Perfluoropropionic acid

Diketones are synthesized by Claisen condensation of appropriate acetyl methyl ketone and ethyl perfluoroalkyl carboxylate. For example, 4,4/-bis(l",l,/,l//,2//,2",3//,3//-heptafluoro-4//,6//-hexanedion-6"-yl)-chlorosulfo-o-terphenyl (BHHCT) was synthesized from o-terphenyl by three step reactions (scheme 3 (Yuan et al., 1998a, 1998b)). The o-ter-phenyl are acetylated by acetyl chloride with anhydrous aluminum chloride as a Lewis acid and 4,4 -diacetyl-e>-terphcnyl is obtained. Then, the 4,4/-diacetyl-o-terphenyl is reacted with perfluoropropionic acid ethyl ester with sodium methoxide as a base. Finally, 4,4,-bis(l", 1",l//,2,2,3,/,3"-heptafluoro-4//,6"-hexanedion-6//-yl)-o-terphenyl is chloro-sulfonylatcd by chlorosulfonic acid to form BHHCT. 

Methyl-2-pentafluoroethyl-J -5-oxazolone (as a mixture with perfluoropropionic acid from its prepn. with perfluoropropionic anhydride and DL-alanine) added dropwise with stirring and ice-cooling to a mixture of HBr-glacial acetic acid and ethyl mercaptan, well shaken, and allowed to stand 1 hr. in the ice-bath 2,2,3,3,3-pentafluoro-l-ethylthiopropylamine hydrobromide. Y 79%. F. e. s. F. Weygand, W. Steglidi, and W. Oettmeier, B. 103, 818 (1970). 

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