Fluorine product yields

Starting material Fluorination conditions Fluorinated product Yield mp. Subl. 

Time hrs. Fluorinated Product Yield y /o Bp. °C mp. °C in sealed glass-tubes Sublima- tion temp. °C at 10" mm... 

Entry Starting material Fluorination product Yield (%)... 

Nonmeta.ls, Sulfur reacts with fluorine to yield the remarkably stable sulfur hexafluoride, SF. Operating conditions must be controlled because a mixture of the lower fluorides such as disulfur difluoride [13709-35-8] 2 2 disulfur decafluoride [5714-22-7] 2 10 sulfur tetrafluoride [7783-60-0] SF4, may also be formed. When this reaction is carried out between 310 and 340°C, SF is primarily obtained and essentially no SF and only trace amounts of lower fluorides. Below 300°C, and preferably at ca 275°C, SF is the primary product. At 450—500°C, a mixture comprising ca 50% SF and the lower sulfur fluorides is formed (see Fluorine compounds, inorganic-sulfur). 

The interaction between metal oxides and ammonium hydrofluoride at 100-250°C yields complex fluorometalates of ammonium and water. The water formed evaporates from the mixture, but can also lead to hydrolysis of the fluorination product in the process. In the very common form the fluorination of metal oxides by ammonium hydrofluoride can be described as follows ... 

Becker and Israel (1979) have studied the influence of the solvent in more detail. They determined the constant KD of the equilibrium between free ions and ion pairs (Schemes 10-12 and 10-13) conductometrically in five solvents (H20, MeCN, MeOH, EtOH, and Me2CO). An inverse linear relationship was found between the ratio of products [ArOS]/[ArF] (where ArOS is the product of heterolytic solvolysis) and Kd/e (e = dielectric constant). This result indicates that solvolysis products are formed mainly from free diazonium ions, whereas fluoro-de-diazoniation takes place in the ion pair. Of the solvents used, acetone gives the lowest value of KD, and thus the yield of the fluorinated product is highest in this solvent. 

Displacement of the 3-hydroxyl group of 74 was carried out with Et2NSF3 (DAST) (DAST - diethylaminosulfur trifluoride) in dichloromethane. The expected fluorinated product 75 on treatment with aqueous perchloric acid led to regioselective epoxide ring opening to give 76, which on treatment with hydrazine hydrate at 100 °C for 18 h yielded 3,4-dihydroxy-8-oxo-octahydropyridazino[l,6-r/][l,2,4]triazine-l-carboxylic acid phenylamide 77 (Scheme 3) <1997T9357>. 

The reactivity of dipyrrolylmethane 236 has similarly been exploited in its reaction with 4-dimethylamino-l,l,l-trifluoro-3-buten-2-one 239 and trifluoromethanesulfonic anhydride to generate the iminium ion 240 followed by hydrolysis to give the fluorinated product 241 in 56% yield (Scheme 16) <2003CHE776>. 

An ideal derivation would be via direct fluorination of Re and hydrolysis of ReF7 to perrhenic acid, especially since A/2f (Re207) has been determined by oxygen combustion of Re. However, ReF6 is the main fluorination product under normal conditions. It seems that further work on iodine fluorination to produce enhanced yields of the hepta-fluoride, and the hydrolysis of IF7 to periodic acid, is potentially the best route for improving the AHf(F( aq)) value. 

Asymmetric C-H amination has progressed through the apphcation of rathenium(II) porphyrin catalysts. Che has employed fluorinated ruthenium porphyrin complexes with added AI2O3 (in place of MgO) to catalyze suifamate ester insertion (Scheme 17.31) [98]. These systems show exceptional catalyst activity (>300 turnovers) and afford product yields that are comparable to rhodium tetracarboxylate-promoted reactions. Of perhaps greater significance is that the use of the chiral rathenium complex... 

In a recent review, Tao etal. [34] describe the partial fluorination and the perfluorination of organics with particular emphasis on medically important compounds and pharmaceuticals. The selective electrofluorination (SEF) of olefins and active methylene groups is reviewed by Noel et al. [35] In the case of heterocycles, nuclear fluorination is known to be the predominant process. However, in aromatic compounds, nuclear substitution as well as addition proceeds simultaneously, leading to the formation of a mixture of products. The influence of solvents, supporting electrolytes, and adsorption on product yield and selectivity is summarized and evaluated. Dimethoxyethane is found to be a superior solvent for SEF processes. Redox mediators have been employed to minimize anode passivation and to achieve better current efficiencies. 

Typically, these reactions yield only partially fluorinated products, introducing one, two, or a maximum of four fluorine atoms into the organic substrate. This is in stark contrast to the other methods described later, which readily yield perfluorinated products. 

The process usually yields fully fluorinated products, with the great benefit that certain important functional groups are retained in the products. 

Generally, the fluorination products obtained could be classified into three groups - i) degradation products, ii) cyclisation products, iii) expected products - with the yields of the desired compounds ranging from fair to good, depending upon the structure of the acid skeleton, and the nature and position of the substituent (e.g., to block cyclisation by-product formation). 

The application of a very similar system using foam electrodes has been patented by ICI pic [79] for the controlled fluorination of partially fluorinated volatile materials to give excellent yields of more highly fluorinated products. 

Using this equipment, the group studied the fluorination of methanedisul-phonyl fluoride [127] at constant anodic potential (vs Cu/CuF2 reference electrode) and report product yields of difluoromethanedisulphonyl fluoride of... 

In an earlier patent [148] they claim that a two-stage fluorination at different specific voltages and current densities (0.1-1.0 A dm-2, and 2-4 A dm 2) significantly increases the yield of fluorinated products. 

A slightly exothermic reaction took place when the antimony trifluoride was gradually added to the chlorophosphine. The temperature in flask I was maintained sufficiently high to allow distillation of the volatile fluorination products immediately after their formation. Material boiling at 35° to 55° was carefully redistilled at a slow rate. Chloromethyldifluorophosphine was collected, boiling at 33.5°-34.5°. Yield was 29.7 grams (83.5%). 

Fluorination of tris(fluorosulfonyl)methane (10) with xenon difluoride in dichlorodifluoro-methane solution gives fluorotris(fluorosulfonyl)methane in quantitative yield.24 In contrast, no fluorination product has been obtained in the reaction of tris(trifluoromethylsulfonyl)meth-ane with xenon difluoride.25... 

The hydrogen fluoride catalyzed fluorination of norbornene by xenon difluoride at room temperature leads to a mixture of at least seven components,39 but under milder conditions (— 78 to 26 C, 22 hours) the reaction affords a mixture of two main products 2-e,xo-5-cxo-difluoro-norbornane and 2-c-wfo-5- Yo-difluoronorbornane, ratio 2 1, in a total yield of 51-76%. If the same reaction is carried out in a limited temperature range between — 46 and — 39 C the yield of these products decreases, their ratio becomes equal, and the main product is 2-exo-l-ff //-difluoronorbornane (42 %).40 The structure dependence of the fluorination products of norbornene with xenon difluoride was studied. Solvent, temperature, reaction duration, catalyst (hydrogen fluoride, boron trifluoride, trifluoroacetic acid, pentafluorobenzenethiol) and the routes of product isomerization were analyzed.41-42... 

To overcome problems associated with the removal of iodobenzene and its derivatives formed upon fluorination of arylalkenes and arylalkynes with (difluoroiodo)arenes, polymer-supported (difluoroiodo)arenes were proposed.139 With these agents, the separation procedures are reduced to filtration of the iodinated polymer. For this purpose popcorn polystyrene is io-dinated and then transformed into the difluoroiodide by treatment with xenon difluoride in the presence of hydrogen fluoride in dichloromelhane at 25 C. The amount of active fluorine bonded to iodine atoms on the polymer support is estimated by iodometric titration. The reactions with phenyl-substituted alkenes result in rearranged gew-difluorides. The procedure provides the same fluorination products as with (difluoroiodo)benzenc (see Section 4.13.) but in much higher yields, e.g. PhCF2CH2Ph (96%), PhCF2CH(Me)Ph (95%). PhCH2CF2H (86%), and l,l-difluoro-2-phenylcyclopentanc (91 %). 

Various steroids are fluorinated by conversion into the enolates, followed by fluorination with perchloryl fluoride to give the 16-fluorinated products 16.19 28 The Schiff base of 7-aminodeacetoxyeephalosporanic acid tart-butyl ester is converted into an anion with potassium tm-butoxide,29 while further reaction with perchloryl fluoride diluted with nitrogen at — 50 C gives 7-(benzylideneamino)-7-fluorodeacetoxycephalosporanicacid fer/-butyl ester (17) in high yield. An attempt to prepare 2-fluoropodophyllotoxin by reaction of the enolate with perchloryl fluoride resulted in a violent explosion.30... 

The electrochemical perfiuorination was carried out in a PTFE cell (capacity 450 raL) with nickel anodes (4 dm2) and cathodes at ca. 19 C, 5 6.5 V, and 5 10 A. The cell was fitted with a reflux condenser, maintained at —20 C, and cooling traps to condense volatile products. The fluorination was started with about 10% concentration of the substrate, additional portions were added during the electrolysis. 4-(2-F,thoxy-ethyl)inorpholine (3. R = Et 69.4 g) was added and a load of 972 kC was passed (75% of the theoretical amount). Liquid, in the electrolyte insoluble fluorination products, was drained olT [yield of pcrfluoro[4-(2-ethoxyethyl)morpholine] was 20-30 % j, washed wilh H20 and aq NaHCO, refluxed for 12 h with EtOH/ KOH, again washed with H20, and distilled. During this procedure 10 to 30% of the obtained perfluorinated product was lost. 

The result of the reaction of sulfur tetrafluoride with alcohols strongly depends on the structure of the alcohol. Simple aliphatic alcohols, such as methanol, ethanol and propan-2-ol, give alkyl ethers as the main product with only small amounts of fluoroalkanes.41 42 Yields of fluorinated products increase with increasing acidity of the hydroxy group and, in general, the reaction is only synthetically useful with alcohols equally or more acidic than tropolone (p K, = 6.42). 

Ratio (arene/1 d) > 2 1 moles. b No reaction. c Without solvent. d NMR yield (a percent of fluorinated products). 

When estra-l,3,5(10)-trien-3-ols are treated with Wfluorobis rifluoromethylsulfonyljamine (Id) in chloroform the ortho and para fluorination products 18-20 are formed. In contrast, when acetic acid is used as a solvent, fluorination in the para position occurs selectively and 10/ -fluoroestra-1,4-dien-3-one derivatives 20 are formed in high yield.147... 

A comparison between the observed rate constants of electrophilic fluorination and the calculated rates for electron transfer gives, for the first time, kinetic proof that nucleophilic attack at fluorine has to occur in order to explain the high reaction rates. The low yields of fluorinated products under conditions where electron transfer becomes important are an indication that Sn2 and electron transfer are competing and different pathways.10,11... 

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