Reagents tetrabutylammonium fluoride

Various sources of fluoride ion have been investigated, of which highly nucleophilic tetraalkylammonium fluorides ate the most effective Thuf, fluoro alkyl halides and N (fluoroalkyl)amines are efficiently synthesized by treatment of the corresponding trifluoromethanesulfonic esters with tetrabutylammonium fluoride trihydrate in aprotic solvents [5fl] (equation 34) The displacement reactions proceed quantitatively at room temperature within seconds, but tail with hydrogen fluoride-pyridine and give reasonable yields only with hydrogen fluo ride-alkylamine reagents... 

Thus removal of water from classical rather inactive fluoride reagents such as tetrabutylammonium fluoride di- or trihydrate by silylation, e.g. in THF, is a prerequisite to the generation of such reactive benzyl, allyl, or trimethylsilyl anions. The complete or partial dehydration of tetrabutylammonium fluoride di- or trihydrate is especially simple in silylation-amination, silylation-cyanation, or analogous reactions in the presence of HMDS 2 or trimethylsilyl cyanide 18, which effect the simultaneous dehydration and activation of the employed hydrated fluoride reagent (cf, also, discussion of the dehydration of such fluoride salts in Section 13.1). For discussion and preparative applications of these and other anhydrous fluoride reagents, for example tetrabutylammonium triphenyldifluorosilicate or Zn(Bp4)2, see Section 12.4. Finally, the volatile trimethylsilyl fluoride 71 (b.p. 17 °C) will react with nucleophiles such as aqueous alkali to give trimethylsilanol 4, HMDSO 7, and alkali fluoride or with alkaline methanol to afford methoxytri-methylsilane 13 a and alkali fluoride. 

Because allyltrimethylsilane 82 or benzyltrimethylsilane 83 can be regarded as combinations of the hard trimethylsilyl cation and the soff allyl or benzyl anions, pyridine N-oxide 860 reacts with excess 82 or 83 in the presence of catalytic amounts of tetrabutylammonium fluoride di- or trihydrate in THF to give 2-allyl-or 2-benzylpyridines 948 and 950 [60]. The general reaction of silicon reagents such as 82 and 83 or of trimethylsilyl cyanide 18 with fluoride to generate allyl or... 

The THF-soluble salt tetrabutylammonium fluoride (TBF) is a common source of fluoride. An alternative reagent is tetrabutylammonium triphenyldifluorosilicate (TBAF).115 Unsymmetrical allylic anions generated in this way react with ketones at their less-substituted terminus. 

A new deboronating agent for icosahedral carboranes, dry tetrabutylammonium fluoride (TBAF), was found to degrade some small carboranes, ortho- and t( / -carborane(COMC (1995 ) 6.2.4.6).55 As it was clear that water plays a part in the process, this reagent in its wet form was used to deboronate a large number of z< /carborane derivatives.257-259 264 Wet TBAF proved to be superior to alcoholic potassium hydroxide for effective deboronation of meta-... 

Reaction of allylic silanes with aldehydes and ketones can also be induced by fluoride ion, which is usually supplied by the THF-soluble salt tetrabutylammonium fluoride (TBAF). Fluoride adds at silicon to form a hypervalent anion with much enhanced nucleophilicity.73 An alternative reagent to TBAF is tetrabutylammonium triphenyldi-fluorosilicate.74... 

The hetero[3,2- ]thiophenes were prepared from the corresponding 1,4-dilithium intermediates, derived from 3-bromo-2-(trimethylsilyl)ethynylthiophene 362. Treatment of 363 with /< /7-butyllithium and the appropriate reagents resulted in the formation of 364, which afforded targets 12, 13, 15, and 365-367 by treatment with tetrabutylammonium fluoride (TBAF) (Scheme 38) <1997H(45)1891>. 

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... 

Lithium butyldimethylzincate, 221 Lithium sec-butyldimethylzincate, 221 Organolithium reagents, 94 Organotitanium reagents, 213 Palladium(II) chloride, 234 Titanium(III) chloride-Diisobutylalu-minum hydride, 303 Tributyltin chloride, 315 Tributyl(trimethylsilyl)tin, 212 3-Trimethylsilyl-l, 2-butadiene, 305 Zinc-copper couple, 348 Intramolecular conjugate additions Alkylaluminum halides, 5 Potassium t-butoxide, 252 Tetrabutylammonium fluoride, 11 Titanium(IV) chloride, 304 Zirconium(IV) propoxide, 352 Miscellaneous reactions 2-(Phenylseleno)acrylonitrile, 244 9-(Phenylseleno)-9-borabicyclo[3.3.1]-nonane, 245 Quina alkaloids, 264 Tributyltin hydride, 316 Conjugate reduction (see Reduction reactions)... 

Tetrabutylammonium fluoride, 286 Reformatsky reaction Reformatsky reagent, 348 Zinc, 346... 

Organocopper reagents, 207 Organovanadium reagents, 219 By desilylation of vinylsilanes Tetrabutylammonium fluoride, 286 By desulfurization of vinyl sulfides and related sulfur compounds Sodium dithionite, 281 Elimination reactions By dehalogenation Dichlorobis(cyclopentadienyl)-titanium, 102... 

The ring opening of several oxiranes by various thiosilanes (promoted by tetrabutylammonium fluoride as catalyst) occurs regioselectively under mild conditions.32 With the amphiphilic reagents isothiocyanatotrimethylsilane and O-trimethylsilyl thioacetate the sulfur centre exclusively attacks the oxiranes. A plausible reaction mechanism was suggested to explain the role of F as promoter. 

For the removal of this protecting group, tetrabutylammonium fluoride in oxolane is the most frequently used [388, 389, 409-411]. A much simpler reagent to prepare, potassium fluoride — crown ether, has been introduced for the same purpose [427]. Silyl group at 0-2 of nucleosides is cleaved more rapidly [411] than at 0-5. Acyl migrations occurred under the tetrabutylammonium fluoride-catalyzed desilyla-tion [432, 434, 443], Differencies between the primary and secondary position were also observed for acid- or base-catalyzed solvolysis [391, 409-412], 5 -0-(7ert-butyl-dimethylsilyl)nucleosides are much more labile towards acid than either 2 - or 3 -silyl ethers [391, 410-412], whereas the situation is reversed for base hydrolysis [411], /V-Bromosuccinimide in aqueous DMSO is another alternative for the removal of this type of silyl group [444]. 

The treatment of reagent 109 with tetrabutylammonium fluoride in dichloro-methane at room temperature generates benzyne, which can be trapped with the appropriate diene to afford the benzyne adducts 110-114 in high yields (Scheme 48) [105, 106]. Similarly, 3- and 4-methylbenzynes can be efficiently... 

Synthetic applications of the /1-pathway include conversions of the TIPS allylic azides to enones with tetrabutylammonium fluoride, ionization of the C-N3 bond with alkylaluminum reagents and capture of the TIPS enonium ions with carbon nucleophiles, and development of a procedure for y-lactamization [15-17]. Allylic azidonations of TIPS enol ethers have also been incorporated into syntheses of (+)-pancratistatin [18,19] and the core structure of lycorane [20]. 

Glyculosonates of type 105 and 4-glyculosonates such as 106 were prepared from protected aldonolactones by Reformatsky-like reactions.281 Similar products, with either furanose or pyranose rings, can also be made from aldonolactones by using such reagents as ethyl 2-trimethylsilylacetate in the presence of tetrabutylammonium fluoride.282... 

Table 16 shows the influence of reaction conditions and of activation reagents such as TMSC1, hexamethylphosphoric triamide (HMPA), M-methyl-imidazole (NMI), saccharin and tetrabutylammonium fluoride (TBAF) on the DS of silyl dextran. For complete silylation, a mixture of 1.8 mol HMDS and 0.2 mol chlorotrimethylsilane (TMSC1) per mol OH groups have to be used. The more reactive TMSC1 reacts in a first step with hydroxyl groups to trimethylsilyl dextran and HC1. Subsequently, the HC1 cleaves HMDS in TMSC1 and NH3 [218]. Complete silylation of dextran could also be carried... 

In analogy to the preparation of the cyclopropanone hemiacetal 3 (vide supra, Eq. (1)7), reductive cyclization of the piperidide of 3-chloropropionic acid 193 with sodium in ether in the presence of ClSiMe3, gave the 1-piperidino-l-trimethylsilyloxy-cyclopropane 194 a which was converted to the cyclopropanol 194 b upon treatment with methanolic tetrabutylammonium fluoride. Both 194 a and 194 b can be used for the ready generation of cyclopropane derivatives thus the silyl ether 194a could be reacted directly with the vinylic Grignard reagents 195 to provide the vinyl cyclopropane derivative 196, (Eq. (61)128). 

Tetrabutylammonium fluoride is very hygroscopic. A drybox may be used to avoid rapid manipulation of the fluoride in the atmosphere and exposure of the reagent in the storage vessel to moisture. Alternatively, hydrated tetrabutylammonium fluoride (Note 11) can be dried in the reaction vessel and used directly. 

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