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

Abstract

Three ring-substituted 3-aryl analogs of 2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one, namely 3-(4-methoxyphenyl)-2-phenyl-4H-1,3-benzothiazin-4-one, C21H17NO2S, (I), 2-phenyl-3-[4-(trifluoromethyl)phenyl]-2,3-dihydro-4H-1,3-benzothiazin-4-one toluene hemisolvate, C21H14F3NOS·0.5C7H8, (II), and 3-(3-bromophenyl)-2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one toluene hemisolvate, C20H14BrNOS·0.5C7H8, (III), were synthesized and their crystal structures determined. The hemisolvates differ in that in (II), the asymmetric unit comprises two molecules of the benzothiazinone compound and a toluene solvent molecule, whereas in (III), the unit comprises one benzothiazinone molecule and a half-occupancy toluene solvent molecule. All crystals are of racemic mixtures of the chiral 2-C atom of the thiazine moiety, which in all structures has a screw-boat puckering, with the puckering amplitude values within the range 0.575–0.603 Å. In all three structures, the benzene plane of the benzothiazine system makes a dihedral angle in the range 78.60 (5) to 98.40 (5)° with the unsubstituted benzene plane and in the range 70.50 (1) to 121.00 (5)° with the substituted benzene plane. The CF3 substituent group in one of the molecules of (II) shows positional disorder, with an occupancy ratio of 0.57 (3):0.43 (3). In the crystals of (I) and (II), weak intermolecular C—H...O interactions are present, giving in (I), molecules arranged in a plane parallel to (010), and in (II), chains along a. In addition, all three structures show weak C—H...π interactions involving various aromatic rings.

Keywords

• crystal structure
• benzothiazinones
• screw-boat thiazine pucker
• aromatic ring interactions