Potassium fluoride in dimethylformamide

In the presence of potassium fluoride in dimethylformamide, trifluoroacetyl nitrite converts perfluoroisobutylene to tris(trifluoromethyl)nitrosomethane via the carbanion generated by the nucleophilic attack of fluoride ion on perfluoro-isobutylene [5] (equation 5)... 

Good yields of fluoro-substituted aromatics have been obtained when 1 -chloro-2,4-dinitrobenzene (10) and 1-chloro-2,6-dinitrobenzene (13) are first treated with pyridine or methyl-substituted pyridines to form intermediate salts 11 and 14 and then reacted with potassium fluoride in dimethylformamide or nitrobenzene to give the fluorides 12 and 15."°... 

Dinitrobenzene is unreactive under these conditions. Replacement with fluorine appears to take place only when a halogen atom is present in the ortho- or meta-position relative to the nitro group. 4-Bromo-l,2-dinitrobenzene (3) has been converted to 4-bromo-2-fluoro-l-nitrobenzene (4) by heating with potassium fluoride in dimethylformamide at 100 C for 2 hours.138... 

Andreev and co-workers have undertaken extensive studies on the reactions of allyl, crotyl, and propargyl alcohols with 2-substituted pentafluoropropenes 14.11 Allyl and crotyl alcohol react at 5-20 C with various 2-substituted pentafluoropropenes 14 in the presence of potassium fluoride in dimethylformamide to give -substituted a-(trifluoromethyl) esters 16. Saponification yields the corresponding acids. 

Aryl ethers can also represent the dominant product For example, 3,3 -bis(tri fluoromethyl)-5,5 -dinitrodiphenyl ether is obtained in 54% yield from 3,5-dim trobenzotnfluoride and potassium fluoride in A(A-dimethylformamide with catalytic amounts of water at 160 °C after 24 h [110]... 

Most recent syntheses of fluorinated benzothiazoles make use of nucleophilic substitution. Potassium fluoride in acetonitrile converted 40 into the 2-fluoro derivative (R = 6-nitro) in 99% yield. When the solvent was dimethylformamide the 2-dimethylamino derivative was formed instead [80JCS(P1)2358], and similar behavior was reported earlier (77BSF171). 

Several fluoro analogs of ketoses have been reported 1,6-dideoxy-1,6-difluoro-D-fructose was readily obtained from 2,3-O-isopropyli-dene-l,6-di-0-p-tolylsulfonyl-)3-D-fructofuranose by treatment with potassium fluoride in 1,2-ethanediol under a stream of carbon dioxide.96 Surprisingly, although the 6-sulfonyloxy group would be expected to be more reactive than the 1-sulfonyloxy group,97-99 no selectivity was observed. The failure to obtain 1-deoxy-l-fluoro-D-fructopyranose96 from 2,3 4,5-di-0-isopropylidene-l-0-(methylsulfonyl) (or p-nitro-phenylsulfonyl)-/3-D-fructopyranose or phenyl 3,4,5-tri-O-acetyl-l-O-(methylsulfonyl)-/3-D-fructopyranoside by treatment with potassium or sodium fluoride in 1,2-ethanediol, N,N-dimethylformamide, or form-amide at elevated temperatures may be attributed to the fact that nu-... 

The effectiveness of various sources of fluoride ion in the displacement of the trifluoromethanesulfonic group has been demonstrated while introducing a fluorine atom into the five-membered carbocychc ring of a prostaglandin precursor Treat merit of the corresponding triflyl derivative with potassium fluoride in acetonitrile or with cesium fluoride in refluxing dimethylformamide or hexamethylphosphonc... 

To a cooled solution of 3.4 g of 6a-fluoro-16a,17a-isopropylidenedioxypregna-l,4,9(ll)-trien-21-ol-3,20-dione in 20 ml of 9 1 chloroform pyridine is added in small portions 1.4 g of tosyl chloride. The reaction mixture is allowed to stand for 14 hours at 0°C and is then washed with dilute hydrochloric acid, water and sodium bicarbonate solution. The chloroform is removed by evaporation under reduced pressure and the residue is dissolved in acetone. This acetone solution is added to a refluxing suspension of 10 g of potassium fluoride in 50 ml of dimethylformamide. After refluxing for 5 hours, the mixture is cooled and poured into water. The solid which forms is collected by filtration, dried and recrystallized from acetone and hexane to yield 6a,21-difluoro-16a,17a-isopropylidenedioxypregna-l,4,9 (ll)-triene-3,20-dione, M.P. 267°C (dec.), [a]D = +9°. 

Earlier methods of preparing 2,2,4,4-tetrakis(trifluoromethyl)-l,3-dlthletane (hexafluorothioacetone dimer, HFTA dimer) include the reaction of hexafluoropropene (HEP) and sulfur over a carbon bed at 425< C,3 and the reaction of HFP and sulfur in tetramethylene sulfone at 120°C 1n the presence of potassium fluoride (autoclave). Dimethylformamide appears to be a far superior solvent for this reaction, permitting the use of atmospheric pressure and modest temperatures, as well as affording a cleaner product. 

An improved method of 3-trifluoromethylthiophene 79 synthesis was the reaction of methyl-2-chloro-2,2-difluoroacetate with 3-iodothiophene 98 in the presence of copper(I) iodide and potassium fluoride in N,N-dimethylformamide. The reaction was carried out at 125 °C and gave 3-trifluoromethylthiophene 79 in 46 % as the sole product [61], The proposed mechanism includes the formation of the copper(I)... 

The chlorine/fluorine exchange reaction is an equilibrium reaction and can be influenced by altering the pressure, time, temperature and the ratio of the reactants. Usually high-temperature igh-pressure autoclave technique was used for shifted the equilibrium to fluorinated product. Anhydrous potassium fluoride in tetraglyme with a catalytic amount of dicyclohexano-18-crown-6 at 15-16 °C converted 2,4-dichloropyrimidine into 2,4-difluoropyrimidine. This process solved the problem of having to use an autoclave or dimethylformamide as solvent, because in tetraglyme (bp 275-276 °C) the more volatile fluoro products could be distilled directly from the reaction mixture uncontaminated by solvent. Under similar conditions 2-chloro-5-methoxypyrimidine was converted into the 2-fluoro analogue [65]. 

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