I. M. Khazi

Synthesis, characterization and biological evaluation of thiazolopyrimidine derivatives

AbstractDifferent substituted diesters of thiazolopyrimidine were prepared by the treatment of 3,4 dihydropyrimidine2-thione with α-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-thiazolo[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. Graphical AbstractWe have reported the synthesis of some thiazolopyrimidine derivatives by cyclo-condensation of dihydropyrimidine with halo esters. Crystal structure analysis of one of the derivatives has been carried out. Some of the derivatives exhibited antibacterial and antifungal activities.

Synthesis and local anaesthetic activities of 2-aminothiazole/thiadiazole analogues of lidocaine

Various 2-aminothiazole and 2-aminothiadiazole derivatives viz N-[4-(2-Chloro-4-fluoro-phenyl)-thiazol-2-yl]-2-substituted acetamides (3a, 4a, 5a) and N-[5-(4-substituted aryl)-[1,3,4]thiadiazol-2-yl]-2-acetamides (3b, 3c, 4b, 4c, 5b, 5c) were synthesized from their corresponding properly substituted 2-aminothiazoles and 2-aminothiadiazoles. Structures of all the newly synthesized compounds were established by analytical and spectral data. Synthesized compounds were screened for their local anaesthetic activity using the rat sciatic nerve model.Graphical AbstractVarious 2-aminothiazole and 2-aminothiadiazole derivatives viz N-[4-(2-Chloro-4-fluoro-phenyl)-thiazol-2-yl]-2-substituted acetamides (3a, 4a, 5a) and N-[5-(4-substituted aryl)-[1,3,4]thiadiazol-2-yl]-2-acetamides (3b, 3c, 4b, 4c, 5b, 5c) were synthesized from their corresponding properly substituted 2-aminothiazoles and 2-aminothiadiazoles. Structures of all the newly synthesized compounds were established by analytical and spectral data. Synthesized compounds were screened for their local anaesthetic activity using the rat sciatic nerve model.

Synthesis and Crystal Structure of 2-(4-Fluorobenzyl)-6-Phenylimidazo[2,1-b][1,3,4]Thiadiazole-5-Carbaldehyde

The crystal and molecular structure of 2-(4-fluoro-benzyl)-6-phenyl-imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde is described. The compound crystallizes in the monoclinic space group P21/n with a = 7.419(3)Å, b = 8.287(3)Å, c = 25.734(10)Å, β = 91.686(8)°, V = 1,581.6(10)Å3, z = 4. The crystal structure is stabilized by intermolecular C-H…N, C-H…O, and C-H…F interactions.

Synthesis & Evaluation of Antitubercular Activity of Novel Mannich Bases of imidazo[2,1-b][1,3,4]thiadiazoles

A series of 2-(4-methoxybenzyl)-6-aryl-5-pyrrolidin/piperidin/morpholin-1-ylmethyl-imidazo [2,1-[1,3, thiadiazoles (3a-e, 4a-e & 5a-e) were synthesized by Mannich reaction by condensing 2-(4-methoxybenzyl)-6-arylimidazo [2,1-[1,3,thiadiazoles with pyrrolidine, piperidine and morpholine. The title compounds were screened for antitubercular activity against Mycobacterium tuberculosis H37Rv using the BACTEC 460 radiometric assay. Mannich bases with pyrrolidine substitution were found to be most active antitubercular agents. It proves that as the ring size decreases it becomes much potent in its activity. Pyrrolidine being 5 membered ring structure & further combined with imidazothiadiazole nucleus enhances the pharmacological activity.

3-{[6-(4-Chloro-phen-yl)imidazo[2,1-b][1,3,4]thia-diazol-2-yl]meth-yl}-1,2-benzoxazole.

In the title compound, C18H11ClN4OS, the benzisoxazole and imidazothiadiazole rings are inclined at an angle of 23.81 (7)° with respect to each other. The imidazothiadiazole and chlorophenyl rings make a dihedral angle of 27.34 (3)°. In the crystal, intermolecular C—H⋯N interactions generate a chain along the c axis and C—H⋯O interactions form centrosymmetric dimers resulting in an R 2 2(26) graph-set motif. Moreover, the C—H⋯N and S⋯N [3.206 (4) Å] interactions links the molecules into R(7) ring motifs. The packing is further stabilized by π–π stacking interactions between the thiadiazole rings with a shortest centroid–centroid distance of 3.497 (3) Å. In addition, C—H⋯π interactions are observed in the crystal structure

2-Phenyl-8,9,10,11-tetra­hydro-1-benzo­thieno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidine

In the title compound, C17H14N4S, the benzothieno moiety is fused at one end of the pyramidine ring while the triazole ring with a phenyl substituent is fused at the other side. The triazole ring is almost planar [maximum deviation = 0.0028 (3) Å] while the cyclohexane ring adopts a half-chair conformation. In the crystal, pairs of intermolecular C—H⋯N hydrogen bonds form centrosymmetric head-to-head dimers, corresponding to an R 2 2(8) graph-set motif. Further C—H⋯N interactions generate a zigzag chain of molecules along the c axis. The supramolecular assembly is consolidated by π–π stacking interactions [centroid–centroid distance = 3.445 (4) Å].

6-(4-Bromo­phen­yl)-2-(4-fluoro­benz­yl)imidazo[2,1-b][1,3,4]thia­diazole

In the title compound, C17H11BrFN3S, the imidazothiadiazole and bromophenyl rings are individually almost planar, with maximum deviations of 0.0215 (4) and 0.0044 (4) Å, respectively, and are inclined at an angle of 27.34 (3)° with respect to each other. The dihedral angle between the mean planes of the fluorobenzyl and imidazothiadiazole rings is 79.54 (3)°. The crystal structure is stabilized by intermolecular C—H⋯N interactions resulting in chains of molecules along the b axis.

2-Amino-6-methyl-4,5,6,7-tetra­hydro-1-benzothio­phene-3-carbonitrile

In the title compound, C10H12N2S, one of the C atoms of the cyclohexene ring (at position 6) and the methyl group attached to it are disordered over two sets of sites in a 0.650 (3):0.350 (3) ratio. The cyclohexene ring in both the major and minor occupancy conformers adopts a half-chair conformation. The thiophene ring is essentially planar (r.m.s. deviation = 0.05 Å). In the crystal, N—H⋯N hydrogen bonds involving the amino groups result in inversion dimers with R 2 2(12) graph-set motif. Further N—H⋯N hydrogen bonds involving the amino and carbonitrile groups generate zigzag chains along the a axis.

Synthesis and Crystal Structure Analysis of 2-(Fluorobenzyl)-6-(4-Nitrophenyl) Imidazo[2,1-b][1,3,4]Thiadiazole

Preparation of 2-(4-fluorobexzyl)-6-(4-nitrophenyl)imidazo[2,1-b][1,3,4]thiadiazole is described and its crystal structure is discussed. The compound crystallizes in the monoclinic space group C2/c with a = 39.941(6) Å, b = 5.698(2) Å, c = 13.272(5) Å β = 90.880°, V = 3020(2) Å3, z = 8. The crystal structure is stabilized by weak intermolecular C-H…N,C-H…O,C-H…S, and C-H…F interactions.

6-Chloro-3-[(di­methyl­amino)­methyl­idene]thio­chroman-4-one

The asymmetric unit of the title compound, C12H12ClNOS, contains three independent molecules, with the thiochroman ring adopting a sofa conformation in each one. The crystal structure features C—H⋯O interactions; one of the O atoms accepts three such bonds. Together, the hydrogen bonds give rise to a molecular tape propagating in [010].