Chiral fluonnation

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)... 

Fluonnations of enolates with chiral reagent D (Table 3a) give moderate degrees of enantiomeric excess [67] (equation 43). 

Morpholinosulfur trifluoride is more thermally stable and therefore safer to handle than DAST and gives a slightly higher yield of the fluoride in the fluonnation of cyclohexanol [93,150] Both solvent and conformational effects are pronounced in the fluonnation of cyclohexanols [750] The chiral (5)-2-(methoxymethyl)pyr-rolidin-1 -ylsulfur tnfluonde is an effective enantioselective fluorodehydroxylating agent [757]... 

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