Noor Shahina Begum

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.

2-[4-(Trifluoro­meth­oxy)phen­yl]-1H-benzimidazole

In the title compound, C14H9F3N2O, the best planes of the benzimidazole group and benzene ring form a dihedral angle of 26.68 (3)°. In the crystal, N—H⋯N hydrogen bonds link the molecules into infinite chains parallel to the c axis. Stacking interactions between the benzimidazole groups [centroid–centroid distance = 3.594 (5) Å] assemble the molecules into layers parallel to (100). The trifluoromethyl group is disordered over three sets of sites with site-occupancy factors of 0.787 (4), 0.107 (7) and 0.106 (7).

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 engineering: fluorine as a new steering group

For the first time fluorine has been examined as a steering group for crystal engineering. In sharp contrast to the packing and photo behaviour of unsubstituted coumarin, molecules of both 6- and 7-fluorocoumarins are found to attain a packing mode which enables them to undergo [2 + 2] photodimerization in the solid state leading stereospecifically to a mirror symmetric dimer.

Electrodeposition and characterization of Ni-Cr alloy coating

Simultaneous deposition of both nickel and chromium in the form of alloy is a subject with pronounced practical significance in automobile industries. Electroplating of Ni-Cr alloy has been carried out using suitable plating bath solution and working conditions. The alloys are partially crystalline and new phases appear on heat-treatment of the coating. Surface morphology and microstructure of the coating are closely related to the nature of the bath components, bath composition, alloy composition, and post-treatment of the coating. X-ray photoelectron spectroscopy studies indicated that the alloy contains nickel in +2 and +3 oxidation states, whereas it contains chromium in the +3 oxidation state in the deposited Ni-Cr coating. The sputtering of the coatings up to 20 min changed the nickel and chromium to metallic state. The coated alloys exhibited good corrosion resistance to acidic media, e.g., 0.5 M H2 S O4, 1 M HCl, and 5 NaCl (pH 5), and heat-treatment of the coating enhanced the corrosion resistance. © 2006 The Electrochemical Society. All rights reserved.

Addition of NOCl to cyclic vinylsilanes: An unexpected reversal of regiochemistry

NOCl adds to cyclic vinylsilanes in a syn manner with NO+ bonding to the beta -carbon and Cl- to the alpha -carbon, which is a reversal of the regiochemistry expected from the beta -silicon effect. The adducts dimerize to a single diastereomer containing enantiomeric pairs and/or give secondary products on further reaction

Structural modifications leading to changes in supramolecular aggregation of thiazolo(3, 2-a)pyrimidines: Insights into their conformational features

AbstractThe 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 Pı̄ with Z=8, with four molecules in the asymmetric unit. Compound 2 also crystallizes in the space group Pı̄ 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 Pı̄ 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…π and π…π weak interactions. Graphical AbstractConformational features of some thiazolopyrimidines are described. In addition, by varying the substituents at positions C2, C3, C6 and on the aryl at C5 in the main molecular scaffold of (1-5), resulted in 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…π and π…π weak interactions.

2-(3,4-Di­fluoro­phen­yl)-1H-benzimidazole

In the title molecule, C13H8F2N2, the dihedral angle between the benzimidazole ring system and the difluoro-substituted benzene ring is 30.0 (1)°. In the crystal, molecules are linked by N—H⋯N hydrogen bonds, forming chains along [010]. In addition, weak C—H⋯F hydrogen bonds connect chains into a two-dimensional network parallel to (001). A weak C—H⋯π interaction is observed between an H atom of the benzimidazole ring sytem and the π system of the difluoro-substituted benzene ring.

Synthesis, spectroscopic and crystal structure analysis of two dihydropyrimidines

The preparation of two reduced pyrimidine derivatives, ethyl 3-acetyl-4-(4-methoxyphenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate and ethyl 4-(3,4-dimethoxyphenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylate, is described, along with details of their crystal structure analysis.

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.