In the title compound, C16H14N4O4S·H2O, the benzene and pyridine rings make a dihedral angle of 85.8 (1)°. Both enanti­omers of the chiral title compound are statistically disordered over the same position in the unit cell. The methyl and carbonyl group attached to the stereogenic center (C5 of the thia­zolidine ring) were therefore refined with common site-occupation factors of 0.531 (9) and 0.469 (9), respectively, for each stereoisomer. In the crystal, inter­molecular N—H⋯O, O—H⋯O and O—H⋯N hydrogen bonds link the mol­ecules, forming a three-dimensional supra­molecular network. The crystal structure further shows π–π stacking inter­actions [centroid–centroid distance = 3.5063 (13) Å] between the pyridine rings.

In the title compound, C16H14BrN3O2S, the atoms of the 1,3-thia­zolidine group, except for the N and the C atoms attached to the bromo­benzene ring, are disordered over two sets of sites with occupancies of 0.605 (13) and 0.395 (13). The benzene and pyridine rings make a dihedral angle of 86.2 (2)°. In the crystal, mol­ecules are linked by inter­molecular N—H⋯N and C—H⋯O hydrogen bonds, forming a three-dimensional network. Furthermore, there is a π–π stacking inter­action [centroid–centroid distance = 3.758 (2) Å] between the pyridine and benzene rings.

In the title compound, C15H12BrN3O2S, the dihedral angle between the pyridine and benzene rings is 73.17 (19)°. The five-membered 1,3-thia­zolidine ring has an envelope conformation, with the S atom displaced by 0.196 (1) Å from the mean plane of the four other ring atoms. An intra­molecular C—H⋯N inter­action occurs. The crystal structure is stabil­ized by inter­molecular N—H⋯O and C—H⋯O hydrogen bonds and C—H⋯π inter­actions. In addition, a weak π–π stacking inter­action is also observed between the 1,3-thia­zolidine and pyridine rings [centroid–centroid distance = 3.805 (2) Å].

Key indicators: single-crystal X-ray study; T = 296 K; mean (C-C) = 0.007 Å; disorder in main residue; R factor = 0.079; wR factor = 0.225; data-to-parameter ratio = 16.4.The title compound, C 16 H 14 ClN 3 O 2 S, crystallizes with two molecules in the asymmetric unit. In the 1,3-thiazolidine rings, the carbonyl O atoms, the S atoms, the methyl groups and the ring carbon attached to the methyl groups are disordered with occupancy ratios of 0.509 (7):0.491 (7) in one molecule and 0.464 (14):0.536 (14) in the other. The crystal structure is stabilized by intermolecular N-HÁ Á ÁN, C-HÁ Á ÁO hydrogen bonds and C-HÁ Á ÁCl interactions. In addition, there is astacking interaction [centroid-centroid distance = 3.794 (3) Å ] between the benzene and pyridine rings. Related literature