Tetramethylammonium fluoride

Cyclic sulfates rapidly react with the fluoride ion sources to give monofluoro derivatives Thus, the 2,3-cyclic sulfate of methyl-4 6 O benzylidene p D manno pyranoside cleanly reacts with tetramethylammonium fluoride to give methyl 4,6-0-benzylidene 2 deoxy 2 fluoro-p-D-glucopyranoside-3-sulfate Acid hydrolysis followed by acetylation gives 2 deoxy 2 fluoro-P-D-glucopyranoside triacetate in 84% isolated yield [5S] (equation 38)... 

Double asymmetric induction operates when the azomethine compound is derived from a chiral a-amino aldehyde and a chiral amine, e.g., the sulfin-imine 144 [70]. In this case, the R configuration at the sulfur of the chiral auxihary, N-tert-butanesulfinamide, matched with the S configuration of the starting a-amino aldehyde, allowing complete stereocontrol to be achieved in the preparation of the diamine derivatives 145 by the addition of trifluo-romethyl anion, which was formed from trifluoromethyltrimethylsilane in the presence of tetramethylammonium fluoride (Scheme 23). The substituents at both nitrogen atoms were easily removed by routine procedures see, for example, the preparation of the free diamine 146. On the other hand, a lower diastereoselectivity (dr 80 20) was observed in one reaction carried out on the imine derived from (it)-aldehyde and (it)-sulfinamide. 

The cyclocondensation of (imidazolidin-2-ylidene)malonates (1293, R = z Pr, Ph) and phenyl isocyanate in boiling methylene chloride in the presence of tetramethylammonium fluoride and triethylamine for 10.5 hr gave imidazo[l,5-c]pyrimidines (1403) in low yields [83JAP(K)88383]. 

The first additions to a fluoro-ene were of chlorine and bromine to the C = C bond of allyl fluoride. Meslans used silvcr(I) fluoride, arsenic(III) fluoride, zinc(II) fluoride and antimony(III) fluoride to convert21 acetyl chloride to the fluoride, which was shown to have a reactive C — F bond. The first reaction on a saturated fluoride to retain the C —F link was by Collie.22 Tetramethylammonium fluoride was transformed to fluoromethane on heating which was then converted to chlorofluoromethane by treatment with chlorine. 

Ammonium fluoride itself is not widely used, however, sporadic reference to it exists.187 Tetramethylammonium fluoride gives very good yields of the fluoro derivative 2 on reaction with l,6-anhydro-3,4-di-0-benzyl-2-0-(trifluoromethanesulfonyl)-/l-D-mannopyranose (1) in... 

Nucleophilic substitution on cyclic sulfates 3 with tetramethylammonium fluoride gives 1,2-fluoro sulfates which can be hydrolyzed to l-fluoro-2-hydroxy derivatives.189 Thus propane-1,2-cyclic sulfate 3 affords after hydrolysis l-fluoro-2-hydroxypropane (4). 

Tetramethylammonium fluoride is a highly effective reagent for the preparation of selectively fluorinated aromatic compounds. 2-Nitrobenzaldehyde (5) is converted to 2-fluorobenzalde-hyde (6) in 60% yield.190... 

The reaction of thiopyrylium salts with tetramethylammonium fluoride or AgF yields 2-fluoro-2//-thiopyran together with very minor amounts of 4-fluoro-4//-thiopyran (Equation 111). In like manner, the 2,4,6-tri-/-butyl derivative gives mainly the 2-fluoro compound and bcnzo /( thiopyrylium salts mainly afford 2-fluoro-2//-l-ben-zothiopyran (Equation 112). Both thioxanthylium tetrafluoroborate and the 9-phenyl derivative give the 9-fluoro-thioxanthene. In no reaction was there any evidence of attack of F at sulfur <2003JFC(120)49>. 

MATFA was originally prepared as the product obtained from the dissolution of aluminum trifluoride in aqueous HF in the presence of tetramethylammonium fluoride [44]. Dehydration of the resulting precipitate below 120 °C produces hygroscopic MATFA. 

McLean WJ, Jeffrey GA (1967) Crystal structure of tetramethylammonium fluoride tetrahydrate. J Chem Phys 47 414-417... 

Carbon dioxide Tetramethylammonium fluoride tetrahydrate Liquid membrane TR + R Quinn et al. (1995)... 

The fluoride ion complex of 5-octamethyl-[12]-mercuracarborand-4 26 is an effective source of naked fluoride <2004AGE1854>. Treatment of a tosylated sugar with fluoride 26, in the presence of tetra- -butyl ammonium iodide 27, leads to 49% tosylate replacement. The reaction does not occur without co-reagent 27, so presumably its role is to help release fluoride ion from complex 24. Scheme 3 illustrates the preparation of fluoride reagent 26 by decomplexa-tion of diiodide 25 with AgBp4 forming neutral tetramer 24, followed by treatment with tetramethylammonium fluoride. 

Carbon dioxide behaves as a weak fluoride ion acceptor towards naked fluoride ion sources such as tetramethylammonium fluoride, neopentyl(trimethyl)-ammonium fluoride and piperidinium fluoride (pip+F ) in the absence of a solvent and in CH2F2 and CF3CHFCF3 solvents for pip+F [25]. The C02F anion has been characterized in the solid state by 1H 13C MAS NMR spectroscopy and... 

Batchwise Fluorodenitration Using Anhydrous Tetramethylammonium Fluoride... 

Fluoroaromatic Compounds by Fluorodenitration with Azeotropically Dried Tetramethylammonium Fluoride General Procedure ... 

In another approach, 3,4-di-0-beiizyl-2-0-triflyl-l,6-anhydro-/i-D-mannopyranose (3) is treated with tetrabutyl- or tetramethylammonium fluoride in anhydrous acetonitrile, acetone, or tetrahydrofuran to yield 3,4-di-0-benzyl-2-fluoro-1.6-anhydro-2-deoxy-/TD-glucopyranose (4) as a syrup ([a]D — 28) in up to 91 % yield. With cesium fluoride in dimethylformamide only decomposition was observed in an attempted synthesis of 4 from 3. Fluoride 4 is converted into 2-fluoro-2-deoxy-D-glucose (2) in 70% yield by heating with 50% (v/v) methancsulfonic acid at 120 C for 30 minutes.t,( ... 

Tetramethylammonium fluoride and potassium fluoridc/letraethylammonium iodide have also been used as the fluoride ion source.84... 

Aromatic aldehydes give the corresponding alcohols on reaction with trimethylfpolyfluoroal-kyl)silanes in Lclrahydrofuran in the presence of tetramethylammonium fluoride.26-85-91 The reaction of perfluoro-2-propoxypropanoyl fluoride with trimethyl(perfluoroalkyl)silane leads to the perfluoroalkylated ketone product.47... 

Only a few diorganotrihalotellurates(IV) have been prepared. Bis[trifluoromethyl] tellurium difluoride reacted with equimolar amounts of potassium, rubidium, cesium, or tetramethylammonium fluoride in acetonitrile at 20° to produce the bis[trifluorometh-yl]trifluorotellurates(IV) as precipitates . They are hygroscopic, moisture-sensitive substances. 

Recently, Shibata, Tom, and coworkers demonstrated that a mixture of chiral ammonium bromides, 146 and 147, and tetramethylammonium fluoride (TMAF) [67] or KF [68] can be directly used as a catalyst without the need for the prior isolation of the fluoride salts. By utilizing this catalyst system, the reactions ofvarious aromatic ketones or aldehydes with (TMS)CF3 were completed within a few hours to afford the corresponding products in moderate to high enantioselectivities (Schemes 8.56 and 8.57). 

In 2006, Scheidt and coworkers [44] reported the first enantioselective direct nucleophilic addition ofthe silylated thiazolium salt 148, a precursor of the equivalent acyl anion, to nitroalkene 149 in the presence of tetramethylammonium fluoride (TMAF) and stoichiometric amounts of quinine-based thiourea 81b, producing the chiral [3-nitroketone 150 in 67% yield and with 74% ee (Scheme 9.51). The acyl anion equivalent 152 can be generated by the desilylation of 148 with TMAF, followed by the 1,2-H shift of the resulting alkoxide 151. The observed asymmetric induction indicates that there is a strong interaction between the thiourea and the nitroalkene during the carbonyl anion addition step. 

If equimolar quantities of tetramethylammonium fluoride and a threefold excess of Me3SiCF3 or its homologues are used the perfluoroalkyltrimethyl silane acts as an effective source of nucleophilic perfluoroalkyl equivalents for nucleophilic substitution of aliphatic triflates [90] (Scheme 2.136). This method enables the simple synthesis of partially fluorinated alkane structures which are of interest in the chemistry of liquid crystals and other functional materials. 

To take advantage of l9F NMR, carbonyl groups including quinones have been derivatized by reaction with trifluoromethyltrimethyl-silane in the presence of tetramethylammonium fluoride followed by hydrolysis of the trimethylsilyl ethers (Ahvasi et al. 1999). The method was applied to analysis of the various carbonyl groups in lignin. 

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