Ammonium fluoride, fluonnation

Benzyl and alkyl tnalkylsilyl ethers undergo clean fluonnation to give good yields of benzyl and alkyl fluorides, respectively, when reacted with a combination of d quaternary ammonium fluoride and methanesulfonyl orp- toluenesulfonyl fluoride. The reactions are applicable strictly to a primary carbon-oxygen bond, secondary and tertiary alkyl silyl ethers remain intact or, under forcing conditions, aie dehydrated to olefins [29] (equation 22)... 

Fluonnation of hexamethylphosphoramide with ammonium fluoride gives 85-90% yield of the insecticide bis(dimethylamine)fluotophosphine oxide (Dimefox) [SO] (equation 18). 

When potassium fluoride is comhined with a variety of quaternary ammonium salts its reaction rate is accelerated and the overall yields of a variety of halogen displacements are improved [57, p 112ff]. Variables like catalyst type and moisture content of the alkali metal fluoride need to be optimized. In addition, the maximum yield is a function of two parallel reactions direct fluonnation and catalyst decomposition due to its low thermal stability in the presence of fluoride ion [55, 59, 60] One example is trimethylsilyl fluoride, which can be prepared from the chloride by using either 18-crown-6 (Procedure 3, p 192) or Aliquat 336 in wet chlorobenzene, as illustrated in equation 35 [67]. 

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