R. Venkat Ragavan

Synthesis and antimicrobial activities of novel 1,5-diaryl pyrazoles.

Novel 1,5-diaryl pyrazole derivatives viz. 5-(4-chlorophenyl)-1-(4-fluorophenyl)-1H-pyrazole-3-carboxamides (2a-e, 3, 3a-f), 2-(5-(4-chlorophenyl)-1-(4-fluorophenyl)-1H-pyrazole-3-yl)thiazoles (6a-c,7, 8, 9a-c, 10, 11) were synthesized by varying the active part (amide group) of pyrazole, characterized using IR, (1)H NMR, mass spectral data and screened for their antibacterial activity against Escherichia coli (ATTC-25922), Staphylococcus aureus (ATTC-25923), Pseudomonas aeruginosa (ATTC-27853), Klebsiella pneumonia. Similarly all these compounds were screened for their antifungal activity against Aspergillus flavus (NCIM No. 524), Aspergillus fumigates (NCIM No. 902), Penicillium marneffei and Trichophyton mentagrophytes. Interestingly all the synthesized compounds exhibited good antibacterial (except 2a-c, 8, 9a) and antifungal activity (except 2a-c, 6a, 8, 9a).

Synthesis of some novel bioactive 4-oxy/thio substituted-1H-pyrazol-5(4H)-ones via efficient cross-Claisen condensation

alpha-Oxy/thio substituted-beta-keto esters were synthesized through an efficient cross-Claisen condensation of aryl oxy/thio acetic acid ethyl esters with acid chlorides, then it is converted in situ into 4-oxy/thio substituted-1H-pyrazol-5(4H)-ones by the addition of hydrazine or hydrazine derivatives and screened for their antibacterial, antifungal activities.

Hantzsch 1,4-dihydropyridine esters and analogs: candidates for generating reproducible one-dimensional packing motifs.

Examination of the symmetric Hantzsch 1,4-dihydropyridine ester derivatives of the prototypical nifedipine molecule indicates the tendency of this class of molecule to form a common packing motif. Crystal structure analysis of 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylic diesters and analogs reveals that they form extended chains, characterized as the C(6) packing motif, via intermolecular (amine) N-H...O=C (C3,C5 carbonyl) hydrogen bonds. In addition, all the prepared derivatives also satisfy the basic structural requirements for their high binding efficiency to the receptor. The reproducible C(6) packing motif observed among these compounds has a use in the design of solid-state materials.

Tert-butyl 3-oxo-2,3,4,5,6,7-hexa­hydro-1H-pyrazolo[4,3-c]pyridine-5-carboxyl­ate

In the title compound, C11H17N3O3, the pyrazole ring is approximately planar, with a maximum deviation of 0.005 (2) Å, and forms a dihedral angle of 5.69 (13)° with the plane through the six atoms of the piperidine ring. In the crystal, pairs of intermolecular N—H⋯O hydrogen bonds form dimers with neighbouring molecules, generating R 2 2(8) ring motifs. These dimers are further linked into two-dimensional arrays parallel to the bc plane by intermolecular N—H⋯O and C—H⋯O hydrogen bonds.

5-Methoxy-methyl-4-phen-oxy-1H-pyrazol-3-ol.

In the title compound, C11H12N2O3, the pyrazole ring system is essentially planar [maximum deviation = 0.002 (2) Å] and forms a dihedral angle of 66.93 (9)° with the benzene ring. In the crystal packing, pairs of intermolecular N—H⋯O and O—H⋯N hydrogen bonds connect neighbouring molecules into dimers, generating R 2 2(10) and R 2 2(8) ring motifs, respectively. The crystal structure is further stabilized by C—H⋯π interactions.

(E)-1-(6-Chloro-2-methyl-4-phenyl-3-quinol­yl)-3-(2-methoxy­phen­yl)prop-2-en-1-one

In the title compound, C26H20ClNO2, the quinoline ring system and the methoxyphenyl ring form dihedral angles of 69.97 (6) and 22.10 (10)°, respectively, with the propenone linkage. The 4-phenyl ring substituent on the quinoline ring system is oriented at a dihedral angle of 66.47 (3)°. In the crystal, molecules exist as C—H⋯O hydrogen-bonded dimers. The structure is further stabilized by C—H⋯π interactions.

5-Pentyl-4-phenyl­sulfonyl-1H-pyrazol-3-ol

In the title compound, C14H18N2O3S, the 1H-pyrazole ring is approximately planar, with a maximum deviation of 0.005 (1) Å. The dihedral angle formed between the 1H-pyrazole and phenyl rings is 79.09 (5)°. Pairs of intermolecular N—H⋯O and O⋯H⋯N hydrogen bonds form dimers between neighboring molecules, generating R 2 2(10) ring motifs. These dimers are further linked by intermolecular N—H⋯O and O—H⋯N hydrogen bonds into two-dimensional arrays parallel to the ac plane. The crystal structure is also stabilized by C—H⋯π interactions.

4,5,6,7,8,9-Hexahydro-2H-cyclo­octa[c]pyrazol-1-ium-3-olate

The title compound, C9H14N2O, exists in the zwitterionic form in the crystal. The cyclooctane ring adopts a twisted boat-chair conformation. In the crystal, intermolecular N—H⋯O hydrogen bonds link the molecules into sheets lying parallel to bc. The structure is also stabilized by π–π interactions, with a centroid-to-centroid distance of 3.5684 (8) Å.

3-Ethyl-4-methyl-1H-pyrazol-2-ium-5-olate

The title compound, C6H10N2O, is a zwitterionic pyrazole derivative. The crystal packing is predominantly governed by a three-center iminium–amine N+—H⋯O−⋯H—N interaction, leading to an undulating sheet-like structure lying parallel to (100).

5-Ethyl-4-phenyl-1H-pyrazol-3(2H)-one.

The asymmetric unit of the title compound, C11H12N2O, consists of two crystallographically independent molecules (A and B) with similar geometries. Both molecules exist in a keto form, the C=O bond length being 1.286 (2) Å in A and 1.283 (2) Å in B. The dihedral angles between the pyrazole ring and the attached phenyl ring are 43.28 (12) and 46.88 (11)°, respectively, for A and B. The ethyl unit in molecule B is disordered over two positions with a site-occupancy ratio of 0.508 (5):0.492 (5). In the crystal, each of the independent molecules forms a centrosymmetric dimer with an R 2 2(8) ring motif through a pair of N—H⋯O hydrogen bonds. These dimers are further connected into a three-dimensional network by intermolecular N—H⋯O and C—H⋯O hydrogen bonds. Intermolecular C—H⋯π interactions are also present.