Fluoride-Promoted Cross-Coupling Reactions of Alkenylsilanols. Elucidation of the Mechanism through Spectroscopic and Kinetic Analysis

Scott E. Denmark, Ramzi F. Sweis, Daniel Wehrli

Research output: Contribution to journalArticle

Abstract

The mechanism of the palladium-catalyzed cross-coupling reaction of (E)-dimethyl-(1-heptenyl)-silanol ((E)-1) and of (E)-diisopropyl-(1-heptenyl)silanol ((E)-2) with 2-iodothiophene has been investigated through spectroscopic and kinetic analysis. A common intermediate in cross-coupling reactions of several types of organosilicon precursors has been identified as a hydrogen-bonded complex between tetrabutyl-ammonium fluoride (TBAF) and a silanol. The order in each component has been determined by plotting the initial rates of the cross-coupling reaction at varying concentrations. These data provide a mechanistic picture that involves a fast and irreversible oxidative insertion of palladium into the aryl iodide and a subsequent turnover-limiting transmetalation step achieved through a fluoride-activated disiloxane derived from the particular silanol employed. The inverse order dependence of TBAF at high concentration is consistent with a pathway that proceeds through a hydrogen-bonded complex which is the lowest energy silicon species in solution.

Original languageEnglish (US)
Pages (from-to)4865-4875
Number of pages11
JournalJournal of the American Chemical Society
Volume126
Issue number15
DOIs
StatePublished - Apr 21 2004

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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