Reaction with fluondes

The striking nucleofugacity of the trimethylammonium leaving group compared with the nitro group in the reaction with fluonde ion is illustrated by the relative reactivities of p-nitrophenyltnmethylammonium perchlorate and p dmi-trobenzene [7J] (Table 4)... 

Mixtures of anhydrous hydrogen fluoride and tetrahydrofuran are successfully used as fluorinating agents to convert 1,1,2-trifluoro-l-allcen-3-ols, easily prepared from bromotrifluoroethene via lithiation followed by the reaction with aldehydes or ketones, to 1,1,1,2-tetrafluoro-2-alkenes The yields are optimal with a 5 1 ratio of hydrogen fluoride to tetrahydrofuran The fluorination reaction involves a fluonde lon-induced rearrangement (Sf,j2 mechanism) of allylic alcohols [65] (equation 40)... 

Perfluoropyridine gives the usual replacement of the 4-fluonne on reactions with either aromatic or aliphatic mercaptides [55, 36] The reaction of perfluoropyridine with cesium tnfluoromethyl mercaptide, generated from thiocarbonyl fluoride and cesium fluonde, shows temperature dependence of selectivity in fluonne displacement [55 36] (equation 24)... 

Fluonnated ylides have also been prepared in such a way that fluonne is incorporated at the carhon P to the carbamonic carbon Vanous fluoroalkyl iodides were heated with tnphenylphosphine in the absence of solvent to form the necessary phosphonium salts Direct deprotonation with butyUithium or hthium dusopropy-lamide did not lead to yhde formation, rather, deprotonation was accomparued by loss of fluonde ion Flowever deprotonation with hydrated potassium carbonate in thoxane was successful and resulted in fluoroolefin yields of45-S0% [59] (equation 54) P-Fluorinated ylides may also be prepared by the reaction of an isopropyli-denetnphenylphosphine yhde with a perfluoroalkanoyl anhydnde The intermediate acyl phosphonium salt can undergo further reaction with methylene tnphenylphosphorane and phenyUithium to form a new yhde, which can then be used in a Wittig olefination procedure [60] (equation 55) or can react with a nucleophile [6/j such as an acetyhde to form a fluonnated enyne [62] (equation 56)... 

These products are thermally stable at room temperature but decompose at elevated temperatures by ehtmnation of CFj The reaction with hydrogen fluonde IS different from that with hydrogen chlonde and hydrogen bromide Presumably this difference is derived from the strength of the boron-fluonne bond [108 (equauon 86)... 

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