Use Of Tetrabutylammonium Fluoride Research Articles

Hexafluoroisobutylation of enolates through a tandem elimination/allylic shift/hydrofluorination reaction.

The isobutyl side chain is a highly prevalent hydrophobic group in drugs, and it notably constitutes the side chain of leucine. Its replacement by a hexafluorinated version containing two CF3 groups may endow the target compound with new and advantageous properties, yet this modification remains overlooked due to the absence of a general and practical synthetic methodology. Herein, we report the first general method to introduce the hexafluoroisobutyl group into ketoesters, malonates, 1,3-diketones, Schiff base esters and malononitrile. We demonstrated that the reaction occurs through an elimination/allylic shift/hydrofluorination cascade process which efficiently overcomes the usual fluoride β-elimination observed with α-CF3-vinyl groups. We showed that with alkali metal bases, a pentafluorinated alkene is obtained predominantly, whereas the use of tetrabutylammonium fluoride (TBAF) allows hydrofluorination to occur. This tandem process represents a conceptually new pathway to synthesize bis-trifluoromethylated compounds. This methodology was applied to the multigram-scale synthesis of enantiopure (S)-5,5,5,5′,5′,5′-hexafluoroleucine.

Creating surface patterns of polymer brushes by degrafting via tetrabutyl ammonium fluoride

We demonstrate the use of tetrabutyl ammonium fluoride (TBAF) for creating spatial patterns of poly(methyl methacrylate) (PMMA) brushes on a flat silica support by degrafting PMMA grafted chains from selected regions on the substrate.

Alginate esters via chemoselective carboxyl group modification

Alginates are (1→4) linked linear copolysaccharides composed of β-d-mannuronic acid (M) and its C-5 epimer, α-l-guluronic acid (G). Several strategies for synthesis of carboxyl modified alginate derivatives exist in the literature. Most of these however employ aqueous chemistries, such as carbodiimide coupling reactions. Based on our recently discovered method for homogeneous dissolution of tetrabutylammonium (TBA)-alginate, we now describe use of tetrabutylammonium fluoride (TBAF)-based two component solvent systems as media for synthesis of carboxyl-modified alginate esters. Partially and fully esterified benzyl, butyl, ethyl, and methyl alginates were synthesized via reaction with the corresponding alkyl halides. The newly synthesized derivatives were soluble in polar aprotic solvents without the addition of TBAF. Saponification was performed to demonstrate that alkylation was completely regioselective for carboxylate groups in preference to hydroxyl groups to form esters. We demonstrate the utility of these alginate esters to enhance aqueous solubility of the flavonoid naringenin by formation of solid dispersions.

The use of tetrabutylammonium fluoride to promote N- and O-(11) C-methylation reactions with iodo[(11) C]methane in dimethyl sulfoxide.

The N- or O-methylation reactions of compounds bearing amide, aniline, or phenol moieties using iodo[(11) C]methane (1) with the aid of a base are frequently applied to the preparation of (11) C-labeled radiopharmaceuticals. Although sodium hydride and alkaline metal hydroxides are commonly employed as bases in these reactions, their poor solubility properties in organic solvents and hydrolytic activities have sometimes limited their application and made the associated (11) C-methylation reactions difficult. In contrast to these bases, tetrabutylammonium fluoride (TBAF) is moderately basic, highly soluble in organic solvents, and weakly nucleophilic. Although it was envisaged that TBAF could be used as the preferred base for (11) C-methylation reactions using 1, studies concerning the use of TBAF to promote (11) C-methylation reactions are scarce. Herein, we have evaluated the efficiency of the (11) C-methylation reactions of 13 model compounds using TBAF and 1. In most cases, the N-(11) C-methylations were efficiently promoted by TBAF in dimethyl sulfoxide at ambient temperature, whereas the O-(11) C-methylations required heating in some cases. Comparison studies revealed that the efficiencies of the (11) C-methylation reactions with TBAF were comparable or sometimes greater than those conducted with sodium hydride. Based on these results, TBAF should be considered as the preferred base for (11) C-methylation reactions using 1.

ChemInform Abstract: Use of Tetrabutylammonium Fluoride as a Facile Deprotecting Reagent for 4-Nitrobenzyl, 2,2,2-Trichloroethyl, and Phenacyl Esters of Amino Acids.

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Fluoride‐Triggered Domino Reactions Involving Ammonium Acetylides and Carbonyl Compounds

AbstractWe describe the use of tetrabutylammonium fluoride as a basic trigger for reactions capable of generating structurally diverse products from methyl propiolate and carbonyl derivatives. The processes are based on either chemodifferentiating multicomponent ABB′ three‐component reactions or bimolecular domino reactions, and they operate through three different and well‐defined autocatalytic cycles. These catalytic cycles share a common property: they are launched by the acid–base reaction of fluoride ions to give catalytic amounts of acetylide or enolate salts, but they are maintained by the autocatalytic generation of these salts.

Rhenium-Catalyzed Formation of Bicyclo[3.3.1]nonene Frameworks by a Reaction of Cyclic β-Keto Esters with Terminal Alkynes

Treatment of cyclic beta-keto esters with terminal alkynes in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)(3)(thf)](2), gave bicyclo[3.3.1]nonene derivatives. The reaction conditions and yields of the bicyclo[3.3.1]nonenes were improved by the sequential use of tetrabutylammonium fluoride (TBAF) after the rhenium-catalyzed reactions.

Synthesis and fluoride-induced chemiluminescent decomposition of bicyclic dioxetanes substituted with a 2-hydroxynaphthyl group

Abstract Five bicyclic dioxetanes bearing a 2-hydroxynaphthyl group, 1aA – 1eA , were synthesized and their chemiluminescent decomposition was examined by the use of tetrabutylammonium fluoride (TBAF) as a base in DMSO. It was found that these dioxetanes hold completely the ‘ odd / even ’ relationship between the substitution pattern of hydroxy as a trigger on the naphthalene ring and their chemiluminescent efficiency, and that dioxetane 1aA exhibited chemiluminescence with the highest efficiency among those for the oxynaphthyl-substituted dioxetanes hitherto known. The significant change in chemiluminescent efficiency depending on the substitution pattern was clarified to be attributed to the marked change in singlet-chemiexcitation efficiency for charge-transfer-induced chemiluminescence (CTICL) of 1aA – 1eA . In respect of the rate of CTICL-decomposition, ‘ odd / even ’ relationship was observed for 1aA – 1dA .

Vinylation of Aryl Bromides Using an Inexpensive Vinylpolysiloxane

[reaction: see text] A mild and general method for the palladium-catalyzed vinylation of aryl bromides has been developed. The use of tetrabutylammonium fluoride (TBAF) as the activator and an inexpensive and nontoxic vinyl donor, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (D(4)(V), 1), allows for a general and high-yielding preparation of substituted styrenes.

Tandem Hass—Bender/Henry Reaction for the Synthesis of Dimethylnitro Alcohols from Benzylic Halides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Tandem Hass–Bender/Henry reaction for the synthesis of dimethylnitro alcohols from benzylic halides

Dimethylnitro alcohols are constructed in a one-pot process from benzylic halides and 2-nitropropane. The use of tetrabutylammonium fluoride (TBAF) as the promoter is essential for this tandem Hass–Bender/Henry reaction to proceed.

Cross‐Coupling of Triallyl(aryl)silanes with Aryl Bromides and Chlorides: An Alternative Convenient Biaryl Synthesis

AbstractCross‐coupling of a diverse range of aryl bromides with triallyl(aryl)silanes is effective in the presence of PdCl2/PCy3 and tetrabutylammonium fluoride (TBAF) in DMSO‐H2O to give various biaryls in good yields. It is worthwhile to note that the all‐carbon‐substituted arylsilanes, stable towards moisture, acid, and base and easily accessible, serve as a highly practical alternative to their aryl(halo)silane counterparts. A catalyst system consisting of [(η3‐C3H5)PdCl]2 and 2‐[2,4,6‐(i‐Pr)3C6H2]‐C6H4PCy2 and use of TBAF⋅3 H2O in THF‐H2O are effective especially for the cross‐coupling with aryl chlorides. Both of the catalyst systems tolerate a broad spectrum of common functional groups. The high efficiency of reactions is presumably due to the ready cleavage of the allyl groups upon treatment with TBAF⋅3 H2O and an appropriate amount of water. Diallyl(diphenyl)silane also cross‐couples with various aryl bromides and chlorides in good yields, whereas allyl(triphenyl)silane gives the cross‐coupled products in only moderate yields. Through sequential cross‐coupling of bromochlorobenzenes with different arylsilanes, a range of unsymmetrical terphenyls are accessible in good overall yields.

Organic Bases as Additives to Improve the Radiochemical Yields of [11C]Ketones Prepared by the Suzuki Coupling Reaction

AbstractThe Suzuki cross‐coupling reaction was employed in the syntheses of eight new [11C‐carbonyl]ketones. The reactions between the corresponding boronic acids and the corresponding triflates were performed in the presence of [11C]carbon monoxide and a palladium(0) complex as the catalyst. Lithium bromide was added to facilitate the reactions, and different bases were tested to improve the radiochemical yields. All the ketones were synthesised, with the achievement of isolated radiochemical yields (decay‐corrected) of between 14 and 74%. Important improvements in the radiochemical yield were achieved by use of tetrabutylammonium fluoride in the synthesis of ketones incorporating alkyl groups, while potassium tert‐butoxide was the best base among those tested for improving the radiochemical yields in the syntheses of biaryl ketones. The optimal amount of base was determined in all cases. Only for compounds 3e and 3h were better radiochemical yields obtained when no base was used. No radiochemical impurities were detected after isolation of the compounds. The specific radioactivity for compound 3a was determined, and a value of 200 GBq/μmol was obtained. Compound 3b was labelled simultaneously with [11C] and (13C)carbon monoxide and the position of the labelled atom was determined and confirmed by 13C NMR spectrometry. Tetrabutylammonium fluoride and potassium tert‐butoxide are reported as useful bases for Suzuki carbonylation with [11C]/(13C)carbon monoxide. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

An Efficient Method for the Isolation and Purification of Oligoribonucleotides

Abstract Problems associated with the use of tetrabutylammonium fluoride like incomplete desilylation and removal of the tetrabutylammonium salts during large scale syntheses of oligoribonucleotides (RNA) have been eliminated by the use of triethylamine trihydrofluoride and precipitation of the RNA with 1-butanol. An efficient anion-exchange HPLC method has been developed for the purification of chemically synthesized RNA and the resulting product precipitated directly by the addition of 1-propanol. A new activator, 5-ethylthio-1H-tetrazole significantly enhances the synthesis quality and yield of oligoribonucleotides. RNA synthesized using these improvements has been shown to be biologically active by a comparative ribozyme-substrate assay.

Polystyrene Reverse-Phase Ion-Pair Chromatography of Chimeric Ribozymes

The use of a reverse-phase polystyrene resin for ion-pair HPLC purification of large amounts of synthetic chimeric DNA-RNA oligomers that is faster and more reliable than previously used techniques has been developed. The preparation of synthetic oligomers containing RNA requires the use of tetrabutylammonium fluoride in the final step, the cleavage of the tert-butyldimethyl silyl protecting group from the ribonucleotides. Cleavage is accompanied by the serendipitous formation of ion pairs between tetrabutylammonium cations and the oligomer phosphates. The formation of these ion pairs retards the elution of the oligomer during HPLC, which allows rapid removal of excess tetrabutylammonium fluoride and the concomitant purification of chimeric ribozymes. This technique is based on a correlation between the length of ion-paired oligomers and their retardation during HPLC. The advantages of reverse-phase ion-pair HPLC on polystyrene resin for the fast purification of oligoribonucleotides are discussed and illustrated through the examples of synthesized chimeric ribozymes.

Use of tetrabutylammonium fluoride as a facile deprotecting reagent for 4-nitrobenzyl, 2,2,2-trichloroethyl, and phenacyl esters of amino acids

Use of tetrabutylammonium fluoride as a facile deprotecting reagent for 4-nitrobenzyl, 2,2,2-trichloroethyl, and phenacyl esters of amino acids

ChemInform Abstract: The Use of Tetrabutylammonium Fluoride as a Cyclization Reagent in the Synthesis of Antibacterial Pyridone‐4‐carboxylic Acid Derivatives (II) and (IV).

ChemInformVolume 19, Issue 36 Preparative Organic Chemistry ChemInform Abstract: The Use of Tetrabutylammonium Fluoride as a Cyclization Reagent in the Synthesis of Antibacterial Pyridone-4-carboxylic Acid Derivatives (II) and (IV). D. BOUZARD, D. BOUZARD Centre Rech. Bristol-Myers, 77422 Marne la Vallee, FranceSearch for more papers by this authorP. DI CESARE, P. DI CESARE Centre Rech. Bristol-Myers, 77422 Marne la Vallee, FranceSearch for more papers by this authorM. ESSIZ, M. ESSIZ Centre Rech. Bristol-Myers, 77422 Marne la Vallee, FranceSearch for more papers by this authorJ. P. JACQUET, J. P. JACQUET Centre Rech. Bristol-Myers, 77422 Marne la Vallee, FranceSearch for more papers by this authorP. REMUZON, P. REMUZON Centre Rech. Bristol-Myers, 77422 Marne la Vallee, FranceSearch for more papers by this author D. BOUZARD, D. BOUZARD Centre Rech. Bristol-Myers, 77422 Marne la Vallee, FranceSearch for more papers by this authorP. DI CESARE, P. DI CESARE Centre Rech. Bristol-Myers, 77422 Marne la Vallee, FranceSearch for more papers by this authorM. ESSIZ, M. ESSIZ Centre Rech. Bristol-Myers, 77422 Marne la Vallee, FranceSearch for more papers by this authorJ. P. JACQUET, J. P. JACQUET Centre Rech. Bristol-Myers, 77422 Marne la Vallee, FranceSearch for more papers by this authorP. REMUZON, P. REMUZON Centre Rech. Bristol-Myers, 77422 Marne la Vallee, FranceSearch for more papers by this author First published: September 6, 1988 https://doi.org/10.1002/chin.198836101AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume19, Issue36September 6, 1988 RelatedInformation