Title
On the triple role of fluoride ions in palladium-catalyzed stille reactionsOn the triple role of fluoride ions in palladium-catalyzed stille reactions
Author
Faculty/Department
Faculty of Sciences. Chemistry
Research group
Organic synthesis
Publication type
article
Publication
Weinheim,
Subject
Chemistry
Source (journal)
Chemistry: a European journal. - Weinheim
Volume/pages
21(2015):50, p. 18401-18406
ISSN
0947-6539
ISI
000367186000050
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
The mechanism of Stille reactions (cross-coupling of ArX with Ar'SnnBu3) performed in the presence of fluoride ions is established. A triple role for fluoride ions is identified from kinetic data on the rate of the reactions of trans[ArPdBr(PPh3)(2)] (Ar=Ph, p-(CN)C6H4) with Ar'SnBu3 (Ar'=2thiophenyl) in the presence of fluoride ions. Fluoride ions promote the rate-determining transmetallation by formation of trans-[ArPdF(PPh3)(2)], which reacts with Ar'SnBu, (Ar' = Ph, 2-thiophenyl) at room temperature, in contrast to trans- [ArPdBr(PPh3)(2)], which is unreactive. However, the concentration ratio [F-]/[Ar'SnBu3] must not be too high, because of the formation of unreactive anionic stannate [Ar'Sn(F)Bu-3](-). This rationalises the two kinetically antagonistic roles exerted by the fluoride ions that are observed experimentally, and is found to be in agreement with the kinetic law. In addition, fluoride ions promote reductive elimination from trans-[ArPdAr(PPh3)(2)] generated in the transmetallation step.
E-info
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