Potassium fluonde

Anhydrous hydrogen fluonde, potassium fluonde, and sodium fluonde have all been used to promote the chlorine-fluonne exchangein tetmchloropyrukizine All three fliionne sources replace the chlonne in position 3 first Both sodium and potassium... 

A second variable is the amount of residual moisture present in the extremely hygroscopic potassium fluonde Solvents are often used to remove this moisture hy azeotropic distillation When the reaction mass is anhydrous, the solvent is... 

The conversion of octachloronaphthalene to octafluoronaphthalene with potassium fluoride and either 18-crown-6, dibenzo-18-crown-6, cis,j>m,cis-dicyclohexano-18-crown-6, cis,anti,cis-dicyclohexano-l 8-crown-6, or irons,syn,trails-dicyclohexano-18-crown-6 demonstrates that 18-crown-6 or dibenzo-18-crown-5 increases the yield and selecuvity and decreases the reaction time [55] Treatment of 3,4-dichloro-],2,5-thiadiazole with potassium fluonde in sulfolane with and without 18-crown-6 present shows that less severe conditions can be used with either 18-crown-6 or dibenzo-18-crown-6 to form 3,4-difluoro-l,2,5-thiadiazole (equation 34)... 

A slurry of pure calcium fluoride in a solution of potassium fluoride in methanol is slowly evaporated to dryness (KF CaF molar ratio of 1 5) for ca 1 h at 80 °C under reduced pressure Fluonnation of benzyl bromide for 2 h at 120 °C in sulfolane gives 74% yield (92% conversion), compared with 36% with potassium fluonde alone... 

Potassium nitrite by-product can react with nitroaromatic substrate to suppress yields of aryl fluorides Modest yields (40-60%) of fluorophthafic anhydride are obtained from 3- or 4-nitiophthalic anhydride and potassium fluonde due to formation of by-product dipotassium salt of 3- or 4-nitrophtlialic acid [1/3,114, 115] (equation 33) Higher yields (93%) of 3-fluorophfhalic anhydride can be realized by regenera tion of 3-nitrophthalic anhydride from the dipotassium salt with thionyl chloride, followed by addition of fresh potassium fluoride [7/5] (equation 33)... 

When vmyl silicon tnfluonde is treated with two equivalents of potassium fluonde, a new reagent, a dipotassium organopentafluorosilicate, is formed [101] This intermediate has found applicahon as a component in an efficient stereoselective copper chlonde-promoted couplmg reaction (equation 81)... 

Boron tnfluonde also reacts with hydroxy acndones to form difluoro boron complexes [111] (Table 28) Another route to fluoroboraties involves transhalogen-ation by fluonnation of the correspondmg chloro- and bromoboranes with lithium or potassium fluonde under mild conditions [112] (Table 29)... 

Tetrakis(trifluoromethyl)dithietane is generated by dimerization of hexa-fluorothioacetone which is prepared m situ from hexafluoropropylene with potassium fluonde and sulfur [789] or with sulfur and antimony pentafluoride [190] (equation 27)... 

The use of cesium fluoride is limited because of its cost and its availability as a truly anhydrous reagent. Its use with 18-crown-6 shows a 5 times higher rate for the formation of benzyl fluoride from benzyl bromide when compared with cesium fluoride or potassium fluonde supported on calcium fluoride [21] Either cesium fluoride or potassium fluoride supported on calcium fluoride (Procedures 5a and 5b, p 194) provides about a twofold improvement over either unsupported alkali metal fluoride [55, 69]. Cesium fluoride and Aliquat 336 convert benzyl bromide to the fluonde in 94% yield. Using tetrabutylammonium fluoride in place of Aliquat... 

Condensation of sodium phenoxide with 2,2,2-trifluoroethyl iodide gives a product of direct substitution in a low yield, several other ethers are formed by elimination-addition reactions [7] Use of mesylate as a leaving group and hex amethyl phosphoramide (HMPA) as a solvent increases the yield of the substitution [5] Even chlorine can be replaced when the condensation is performed with potassium fluonde and acetic acid at a high temperature [9] (equations 6-8)... 

Desflurane can be made by fluonnation of isoflurane with potassium fluonde [/J] or with bromine tnfluonde [14] (equation 2) Although approximately six times more desflurane than isoflurane is required for anesthesia, it achieves the anesthetic state and the patient recovers from this state more rapidly This feature seems to be of interest to some anesthesiologists One negative property is that it irritates the breathmg passageway, especially in children Desflurane is flammable at higher levels of anesthetic use It is the least metabolized of all the commercial anesthetics, producing tnfluoroacetic acid and fluonde ion [75]... 

Another approach is to omit the solvent andrun the reaction mAet supercritical conditions where potassium fluoride dissolves in the superheated reactant This approach is illustrated by the conversion of 2-chloromethoxy-l,l,l,3.3,3-hexa fluoropropane to 2-fluoromethoxy-l,1,1,3.. hexafluoropropane with either potassium fluonde or sodium fluoride as the fluorine source (equation 31)... 

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