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|Title:||Reaction of Nucleophiles With Perfluoroalkyl, Perfluoroacyl and Perfluoroalkanesulfonyl Groups|
|Author(s):||Taylor, Stephen Lee|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Trifluoroacetyl triflate is readily prepared in 82% yield by the dehydration (phosphorus pentoxide) of a 2:1 mixture of trifluoroacetic acid and trifluoromethanesulfonic (triflic) acid. Reactions of this highly electrophilic trifluoroacetylating reagent with alcohols, ketones, ethers, amines, pyridines, and with ionic and covalent halides are reported. Trifluoroacetyl triflate is used in the synthesis of the first member of a new class of pyrylium salts, 2,6-dimethoxypyrylium triflate.
A new and convenient synthesis of trifluoromethyl triflate (TFMT) has been devised. The addition of triflic anhydride to a catalytic amount of antimony pentafluoride produces TFMT in 94% yield utilizing a new and stronger Lewis acid catalyst produced in the reaction, F(,4)SbOSO(,2)CF(,3). A mechanism is presented which accounts for the substitution of fluorine ligand with a triflate ligand. Trifluoromethyl triflate does not trifluoromethylate nucleophiles (pyridine, triethylamine, iodide, phenyllithium, phenylmagnesium bromide, lithium thiophenolate, or sodium naphthalenide) but gives products which result from an initial attack of the nucleophile at sulfur. Fluoride ion, which is formed from the displacement of trifluoromethoxide ion from sulfur, is a chain carrier in the rapid decomposition of TFMT to give trifluoromethanesulfonyl fluoride and fluorophosgene.
Efficient synthetic routes to 2-substituted pyridines and 2,6-disubstituted pyridines and pyridine 1-oxides involving direction lithiation with the sterically hindered bases, lithium 2,2,6,6-tetramethylpiperidide (LiTMP) and lithium diisopropylamide (LDA), in the presence of electrophiles that are compatible with the base, e.g., trimethylsilylchloride (Me(,3)SiCl) and hexafluoroacetone (HFA), are described.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.
|Date Available in IDEALS:||2014-12-15|