Kammasandra N. Shivananda

Hantzsch reaction: Synthesis and characterization of some new 1,4-dihydropyridine derivatives as potent antimicrobial and antioxidant agents

In the present study two new series of Hantzsch 1,4-dihydropyridine derivatives (1,4-DHPs) containing substituted pyrazole moiety (4a-f and 5a-f) were synthesized by the reaction of 3-aryl-1H-pyrazole-4-carbaldehydes with 1,3-dicarbonylcompounds (ethylacetoacetate and methylacetoacetate) and ammonium acetate. The newly synthesized compounds were characterized by IR, NMR, mass spectral study and also by C, H, N analyses. New compounds were screened for their antimicrobial activity by well plate method (zone of inhibition). Antioxidant studies of the synthesized compounds were also performed by measuring the DPPH radical scavenging assay. Compounds 4c, 4e and 4f were found to be potent antibacterial and antioxidant agents. The acute oral toxicity study for the compounds 4c, 4e and 4f were carried out and the experimental studies revealed that compounds 4c and 4e is safe up to 3000 mg/kg and no death of animals were recorded. However in compound 4f, we found mortality above 2000 mg and also significant behavioral changes in experimental animals.

Synthesis, characterization and antimicrobial studies of some new quinoline incorporated benzimidazole derivatives.

Two new series of quinoline incorporated benzimidazole derivatives (4a-i and 8a-f) were synthesized from substituted aniline and isatin through multi-step reaction. 6-substituted-4-carboxyquinolines (3a,b and 7) were synthesized by multi component one pot reactions (via Doebner reaction and Pfitzinger reaction respectively) and the targeted benzimidazole derivatives were obtained by the reaction of 6-substituted-4-carboxyquinolines (3a,b and 7) with substituted aromatic diamines in acidic media. All the newly synthesized compounds were characterized by IR, NMR mass spectral study and also by C, H, N analyses. The final compounds were screened for their in-vitro antibacterial and antifungal activity by well plate method (zone of inhibition). The results revealed that, compounds 4c, 4d, 8c and 8d showed significant antibacterial activity. The compound 8b was found to be potent antifungal agent. 4a, 8a and 8f showed moderate to good antimicrobial activity as compared to the standard drugs against all tested microbial strains.

2-(4-Chlorophenyl)-2-oxoethyl 3-(trifluoromethyl)benzoate

In the title compound, C16H10ClF3O3, the two benzene rings are slightly twisted from each other, with a dihedral angle of 15.50 (8)° between the planes. In the crystal, intermolecular C—H⋯O hydrogen bonds link the molecules into a layer parallel to the bc plane.

2-(4-Fluoro­phen­yl)-2-oxoethyl 3-(trifluoro­meth­yl)benzoate

In the title compound, C16H10F4O3, the fluoroform group is disordered over two orientations with an occupancy ratio of 0.834 (4):0.166 (4). The dihedral angle between the two aromatic rings is 20.34 (9)°. In the crystal, C—H⋯O hydrogen bonds link the molecules into layers lying parallel to the bc plane.

2-(4-Chloro­phen­yl)-2-oxoethyl 4-hy­droxy­benzoate

The title compound, C15H11ClO4, consists of a chlorobenzene ring and a phenol ring which are linked together by a 1,4-dioxo-2-oxabutane-1,4-diyl group. The dihedral angle between the chlorobenzene and phenol rings is 65.70 (11)°. In the crystal, intermolecular O—H⋯O hydrogen bonds link the molecules into chains along [010].

(E)-1-(2,4-Dichloro-phen-yl)-3-(1,3-diphenyl-1H-pyrazol-4-yl)prop-2-en-1-one.

In the title molecule, C24H16Cl2N2O, the dihedral angles between the pyrazole ring and its N- and C-bonded phenyl rings are 7.06 (10) and 53.15 (10)°, respectively. The dihedral angle between the two pendant rings is 52.32 (10)°. The molecule exists in a trans conformation with respect to the acyclic C=C bond. In the crystal, inversion dimers occur in which each molecule is linked to the other by two C—H⋯O hydrogen bonds to the same acceptor O atom. There are also short Cl⋯Cl contacts [3.3492 (9) Å] and C—H⋯π interactions.

4-(Morpholin-4-yl)-3-(trifluoro­meth­yl)­benzonitrile

In the title benzonitrile compound, C12H11F3N2O, an intramolecular C—H⋯F hydrogen bond generates an S(7) ring motif. The trifluoromethyl group is disordered over two orientations with a refined occupancy ratio of 0.549 (16):0.451 (16). The morpholine ring adopts a chair conformation. The benzene ring and mean plane of the morpholine ring make a dihedral angle of 58.04 (10)° with each other. In the crystal, molecules are connected by intermolecular C—H⋯F and C—H⋯O interactions to form R 2 2(8) ring motifs. These interactions also link the molecules into chains parallel to the [10] direction.

2-[(E)-4-Diethyl-amino-2-hy-droxy-benzyl-idene]hydrazinecarboxamide.

Two molecules make up the asymmetric unit of the title compound, C12H18N4O2, and both feature an intramolecular O—H⋯N hydrogen bond, which generates an S(6) ring. The diethylamino group of one of the molecules is disordered over two sets of sites in a 0.59 (2):0.41 (2) ratio. In the crystal, N—H⋯O hydrogen bonds link the molecules into sheets lying parallel to the ac plane and C—H⋯π interactions are also observed.

Ethyl 4-({1-[2-(4-bromo-phen-yl)-2-oxo-eth-yl]-1H-1,2,3-triazol-4-yl}meth-oxy)-8-(trifluoro-meth-yl)quinoline-3-carboxyl-ate.

The title compound, C24H18BrF3N4O4, is a 1,2,3-triazole derivative featuring, among others, a quinoline-derived substituent. In the crystal, C—H⋯O, C—H⋯N and C—H⋯F contacts connect the molecules into a three-dimensional network. The shortest centroid–centroid distance between two aromatic systems is 3.896 (2) Å and is found between the two different six-membered rings of the quinoline scaffold in neighbouring molecules.

(E)-3-[3-(4-Bromo-phen-yl)-1-phenyl-1H-pyrazol-4-yl]-1-(2,4-dichloro-phen-yl)prop-2-en-1-one.

In the title molecule, C24H15BrCl2N2O, the dihedral angles betwen the pyrazole ring and its N-bonded phenyl (A) and C-bonded bromobenzene (B) rings are 10.34 (16) and 40.95 (15)°, respectively. The dihedral angle between rings A and B is 56.89 (17)°. The title molecule exists in a trans conformation with respect to the acyclic C=C bond. In the crystal, molecules are linked into inversion dimers by pairs of C—H⋯O hydrogen bonds, generating R 2 2(14) loops. The crystal structure is further consolidated by C—H⋯π interactions.