Elimination tetrabutylammonium fluoride

In the 1,6-elimination of j -trimethy1si1y1methy1henzy1trimethy1 ammonium iodide with tetrabutylammonium fluoride, yields as high as 56% have been reported (18). The starting materials are not readily accessible, however, and are cosdy. 

A simple procedure for the synthesis of 4,5-disubstituted 1,2,3-triazoles 1247 involves stirring a mixture of nitroethene 1245 with trimethylsilyl azide and tetrabutylammonium fluoride at 30 °C for 3h. No solvent is needed. Triazoline 1246, which forms in the first step of the reaction, eliminates nitrous acid, and the trimethylsilyl group is cleaved off by the fluoride anion to afford triazole 1247. Various aryl and heteroaryl substituents R are used providing triazoles 1247 in 70-90% yield (Scheme 207) <2005JOC6526>. 

In a comparative study of fluorination of l,2 3,4-di-0-isopropyli-dene-6-O-p-tolylsulfonyl-a-D-galactopyranose with tetrabutylammonium fluoride in a variety of dipolar, aprotic solvents (as well as 1,2-eth-anediol, in which no reaction was observed), acetonitrile was found to give the highest proportion of substitution of the sulfonic esters relative to their elimination.106 Elimination is the major, competing reaction in these nucleophilic-substitution reactions, because of the high basicity and low nucleophilicity of the fluoride ion or, in terms of the... 

Tetrabutylammonium fluoride can also be employed under pressure to substitute tosylate with fluorine. l-(2,5-Dimethoxyphenyl)-2-tosyloxyethane (30) gives the corresponding fluoride 31 in 69 % yield without elimination product at 11.25 Torr.220 The reaction at 760 Torr furnishes only 38 % yield with 26 % of the elimination product. 

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... 

Other methods used for effecting elimination of water from monohydroxy compounds include treatment with thionyl chloride in pyridine167and sulfonylation followed by treatment with tetrabutylammonium fluoride-potassium fluoride168 or DBU.169... 

The oxoniastannaboratole derivatives 357 are synthesized by the reaction of zwitterionic r/2-(alkynylborate)alkenyl stannane derivatives 356 with tetrabutylammonium fluoride (TBAF) followed by water. The stannanes 356 react readily with TBAF even at — 65 °C yielding the Sn-F compounds, which then react with water with concomitant elimination of alkyne to yield the stannaboratole 357 in high yield (Scheme 57) <1999JOM93>. 

Silylmethyl oxetanes were converted to allylic alcohols when added to a solution of tetrabutylammonium fluoride (TBAF) in THF (Equation 15) <1998JOC5517>. Treatment with TBAF is a commonly known method of removing silyl protecting groups. In this case, attack of the fluoride ion on the silica atom lead to elimination of the silyl group and ring opening of the oxetane. 

Elimination of iodobenzene alone from 2-phenyliodonio benzoate leads to generation of another transient 1,4-dipole which was trapped by phosphaalkynes [55], A new precursor, 2-trimethylsilyl-diphenyliodonium triflate, obtained from 1,2-bis-trimethylsilylbenzene, (diacetoxyiodo)benzene and triflic acid, permitted the generation of benzyne with tetrabutylammonium fluoride, at room temperature [56] ... 

The reaction of the decenyliodonium tetrafluoroborate with tetrabutylammonium fluoride has also been studied but follows a different course84. Thus, the relatively basic fluoride ion induces the a-elimination of iodobenzene and affords products derived from an intermediate alkylidenecarbene (equation 205). 

Once again (cf equation 205), the behavior of tetrabutylammonium fluoride (TBAF) is exceptional. Thus, the treatment of (E)-1 -decenyl(phenyl)iodonium tetrafluoroborate with ten equivalents of TBAF in acetonitrile leads exclusively to 1-decyne (equation 212)146. Furthermore, the reactions of the a- and /1-deuterio isotopomers of the decenyliodonium salt with one equivalent of TBAF in dichloromethane are clearly consistent with alkyne formation via the a-elimination-alkylidenecarbene pathway (equations 213 and 214)146. 

An efficient procedure for the nucleophilic displacement of the A, A -dimethylamino group of 1-triisopropylsilyl-gramines via the fluoride ion-induced elimination-addition reaction has been devised. 1-Triisopropylsilylgramine methiodide 1371 reacted smoothly with a variety of nucleophiles in the presence of tetrabutylammonium fluoride (TBAF) to give 3-substituted indoles 1372 (Scheme 262) <1995TL5929>. 

It is remarkable that the attempted synthesis of 2 from the corresponding hydroxy compound with diethylaminosulfur trifluoride (DAST) failed87 and that the mesylate of the hydroxy compound gives only a very poor yield of the fluoride upon treatment with tetrabutylammonium fluoride.88 On the other hand, even with TASF(Me), elimination may predominate in cases where nucleophilic displacement by an ordinary SN2 mechanism is hindered.86... 

A similar reaction via addition-elimination occurs with diethoxythioxaphosphorane sulfenyl bromide <1994SL267> or diethoxyoxophosphoranesulfenyl chloride <1997HAC429> and subsequent treatment of the 1,2-adduct with tetrabutylammonium fluoride (TBAF). The advantage of this protocol is the smooth formation of adducts of type 90 and their transformation into the corresponding thiiranes under neutral reaction conditions (Scheme 49). The entire sequence can be carried out as a one-pot reaction. 

Tetrabutylammonium salts can be difficult to remove from cmde reactions without the use of an aqueous work-up. One non-aqueous approach to remove them was reported by Parlow, who applied a calcium sulfonate scavenger [52], The resin reacts with excess tetrabutylammonium fluoride to afford insoluble calcium fluoride, which the acidic polymer protonates to afford the corresponding salt, thereby eliminating the need for standard aqueous work-up (Scheme 8.39). 

Recently, an acene fused-thiophene hybrid, p-channel semiconductor using a soluble precursor in which the solubility originates from trimethylsilyl groups was reported.[256] The elimination of two trimethylsilyl groups from the soluble precursor is accomplished through treatment with tetrabutylammonium fluoride in pyridine to give 43e. OTFTs made by thermally evaporated 43e showed mobility of 10 cm V s . ... 

Desilylation with tetrabutylammonium fluoride gave a mixture of hydroxy acetates, which were oxidised with pyridinium chlorochromate to the ketoacetates 94. (5-Elimination under basic conditions and deacetylation gave the mixture of diols 95 and 8-epi-95, which were separated by chromatography. 

---