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′SnBu 3 , respectively], where they exert a similar triple role: (1) They favor transmetalation by formation of trans -ArPdFL 2 (L = PPh 3 ) complexes that react with the nucleophiles in contrast to trans -ArPdXL 2 . (2) They catalyze the reductive elimination from trans -ArPdAr′L 2 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′SnFBu 3 ] – , 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 ArPdXL 2 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