title: Radical Reactions of Alkyl 2-Bromo-2,2-difluoroacetates with Vinyl Ethers: "Omitted" Examples and Application for the Synthesis of 3,3-Difluoro-GABA.
abstract: Addition reactions of perfluoroalkyl radicals to ordinary or polyfluorinated alkenes have been frequently used to synthesize perfluoroalkylated organic compounds. Here ethyl/methyl 2-bromo-2,2-difluoroacetate, diethyl (bromodifluoromethyl)phosphonate, [(bromodifluoromethyl)sulfonyl]benzene, and ethyl 2-bromo-2-fluoroacetate were involved in Na2S2O4-mediated radical additions to vinyl ethers in the presence of alcohols to give difluoro or monofluoroacetyl-substituted acetals or corresponding difluoromethylphosphonate- and (difluoromethylphenyl)sulfonyl-substituted alkyl acetals. This methodology has also been applied as a key step in the synthesis of hitherto unknown 3,3-difluoro-GABA, completing the series of isomeric difluoro GABAs. Comparison of the pKa values of 3-fluoro- and 3,3-difluoro-GABA with that of the fluorine free parent compound showed that introduction of each fluorine lead to acidification of both the amino and the carboxyl functions by approximately one unit.
authors.affiliation: Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine , Murmanska Str. 1, Kyiv, 02660, Ukraine.
authors.forename: Ivan S
authors.initials: IS
authors.lastname: Kondratov
authors.affiliation: Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine , Murmanska Str. 1, Kyiv, 02660, Ukraine.
authors.forename: Maksym Ya
authors.initials: MY
authors.lastname: Bugera
authors.affiliation: Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine , Murmanska Str. 1, Kyiv, 02660, Ukraine.|Enamine Ltd , Chervonotkatska Str. 78, Kyiv, 02094, Ukraine.
authors.forename: Nataliya A
authors.initials: NA
authors.lastname: Tolmachova
authors.affiliation: Enamine Ltd , Chervonotkatska Str. 78, Kyiv, 02094, Ukraine.
authors.forename: Ganna G
authors.initials: GG
authors.lastname: Posternak
authors.affiliation: Organisch-Chemisches Institut, Universität Münster , Corrensstraße 40, 48149 Münster, Germany.
authors.forename: Constantin G
authors.initials: CG
authors.lastname: Daniliuc
authors.affiliation: Organisch-Chemisches Institut, Universität Münster , Corrensstraße 40, 48149 Münster, Germany.|Cells-in-Motion Cluster of Excellence, Universität Münster , Waldeyerstraße 15, 48149 Münster, Germany.
authors.forename: Günter
authors.initials: G
authors.lastname: Haufe