Gopalpur Nagendrappa

Organic synthesis using clay catalysts

ConclusionThe clay minerals can catalyze a variety of organic reactions occurring on their surface and interstitial space. Synthetic organic chemists have been attracted to their tremendous potential as catalysts only relatively recently. Modification of their properties by incorporating different metal cations, molecules or complexes, can lead to catalysts that are useful in effecting even more varieties of reactions and higher selectivity in product structure and yield. There is a theory that the molecules of life actually developed in sedimentary clays. As the organic chemist is becoming more aware of the clay’s efficacy, its uses in organic synthesis are bound to increase, especially because it helps in developing eco-friendly chemical processes. The dark clay has a bright future in the area of organic synthesis.

Organic synthesis under solvent-free condition: an environmentally benign procedure—II

In the first part of the article, thermal solvent-free reactions were described. In this part solvent-free reactions brought about by light radiation are discussed.

New polyfunctional imidazo[4,5-C]pyridine motifs: Synthesis, crystal studies, docking studies and antimicrobial evaluation

New antimicrobial agents, imidazo[4,5-c]pyridine derivatives have been synthesized. We have developed a new synthetic protocol for the final reaction, an efficient microwave-assisted synthesis of imidazo[4,5-c]pyridines from substituted 3,4-diaminopyridine and carboxylic acids in presence of DBU mediated by T3P. The chemical structures of the new compounds were characterized by IR, (1)H NMR, (13)C NMR, mass spectral analysis and elemental analysis. In addition, single crystal X-ray diffraction has also been recorded for compound 9c. The inxa0vitro antimicrobial activities of the compounds were conducted against various Gram-negative, Gram-positive bacteria and fungi. Amongst the tested compounds 9c, 9e, 9g, 9k and 9l displayed promising antimicrobial activity. The molecular docking of GlcN-6-P synthase with newly synthesized compounds was carried out.

Synthesis, molecular docking and anti-mycobacterial evaluation of new imidazo(1,2-a)pyridine-2-carboxamide derivatives

New anti-tubercular agents, imidazo[1,2-a]pyridine-2-carboxamide derivatives (5a-q) have been designed and synthesized. The structural considerations of the designed molecules were further supported by the docking study with a long-chain enoyl-acyl carrier protein reductase (InhA). The chemical structures of the new compounds were characterized by IR, (1)H NMR, (13)C NMR, HRMS and elemental analysis. In addition, single crystal X-ray diffraction has also been recorded for compound 5f. Compounds were evaluated in vitro against Mycobacterium tuberculosis H37Rv, and cytotoxicity against HEK-293T cell line. Amongst the tested compounds 5j, 5l and 5q were emerged as good anti-tubercular agents with low cytotoxicity. The structure-anti TB activity relationship of these derivatives was explained by molecular docking.

Synthesis, ABTS-Radical Scavenging Activity, and Antiproliferative and Molecular Docking Studies of Novel Pyrrolo1,2-a]quinoline Derivatives

Abstract A new 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)-radical scavenging and antiproliferative agents of pyrrolo[1,2-a]quinoline derivatives have been synthesized. An efficient method for the synthesis of 14 novel diversified pyrrolo[1,2-a]quinoline derivatives has been described using 4-(1,3-dioxolan-2-yl)quinoline and different phenacyl bromides in acetone and followed by reacting with different acetylenes in dimethylformamide/K2CO3. The structure of the newly synthesized compounds was determined by infrared, 1H NMR, 13C NMR, mass spectrometry, and elemental analysis. The in vitro antioxidant activity revealed that among all the tested compounds 5n exhibited maximum scavenging activity with ABTS. Compound 5b has showed good antiproliferative activity as an inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase. GRAPHICAL ABSTRACT

An Epitome of K Venkataraman's Chemistry

ConclusionKrishnaswami Venkataraman’s contribution to the chemistry of flavones and other natural products, and his work on dyes is not limited to the examples very briefly recorded here. His work covered also the dyes developed for colouring cements, dyemetal complexes, health concerns in case of food colourants, and many other aspects. He put his heart, soul and brainpower for the growth and promotion of his chosen field of research, a good part of which is important even today.

Reactions between arylhydrazinium chlorides and 2‐chloroquinoline‐3‐carbaldehydes: molecular and supramolecular structures of a hydrazone, a 4,9‐dihydro‐1H‐pyrazolo[3,4‐b]quinoline and two 1H‐pyrazolo[3,4‐b]quinolines

Hydrazone derivatives exhibit a wide range of biological activities, while pyrazolo[3,4-b]quinoline derivatives, on the other hand, exhibit both antimicrobial and antiviral activity, so that all new derivatives in these chemical classes are potentially of value. Dry grinding of a mixture of 2-chloroquinoline-3-carbaldehyde and 4-methylphenylhydrazinium chloride gives (E)-1-[(2-chloroquinolin-3-yl)methylidene]-2-(4-methylphenyl)hydrazine, C17H14ClN3, (I), while the same regents in methanol in the presence of sodium cyanoborohydride give 1-(4-methylphenyl)-4,9-dihydro-1H-pyrazolo[3,4-b]quinoline, C17H15N3, (II). The reactions between phenylhydrazinium chloride and either 2-chloroquinoline-3-carbaldehyde or 2-chloro-6-methylquinoline-3-carbaldehyde give, respectively, 1-phenyl-1H-pyrazolo[3,4-b]quinoline, C16H11N3, (III), which crystallizes in the space group Pbcn as a nonmerohedral twin having Z = 3, or 6-methyl-1-phenyl-1H-pyrazolo[3,4-b]quinoline, C17H13N3, (IV), which crystallizes in the space group Roverline{3}. The molecules of compound (I) are linked into sheets by a combination of N-H...N and C-H...π(arene) hydrogen bonds, and the molecules of compound (II) are linked by a combination of N-H...N and C-H...π(arene) hydrogen bonds to form a chain of rings. In the structure of compound (III), one of the three independent molecules forms chains generated by C-H...π(arene) hydrogen bonds, with a second type of molecule linked to the chains by a second C-H...π(arene) hydrogen bond and the third type of molecule linked to the chain by multiple π-π stacking interactions. A single C-H...π(arene) hydrogen bond links the molecules of compound (IV) into cyclic centrosymmetric hexamers having overline{3} (S6) symmetry, which are themselves linked into a three-dimensional array by π-π stacking interactions.

cis-[3-(2-Chloro-6-methyl­quinolin-3-yl)oxiran-2-yl](p-tol­yl)methanone

In the title compound, C20H16ClNO2, the dihedral angle between the quinolyl ring system and the p-tolyl ring is 65.80u2005(7)°. The rings are bridged by a functionalized epoxide system, with the exocyclic bonds in a cis configuration. In the crystal, weak C—H⋯O and C—H⋯Cl interxadactions link the molxadecules into [100] chains.