Tetrafluoro phosphane

The most convenient substrates for fluorination with tetrafluoro(phenyl)-25-phosphane are silyl ethers of alcohols 7.13 17 The trimethylsilylation of alcohols with chlorotrimethylsilane in the presence of pyridine is generally quantitative. 

A comparison of various fluorinating agents in the preparation of fluoride 13, i.e. (2-chloro-1,1,2-trifluoroethyl)diethylamine and diethylaminosulfur trifluoride (R = H), tetrafluoro(phen-yl)-A5-phosphane (R = TMS), and potassium fluoride (R = Ts), has shown that the highest stereoselectivity is achieved with potassium fluoride and (2-chloro-l,1,2-trifluoroethyl)-diethylamine.19 The fluorination with tctrafluoro(phenyl)-7.5-phosphane proceeds, at least in part, via a carbocation and with a relatively low enantioselectivity.15... 

The interaction of antimony(III) fluoride with dichloro(phenyl)phosphane leads to oxidative fluorination of the phosphorus atom with the formation of tetrafluoro(phenyl)-/5-phosphane and partial reduction of antimony(III) fluoride to antimony.43... 

Ary)tetrafluoro-25-phosphanes are also obtained by reacting their chloro analogs with anti-mony(III) fluoride.43,55... 

In cases where only difluorophosphanes are formed from dichlorophosphanes by halogen exchange with antimony(III) fluoride, the former can be converted into tetrafluoro-25-phosphanes by treatment with chlorine gas in the presence of antimony(III) fluoride.46,52... 

In this way tetrafluoro(trichloromethyl)- and tetrafluoro(perfluoroalkyl)-25-phosphanes are obtained.46... 

Antimony(V) fluoride adds two fluorine atoms to tcrvalent phosphorus attached to electron-withdrawing fluorinated groups 44100 e.g. tetrafluoro(penlafluorophenyl)-/l5-phosphane (7) is obtained by this reaction in 57% yield."... 

Dichloro(trifluorovinyl)phosphane and chlorobis(trifluorovinyl)phosphane react with anti-mony(V) fluoride at room temperature undergoing not only substitution of chlorine but also addition of two fluorine atoms to the phosphorus to give tetrafluoro(trifluorovinyl)-A5-phos-phane and trifluorobis(trifluorovinyl)-A5-phosphane, respectively.100... 

Phosphane (1.2-Difluoro-elhenyl)-methoxy-( tetrafluoro-1 H-ethyl)-EI0b2, 153 (— F2 - En PH - P-OR)... 

The mechanism of the formation of organic fluorides from silyl etliers and fluoro-/. -phosphanes has been studied in some detail for tetrafluoro(phcnyl)-A -phosphane. The first step, which is usually quantitative at low temperatures, is the formation of an intermediate alkoxyfluoro-A -phosphane 1 and fluorotrimethylsilanc. 

It should be noted that fluorophosphates are usually highly toxic compounds and, for this reason, fluorination with tetrafluoro(phenyl)-3, -phosphane cannot be recommended. Moreover, other methods usually give better results. 

Another 10 examples are known with yields of 46-100 /o. It is interesting that 5 cannot be obtained from 4 with tetrafluoro(phcnyl)-A -phosphane. In the synthesis of 2-(3,4-dimeth-oxyphcnyl)-2-fluoroacetonitrile by this method the overall yield from 3,4-dimethoxybenz-aldehyde is 82%. In eontrasl, the unsilylated 3,4-dimethoxyben7aldehydc cyanohydrin gives only 43 % of the same fluorination product when treated with DAST. ... 

When perflluoro(2-methylpropene) reacts with tributylphosphane in acetonitrile at — 30"C, the reaction does not stop with the formation of fluoro-2 -phosphanes, and, as a result of a series of transformations, perfluorodiene 3 and conjugated cross-triene 4 are formed. When the reaction is carried out with triphenylphosphane in acetonitrile without cooling triene 4 is obtained in 67 % yield.On the other hand, the reaction of perfluoro(2-methylpropcnc) with tributylphosphane in diethyl ether at — 70 C leads to the corresponding fluoro-A -phos-phane treating this compound with potassium fluoride dihydrate in tetraglyme gives 1,1,1,3-tetrafluoro-2-(trifluoromethyl)hept-3-ene in 75% yield,... 

Fluorination of Silyl Ethers with Tetrafluoro(phenyl)-25-phosphane General Procedure 13... 

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