetrahydrofuran (2.3 ml) was added, the solid dissolved and the solution stirred. Pyridine (1.95 ml, 24 mmol) was added, followed by thiosalicylic acid (0.93 g, 6 mmol). Finally, 2,4,6tripropyl-1,3,5,2,4,6-trioxatriphosphorinane 2,4,6-trioxide (T3P) in 2-methyltetrahydrofuran (50 wt%, 7.3 ml, 12 mmol) was added. The mixture was stirred at room temperature and the reaction was followed using thin-layer chromatography. The mixture was then poured into a separatory funnel and dichloromethane and distilled water were added. The layers were separated and the aqueous layer was then extracted twice with dichloromethane. The organics were combined and washed with saturated sodium bicarbonate and then saturated sodium chloride. The organic extract was dried over sodium sulfate and concentrated under vacuum. The crude product was chromatographed on 30 g of flash silica gel using mixtures of ethyl acetate and hexanes, and then further purified as indicated below. Compound (I) was recrystallized from ethanol solution to give yellow crystals (yield 0.72 g, 34.6%; m.p. 365-369 K). R F = 0.52 (50% ethyl acetate/hexanes). Colorless block-shaped crystals suitable for the X-ray analysis were grown by slow evaporation from ethanol solution.
Compound (III) was triturated with hexanes solution to give a solid (0.7242 g) and then recrystallized from toluene/ hexanes to give white crystals (yield 0.3544 g, 14.5%; m.p.: 358-359 K). R F = 0.39 (20% ethyl acetate/hexanes). A second crop of 0.30 g (12.7%) was obtained by slow evaporation of the mother liquor, giving colorless blocks suitable for the X-ray analysis.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. In the refinement of (II), the two molecules in the asymmetric unit were restrained using the SAME command in SHELXL2014 (Sheldrick, 2015). One of the molecules shows positional disorder in the -CF 3 group, with the occupancy ratio refining to 0.57 (3):0.43 (3). We tried to address the high R values (relative to R int ) by looking for twinning and using restraints but we have had no success in achieving respectable R values. In (III), the disordered partial toluene molecule was refined with a site-occupancy factor determined as 0.50 and with positional constraints (AFIX 6). In all three compounds, the H atoms were placed geometrically and allowed to ride on the C atoms during refinement, with C-H distances of 0.98 (methine), 0.96 (methyl) or 0.93 Å (aromatic) and with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) otherwise. . E72, 1108-1112 research communications

Special details
Experimental. Absorption correction: SADABS (Bruker, 2001) was used for absorption correction. R(int) was 0.0415 before and 0.0233 after correction. The λ/2 correction factor is 0.0015. 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.

Special details
Experimental. Absorption correction: SADABS (Bruker, 2001) was used for absorption correction. R(int) was 0.0709 before and 0.0303 after correction. The Ratio of minimum to maximum transmission is 0.5920. The λ/2 correction factor is 0.0015. 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.

sup-7
Acta Cryst. (2016). E72, 1108-1112 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (

Special details
Experimental. Absorption correction: SADABS was used for absorption correction. R(int) was 0.2680 before and 0.0355 after correction. The Ratio of minimum to maximum transmission is 0.1027. The λ/2 correction factor is 0.0015. 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.