title: alpha-Vinylation of 1,3-Dicarbonyl Compounds with Alkenyl(aryl)iodonium Tetrafluoroborates: Effects of Substituents on the Aromatic Ring and of Radical Inhibitors.
abstract: Direct alpha-vinylations of enolate anions derived from 1,3-dicarbonyl compounds with 4-tert-butyl-1-cyclohexenyl(aryl)iodonium 2 and 1-cyclopentenyl(aryl)iodonium tetrafluoroborates 3 are reported. Frequently, alpha-phenylations compete with the vinylations in the reaction of 1,3-dicarbonyl compounds with alkenyl(phenyl)iodonium salts 2a and 3a. Use of alkenyl(p-methoxyphenyl)iodonium salts 2b and 3b, however, leads to selective alpha-vinylation at the expense of the competing arylation of 1,3-dicarbonyl compounds. Use of an efficient aryl radical trap, 1,1-diphenylethylene, inhibits radical-induced decomposition of the alkenyl(aryl)iodonium salts, thereby improving the yields of alpha-vinylations of enolate anions derived from 1,3-dicarbonyl compounds.
authors.affiliation: Faculty of Pharmaceutical Sciences, University of Tokushima, 1-78 Shomachi, Tokushima 770, Japan.
authors.forename: Masahito
authors.initials: M
authors.lastname: Ochiai
authors.forename: Toshifusa
authors.initials: T
authors.lastname: Shu
authors.forename: Takema
authors.initials: T
authors.lastname: Nagaoka
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kitagawa