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.

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