2-Chloro-3-nitro-5-(trifluoromethyl)benzoic acid and -benzamide: structural characterization of two precursors for antitubercular benzothiazinones

8-Nitro-1,3-benzothiazin-4-ones are a promising class of new antitubercular agents, two candidates of which, namely BTZ043 and PBTZ169 (INN: macozinone), have reached clinical trials. The crystal and molecular structures of two synthetic precursors, 2-chloro-3-nitro-5-(trifluoromethyl)benzoic acid, C8H3ClF3NO4 (1), and 2-chloro-3-nitro-5-(trifluoromethyl)benzamide, C8H4ClF3N2O3 (2), are reported. In 1 and 2, the respective carboxy, carboxamide and the nitro groups are significantly twisted out of the plane of the benzene ring. In 1, the nitro group is oriented almost perpendicular to the benzene ring plane. In the crystal, 1 and 2 form O—H...O and N—H...O hydrogen-bonded dimers, respectively, which in 2 extend into primary amide tapes along the [101] direction. The trifluoromethyl group in 2 exhibits rotational disorder with an occupancy ratio of 0.876 (3):0.124 (3).

Methyl 3-(2,5-dimethoxy-3,4,6-trimethylphenyl)propanoate

In the title compound, C15H22O4, the fully substituted benzene ring carries a methyl propanoate, two methoxy and three methyl substituents. Both methoxy substituents are almost orthogonal to the benzene ring plane. The methyl propanoate group is almost planar, r.m.s. deviation 0.0138 Å, and is inclined to the benzene ring plane by 80.26 (14)°. In the crystal, C—H...O hydrogen bonds form head-to-tail chains of molecules along theb-axis direction that are supported by very weak C—H...π(ring) contacts.

Hydrogen-bonded network in the salt 4-methyl-1H-imidazol-3-ium picrate

In the title molecular salt, C4H7N2+·C6H2N3O7−, the phenolic proton of the starting picric acid has been transferred to the imidazole N atom. The nitro groups are twisted away from the benzene ring plane, making dihedral angles of 12.8 (2), 9.2 (4) and 29.3 (2)°. In the crystal, the component ions are linked into chains along [010]viaN—H...O and bifurcated N—H...(O,O) hydrogen bonds. These chains are further linked by weak C—H...O hydrogen bonds into a three-dimensional network. The complex three-dimensional network can be topologically simplified into a 4-connected uninodal net with the point symbol {4.85}.

Crystal structure of (5′S,8′S)-3-(2,5-dimethylphenyl)-8-methoxy-3-nitro-1-azaspiro[4.5]decane-2,4-dione

The title compound, C18H22N2O5, was synthesized by nitrification of its enol precursor. The pyrrolidine ring plane adopts a twisted conformation about the C—C bond linking the spiro centre and the C=O group remote from the N atom. It makes dihedral angles of 71.69 (9) and 88.92 (9)°, respectively, with the benzene ring plane and the plane defined by the four C atoms that form the seat of the of the cyclohexane chair. At the spiro centre, the NH group is axial and the C=O group is equatorial with respect to the cyclohexane ring. In the crystal, inversion dimers linked by pairs of N—H...O hydrogen bonds generateR22(8) loops. The dimers are linked by C—H...O interactions, generating a three-dimensional network.

Crystal structure of ethyl 2-(diethoxyphosphoryl)-2-(2,3,4-trimethoxyphenyl)acetate

The title compound, C17H27O8P, was prepared by Michaelis–Arbuzov reaction of ethyl 2-bromo-2-(2,3,4-trimethoxyphenyl)acetate and triethyl phosphite. Such compounds rarely crystallize, but single crystals were recovered after the initial oil was left for approximately 10 years. The bond angle of thesp3-hybridized C atom connecting the benzene derivative with the phospho unit is widened marginally [112.5 (2)°]. The terminal P—O bond length of 1.464 (2) Å clearly indicates a double bond, whereas the two O atoms of the ethoxy groups connected to the phosphorous atom have bond lengths of 1.580 (2) Å and 1.581 (3) Å. The three methoxy groups emerge out of the benzene-ring plane due to steric hindrance [C—C—O—C torsion angles = −179.9 (3)°, −52.9 (4)° and 115.3 (4)°]. In the crystal, inversion dimers linked by pairs of C—H...O=P hydrogen bonds generateR22(14) loops. The chosen crystal was modelled as a non-merohedral twin.

Diafenthiuron: 1-tert-butyl-3-(2,6-diisopropyl-4-phenoxyphenyl)thiourea

The title compound, C23H32N2OS, is a thiourea-based insecticide. The dihedral angle between the phenyl ring and the diisopropyl benzene ring plane is 73.18 (6)°, while that between the plane of the thiourea group and the diisopropyl benzene ring is 86.00 (5)°. Disorder was modelled for the S atom and the two methyl C atoms of the isopropyl group over two sets of sites with an occupancy ratio of 0.742 (4):0.258 (4). In the crystal, N—H...S hydrogen bonds link adjacent molecules, formingR22(8) inversion dimers that pack into chains along theb-axis direction.

1-(2-Bromo-4-chlorophenyl)-3,3-dimethylthiourea

In the title compound, C9H10BrClN2S, the dimethylthiourea group is twisted from the benzene ring plane by 54.38 (6)°. In the crystal, the amino groups are involved in the formation of N—H...S hydrogen bonds, which link the molecules into chains along [010]. Weak C—H...Cl interactions further link these chains into layers parallel to theabplane.

Methyl 5-iodo-2-methoxybenzoate

In the title compound, C9H9IO3, the molecules are close to planar [maximum deviation from benzene ring plane = 0.229 (5) Å for the methyl carboxylate C atom] with the methyl groups oriented away from each other. In the crystal, molecules form stacked layers parallel to theabplane, where every layer has either the iodine or methoxy/methyl carboxylate substituents pointing towards each other in an alternating fashion.

The structural properties of a noncentrosymmetric polymorph of 4-aminobenzoic acid

The crystal structure of a polymorph of 4-aminobenzoic acid (PABA), C7H7NO2, at 100 K is noncentrosymmetric, as opposed to centrosymmetric in the structures of the other known polymorphs. The two crystallographically independent PABA molecules form pseudocentrosymmetric O—H...O hydrogen-bonded dimers that are further linked by N—H...O hydrogen bonds into a three-dimensional network. The benzene rings stack in thebdirection. The CO2moieties are bent out slightly from the benzene ring plane.

rac-2-Phenyl-1-[(2,4,6-triisopropylbenzene)sulfonyl]aziridine

In the title compound, C23H31NO2S, the geometry of the triisopropylphenyl group is slightly distorted, with elongated C—C bonds at theipso-C atom, and an S atom which deviates from the benzene ring plane by 0.228 (2) Å. This distortion is caused by the bulky substituents and, in comparison, an unbent geometry is observed inN-toluenesulfonylaziridine [Zhuet al.(2006).Acta Cryst.E62, o1507–o1508]. π–π interactions between adjacent benzene rings [centroid–centroid distance = 3.7928 (11) Å] and are observed.