Polyfluorinated furans

Polyfluorinated furans have also been prepared by electrochemical methods in which the substrates are treated with CoF3 (or the less reactive KCoF4), followed by base-induced elimination of HF [70JCS(C)2146 73MI1]. 

Luijk R, Dorland K, Smit P, Govers HAJ (1993), in Polycyclic aromatic compounds", prediction of the gas chromatographic retention behaviour of polybrominated dibenzo-p-dioxins , p. 565-572, Garrigues Ph, Lamotte M (Eds.), Gordon and Breach, Yverdon Weber R, Hagenmaier H (1994), Organohalogen Compounds 19 7-11. Polyfluorinated diben-zodioxins/furans - Synthesis, analysis and formation", Eds. University of Kyoto, Japan... 

Dielectrophilic species are 1,4-diketones, certain 1,3-dienes, a,B-unsaturated isocyanates, isothiocyanates, cyanates, and thiocyanates bearing electron-withdrawing (e.g., polyfluorinated and perfluorinated) substituents the most frequently used 1,1-dinucleophiles are water, potassium sulfide, primary amines, and ammonia. From this repertoire of building blocks many combinations are possible. Tetrakis(trifluoro-methyl)furans, thiophenes, and pyrroles have been synthesized from per-fluoro-3,4-dimethylhexa-2,4-diene on addition of water, potassium sulfide, or aniline (90CC1127) (Scheme 39). 

The inoeased ability of polyfluorinated compounds to undergo fluorine substitution was used for the synthesis of trifluoromethyl-substituted furans. Reaction of perfluorobut-2-ene 131 with acetylacetone or acetoacetic ester furnished 2,3-bis(trifluoromethyl)furans 132 through two sequential fluorine substitutions [97]. Similarly, fluoride-ion catalyzed reaction of fluorinated enol phosphates 133 led to dihydrofurans 134 which treatment with a base produced furans 135 in 44-56 % yields [98]. 

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