Sulfur tetrafluonde

A variety of reagent combinations add fluorine and sulfur to fluonnated olefins. Typically the olefin is reacted with fluoride ion and a source of electrophilic sulfur, such as sulfur tetrafluonde[757,178,179, 7S0], alkyl or amino sulfur tnfluondes [757, 787],... 

Perfluoropmacol reacts with sulfur tetrafluonde in an unconventional way instead of replacement of the hydroxyl groups by fluorine, the substitution of four fluonne atoms in the sulfur tetrafluonde molecule with oxygen occurs to give the corresponding spirosulfurane [J6J] (equation 79)... 

The reaction of diethyl tartrate with sulfur tetrafluonde at 25 °C results in replacement of one hydroxyl group, whereas at 100 °C, both hydroxyl groups are replaced by fluonne to form a,a -difluorosuccinate [762] The stereochemical outcome of the fluonnation of tartrate esters is retention of configuration at one of the chiral carbon atoms and inversion of configuration at the second chiral center [163,164, 165] Thus, treatment ofdimethyl(+)-L-tartrate with sulfur tetrafluonde gives dimethyl meso-a,a difluorosuccinate as the final product [163, 164], whereas dimethyl meso tartrate is converted into a racemic mixture of D- and L-a,a -difluorosuccmates [765] (equation 80)... 

Treatment of glyoxal with sulfur tetrafluoride in the presence of sodium fluoride results iii the formation of difluoroethylene glycol orthosulfite [174] (equation 89) Similarly, perfluonnated 1,2-diketones react with sulfur tetrafluonde to give tetraoxyspirosulfuranes as the only products Thus, perfluorobiacetyl gives a ciystalhne product, perfluorobutylene glycol 2,3 orthosulfite [175] (equation 89)... 

Carboxylic acids react both with fluoroaminosulfiiranes such as DAST and with sulfur tetrafluonde. Whereas DAST converts the acids to acyl fluorides only, sulfur tetrafluonde further fluorinates the primarily formed acyl fluorides and ultimately converts the carboxyl group to a trifluoromethyl group. 

Aliphatic carboxylic acids react with sulfur tetrafluonde to give, in addition to 1,1,1-trifluoromethylalkanes, considerable amounts of symmetrical bis(l,l-di-fluoroalkyl)ethers. Yields of the ethers are related to the nature of the acids and to the reaction conditions. The optimum conditions for the formation of the ethers depend on their stability in highly acidic reaction medium and on the reactivity of the acids toward sulfur tetrafluonde Simple unsubstituted acids form the ethers only at low temperatures, whereas longer chain and cycloaliphatic acids give the corresponding ethers at somewhat higher temperatures Halosubstituted acids form the ethers at the relatively high reaction temperatures necessary for these reactions to proceed [203, 204, 205] (equation 101). 

Fluorination of tetrachlorophthalic acid hemihydrate with an excess of sulfur tetrafluoride, or of tetrachlorophthalic anhydride with a sulfur tetrafluonde-hydro-gen fluoride reagent, provides an efficient synthesis of 4,5,6,7- tetrachloro-1,1,3,3-tetrafluorol,3-dihydroisobenzofuran. 3,4,5,6-Tetrachloro-2-(trifluoromethyl)-benzoyl fluoride is formed as a by-product [217] (equation 111). 

Furantetracarboxylic acid reacts with sulfur tetrafluonde to giveperfluoro-2,5-ditnethyl-2, 5 -dihydro-3, 4 -difuran as the only product [223] (equation 116)... 

Treatment of 2,5 and 2,4-furandicarboxylic acids with sulfur tetrafluonde in an excess of hydrogen fluoride leads simultaneously to conversion of the carboxylic groups into trifluoromethyl groups and addition of two fluorine atoms to the furan ring to give highly fluorinated diastereoisomersof2,5-dihydrofuran [225,226,227] (equations 117 and 118)... 

Cyclic ethylene carbonate and its halogeno derivatives are converted into 2 2 difluoro 1,3 dioxolanes, which are useful as inhalation anaesthetics by treatment with sulfur tetrafluonde m an anhydrous hydrogen fluoride solution at 100-150 °C [239] (equation 126)... 

Besides sulfur tetrafluonde, only a very few reagents can convert a carboxylic group into a trifluoromethyl group... 

A nonconventional synthesis of the known inhalation anaesthetic, 2-bromo-2 chloro-l,l,l-trifluoroethane (Halothane), based on the reaction of ethyl 1,2 di bromo-l,2-dichloroethyl ether with anhydrous hydrogen fluoride and sulfur tetrafluonde, has been patented The reaction presumably involves cleavage of the ether linkage, followed by fluorination of the intermediate bromochloroacetyl halide with sulfur tetrafluonde, ethyl halides are the by-products [2] (equation 2)... 

Highly fluorinated tertiary alcohols usually give olefins on fluonnation with sulfur tetrafluonde [759/, but in certain cases, replacement of the hydroxyl group with fluorine occurs under mild conditions Hexafluoro-2-arylpropan-2-ols react with sulfur tetrafluonde at low temperatures to give high yields of heptafluoro-lsopropylarenes [769] (equation 77), and similarly, 3,8 dihydroxy 9,9,9,10,10,10-hexafluoro-p-menthane affords 3,8,9,9,9,10,10,10-octafluoromenthane [769] (equation 78)... 

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