Role of Fluoride Ions in Palladium-Catalyzed Cross-Coupling Reactions­

Abstract

Fluoride ions are known to promote Suzuki–Miyaura, Hiyama, and Stille reactions [cross-coupling between aryl halides ArX and nucleo­philes Ar′B(OH)₂, Ar′Si(OMe)₃, and Ar′SnBu₃, respectively], where they exert a similar triple role: (1) They favor transmetalation by formation of trans-ArPdFL₂ (L = PPh₃) complexes that react with the nucleophiles in contrast to trans-ArPdXL₂. (2) They catalyze the reductive elimination from trans-ArPdAr′L₂ generated in the transmetalation. (3) The final role is negative, by formation of unreactive anionic species [Ar′BF(OH)₂]^–, [Ar′SiF(OMe)₃]^–, or [Ar′SnFBu₃]^–, respectively. Consequently the rate of the rate-determining transmetalation is controlled by the concentration ratio [F^–]/[nucleophile] which must be less or close to one to ensure fast transmetalation.

1 Introduction

2 Reaction of Fluoride Ions with ArPdXL₂ Complexes

3 The Triple Role of Fluoride Ions in Suzuki–Miyaura Reactions

4 The Triple Role of Fluoride Ions in Hiyama Reactions

5 The Triple Role of Fluoride Ions in Stille Reactions

6 Conclusion

Key words

palladium - fluoride ions - Suzuki–Miyaura reactions - Hiyama­ reactions - Stille reactions - kinetics - mechanism

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