• PANKAJ DAS

      Articles written in Journal of Chemical Sciences

    • A new PEPPSI type N-heterocyclic carbene palladium(II) complex and its efficiency as a catalyst for Mizoroki-Heck cross-coupling reactions in water

      DHRUBAJIT BORAH BISWAJIT SAHA BIPUL SARMA PANKAJ DAS

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      A new air and moisture stable PEPPSI (PEPPSI: pyridine-enhanced pre-catalyst preparation, stabilisation, and initiation) themed palladium N-heterocyclic carbene (NHC) complex [Pd(L)Br2(Py)] (1) [L:2-flurobenzyl)-1-(4-methoxyphenyl)-1H-imidazolline-2-ylidene] was synthesized and characterized. The structure of complex 1 was determined by X-ray single-crystal analysis. The palladium center in 1 adopted a square planar geometry with carbene and pyridine ligands occupying the mutual trans position. The complex 1 was employed to catalyze the Mizoroki-Heck cross-coupling reactions of aryl bromides/iodides with styrene in water. To the best of our knowledge, this is the first report where a Pd-PEPPSI catalyst was successfully employed in aqueous-phase Mizoroki-Heck reaction. Good to excellent yields of cross-coupling products were obtained with a range of representative aryl bromides/iodides under relatively mild conditions(100 °C, 1 mol% of 1).

    • An unsymmetrical Schiff-base derived recyclable Pd-catalyst for Suzuki–Miyaura and Sonogashira reactions in aqueous media

      AMLAN PUZARI ACHINTA GOGOI PANKAJ DAS

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      A water-soluble palladium (II) complex containing an unsymmetrical Schiff-base ligand was synthesized and applied as catalyst Suzuki–Miyaura and Sonogashira cross-coupling reactions in aqueous media.Notably, moderate to excellent yields of biaryls were obtained in Suzuki reaction with usually less reactive aryland heteroaryl chlorides under relatively mild condition. Moderate-to-high yields of aryl-alkynes were also obtained in Sonogashira reactions using aryl bromides. Apart from hydrophilic nature, the accomplishment of reactions in water, high recyclability, broad functional group tolerance, etc., are other advantages of the system.

    • Highly efficient aqueous-phase Sonogashira coupling catalyzed by Pd-PEEPSI/PPh3 under aerobic condition

      DHRUBAJIT BORAH AMLAN PUZARI PANKAJ DAS

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      An in situ generated catalytic system comprised of a Pd-PEPPSI [Pyridine enhanced pre-catalystpreparation, initiation, and stabilization] complex, (NHC)PdBr2(Pyridine), and PPh3 co-ligand demonstratedexcellent activity for the Sonogashira cross-coupling reactions between phenylacetylene with aryl halides inneat water under the aerobic condition in presence of CuI as co-catalyst. The catalytic system was not onlycompatible with electronically diverse aryl bromides/ iodides but also effective for relatively difficult substrateslike heteroaryl bromides. Notably, under similar experimental conditions, the mixed PEPPSI/PPh3system displayed superior activity over the free Pd-PEPPSI or Pd-phosphine system.

      This article presents an in situ Pd-PEPPSI/PPh3 catalytic system for aqueous Sonogashira reaction in presence of CuI under aerobic condition which was found to be highly efficient for coupling of anyl/heteroaryl halides with phenylacetylene to form substituted alkynes. Interestingly, it displayed superior activity over simple Pd-PEPPSI or Pd-PPh3 catalysts

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