Perfluoroalkyl derivatives boron

The benzene derivatives containing the fluorinated sulfone have been prepared either by nucleophilic substitution of the 4-fluorophenyl derivative (e.g. 1) or by starting with the appropriately substituted sodium thiophenoxide and reacting with perfluoroalkyl iodide follow by oxidation with either MCPBA or chromium oxide (12. li.) The biphenyl derivatives have been prepared by palladium catalyzed cross coupling chemistry of the 4-bromophenyl derivative (e.g. 2) with substituted phenyl boronic acid (yields 37-84%) (JLH, .). Compound 16 has been prepared by palladium catalyzed cross coupling of (4-bromophenyl)perfluorohexyl sulfone with vinyl anisole in 37 % yield (JJL). The vinyl sulfones, 7 and 9, have been prepared by condensation of CH3S02Rf (JJL) with the appropriate aldehyde (yields 70,and 73%) following a literature procedure (1 ). Yields were not optimized. 

The observations that secondary amines, (Rf)2NH, do not react with boron trifluoride, hydrogen chloride or trifluoroacetic acid [13] also serve to indicate a lack of basic properties. Similarly, tertiary perfluoroalkylamines are quite without basic properties. Moreover, the oxygen atoms in perfluoroalkyl ethers and ketones are poor donors this is exemplified by the fact that hexafluoroacetone cannot be protonated by superacids in solution. Such findings parallel similar observations with unsaturated derivatives where the base strength is considerably reduced in, for example, perfluorop3Tidine or perfluoro-quinoline [14] in comparison with the parent compounds. 

Several attempts were made to prepare compounds havii a perfluoro-alkyl group bonded to boron before success was achieved. In the case of tricoordinate boron compounds, Ry—B linkages were expected to be unstable because of the inability of Rp groups to relieve the electrophilic character of the boron atom by tt bonding (44). In confirmation of this idea, bis(perfluoroalkyl)mercury compounds [e.g., (C2Fs)2Hg] afibrd boron trifluoride when heated with boron trichloride (45, 46). Boron trifluoride formation presumably occurs via a transitory Rp—B derivative ... 

The temperatures quoted are those at which decomposition becomes appreciably rapid. Presumably metal fluorides are also formed in these decompositions but this has not been proven. A reaction which is apparently the reverse of these pyrolyses was mentioned above, namely the addition of platinum-fluorine bonds to tetrafluoroethylene 118). The thermal decomposition of perfluoroalkyl and polyfluoroalkyl derivatives of main group elements such as boron, silicon, or tin was mentioned in earlier sections of this chapter. Transfer of fluorine atoms from the side chains on heating was also a characteristic property. However, it is interesting to compare the reaction (97),... 

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