The transmetalation step in Pd-catalyzed processes: understanding the role of the classical nucleophile, the ligands and the synthetic potential of a third metal

Abstract

The transmetalation step of Pd-catalyzed reactions is studied in-depth in this Doctoral Thesis. New bimetallic systems based on the Au/Pd and the Cu/Pd couple have been developed in the context of the Stille reaction and the Hiyama reaction that are very efficient for the coupling of bulky groups. This type of couplings are very challenging with other methodologies and provide excellent results under a synthetic point of view with our bimetallic approach. The bimetallic systems have been examined under a mechanistic point of view. The role of the cocatalyst, the auxiliary ligands and the tin and silicon organometallics have been understood, providing relevant information for the improvement of these systems and the development of new others. The secondary transmetalations that lead to undesired byproducts in the Negishi reaction have been studied in detail by experimental and computational techniques. The information obtained in our study provides important information that will contribute to develop more efficient Negishi reactions. A ligand designed in our group to promote challenging reductive eliminations has been tested for the Pd-catalyzed fluorination and trifluoromethylation of aryl halides. The ligand is not effective for this reaction due to the existence of a migratory insertion process that prevents the desired reductive elimination. This process has been studied by DFT calculations. The mechanisms of the N-H activation of anilines by Ir(PCP) complexes has been carried out by experimental and computational techniques. The information obtained will be used to design more efficient reactions based on this activation.