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Crystallization of the nonsteroidal anti-inflammatory drug (NSAID) flunixin in acetone and in acetone–hexane produced two conformational polymorphs, as predicted by hydrogen-bond propensity analyses, which are similar to three of the polymorphs of the related NSAID clonixin. The two polymorphs of flunixin display an intramolecular hydrogen bond between the amine N–H and the carbonyl oxygen of the carboxylic group. However, the intermolecular hydrogen-bond pattern of Form I (crystallized from acetone) is characterized by the acid–pyridine heterosynthon, while Form II (from acetone-hexane) displays the acid–acid homosynthon. Form I of flunixin is similar to form I of clonixin, while form II of flunixin is related to forms III and IV of clonixin. Hirshfeld surface maps were used to show the differences in the interactions present in the two flunixin polymorphs and the similarities with the polymorphs of the related compound clonixin. Energy framework calculations corroborate the similarity between Form I of flunixin and clonixin and indicate that Form II of flunixin is more closely related to Form IV of clonixin than to Form III.

The structure of racemic (RS)-trichlormethiazide [systematic name: (RS)-6-chloro-3-(dichloromethyl)-1,1-dioxo-3,4-dihydro-2H-1λ6,2,4-benzothiadiazine-7-sulfonamide], C8H8Cl3N3O4S2 (RS-TCMZ), a diuretic drug used in the treatment of oedema and hypertension, was determined from laboratory X-ray powder diffraction data using DASH [David et al. (2006). J. Appl. Cryst. 39, 910–915.], refined by the Rietveld method with TOPAS-Academic [Coelho (2018). J. Appl. Cryst. 51, 210–218], and optimized using DFT-D calculations. The extended structure consists of head-to-tail dimers connected by π–π interactions which, in turn, are connected by C—Cl...π interactions. They form chains propagating along [101], further connected by N—H...O hydrogen bonds to produce layers parallel to the ac plane that stack along the b-axis direction, connected by additional N—H...O hydrogen bonds. The Hirshfeld surface analysis indicates a major contribution of H...O and H...Cl interactions (32.2 and 21.7%, respectively). Energy framework calculations confirm the major contribution of electrostatic interactions (E elec) to the total energy (E tot). A comparison with the structure of S-TCMZ is also presented.

A Na-P zeolite was synthesized and subjected to ion exchange with Ca2+, Cu2+, Al3+, and In3+, and supported with H+/NH4Cl (NH4-P) by in situ reaction of EtOH and NH4Cl. All the exchanged zeolites showed catalytic activity in the ABB’ Povarov reaction. However, zeolite NH4-P promoted a better yield. In all reactions two products were obtained, 2,6-dimethyl-4-(2-oxopyrrolidin-1-yl)-1,2,3,4-tetrahydroquinoline and 1-(1-(4-methylphenylamino)ethyl)pyrrolidin 2-one. Synthesis using zeolite P as catalyst proves to be a simple method with high yields, short reaction times and easy preparation. The catalyst can be recovered by filtration and reused up to three times in good yields.

Thiocolchicoside (THC) is an important active pharmaceutical ingredient (API) used as a muscle relaxant because of its anti-inflammatory and analgesic effects. The only entry for a THC-related compound present in the Cambridge Structural Database (CSD) corresponds to a THC ethanol solvate hydrate (refcode: THCLCS). The diffraction pattern recorded for the THC raw material (C 27 H 33 NO 10 S·xH 2 O) is different from the pattern calculated using the THCLCS crystallographic data contained in the CSD. The indexing of the THC raw material pattern, produced an orthorhombic unit cell with a = 28.018(7) Å, b = 12.519(2) Å, c = 8.519(1) Å, and V = 2988.01 Å 3 . All the diffraction maxima of the powder pattern of a phase recrystallized in water (C 27 H 33 NO 10 S·2H 2 O) can be indexed in an orthorhombic cell with a = 25.264(4) Å, b = 13.537(3) Å, c = 8.553(1) Å, and V = 2925.12 Å 3 . Thermogravimetric analysis shows that this compound is a dihydrate phase. Upon heating, a new anhydrous phase (C 27 H 33 NO 10 S) with a monoclinic cell and unit cell parameters: a = 17.090(5) Å, b = 19.485(5) Å, c = 8.526(3) Å, β = 100.30(2)°, and V = 2793.34 Å 3 is obtained.