Large rate accelerations in the stille reaction with tri-2-furylphosphine and triphenylarsine as palladium ligands: mechanistic and synthetic implications

Article abstract of DOI:10.1021/ja00025a025

The effect changing the palladium ligands on the rates of typical Stille cross-coupling reactions was studied. Large rate enhancements (typically 10²-10³ over triphenylphosphine-based catalysts) were observed with tri-2-furylphosphine (TFP) and triphenylarsine, which are recommended as the new ligands of choice in the palladium-catalyzed coupling between olefinic stannanes and electrophiles. On the basis of the evidence presented, the transmetalation, which is the rate-determining step in the catalytic cycle, is postulated to involve a π-complex between the metal and the stannane double bond. In general, ligands that readily dissociate from Pd(II) and allow ready formation of this π-complex are the ones that produce the fastest coupling rates. The utility of the new ligands is demonstrated with several synthetic examples.