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Keywords:

  • palladium catalyst;
  • phosphine;
  • carbon dioxide;
  • carbon–carbon bond formation;
  • telomerization;
  • butadiene;
  • isoprene

Abstract

Two-coordinate Pd(0) complexes are shown to be important intermediates in the telomerization of 1,3-dienes and CO2 using palladium/phosphine catalysts without additives. Only one phosphorus atom is bound to palladium during the C–C bond forming steps, but the second phosphorus atom is crucial in the early stages of the catalytic cycle and for the elimination of the product. A ligand that gave an active palladium catalyst for the coupling of 1,3-butadiene and CO2 has been designed. Use of a palladium catalyst in the reaction of isoprene with CO2 allowed for the first time isolation and NMR spectroscopic characterization of the resulting mixture of lactones.