The title compound, C(16)H(12)ClN(3)S, was synthesized by the reaction of 5-(4-methyl-phen-yl)-1,3,4-thia-diazol-2-amine and 4-chloro-benzaldehyde. The thia-diazole ring is essentially planar with mean deviation of 0.0042 Å.

In the title compound, C(19)H(16)N(4)S(4), the mol-ecules exhibit a butterfly conformation, where the thia-diazole and attached benzene rings in two wings are almost coplanar, with dihedral angles of 0.8 (3) and 0.9 (3)°, respectively, while the two thia-diazole rings form a dihedral angle of 46.3 (3)°.

In the title compound, C(14)H(17)NO(5)S, the thia-zine ring adopts a half-chair conformation. The mol-ecule exhibits an intra-molecular O-H⋯O hydrogen bond, which forms a six-membered S(6) ring motif. The planes of the benzene and thia-zine rings are inclined at a dihedral angle of 15.30 (12)°.

In the title compound, C(8)H(9)N(3)S(2), the n-propyl chain is disordered over two orientations (site-occupancy ratio = 0.522:0.478) and is roughly perpendicular to the fused thia-zolotriazine system. The angle between the fused ring and the propyl chain is 83.6 (1)° [ 82.2 (1)° for the disordered chain]. The structure is stabilized by C-H⋯N hydrogen bonds.

The title compound, C(14)H(17)NO(2)S(2), was synthesized by asymmetric aldol condensation of N-acyl-thia-zolidinethione with acetaldehyde. In the mol-ecule, the thia-zolidine five-membered ring assumes an envelope conformation. Inter-molecular C-H⋯O and intra-molecular O-H⋯O and C-H⋯S hydrogen bonding helps to stabilize the structure.

In the title compound, C(11)H(9)ClN(2)OS, the thia-zole ring is nearly planar (r.m.s. deviation = 0.003 Å) and forms a dihedral angle of 64.18 (7)° with the bezene ring. In the crystal, inversion dimers linked by pairs of N-H⋯N(t) (t = thia-zole) hydrogen bonds generate R(2) (2)(8) loops.

In the title mol-ecule, C(5)H(7)N(3)S, the thia-zine ring shows a conformation close to a half-boat. The Cremer & Pople puckering parameters of the thia-zine ring are q2 = 0.4645 (2) Å, θ = 132.4 (3) and ϕ = 285.52 (2)°. The packing is stabilized by inter-molecular N-H⋯N and C-H⋯S inter-actions.

In the title compound, C10H8ClN3S, the dihedral angle between the mean planes of the benzene and imidazo[2,1-b][1,3,4]thia-diazole rings is 6.0 (9)°. In the crystal, mol-ecules are assembled by the formation of centrosymmetric dimers by π-stacking of the thia-diazole and benzene rings of neighboring mol-ecules [centroid-centroid distance = 3.6938 (11) Å] along [010].