Fluorinations cesium fluoroxysulfate

Eused-ring polycycHc fluoroaromatics can be made from the corresponding amino fused-ring polycycHc or from preformed fluoroaromatics, eg, 4-fluorophenyl-acetonitrile [459-22-3] (275). Direct fluorination techniques have been successfully appHed to polycycHc ring systems such as naphthalene, anthracene, benzanthracenes, phenanthrene, pyrene, fluorene, and quinoHnes with a variety of fluorinating agents xenon fluorides (10), acetyl hypofluorite (276), cesium fluoroxysulfate (277), and electrochemical fluorination (278,279). 

The white cesium fluoroxy sulfate precipitates from the reaction medium and may be kept for several months in the cold (0 to -15 °C) Metal surfaces can cause detonation of the reagent. The reaction scope of cesium fluoroxysulfate seems narrower than that of acetyl hypofluorite because of its limited solubility in organic solvents Cesium fluoroxysulfate has not been prepared with a fluorine-18 label. 

Fluororesorcinol can be prepared from derivatives of resorcinol and fluo-roxytrifluoromethane [15, 24] (equation 4) or by fluorination of resorcinol with cesium fluoroxysulfate [25] (equation 5). Reaction of acetyl hypofluorite with M-acetyl-O-methyltyrosine methyl ester provides a good route to 3-fluorotyrosine derivatives [26] (equation 6). 

The aryl tin compounds are better substrates for fluorination because they give high yields of fliiorinated aromatics and they may be fluorinated with acetyl hypofluorite, cesium fluoroxysulfate, or fluorine [52, 54 (equation 28). Aryl boronic esters react with cesium fluoroxysulfate to produce fluoroaromatics [55] (equation 29). 

Aerosol Fluorination of Dimethoxymethane, 111 Fluorination with Cesium Fluoroxysulfate... 

Fluorination of Alkenes 2 by Cesium Fluoroxysulfate (NuH =. YleOH) General Procedure 8... 

Cesium fluoroxysulfate in acetonitrile medium at 35 C converts primary alcohols and alkyl and aryl aldehydes into acid fluorides in high yields.i" Hammett correlation analysis of the fluorination of various benzene-substituted aldehydes gives the reactivity constant31 q = —0.38. It has been shown that solvent polarity plays an extremely important role in the conversion of aldehydes into fluorides the conversion is almost quantitative in acetonitrile, but completely stopped in dichloromethane, hexane or tetrahydrofuran. The presence of ni-... 

Trialkylaryltin derivatives 30 are converted into fluoro-substituted derivatives 31. 37-38 (4-Mcth-oxyphenyl)trimethylsilane (32) in acetonitrile gives 4-fluoroanisole and (3-fluoro-4-meth-oxyphenyl)trimethylsilane in the ratio 1 2. A -Methyldiethanol esters of arylboronic acids 33 (l-aryl-5-methyl-2,8-dioxa-5-azonia-l-boranuidabicyclo[3.3.0]octanes) are converted into tluoroaromatic compounds with cesium fluoroxysulfate in acetonitrile in the presence of 1,3-dinitrobenzene at room temperature.39-40 Regiospecific synthesis of 2-fluoro-3-0-methyles-trone in 27 % yield occurs upon fluorination of the corresponding arylboronic acid with cesium fluoroxysulfate.41... 

Regioselective fluorodestannylation of alkenyl and heteroaryl molecules to give 34 can be achieved under mild conditions with cesium fluoroxysulfate, while x-fluoro ketones, e.g. 35, are formed when the tin group is attached to the benzylic position.42 The pyrrole ring in indole derivatives is also successfully fluorinated using this method, e.g. formation of 36.42-45... 

The fluorination of pyridine with cesium fluoroxysulfate in the presence of sodium tetrafluoro-borate in acetonitrile at 0-5 C gives 1-fluoropyridinium tetrafluoroborate (3).42... 

Room-temperature fluorination of aromatic compounds with cesium fluoroxysulfate is generally run in the presence of a polar solvent like acetonitrile and a catalyst like boron trifluoride. Thus benzene yields fluorobenzene (22). 

Cesium fluoroxysulfate, CsSO.,f (1). Mol. wt. 247.97, stable solid at - I O, stable in CHyCN for about a day. The reagent is prepared by reaction of cesium sulfate in water with fluorine.1... 

Benzotriazole can be chlorinated at the N(l) position by NaOCl (85H(23)2225). 1-Chlorobenzotriazole - a rather stable crystalline compound that has found application in organic synthesis as a selective chlorinating reagent and mild oxidant. A-Fluorination of benzotriazole with cesium fluoroxysulfate gives 1-fluorobenzotriazole in 25% yield (91T7447). 

Xenon difluoride and xenon hexafluoride fluorinate pyridine to give a mixture of 2- and 3-fluoropyridines along with 2,6-difluoropyridine (76JFC(7)179). Cesium fluoroxysulfate at room... 

The Role of Reagent Structure in the Mild Introduction of a Fluorine Atom into Organic Molecules Xenon Difluoride, Cesium Fluoroxysulfate and F-TEDA Case ... 

Cesium fluoroxysulfate [5, 61 is prepared by reacting fluorine with cesium sulfate in aqueous solution [20, 21] (equation 3). 

Electrochemical fluorination of pyridine in the presence of a source of fluoride ion gave 2-fluoropyridine in 22% yield (85M11). With xenon difluoride, pyridine formed 2-fluoropyridine (35%), 3-fluoropyridine (20%), and 2,6-difluoropyridine (11%) in a reaction unlikely to be a conventional electrophilic substitution. Xenon hexafluoride has also been used (76JFC179). With cesium fluoroxysulfate at room temperature in ether or chloroform, the major product was 2-fluoropyridine (61 and 47%, respectively). Some 2-chloropyridine was also formed in chloroform solution. In methanol the entire product was 2-methoxypyridine (90TL775). Fluorine, diluted with argon in acetic acid, gave a 42% yield of the 5-fluoro derivative of l-methyl-2-pyridone [82H( 17)429],... 

Cations, polycyclic aromatic nitrogen (review), 55, 261 Cesium fluoroxysulfate fluorination of... 

The fluorination of A-methyldiethanolaminc esters 1 of aromatic boronic acids with cesium fluoroxysulfate in acetonitrile at room temperature results in the formation of fluoroaromatic compounds 2 in low to fair yield. 

The fluorination of pyridine with cesium fluoroxysulfate in a variety of solvents yields a mixture of 2-fluoropyridine (7), 2-(fluorosuIfonyloxy)pyridine (8) and 2-substituted pyridincs 9. ... 

Fluorination of Vinyltin Compounds with Cesium Fluoroxysulfate Geueral Procedure ... 

Xenon difluoride is a better fluorinaling reagent for vinyltin compounds than cesium fluoroxysulfate (compare entry 1 in Tables 1 and 2). Besides this, cesium fluoroxysulfate (which can be prepared from elemental fluorine and cesium sulfate) is known to be shock sensitive and to undergo detonation upon hcaling. However, cesium fluoroxysulfate is the alternative choiee in the ease of some vinyltin compounds, such as 2- and 3-(trimethylstannyl)indolcs (Table 2, entries 5 7), whose reactions with xenon difluoride are not effective. 

Fluoroaromatic compounds 8 are synthesized by reaction of aryltrialkyltin derivatives with electrophilic fiuorinating reagents, such as cesium fluoroxysulfate, trifluoromethyl hypo-fluorite and acetyl hypofluorite, or with elemental fluorine. In Table 4 examples of these reactions arc summarized. 

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