Ring-Fluorinated Naphthalene and Indene Synthesis via 6- and 5-endo-trig Cyclizations of gem-Difluoroalkenes by Carbon Nucleophiles.

Abstract The intramolecular vinylic substitution of gem -difluoroalkenes is accomplished with sp 3 and sp 2 carbon nucleophiles (2-arylethyllithium and aryllithium) in a 6- endo-trig and a normally disfavored 5- endo-trig fashion, leading to the synthesis of 3-fluoro-1,2-dihydronaphthalenes and 3-fluoroindenes, respectively. The dihydronaphthalenes are readily aromatized on treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to afford 2-fluoronaphthalenes.