Tetrabutylammonium fluoride TBAF

The Henry reactions of A, ALdibenzyl-L-phenylalaninal with nitroalkanes using 1.2 equiv of tetrabutylammonium fluoride (TBAF) as the catalyst proceed in ahighly stereoselective manner, as shown in Eqs. 3.82 and 3.83. This reaction provides rapid and stereoselective access to important molecules containing 1,3-diamino-2-hydroxypropyl segments, which are cenhal structural subunit of the HIV protease inhibitor amprenavir (in Scheme 3.21). 

Tetrabutylammonium fluoride (TBAF) is usually used in the form of the trihydrate or as a solution in tetrahydrofuran (THF). The pure form is difficult to isolate, owing to decomposition to FFF, tributylamine, and but-l-ene [18, 19] on dehydration. It has been used for a variety of reactions, including as a catalyst for various reactions with silicon compounds [20, 21]. One of its main uses is in the cleavage of silyl ether protecting groups [22]. 

A solution of tetrabutylammonium fluoride (TBAF) in THF (1.0M) is prepared from colorless, crystalline tetrabutylammonium fluoride trihydrate purchased from Fluka Chemical Corp. 

They react with a wide range of aliphatic and aromatic aldehydes in the presence of catalytic amounts of tetrabutylammonium fluoride (TBAF) to give the trialkylsilyl ethers of P-nitro alcohols with high anti-selectivity (98%). The diastereoselective Henry reaction is summarized in Table 3.2. The products are reduced to P-amino alcohols using Raney Ni-H2 with retention of the configuration of P-nitro alcohols (Scheme 3.12). 

Obtained both from phenyl[2-(trimethylsilyl)phenyl] iodonium trifluoromethane sulphonate and 2-trimethylsilylphenyltrifluoromethanesulfonate in the presence of tetrabutylammonium fluoride (TBAF). They are good benzyne precursors under mild conditions. 

Enantio-pure five-membered cyclic nitrones (154) and (155) were formed in a one-pot synthesis from the corresponding lactols (152) and (153) as the result of their reactions with unsubstituted hydroxylamine and by (a) subsequent treatment with MsCl and NaOH (Scheme 2.55) (310a) or by (b) subsequent treatment with TBDMSC1,12, TPP, imidazole, and tetrabutylammonium fluoride (TBAF) (310b). 

Besides rhodium catalysts, palladium complex also can catalyze the addition of aryltrialkoxysilanes to a,(3-unsaturated carbonyl compounds (ketones, aldehydes) and nitroalkenes (Scheme 60).146 The addition of equimolar amounts of SbCl3 and tetrabutylammonium fluoride (TBAF) was necessary for this reaction to proceed smoothly. The arylpalladium complex, generated by the transmetallation from a putative hypercoordinate silicon compound, was considered to be the catalytically active species. 

The reaction of l-methoxy-3-(trimethylsilyloxy)-l,3-butadiene with enone 286 in refluxing toluene for 48 h, followed by treatment with tetrabutylammonium fluoride (TBAF), gave the adduct 287 as a single diastereomer (Equation 46) <1997T11731>. 

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-... 

Only a few examples exist describing the products from the allenylic/propargylic carbanion resulting from the deprotonation of 18 and reaction with other electrophiles instead of protons which lead to products analogous to 19 [48]. Thus, treating the propargyl compound 21 with tetrabutylammonium fluoride (TBAF) in the presence of benzaldehyde furnishes the C,C-connected compound 22 [41]. 

The aryl bromide 40, prepared from cross-coupling between 1,2-dibromobenzene and (trimethylsilyl)acetylene, was converted to the corresponding arylzinc halide 41a and arylboronic acid 41b for subsequent coupling with the haloallenes 42 to produce the benzannulated enyne-allene 43 in -40% yield (Scheme 20.10) [38]. Desilylation with tetrabutylammonium fluoride (TBAF) then afforded 44 in 67% yield. 

Tetrabutylammonium fluoride (TBAF) trihydrate (99%) was purchased from the Aldrich Chemical Company, Inc. 

Fig. 10 Emission changes of polymer 33 upon addition of tetrabutylammonium fluoride (TBAF). Inset are the respective absorption spectra of the initial solution (0 min, —) and after exposure to TBAF (—). 1.5x10 M in CH2CI2 (repeating group) and TBAF, 1.6x10" M. (Reprinted with permission from Ref. [30]. Copyright 2003 Wiley-VCH Verlag GmbH)...

This reaction proceeds with a variety of aryloxy ligands and a spectrum of substituents R and R at the phosphorus centre. Alkalimetal fluorides, tetrabutylammonium fluoride (TBAF), hypervalent silicon Ph3Sip2 and tin Ph3Snp2 difluorides are suitable fluoride anion donors. The exchange of aryloxy ligand proceeds efficiently in solvents such as THF, MeCN and CH2CI2. 

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... 

Based on the early racemic synthesis of 4 (cis series), it had already been demonstrated that 2-azetidinone ring closure could be achieved via nucleophilic attack of a lithium amine anion on a (3-ester. Cyclization could be accomplished with other strong bases, but sodium bistrimethylsilylamide was found to effect efficient cyclization without significant racemization at C3. During the search for experimentally convenient bases, it was noted that Noyori (Nakamura et al., 1983) reported that tetrabutylammonium fluoride (TBAF) as well as LiF, KF, and CsF could serve as the base in Aldol reactions. Treatment of 17a or 17b with TBAF trihydrate in THF did not affect cyclization. After much experimentation it was found that addition of A,0-bistrimethylacetamide (BSA) to 19 followed by TBAF addition, effected 2-azetidinone ring closure. Further optimization found that use of catalytic TBAF (< 1%) in methylene chloride afforded near quantitative cyclization. 

Cyclizations of o-(a -haloalk oxy)phenols have been widely studied and were used to afford an expedient synthesis of 5-alkyl-2,3-dihydro-l,4-benzodioxins <2004SC2487>. This approach via a nucleophilic substitution was used for the synthesis of 8-substituted-2-hydroxymethyl-l,4-benzodioxane derivatives 164 in an enantiopure form. Use of CsF instead of more basic conditions allowed higher yields and enantiomeric excess (Equation 28) <2001ASC95>. Dry tetrabutylammonium fluoride (TBAF) in THF was required and was basic enough to initiate an intramolecular Sn substitution from the protected phenol 165 to the fluoro-l,4-benzodioxane 166 <1996T6187>. 

The related cyclization of 2-ethynylanilines 67 also represents one of the usefiil methods for the synthesis of 2-substituted indoles since the precursors are easily prepared from 2-haloanilines 66 by Pd-catalyzed cross-coupling with terminal alkynes. Althou cyclizations of such alkynes are normally effected using Cu(I) or Pd(II) species, Sakamoto showed that in the absence of such metals, base catalysis (e.g., NaOEt) alone can accomplish the same goal. This author now reports that tetrabutylammonium fluoride (TBAF) is capable of inducing cyclization to the indoles 68 without affecting functionalities such as bromo, cyano, ethoxycarbonyl, and ethynyl <99JCS(P1)529>. 

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>. 

Pd(PPti3)4, Ag2C03, and an aqueous solution of KOH (77%). Removal of the silyl ether with tetrabutylammonium fluoride (TBAF) and successive oxidation with BaMnC>4 provided the 1 lZ-retinal in 85% yield, Fig. (50). 

A mixture of potassium hydrogen fluoride, 1 M hydrofluoric acid and (V-iodosuccinimide in the presence of tetrabutylammonium fluoride (TBAF) as a phase-transfer catalyst has been shown to effect iodofluorination of alkenes in good yield.163 Dodec-l-ene (6) has been transformed to 2-fluoro-l-iodododecane (7) in 82% yield. TBAF is essential for the reaction to proceed quickly and to improve the yield. The percentage of the side product 1-iodododecan-2-ol is kept to a minimum (0.2%). Many alkenes have been transformed to the corresponding fluoroiodo derivatives by this method.163... 

Further examples are found in references 196 and 197. Tetrabutylammonium fluoride (TBAF) has found many applications in synthesizing several fluoro derivatives via nucleophilic substitution on the appropriate substrates. Organo-fluorine compounds are not only interesting as medicinal drugs, but they are also useful as technical products. 

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