Perchloryl fluoride reactions

Perchlorylation. The stabiUty of perchloryl fluoride [7616-94-6] FCIO, makes possible perchlorylation of aromatics, a reaction closely related to the Friedel-Crafts acylation (159) ... 

The enamines, enol ethers and enol acetates of A -3-keto steroids provide important substrates for fluorination with FCIO3. Reaction of such A -enol ethers and acetates (6) with perchloryl fluoride results in 6a- and 6jff-fluoro-A -3-ketones (7) and (8), the latter representing the more abundant isomer. Tetrahydrofuran or dioxane-water mixtures appear to be particu-... 

The reaction with the jff,y-unsaturated A °k3 ketone (20) in pyridine proceeds in 25% yield to the 10j -fluoro ketone (21). a,yS-Unsaturated ketones do not react with perchloryl fluoride. 

A novel reaction of perchloryl fluoride with aromatic substrates was discovered by Neeman and Osawa, the oxofluorination reaction. These authors found that reaction of indene with perchloryl fluoride in dioxane-water yields five products, the major product being, 2-fluoroindanone. When applied to 6-dehydroestradiol diacetate (24) there is obtained as the major product the 7a-fluoro-6-ketone (25). Borohydride reduction of the... 

C—O bonding and Cl—F fission of the intermediate cw-fluoro chlorate (29a), which in turn undergoes oxidation to the fluoro ketone (25) by a concerted elimination of chlorous acid. A similar transition state (30) approximating an allylic carbonium ion could be involved in the reaction of the dienol derivatives (6) with perchloryl fluoride, which would be expected to give rise to the c/5-adduct (30a). Reaction of the latter with water leads to product and chlorate ion. 

The pyrrolidine enamines of /l -3.]cetosteroids (111), on alkylation with methyl iodide, gave mainly the N-alkylated product (5,55) in nonpolar solvents such as benzene. The reaction in more polar solvents gave the 4-methylated product (5.S). The reaction of (111) with perchloryl fluoride involves attack at the C-4 atom to give, after acid hydrolysis, either 4-fluoro-zJ -3-ketone (119) or 4,4-difluoro-zJ -3-ketone 120), depending on the reaction conditions (59). 

The final route to fluorine compounds is electrofluorination (anodic fluorination) usually in anhydrous or aqueous HF. The preparation of NF tFl3 j (x = 1, 2, 3) has already been described (p. 818). Likewise a reliable route to OF2 is the electrolysis of 80% FIF in the presence of dissolved MF (p. 638). Perchloryl fluoride has been made by electrolysing NaC104 in FIF but a simpler route (p. 879) is the direct reaction of a perchlorate with fluorosulfuric acid ... 

Miscellaneous Reactions.- The Schlosser-Wittig reaction of ylide (209) with aldehyde (208) and treatment of the intermediate 6-oxido ylide with perchloryl fluoride has been used to construct the 13-fluoro unit (210) in a total synthesis of (+)-13-fluoroprosta-... 

An attempt to convert benzocyclobutenylpotassium (prepared from the reagents above) to the fluoro derivative at — 70°C with excess perchloryl fluoride led to a violent explosion when the reaction mixture was removed from the cooling bath after stirring for an hour. 

At ambient temperature, perchloryl fluoride is unreactive with the compounds above, but reaction is explosive at 100-300°C, or if the mixtures are ignited. 

A reaction mixture in aqueous methanol exploded violently at —65°C. (Hydrazine-perchloryl fluoride redox reaction ) A previous reaction at 20°C had been uneventful, and the low-temperature explosion could not be reproduced. 

Addition of solid methoxide to a reaction vessel containing methanol vapour and gaseous perchloryl fluoride caused ignition and explosion. This could be avoided by adding all the methoxide first, or by nitrogen purging before addition of methoxide. 

Rapid heating to above 50°C in an autoclave caused an explosive reaction. Perchloryl fluoride... 

The highest yield of perchloryl fluoride (97%) was achieved with a mixture of fluorosulfonic acid and SbFj as fluorinating medium. Potassium, sodium, lithium, magnesium, barium, calcium, and silver perchlorates and perchloric acid itself undergo the reaction. Commercial reagents are used and their additional puriflcation is not necessary unlike all the previous methods the preparation of perchloryl fluoride by this method can be carried out at room temperature. At high temperature (100°-135°C) the reaction time is 1-10 min in all, which allows the process to be carried out continuously in a packed column. The purity of product obtained after the usual puriflcation reaches 98% and over air and carbon dioxide are present as trace impurities 23). 

Perchloryl fluoride is thermally stable up to about 400°C. The thermal decomposition of FCIO3 in quartz at pressures between 5 and 930 mm and temperatures between 465° and 495°C was studied by Gatti et al. 112). They found that the decomposition reaction. 

Perchloryl fluoride does not attack glass at moderate temperature, but decomposes at 25°C on contact with activated Si02 or AI2O3, particularly in the presence of small amounts of H2O. With other surface-active materials, such as charcoal, ignition may take place. However, there is no reaction at room temperature with synthetic zeolites. It passes freely through a 4 A molecular sieve, but is completely absorbed... 

R.E. Ehrenkaufer, R.R. MacGregor, Synthesis of [ F]-perchloryl fluoride and its reactions with functionalized aryllithiums, Int. J. Appl. Radiat. Isot. 34(1983)613-615. R. Chirakal, G. Firnau, J.G. Schrobilgen, J. McKay, E.S. Garnett, The synthesis of [ F]xenon difluoride from [ F]fluorine gas, Int. J. Appl. Radiat. Isot. 35 (1984) 401-404. 

S. Nakanishi, R.L. Morgan, E.V. Jensen, 4-Fluorinated steroids from the reaction of perchloryl fluoride with steroid enamines, Chem. Ind. (London) (1960) 1136-1137. 

A synthesis of the B-ring aromatic corticosteroid (286), the analogue of cortex-olone, started with the previously reported B-ring aromatic norpregnane (285). Development of the corticosteroid side-chain employed bromination of the 17a-hydroxy-20-oxo-derivative with trimethylphenylammonium bromide perbromide. " Reaction of perchloryl fluoride with the mixed enol ethers (287) and (288) provided, after hydrolysis, the 17a-fluoro-20-oxo-compound (290) and the 21-fluoro-20-oxo-compound (291). In contrast, the enamine (289) led only to the 17a,21-difluoro-20-oxo-compound. A series of 17a-acyloxy-21-deoxy-... 

Fluorination of sulfonamides 147 and 148 takes place upon deprotonation with NaH and reaction with perchloryl fluoride, FCIO3, to give products 149 and 150 (Scheme 19) <2000JOC7583, 2000CPB1954>. The resulting A-fluorosultams 149 and 150 have been used for the asymmetric fluorination of aryl ketone enolates (vide infra). 

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