Dalip Kumar

A facile one-pot green synthesis and antibacterial activity of 2-amino-4H-pyrans and 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromenes

A facile one-pot expeditious synthesis of 2-amino-4H-pyrans and 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromenes has been described under solvent-free conditions using magnesium oxide as a catalyst in very good yields. The reaction catalyst, magnesium oxide was reused and recycled without any loss of activity and product yield. All the synthesized compounds were screened for in vitro antibacterial activity, and compounds 3a, 3b, 3f, 4b, 4c, 4d, 4e and 4g showed complete inhibition of bacterial growth at 128 microg/mL or less and the rest of the compounds exhibited incomplete inhibition.

Microwave-accelerated three-component condensation reaction on clay: solvent-free synthesis of imidazo[1,2-a] annulated pyridines, pyrazines and pyrimidines

A rapid one-pot synthesis of imidazo[1,2-a] annulated pyridines, pyrazines and pyrimidines is described that occurs in the presence of recyclable montmorillonite K 10 clay under solvent-free conditions using microwave irradiation.

Synthesis and biological evaluation of indolyl chalcones as antitumor agents

A series of indolyl chalcones were synthesized and evaluated in vitro for their anticancer activity against three human cancer cell lines. Compounds 3b-d, 3h, 3j, 3l, 3m, 4g, and 4j showed significant cytotoxicity, particularly, indolyl chalcones 3l and 3m were identified as the most potent and selective anticancer agents with IC(50) values 0.03 and 0.09 microM, against PaCa-2 cell line, respectively.

Manganese triacetate mediated oxidation of Hantzsch 1,4-dihydropyridines to pyridines

Abstract A general and practical route for the high yield oxidative conversion of readily accessible 1,4-dihydropyridines to the corresponding pyridines is described using a relatively benign oxidant, manganese triacetate.

FORMATION AND DEHYDRATION OF A SERIES OF 5-HYDROXY-5-TRIFLUOROMETHYL-4,5-DIHYDROPYRAZOLES

Abstract Reaction of five (3-oxo-4,4,4-trifluorobutanoyl)heterocycles with hydrazine hydrate under mild conditions gave the corresponding 3-heterocyclyl-5-hydroxy-5-trifluoromethyl-4,5-dihydropyrazoles. Thermal elimination of water from the 3-(thien-2-yl), 3-(pyridin-2-yl) and 3-(pyridin-4-yl) compounds readily gave the corresponding pyrazoles but acid catalysis was required to form 3-(benzothiazol-2-yl)-5-trifluoromethylpyrazole and 3-(1-methylbenzimidazol-2-yl)-5-trifluoromethylpyrazole. More forcing conditions were required for the analogous dehydration/aromatisations giving 3,5-bis(trifluoromethyl)-1-(4-nitrophenyl)pyrazole and 3,5-bis(trifluoromethyl)-1-pentafluorophenylpyrazole.

Can ultrasound substitute for a phase-transfer catalyst? Triphase catalysis and sonochemical acceleration in nucleophilic substitution of alkyl halides and α-tosyloxyketones: synthesis of alkyl azides and α-azidoketones

Alkyl halides and α-tosyloxyketones afford the corresponding azide derivatives upon treatment with aqueous sodium azide under triphase catalysis or ultrasound irradiation conditions. The use of surfactant pillared clay materials and sonochemistry has been compared and demonstrated in these nucleophilic substitution reactions. It appears that the use of a two-phase system in conjunction with ultrasound irradiation is the method of choice that precludes the need for a catalyst in such reactions.

Hypervalent Iodine Oxidation of 1, 3, 5-Trisubstituted Pyrazolines: A Facile Synthesis of 1,3,5-Trisubstituted Pyrazoles

Abstract 1, 3, 5-Trisubstituted pyrazolines (1a–i) undergo facile oxidation to the corresponding pyrazoles (2a–i) in the presence of iodobenzene diacetate.

Novel bis(indolyl)hydrazide–hydrazones as potent cytotoxic agents

A series of bis(indolyl) hydrazide-hydrazones 5a-n were synthesized and evaluated for their cytotoxicity against selected human cancer cell lines. The reaction of indole-3-carboxaldehyde 2 with indole-3-carbohydrazide 4 in presence of catalytic amount of acetic acid afforded 5a-n in good yields. Among the synthesized bis(indolyl)hydrazide-hydrazones, the compound 5b with N-(p-chlorobenzyl) and bromo substituents was found to be the most potent against multiple cancer cell lines (IC(50)=1.0 μM, MDA-MB-231). The compound 5k exhibited selective cytotoxicity against breast cancer cell line MCF7 (IC(50)=3.1 μM).

Synthesis and anticancer activities of novel 3,5-disubstituted-1,2,4-oxadiazoles

A series of 3,5-disubstituted-1,2,4-oxadiazoles were synthesized and evaluated for their in vitro anti-proliferative activities against various cancer cell lines. Formation of 1,2,4-oxadiazole ring was accomplished by the reaction of amidoxime with carboxylic acids. The in vitro cytotoxic effects of 3,5-disubstituted-1,2,4-oxadiazoles have been demonstrated across a wide array of tumor cell types and a few compounds exhibited specificity towards pancreatic (3f, 3h, 3j, and 3k) and prostate (3n) cancer cells. Among the prepared 3,5-disubstituted-1,2,4-oxadiazoles, compound 3n is the most selective (>450-fold) and compound 3p is the most cytotoxic (10nM) against prostate cancer cell lines.

Click chemistry inspired one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles and their Src kinase inhibitory activity

Two classes of 1,4-disubstituted 1,2,3-triazoles were synthesized using one-pot reaction of α-tosyloxy ketones/α-halo ketones, sodium azide, and terminal alkynes in the presence of aq PEG (1:1, v/v) using the click chemistry approach and evaluated for Src kinase inhibitory activity. Structure-activity relationship analysis demonstrated that insertion of C(6)H(5)- and 4-CH(3)C(6)H(4)- at position 4 for both classes and less bulkier aromatic group at position 1 in class 1 contribute critically to the modest Src inhibition activity (IC(50) = 32-43 μM) of 1,4-disubstituted 1,2,3-triazoles.