Sulfides, -fluoro synthesis

In most oases, the fluoro Pummerer reaction can be carried out with 1.33 to 2.0 equiv of DAST and a "catalytic" amount of antimony trichloride in either refluxing methylene chloride or chloroform at room temperature or 50°C. In the synthesis of fluoromethyl phenyl sulfide, however, the induction period makes room temperature conditions the preferred method for large scale synthesis. 

D.F. Andres, U. Dietrich, E.G. Laurent, B.S. Marquet, Anodic fluorination of vinyl sulfides - synthesis of a-fluoro- -thio-a, -unsaturated carbonyl compounds. Tetrahedron 53 (1997) 647-658. 

On the pages which follow, general methods are illustrated for the synthesis of a wide variety of classes of organic compounds including acyl isocyanates (from amides and oxalyl chloride p. 16), epoxides (from reductive coupling of aromatic aldehydes by hexamethylphosphorous triamide p. 31), a-fluoro acids (from 1-alkenes p. 37), 0-lactams (from olefins and chlorosulfonyl isocyanate p. 51), 1 y3,5-triketones (from dianions of 1,3-diketones and esters p. 57), sulfinate esters (from disulfides, alcohols, and lead tetraacetate p. 62), carboxylic acids (from carbonylation of alcohols or olefins via carbonium-ion intermediates p. 72), sulfoxides (from sulfides and sodium periodate p. 78), carbazoles... 

Not within the scope of this section are the synthesis of a-fluoro sulfides from dithioace-tals, their reduction to alkyl fluorides, and the synthesis of glycosyl fluorides from (phenyl-sulfanyl)glycosides. ... 

The stepwise reduction of 4-fluoro-5-(l,l,2,2-tetrafluoroethyl)-3//-l,2-dithiole-3-thione 153 with Zmolequiv of sodium sulfide, acting both as the reducing and nucleophilic reagent, has found use in a synthesis of the sodium salt of trithiapentalene 154 (Scheme 18), which was converted upon acidification into 3,4-difluoro-2-mercapto-l,6,6aA -trithiapentalene 155 in moderate yield <2006JFC(127)774>. 

Treatment of methyl phenyl sulfoxide with diethylaminosulfur trifluoride (DAST), in the presence of antimony trichloride provides 159 in quantitative yield (66). The reaction proceeds in good yield with dialkyl sulfoxides and alkyl aryl sulfoxides (163). Reoxidation of the a-fluorosulfide (165) to the corresponding sulfoxide (161), followed by pyrolysis, provides a direct synthesis of fluoroolefins (65). The reaction is believed to proceed by a Pummerer-type mechanism (l.e., a fluoro-Pummerer reaction, Scheme 48). Similarly, Umemoto (67) reported that N-fluorocollidine (167) converted sulfides to ot-fluorosulfides (170) presumably via an S-fluorosulfonium cation species 168 (Scheme 49). The synthetically challenging fluorovinyl ether nucleosides (175) and (176) were prepared using the fluoro-Pummerer reaction (Scheme 50) (60) the (E)-isomer (175) could be isomerized to 176 under photolytic conditions. Finch and co-workers (69) converted 160 to the sulfoximine 178 and demonstrated the utility of this compound as a mild fluoromethylene synthon (Scheme 51). Base-catalyzed condensation 178 with a carbonyl compound gave 179 which afforded... 

Addition of a second equivalent of difluoroiodotoluene in this reaction (Scheme 3.5) affords a,a-difluoro sulfides and the reaction with three equivalents of T0IIF2 leads to a,a-difluoro sulfoxides. This sequential fiuorination-oxidation reaction has been exploited in the one-pot synthesis of 3-fluoro-2(5W)-furanone starting... 

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