BITS Faculty Publications
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Item Reaction of Aryl and Heterocyclylhydrazines with 2-Methylchromone: Structural Investigation of the Products(Taylor & Francis, 1996) Kumar, DalipReaction of 2-methylchromone (2) with phenylhydrazine provides 3-methyl-5-(o-hydroxyphenyl)-1-phenylpyrazole (6) as a major product. In contrast under similar conditions, heterocyclylhydrazines (8a-c) yield exclusively 5-ethyl-3-(o-hydroxyphenyl)-1-heterocyclylpyrazoles (9a-c). The structural assignments are based on an unambiguous synthesis and an analysis of NMR (1H & 13C) spectral data.Item Conformation and ortho steric effects in a series of 2-(pyrazol-1-yl)quinolines(Wiley, 1996-04) Kumar, DalipNine 2-(pyrazol-1-yl)-4-methylquinolines bearing substituents on the pyrazole 3- or 5-positions (H, Me, Et, i-Pr, t-Bu) were regioselectively synthesized either using the direct condensation of 2-chloro-4-methylquinoline and sodium salt of 3(5)-substituted pyrazoles or by treatment of 2-hydrazino-4-methylquinoline with an appropriate β-ketoaldehyde. The 1H and 13C chemical shifts were discussed taking into account the preferred conformation about the C-2-N-1′ bond as calculated by the AM1 Hamiltonian. It appears that 5-ethyl and 5-isopropyl substituted derivatives present short C-H-N-1 interactions. Ortho steric effects appear to be responsible for these conformations.Item Hypervalent Iodine Oxidation of 1, 3, 5-Trisubstituted Pyrazolines: A Facile Synthesis of 1,3,5-Trisubstituted Pyrazoles(Taylor & Francis, 1997) Kumar, Dalip1, 3, 5-Trisubstituted pyrazolines (1a–i) undergo facile oxidation to the corresponding pyrazoles (2a–i) in the presence of iodobenzene diacetate.Item A Facile Synthesis of 5-Methyl-1-(phenyl/heterocyclyl)-4-trifluoroacetylpyrazoles(RSC, 1997) Kumar, DalipTreatment of substituted hydrazines (2a–d) with 3-acetyl-4-ethoxy-1,1,1-trifluorobut-3-en-2-one (1) yields the title compounds (3a–d) whereas methylhydrazine on similar treatment gives 4-acetyl-1-methyl-3-trifluoromethylpyrazoleItem Hypervalent iodine oxidation of 2-aryl-1,2,3,4-tetrahydro-4-quinolones: An expedient route to naturally occurring 4-alkoxy-2-arylquinolines(Elsiever, 1998-12-10) Kumar, DalipEasily accessible 2-aryl-1,2,3,4-tetrahydro-4-quinolones are readily oxidized to the corresponding 4-alkoxy-2-arylquinolines using a relatively safe hypervalent iodine reagent, [hydroxy (tosyloxy)iodo]benzene (HTIB), in high yields, thus providing a concise route to an important class of naturally occurring alkaloids. 2-Aryl-1,2,3,4-tetrahydro-4-quinolones are readily oxidized to the corresponding 4-alkoxy-2-arylquinolines by [hydroxy(tosyloxy)iodo]benzene(HTIB), thus providing a concise route to a class of naturally occurring alkaloids.Item Surfactant pillared clays as phase‐transfer catalysts: a facile synthesis of α‐azidoketones from α‐tosyloxyketones and sodium azide(Springer, 1998-08) Kumar, DalipThe use of inexpensive and recyclable phase‐transfer catalysts, surfactant pillared clays, is demonstrated in a simple and highly efficient synthesis of α‐azidoketones from readily accessible α‐tosyloxyketones and sodium azide.Item Solid State Oxidation of Benzoins on Alumina-Supported Copper(II) Sulfate under Microwave Irradiation(RSC, 1998) Kumar, DalipBenzoins are rapidly oxidised to benzils in high yields by the solid reagent system copper(II) sulfate–alumina, under the influence of microwaves.Item An Expeditious Synthesis of Flavones on Montmorillonite K 10 Clay with Microwaves(RSC, 1998) Kumar, DalipA manipulatively simple and rapid method for the synthesis of flavones is described via a solid-state dehydrative cyclization of o-hydroxydibenzoylmethanes on a clay surface using microwaves.Item Microwave-accelerated three-component condensation reaction on clay: solvent-free synthesis of imidazo[1,2-a] annulated pyridines, pyrazines and pyrimidines(Elsiever, 1999-10-22) Kumar, DalipA 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. 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.Item Microwave-Accelerated Solvent-Free Synthesis of Thioketones, Thiolactones, Thioamides, Thionoesters, and Thioflavonoids(RSC, 1999-07-29) Kumar, DalipAn expeditious, solvent-free, and high yield conversion of ketones, flavones, isoflavones, lactones, amides, and esters to the corresponding thio analogues is described utilizing Lawesson's reagent in a process that circumvents the use of dry solvents and excess of the reagent.