Ethers hydrogen fluonde

The tnmethylsilyl enol ether of 1 mdanone (3 2 mmol) in 2 mL of methylene chlonde is added to a mixture of xenon difluonde (4 mmol) and a catalytic amount of pyndimum poly (hydrogen fluonde) m 5 mL of methylene chlonde The mixture IS stured at 0 C for 2 h and poured into dilute sodium bicarbonate solution, tlie organic layer is separated and dned After concentration and column chromatogra phy (silica gel, hexanes), 2-fluoro-1 -mdanone (mp, 59 C) is obtamed in 87% yield... 

Electrochemical oxidation of alkyl aryl ethers results m oxidative dealkylation and coupling of the intermediate radicals ElectrooxidaUon m the presence of hydrogen fluonde salt leads to fluonnated dienones [66] (equation 58)... 

Removal of the TBDPS ether in intermediate 71-1 en route to Myxovirescin A1 [Scheme 4.71] gave the desired alcohol 71.2 along with the acyl migration product 71 3.126 With TBAF, a 1 1 mixture of 71,2 and 71,3 was obtained but the rearrangement was minimised to 10% using the hydrogen fluonde-triethylamine complex at room temperature. 

Selective fluonnation in polar solvents has proved commercially successful in the synthesis of 5 fluorouracil and its pynmidine relatives, an extensive subject that will be discussed in another section Selective fluonnation of enolates [47], enols [48], and silyl enol ethers [49] resulted in preparation of alpha-fluoro ketones, heto-diketones, heta-ketoesters, and aldehydes The reactions of fluorine with these functionalities is most probably an addition to the ene followed by elimination of fluonde ion or hydrogen fluonde rather flian a simple substitution In a similar vein, selective fluonnation of pyndmes to give 2-fluoropyridines was shown to proceed through pyridine difluondes [50]... 

During electrochemical fluorination retention of important functional groups or atoms in molecules is essential. Acyl fluorides and chlorides, but not carboxylic acids and anhydrides (which decarboxylate), survive perfluorination to the perfluorinated acid fluorides, albeit with some cyclization in longer chain (>C4) species [73]. Electrochemical fluorination of acetyl fluoride produces perfluoro-acetyl fluoride in 36-45% yields [85]. Electrochemical fluorination of octanoyl chloride results in perfluorinated cyclic ethers as well as perfluorinated octanoyl fluonde. Cyclization decreases as initial substrate concentration increases and has been linked to hydrogen-bonded onium polycations [73]. Cyclization is a common phenomenon involving longer (>C4) and branched chains. a-Alkyl-substituted carboxylic acid chlorides, fluorides, and methyl esters produce both the perfluorinated cyclic five- and six-membered ring ethers as well as the perfluorinated acid... 

Dehydrochlorination of bis(tnfluoromethyUhio)acetyl chloride with calcium oxide gives bis(tnfluoromethylthio)ketene [5] (equation 6) Elimination of hydrogen chlonde or hydrogen bromide by means of tetrabutylammonium or potassium fluoride from vinylic chlorides or bromides leads to acetylenes or allenes [d] (equation 7) Addition of dicyclohexyl-18-crown-6 ether raises the yields of potassium fluonde-promoted elimination of hydrogen bromide from (Z)-P-bromo-p-ni-trostyrene m acctonitnle from 0 to 53-71 % In dimethyl formamide, yields increase from 28-35% to 58-68%... 

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