On the Triple Role of Fluoride Ions in Palladium-Catalyzed Stille Reactions

Marius Hervé (1) , Guillaume Lefèvre (2) , E.A. Mitchell (3) , B.U.W. Maes (3) , Anny Jutand (1)

1 PASTEUR - Processus d'Activation Sélective par Transfert d'Energie Uni-électronique ou Radiatif (UMR 8640)
2 LCMCE - Laboratoire de Chimie Moléculaire et de Catalyse pour l'Energie (ex LCCEF)
3 UA - University of Antwerp

The mechanism of Stille reactions (cross-coupling of ArX with Ar'SnnBu 3)p erformed in the presenceo ffluoride ions is established. At riple role for fluoridei ons is identified from kinetic data on the rate of the reactions of trans-[ArPdBr(PPh 3) 2 ](Ar = Ph, p-(CN)C 6 H 4)w ith Ar'SnBu 3 (Ar' = 2-thiophenyl) in the presence of fluoride ions. Fluoride ions promote the rate-determining transmetallation by formation of trans-[ArPdF(PPh 3) 2 ], which reacts with Ar'SnBu 3 (Ar' = Ph, 2-thiophenyl)a tr oom temperature, in contrast to trans-[ArPdBr(PPh 3) 2 ], which is unreactive. However, the concentration ratio [F À ]/[Ar'SnBu 3 ]m ust not be too high, because of the formationo fu nreactivea nionic stannate [Ar'Sn(F)Bu 3 ] À. This rationalisest he two kinetically antagonistic roles exerted by the fluoridei ons that are observed experimentally, and is found to be in agreement with the kinetic law.I na d-dition, fluoride ions promote reductive elimination from trans-[ArPdAr'(PPh 3) 2 ]g enerated in the transmetallation step.

Domaines: Matériaux

Marius Hervé, Guillaume Lefèvre, E.A. Mitchell, B.U.W. Maes, Anny Jutand. On the Triple Role of Fluoride Ions in Palladium-Catalyzed Stille Reactions. Chemistry - A European Journal, 2015, 21, pp.18401-18406. ⟨10.1002/chem.201503309⟩. ⟨hal-01245114⟩