Structural modifications leading to changes in supramolecular aggregation of thiazolo3, 2-apyrimidines: Insights into their conformational features

The compounds, 7-methyl-3,5-diphenyl-5H-thiazolo3,2-apyrimidine-6-carboxylic acid ethyl ester (1), 3-amino-2-cyano-7-methyl-5-phenyl-5H-thiazolo3,2-apyrimidine-6-carboxylic acid methyl ester (2), 2-dimethylaminomethylene-7-methyl-3-oxo-5-phenyl-2,3-dihydro-5H-thiazolo3,2-apyrimidine-6-carboxylic acid ethyl ester (3), 2-(3-cyano-benzylidene)-5-(4-hydroxy-phenyl)-7-methyl-3-oxo-2,3-dihydro-5H-thiazolo3,2-apyrimidine-6-carboxylic acid methyl ester; with N,N-dimethyl-formamide (4) and 3-ethoxycarbonylmethyl-5-(4-hydroxy-3-methoxy-phenyl)-7-methyl-5H-thiazolo3,2-apyrimidine-6-carboxylic acid methyl ester (5) have been synthesized and their structures evaluated crystallographically. Compound 1 crystallizes in the space group PI with Z=8, with four molecules in the asymmetric unit. Compound 2 also crystallizes in the space group PI with Z=4 wherein asymmetric unit accommodates two molecules. Compound 3 belongs to P21/c with Z=4, compound 4 crystallizes in Pbc2 1 with Z=4 and compound 5 belongs to PI with Z=2. In all the above compounds, the aryl ring positioned at C5 of thiazolopyrimidine ring is almost perpendicular. In the case of compounds with substituted phenyl ring, aryl group-up conformation predominates. However, for compounds with unsubstituted phenyl ring, aryl group-down conformation is adopted. By varying the substituents at positions C2, C3, C6 and on the aryl at C5 in the main molecular scaffold of (1-5), we have observed significant differences in the intermolecular interaction patterns. The packing features of the compounds are controlled by C-H...O, C-H...N, N-H...N O-H...N, C-H...� and �...� weak interactions. © 2014 Indian Academy of Sciences

Structural Modifications Leading to Changes in Supramolecular Aggregation of Thiazolo[3, 2-A]Pyrimidines: Insights into their Conformational Features

The compounds, 7-methyl-3,5-diphenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid ethyl ester (1), 3-amino-2-cyano-7-methyl-5-phenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid methyl ester (2), 2-dimethylaminomethylene-7-methyl-3-oxo-5-phenyl-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine- 6-carboxylic acid ethyl ester (3), 2-(3-cyano-benzylidene)-5-(4-hydroxy-phenyl)-7-methyl-3-oxo-2,3- dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid methyl ester; with N,N-dimethyl-formamide (4) and 3-ethoxycarbonylmethyl-5-(4-hydroxy-3-methoxy-phenyl)-7-methyl-5H-thiazolo[3,2-a]pyrimidine-6- carboxylic acid methyl ester (5) have been synthesized and their structures evaluated crystallographically. Compound 1 crystallizes in the space group P¯i with Z=8, with four molecules in the asymmetric unit. Compound 2 also crystallizes in the space group P¯i with Z=4 wherein asymmetric unit accommodates two molecules. Compound 3 belongs to P21/c with Z=4, compound 4 crystallizes in Pbc21 with Z= 4 and compound 5 belongs to P¯i with Z=2. In all the above compounds, the aryl ring positioned at C5 of thiazolopyrimidine ring is almost perpendicular. In the case of compounds with substituted phenyl ring, aryl group-up conformation predominates. However, for compounds with unsubstituted phenyl ring, aryl group-down conformation is adopted. By varying the substituents at positions C2, C3, C6 and on the aryl at C5 in the main molecular scaffold of (1-5), we have observed significant differences in the intermolecular interaction patterns. The packing features of the compounds are controlled by C-H…O, C-H…N, N-H…N O-H…N, C-H…p and p…p weak interactions

Methyl 5-(4-hy­droxy-3-meth­oxy­phen­yl)-2-(4-meth­oxy­benzyl­idene)-7-methyl-3-oxo-2,3-dihydro-5H-thia­zolo[3,2-a]pyrimidine-6-carboxyl­ate

In the title compound, C24H22N2O6S, a pyrimidine ring substituted with 4-hy­droxy-3-meth­oxy­phenyl is fused with a thia­zole ring. The 4-hy­droxy-3-meth­oxy­phenyl group is positioned axially to the pyrimidine ring, making a dihedral angle 85.36 (7)°. The pyrimidine ring adopts a twist boat conformation. In the crystal, O—H⋯N inter­actions result in a chain running along the b axis. The carbonyl O atom bonded to the thia­zole ring is involved in two C—H⋯O hydrogen-bond inter­actions forming centrosymmetric dimers; the ten- and six-membered rings resulting from these inter­actions have R 2 2(10) and R 1 2(6) motifs, respectively

Crystal structure of ethyl 5-(3-fluoro-phen-yl)-2-[(4-fluoro-phen-yl)methyl-idene]-7-methyl-3-oxo-2H,3H,5H-[1,3]thia-zolo[3,2-a]pyrimidine-6-carboxyl-ate.

In the title mol-ecule, C23H18F2N2O3S, the pyrimidine ring is in a half-chair conformation and the 3-fluoro-phenyl group is in the axial position. The thia-zole ring (r.m.s. deviation = 0.0252 Å) forms dihedral angles of 84.8 (7) and 9.6 (7)° with the 3-fluoro-substituted and 4-fluoro-substituted benzene rings, respectively. In the crystal, weak C-H⋯F and C-H⋯O hydrogen bonds connect mol-ecules, forming zigzag chains along the b axis. In addition π-π stacking inter-actions with a centroid-centroid distance of 3.7633 (9) Å connect these chains into ladders via inversion-related 4-fluoro-phenyl groups

Methyl 4-(4-hydroxyphenyl)-6-methyl-2-sulfanylidene-1,2,3,4- tetrahydropyrimidine-5-carboxylate

In the title mol­ecule, C13H14N2O3S, the di­hydro­pyrimidine ring is in a flattened sofa conformation, with the methine C atom forming the flap. The dihedral angle between the mean plane of the five essentially planar atoms of the di­hydro­pyrimidine ring [maximum deviation = 0.056 (4) Å] and the benzene ring is 89.4 (2)°. The O atom of the carbonyl group is in a trans conformation with respect to the C=C bond of the di­hydro­pyrimidine ring. In the crystal, N-H...O and O-H...S hydrogen bonds connect mol­ecules, forming a two-dimensional network parallel to (001)

Methyl 2-(2-bromo­benzyl­idene)-5-(4-hy­droxy­phen­yl)-7-methyl-3-oxo-2,3-dihydro-5H-1,3-thia­zolo[3,2-a]pyrimidine-6-carboxyl­ate

In the title compound, C22H17BrN2O4S, the central dihydropyrimidine ring, with a chiral C atom, is significantly puckered and adopts a half-chair conformation with the chiral C atom displaced from the mean plane of the remaining ring atoms by 0.305 (6) Å. The hydroxy-phenyl ring is positioned axially to the pyrimidine ring and almost bisects it, the dihedral angle between the mean-planes of the two rings being 89.78 (12)°. The meth­oxy­carbonyl group is disordered over two sites with an occupancy ratio of 0.568 (5):0.432 (5), resulting in a major and a minor conformer. In the crystal, O—H⋯N and C—H⋯S inter­actions result in sheets along the c axis. The supra­molecular assembly is stabilized by π–π stacking inter­actions between the 2-bromo­benzyl­idene and thia­zolopyrimidine rings [centroid–centroid distance = 3.632 (1) Å]. In addition, C—H⋯π inter­actions are also observed in the crystal structure

Synthesis, Characterization and Biological Evaluationof Thiazolopyrimidine Derivatives

Different substituted diesters of thiazolopyrimidine were prepared by the treatment of 3,4 dihydropyrimidine2-thione with á-haloesters using ethanol under reflux condition affording 71–85% yield. IR, 1HNMR, 13CNMR and elemental analyses were used for the characterization of these compounds. The crystal and molecular structure of one of the product, 5-phenyl-3,7-dimethyl-5H- hiazolo[3,2-a]pyrimidine-2,6- dicarboxylic acid diethyl ester (3e) was verified by single crystal X-ray diffraction method. The antimicrobial activity was evaluated against four bacterial strains and one fungal species. Few of the derivatives exhibited antibacterial and antifungal activities

Ethyl 3-acetyl-4-(3-meth­oxy­phen­yl)-6-methyl-2-sulfanyl­idene-1,2,3,4-tetra­hydro­pyrimidine-5-carboxyl­ate

In the title compound, C17H20N2O4S, the aryl ring is positioned perpendicular to the dihydro­pyrimidine ring, the dihedral angle between the ring planes being 77.48 (9)°. The carboxyl­ate and methyl groups are in a cis conformation with respect to the C=C bond. The dihydro­pyrimidine ring adopts a twist-boat conformation. The crystal structure is stabilized by N—H⋯O and C—H⋯O inter­actions, the former resulting in mol­ecular chains along the b axis and the latter forming inversion dimers

4-Bromomethyl-6-tert-butyl-2H-chromen-2-one

In the crystal structure of the title compound, C14H15BrO2, weak C - H...O interactions link the molecules into zigzag chains extending along the c-axis direction. These chains are further assembled into (100) layers via Ï-Ï stacking interactions between inversion-related chromenone fragments interplanar distance = 3.376 (2) Ã