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

Abstract

The syntheses and crystal structures of 2,3-bis[3-(trifluoromethyl)phenyl]-2,3-dihydro-4H-1,3-benzothiazin-4-one (di-m-CF3; C22H13F6NOS) (1) and 2,3-bis(4-methylphenyl)-2,3-dihydro-4H-1,3-benzothiazin-4-one (di-p-CH3; C22H19NOS) (2) are reported. Each structure is racemic: the asymmetric unit of 2 consists of two molecules. In both 1 and 2, the six-membered 1,3-thiazine ring is close to an envelope conformation with the chiral C atom forming the flap. In 1, the 2-aryl group is pseudo-equatorial, while in 2 it is pseudo-axial. In 1, the pendant aryl rings form a V shape with an inter-centroid distance of 3.938 (3) A and an acute dihedral angle of 48.3 (2)° between them. Both CF3 groups are disordered over two orientations in 0.687 (19):0.313 (19) and 0.667 (16):0.33 (16) ratios. In each of the independent molecules of 2, the aryl rings are almost orthogonal to each other [dihedral angles = 85.50 (12) and 86.07 (11)°]. In both structures, the chiral C atom and the O atoms participate in C - H. . .O-type hydrogen bonding between symmetry-related molecules of 1 or the independent enantiomers in 2, forming chains along the c-axis direction in 1 and the b-axis direction in 2. Additionally, in 1, π-π contacts of both face-to-face and edge-to-face type, as well as π-H. . .O and π-H. . .F interactions are observed. In 2, a racemic mixture of molecules forms layers in the ac plane linked by weak π-π and C - H. . .π interactions.