Publications by authors named "Brajendra Kumar Singh"

The palladium-catalysed regioselective C-H chalcogenation of benzoxazines with disulfides and diselenides in air has been described. In this protocol, palladium acetate serves as the catalyst in conjunction with copper as an oxidizing agent. Through this approach, a wide array of sulfenylation and selenylation reactions of benzomorpholines have been effected, yielding results ranging from good to excellent.

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We report herein an efficient visible-light-promoted approach for the regioselective decarboxylative C-H acylation of -methyl-3-phenylquinoxalin-2(1)-ones using α-oxo-2-phenylacetic acids dual palladium-photoredox catalysis. The reactions were carried out at room temperature in the presence of 24 W blue LEDs. The established protocol tolerated a wide range of functional groups and enabled the synthesis of several acylated -methyl-3-phenylquinoxalin-2(1)-ones in good to excellent yields.

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A rhodium-catalysed, regioselective synthetic methodology for selenylation and sulfenylation of 3-phenyl quinoxolinones has been developed through N-directed C-H activation in the presence of silver triflimide, and silver carbonate using dichalcogenides 'on water'. The methodology has been proven to be efficient, regioselective and green. Using this method, a range of selenylations and sulfenylations of the substrates has been carried out in good to excellent yields.

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A microwave-assisted synthesis of 2-(4-((1-phenyl-1H-1,2,3-triazol-4-yl)methoxy)phenyl)-1H-benzo[d]imidazoles from a phenylazide, propargyloxybenzaldehyde and a 1,2-diaminobenzene is proposed.

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Giardia intestinalis is the most frequent protozoan agent of intestinal diseases worldwide. Though commonly regarded as an anaerobic pathogen, it preferentially colonizes the fairly oxygen-rich mucosa of the proximal small intestine. Therefore, when testing new potential antigiardial drugs, O2 should be taken into account, since it also reduces the efficacy of metronidazole, the gold standard drug against giardiasis.

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The integration of the viral DNA into the host genome is one of the essential steps in the HIV replication cycle. This process is mediated by the viral enzyme integrase (IN) and lens epithelium-derived growth factor (LEDGF/p75). LEDGF/p75 has been identified as a crucial cellular co-factor of integration that acts by tethering IN to the cellular chromatin.

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The application of a palladium-catalyzed Cu(I)-mediated Liebeskind-Srogl protocol for the decoration of the 2(1H)-pyrazinone scaffold resulted in significantly improved yields and rates when performed under microwave irradiation with simultaneous cooling.

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A new transition metal-catalyzed orthogonal solid-phase protocol for the synthesis of highly substituted 2(1H)-pyrazinones was developed, on the basis of Chan-Lam arylation and Liebeskind-Srogl cross-coupling reactions. This strategy opens the way for the generation of small libraries of 2(1H)-pyrazinone analogues for biological screening.

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[reaction: see text] Optimized conditions for the decoration of the 2(1H)-pyrazinone scaffold were developed by applying the Chan-Lam protocol. It was demonstrated that this Cu(II)-mediated cross-coupling reaction resulted in significantly improved yields and rates when performed under microwave irradiation with simultaneous cooling at 0 degrees C, applying a mixture of bases Et(3)N/pyridine.

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