Morpholinosulfur trifluoride

Morpholinosulfur trifluoride is more thermally stable and therefore safer to handle than DAST and gives a slightly higher yield of the fluoride in the fluorination of cyclohexanol [95, ISO] Both solvent and conformational effects are pronounced in the fluorination of cyclohexanols [550] The chiral (S)-2-(methoxymethyl)pyr-rolidin-l-ylsulfur tnfluonde is an effective enantioselective fluorodehydroxylating agent [ISI]... 

A solution of morpholinosulfur trifluoride (1 equiv) was added to a stirred cooled solution of the sulfonyl or sulfinyl chloride (1 equiv) in Et20 (or benzene, hexane, or chlorobenzene). The mixture was stirred at 20 C for 10 min and a precipitation of morpholinosulfur chloride difluoride occurred. The precipitate was filtered off under anhydrous conditions, and the filtrate was evaporated and fractionated to give the sulfonyl or sulfinyl fluoride. 

TTo a stirred solution of morpholinosulfur trifluoride (8.75 g, 0.05 mol) in anhyd benzene (50 mL) at 0 C was added dropwise trimethylpyrrolidin-l-ylsilane (7.15 g, 0.05 mol). Once the addition was complete, the temperature was allowed to rise to 20 " C and stirring was continued for a further 2 h (release of fluoro-trimethylsilane stopped after 2 h which indicated the completion of the reaction). The solvent was removed under reduced pressure to give the title compound as a viscous liquid yield 100%. 

Morpholinosulfur trifluoride and tetrafluoroethylene in the presence of potassium fluoride and 18-crown 6 give morpholinopentatluoroethylsulfur di-fluoride, which is subsequently oxidized sequentially to pentafluoroethanesulfmic acid and pentafluoroethanesulfomc acid [7] (equation 7)... 

In a similar way, but w ith morpholinosulfur trifluoride instead of diethylaminosulfur trifluoride, methyl 4,4-difluorohex-5-ynoate was prepared yield 47% bp 58-60 C/lOTorr. ... 

Dialkylaminosulfur trifluorides convert aldehydes and ketones into gtw-difluorides 1 under mild conditions.60-63 The reagent almost exclusively used is the commercially available diethyl-aminosulfur trifluoride (DAST, see Table 2). Other representatives of this class of compounds which have been employed as fluorinating agents for carbonyl compounds are dimethylamino-, piperidino-. and morpholinosulfur trifluoride, which are also commercially available. For the preparation and properties of dialkylaminosulfur trifluorides, see Vol. ElOa. p 406IT. 

Polyfluorinated aliphatic aldehydes reacted with 1-phenyl-3-methylpyrazol-5-one, l-phenyl-3-methyl-5-amino (N,N-dimethylaminomethylenamino)pyrazole, and l-phenyl-3-aminopyrazol-5-one at room temperature in the absence of catalyst with formation of 4-(l-hydroxypolyfluoroalkyl)pyrazoles <2000JFC(101)111>. Dehydration of the 4-(l-hydroxypolyfluoroalkyOpyrazoles with morpholinosulfur trifluoride generated 4-polyfluoroalkylidenepyrazoles, which were active dienophiles and reacted with 2,3-dimethylbutadiene and cyclopentadiene forming spirocyclic pyrazole derivatives. 

The syntheses of Boc- and Fmoc (97/-fluoren-9-ylmethoxycarbonyl)-protected (2S,4R)- and (25, 45)-fluoroprolines from (25, 31 )-hydroxyproline have been reported. " This synthesis featured a Mitsunobo inversion of the hydroxyproline and fluorination with DAST. A similar synthesis was reported that used morpholinosulfur trifluoride as the fluorinating agent. 

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