title: Enhanced Nucleophilic Fluorination and Radiofluorination of Organosilanes Appended with Potassium-Chelating Leaving Groups.
abstract: Here we aimed to explore the feasibility of enhancing the fluorination of organosilanes by appending potassium-chelating groups to the substrates. For this purpose, eight organosilanes were prepared in which a linear or cyclic leaving group, with putative potassium-chelating ability, was attached covalently to a congested silicon atom via an ether linkage to serve as a potential nucleophilic assisting leaving group (NALG). Organosilicon-NALGs with expected strong potassium-chelating capability enhanced reactions with potassium fluoride in acetonitrile to produce organofluorosilanes without any need to separately add phase transfer reagent. Similar rate enhancements were also observed with cyclotron-produced [18F]fluoride ion (t1/2= 109.7 min, β+= 97%) in the presence of potassium carbonate in MeCN-0.5% H2O. This study found that metal-chelating NALG units can accelerate fluorination and radiofluorination reactions at sterically crowded silicon atoms.
authors.affiliation: Department of Chemistry, Florida Atlantic University, Boca Raton, Florida 33431.
authors.forename: Mohammed H
authors.initials: MH
authors.lastname: Al-Huniti
authors.affiliation: Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892-1003.
authors.forename: Shuiyu
authors.initials: S
authors.lastname: Lu
authors.affiliation: Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892-1003.
authors.forename: Victor W
authors.initials: VW
authors.lastname: Pike
authors.affiliation: Department of Chemistry, Florida Atlantic University, Boca Raton, Florida 33431.
authors.forename: Salvatore D
authors.initials: SD
authors.lastname: Lepore
keywords: chelating leaving group; fluorination; fluorine-18; fluoroorganosilane; radiofluorination