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


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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).

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


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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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