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Thiazolo[3,2-a]pyrimidines namely ethyl 2-acetyl-5-(2-fluorophenyl)-3,7-dimethyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate 3a, ethyl 2-acetyl-5-(3-fluorophenyl)-3,7-dimethyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate 3b, and ethyl 2-acetyl-5-(4-fluorophenyl)-3,7-dimethyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate 3c were obtained by one pot synthesis using substituted 3,4 dihydropyrimidine2-thione (1a–1c) and 3-chloro-2,4-pentanedione in ethanol and characterized by single-crystal X-ray diffraction. The variation in the position of fluorine atom on pyrimidine nucleus and insight into the self-assembly of compounds with varied types of non-covalent interactions has great influence on crystal packing.

1,4-dihydropyridines, namely diethyl 4-(4-fluorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (1a), diethyl 2,6-dimethyl-4-(3,4,5-trimethoxyphenyl)-1,4-dihydropyridine-3,5-dicarboxylate(1b), and diethyl 4-(3,4-dimethoxyphenyl)-2,6-dihydroxy-2,6-bis(trifluoro­methyl)piperidine-3,5-dicarboxylate (2), are synthesized by one-pot multicomponent condensation of aromatic aldehyde with ethyl acetoacetate and liquid ammonia in the presence of an ethanol-water mixture and are characterized by single crystal X-ray diffraction. The effect of a fluorine atom on the dihydropyridine nucleus give insight into the self-assembly of compounds with various types of non-covalent interactions that greatly affect the crystal packing.

In the title compound, C16H19N3O2Si, the dihedral angle between the coumarin ring system (r.m.s. deviation = 0.031 Å) and the triazole ring is 73.81 (8)°. In the crystal, molecules are linked into [010] chains by weak C—H...O interactions.

In the title compound, C21H27NO6, the 1,4-dihydropyridine ring adopts a shallow boat conformation, with the 3-ethoxy-4-hydroxyphenyl substituent in an axial orientation [dihedral angle between ring planes = 85.49 (12)°]. In the crystal, N—H...O and O—H...O hydrogen bonds link the molecules into (001) sheets. The packing is consolidated by C—H...O and π–π stacking interactions, which leads to a three-dimensional network.

In the title compound, C23H25NO4, the 1,4-dihydropyridine ring adopts a flattened boat conformation. The naphthalene ring system forms a dihedral angle of 88.59 (6)° with the pyridine ring. In the crystal, N—H...O and C—H...O hydrogen bonds generate anR12(6) ring motif and result in a zigzag chain along thebaxis. Additional C—H...O hydrogen bonds form infinite chains along thec-axis direction.

In the title compound, C17H18N2O3S2, the pyrimidine ring adopts a shallow sofa conformation, with the C atom bearing the axially-oriented thiophene ring as the flap [deviation = 0.439 (3) Å]. The plane of the thiophene ring lies almost normal to the pyrimidine ring, making a dihedral angle of 79.36 (19)°. In the crystal, pairs of very weak C—H...O hydrogen bonds link the molecules related by twofold rotation axes, formingR22(18) rings, which are in turn linked by another C—H...O interaction, forming chains of rings along [010]. In addition, weak C—H...π(thiophene) interactions link the chains into layers parallel to [001] and π–π interactions with a centroid–centroid distance of 3.772 (10) Å connect these layers into a three-dimensional network.

The asymmetric unit of the title compound, C15H21N3OSi, contains two molecules with similar conformations (r.m.s. overlay fit for the 20 non-H atoms = 0.163 Å). The dihedral angles between the planes of the 1,2,3-triazole and 2,4-dimethylbenzene rings are 27.0 (3) and 19.5 (3)°. In the crystal, molecules are linked by very weak C—H...O and C—H...N hydrogen bonds to generate [100] chains. The chains are cross-linked by C—H...π interactions.

In the title thiophene derivative, C13H18N2O3S, the dihedral angles between the thiophene ring and the [(dimethylamino)methylidene]amino side chain (r.m.s. deviation = 0.009 Å) and the –CO2ester group are 3.01 (16) and 59.9 (3)°, respectively. In the crystal, inversion dimers linked by pairs of C—H...O hydrogen bonds generateR22(16) loops. The dimers are linked by another weak C—H...O interaction, forming chains along [001]. In addition, weak C—H...π interactions are observed, which link the chains into (001) layers.

In the title molecule, C20H22N2O4S, the pyrimidine ring is in a flattened half-chair conformation and the 3-methoxyphenyl substituent is in an axial arrangement. The thiazole ring forms a dihedral angle of 81.3 (1)° with the benzene ring. In the crystal, weak C—H...S interactions link molecules into chains along [001]. In addition, there are π–π interactions between inversion-related thiazole rings with a centroid–centroid distance of 3.529 (2) Å. The ethyl group was refined as disordered over two sets of sites with an occupancy ratio of 0.52 (3):0.48 (2).