Synthesis and reactivity of new functionalized perfluoroalkylfluorophosphates

Abstract

A new efficient synthesis of functionalized perfluoroalkyl fluorophosphates by oxidative addition of Me2NCH2F to the electron-deficient phosphanes (C2F5)(n)PF(3-n) (n=0-3) is reported. The initially formed zwitterionic, hexacoordinated phosphates [(C2F5)(n)F(5-n)P(CH2NMe2-CH2NMe2)] are converted into the corresponding phosphonium salts [(Me3PCH2NMe2](+)[(C2F5)(n)F(5-n)P(CH2NMe2)](-) by treatment with PMe3. In addition [(C2F5)3F2P(CH2NMe2-CH2NMe2)] can undergo a 1,3-methyl shift from the internal to the terminal nitrogen--a structural characterization was achieved from the CF3 analogue. Reaction of [(C2F5)3F2P(CH2NMe-CH2NMe3)] and PMe3 gave rise to the formation of the zwitterionic phosphonium phosphate [(C2F5)3F2P(CH2NMe-CH2PMe3)], which was fully characterized by X-ray diffraction analysis. Moreover, an efficient one-pot synthesis of Cs(+)[(C2F5)3F2P(CH2NMe2)](-) was pursued. This salt turned out to be a useful nucleophile in several alkylation reactions.

Keywords: fluorine; iminium; oxidative addition; phosphate; phosphorus.