Anhydrous tetrabutylammonium fluoride

To achieve reproducible (R. . ) selectivities in these nitroaldol reactions pure, distilled /m-butyldimcthylsilylnitronates and anhydrous tetrabutylammonium fluoride should be used22. The corresponding trimethylsilylnitronates furnish mixtures of (R, S )- and (R, R )-isomers22. 

D.P. Cox, J. Terpinski, W. Lawrynowicz, Anhydrous tetrabutylammonium fluoride—A mild but highly efficient source of nucleophilic fluoride-ion, J. Org. Chem. 49 (1984) 3216-3219. 

Early workers using anhydrous tetrabutylammonium fluoride (TBAF) may have actually used mixtures of TBAF and tetrabutylammonium bifluoride It is known that excessive drying at 77 °C in a vacuum below 2 torr (1 torr =133 322 Pa) produces the bifluoride salt [20] TBAF can be obtained by drying commer... 

Both experimental and theoretical studies have been reported of fluoro-denitration and fluoro-dechlorination reactions using anhydrous tetrabutylammonium fluoride in DMSO. The absences of ion pairing and strong solvation are critical in contributing to the reactivity of the fluorinating agent24 Quaternary ammonium salts derived from cinchona alkaloids have been shown to be effective catalysts in an improved asymmetric substitution reaction of /1-dicarbonyl compounds with activated fluoroarenes. The products may be functionalized to yield spiro-oxindoles.25... 

Tetrabutylammonium lluoride converts primary tosylates and mesylates smoothly and in high yield into the corresponding fluorides. The syntheses of 4-fluorobut-3-ynal. 8-fluorooctanoic acid, and 1-fluorooctane are recent examples. For secondary substrates it has been shown that the reaction proceeds via a clean Ss,2 mechanism, e.g. reaction of ( —)-(/ )-2-(losyloxy)-octane with anhydrous tetrabutylammonium fluoride gives (+ )-(S)-2-fluorooctane in 54% isolated yield, with an optictil purity + 14.2 (neat) which is higher than that reported... 

Batchwise Fluorodenitration Using Anhydrous Tetrabutylammonium Fluoride... 

Anhydrous tetrabutylammonium fluoride (TBAF) has been reported as being a very powerful fluoride source for the preparation of fliioroaromalic derivatives, via fluorodenitration, under mild reaction conditions. In fact, this reagent is not totally anhydrous and water, in less than one molar equivalent, is present together with < 10 mol% of decomposition products that arise during the synthesis of TBAF from commercially available tetrabutylammonium fluoride trihydrate. 

Anhydrous tetrabutylammonium fluoride is much more reactive than potassium fluoride. Thus. 1.2,4.5-tetrachloro-3-fluorobenzene is obtained in 70% yield when "anhydrous" tetrabutylammonium fluoride in tetiahydrofuran is used at room temperature for 1.5 hours, whereas the same product is obtained in only 37% yield when potassium fluoride in dimethyl-formamide is employed at 147 C for 4.5 hours. ... 

Fluoroaromatic Compounds by Fluorodcnitration with Anhydrous Tetrabutylammonium Fluoride General Procedure ... 

Aryl-1 -fluorocyclopropanes 2 were synthesized by irradiation of a 3-aryl-3-fluoro-3//-diazirine and an alkene (2 > 300 nm, 25 °C) in a screw-top Pyrex Carius tube (Houben-Weyl, Vol. E19b, p980). The starting 3-aryt-3-fluoro-3//-diazirines were prepared from the corresponding 3-aryl-3-bromo-3//-diazirines and anhydrous tetrabutylammonium fluoride. The products were purified by column chromatography on silica gel (purity > 97%). Due to the explosive properties of diazirines, this method is not suitable for large-scale preparations. 

Fluoro-3-pyridyl-3//-diazirines were prepared from the corresponding chlorodiazirines by exchange reaction with anhydrous tetrabutylammonium fluoride in dry dimethylformamide (25°C, 15-20 hours). " ... 

Alkoxy-3-chloro-3//-diazirines are obtained by the chlorination (aqueous sodium hypo-chlorite/dimethyl sulfoxide) of the corresponding amidines. They serve as precursors for the synthesis of 3-fluoro derivatives via the reaction with anhydrous tetrabutylammonium fluoride (for an improved procedure for the dehydration of commercial tetrabutylammonium fluoride trihydrate, see ref 26). This is a much simpler method than the earlier described preparation of 3-fluoro-3-methoxy-37/-diazirine involving the elemental fluorination reaction and a shatteringly explosive fluoronitrogen intermediate. 

Difluoroiodo)arenes are extremely sensitive to moisture and are commonly used as a freshly prepared solution, without isolation. DiMagno and coauthors reported a convenient procedure for almost quantitative generation of PhIF2 in acetonitrile solution by the reaction of PhI(OAc)2 with anhydrous tetrabutylammonium fluoride under absolutely dry conditions [58]. 

Anhydrous tetrabutylammonium fluoride will replace the chlorine on a number of pyridine and quinoline compounds (Scheme 17). A number of 3- and 5-chloropyridines undergo fluorination in high yields. The reaction tolerates various functional groups including esters, cyano, and arenes. Moreover, chlorines on phenyl rings are left untouched. Difluorination of electron-deficient 4,5-dichloropyridines also proceeds in good yields (58— 85%). Finally, both quinoline and isoquinoline were fluorinated in almost quantitative yields (14JOC5827). 

If you examine Table 1.1, you are likely to arrive at the conclusion that fluoride is not a particularly good nucleophile. Recently, Stephen DiMagno and coworkers at the University of Nebraska synthesized anhydrous tetrabutylammonium fluoride (TBAFaj j) via the following reaction, and found it to be a highly active form of nucleophilic fluoride in dry DMSO and other polar aprotic solvents (Sun, H. Dimagno, S. J. Am. Chem. Soc. 2005,127, 2050-2051) ... 

Sun and DiMagno demonstrated the rapid generation of Af-methyl-5-fluoro-4-nitroimidazole from the corresponding chloride using anhydrous TBAF that was generated in situ from KF by fluoride relay (Scheme 60) [75]. hi fluoride relay, the reaction of KF with 2,6-dicyano-tetrachlorobenzene transfers the fluoride to the arene that finally produces the activated anhydrous tetrabutylammonium fluoride (TBAF) upon the addition of tetrabutylammonium cyanide (>60 % yield from KF). Other polar aprotic solvents, such as THF and acetonitrile, are also effective for this SnAt fluorination reaction. 

Preparation of Anhydrous Tetrabutylammonium Fluoride (TBAF) [41e]. Tetra-butylammonium fluoride, vhich is commercially available as its trihydrate, vas dried over P2O5 (30-40 °C, 0.5 mmHg, overnight). 

Almost anhydrous tetrabutylammonium fluoride, prepared by heating the corresponding hydrate at 40-45°C, is an excellent source of naked fluoride in organic synthesis. ... 

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