Desilylations, tetrabutylammonium fluoride

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. 

A -Glycosylation of sulfites 55a and 55b using silylated thymine in dry conditions at 125 °C yielded a mixture of 2 -0-silylated and 2 -hydroxy-5-methyluridine derivatives 56a and 56b, and 57a and 57b, respectively (Scheme 2). Subjecting these mixtures to desilylation conditions tetrabutylammonium fluoride, methanol (TBAF, MeOH), gave 2 -hydroxy-5-methyluridine derivatives 57a and 57b. Additionally, epimer 58 was produced as a minor product (13.5%) of N-glycosylation of 5-0-benzoylated compound 55b <2005JME4276>. 

Parlow, J. J. Vazquez, M. L. Flynn, D. L. A Mixed Resin Bed For the Quenching and Purification of Tetrabutylammonium Fluoride Mediated Desilylating Reactions, Bioorg. Med. Chem. Lett. 1998, 8, 2391. 

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... 

V-(a-Trimethylsilyl)alkylbenzothiazoles are easily desilylated by reaction with tetrabutylammonium fluoride (TBAF) and quenching with water.157... 

Similar to these results, but accompanied with ring opening, are the desilylation reactions of substituted aziridines. Treatment with cesium fluoride (1 equiv.) in HMPA (tetrabutylammonium fluoride in THF or DME gives lower yields) at room temperature followed by aqueous work-up, yields desilylated open-chain compounds.320... 

Silyl triflates may also be used as the catalyst to the same goal. In both cases, conjugated base induces desilylation to create the ylid (compare with the action of tetrabutylammonium fluoride on the same imine which led to the anion see Section VI.B.6.a).333,391... 

Numerous dioxetanes with varying atom (X) and protecting group (PG) have been synthesized over the last decade in order to study the CIEEL mechanism. The following serve as prototypical examples. The most prevalent trigger is that of a siloxyphenyl substituent such as that incorporated into dioxetane 54. Tetrabutylammonium fluoride (TBAF) is used in an aprotic solvent, such as dimethyl sulfoxide (DMSO) or acetonitrile, to desilylate to afford the unstable phenolate 55 (Scheme 11) <2002MI305>. 

Copolymerization of l,4-anhydro-2,3-di-0-(to7-butyldimethylsilyl)-a-D-xylopy-ranose (39) with l,4-anhydro-2,3-di-0-benzyl-a-i>xylopyranose (27), followed by desilylation with tetrabutylammonium fluoride gave a partially benzylated sterero-regular (l -->5)-a-D-xylofuranan. [37] A branched polymer (40) was obtained when it was glycosylated with 3,4,6-tri-0-acetyl-P-D-mannose l,2-(methyl orthoacetate). Debenzylation of the polymer having D-mannosyl branches with sodium in liquid ammonia yielded (1 — 5)-a-i>xylofuranans having 2- or 3-O-a-D-mannopyranosyl branches. 

Secondly it has been found that a number of trialkylsilyl groups can be added stereoselectively to the /j-position of the C —C double bond in dioxanone 10 (derived from enantiomerically pure 3-hydroxybutanoic acid)23. In this case the presumed silylcuprate is generated from a chlorosilane and a higher-order organocuprate. In the example shown, with addition of phenyldimethylsilyl chloride, a diastereomeric ratio of 91 9 was obtained. Improved ratios were obtained with other groups (e g., 98 2 for trimethylsily 1), but unfortunately none of the latter were susceptible to oxidative cleavage. The first two steps of the procedure produce a mixture of 11 and its silyl enol ether, which is then desilylated to 11 by treatment with tetrabutylammonium fluoride. 

Another interesting example taken from the synthesis of natural products is reported in equation 6. Epoxidation of 13 with cpba affords a mixture of 14a and 14b, which can be directly desilylated with tetrabutylammonium fluoride to give fi ,Z-isospongiadiol (15). ... 

The synthesis of 2,3-dihydrodiisopropyl-l,3-thiaborol-3-yl-amine 26 and subsequently lithium diisopropyl-1,3-thiaborol-3-ylamine 27 required a four-step synthesis starting from chloromethyl trimethylsilylethynyl sulfide 59 (Scheme 9). Desilylation of compound 59 with tetrabutylammonium fluoride (TBAF) in methanol afforded the labile chloromethyl ethynyl sulfide 60, which was treated with a solution of dibutylstannane and LDA in a mixture of TFIF and hexane at —78°C to give 3,3-dibutyl-2,3-dihydro-l,3-thiastannole 61, in 39% yield. Reaction of compound 61 with 2 equiv of -butyllithium in THF at —78°C gave the dilithio reagent 62, which could be detected by NMR... 

Reactivity of benzo[l,2]oxasilole 21 was also studied <2004GC122>. Homoallylic alcohol 22 was obtained by treatment with tetrabutylammonium fluoride (TBAF). Tamao reaction provided the desilylated ortho-phcnoXxc benzyl alcohol 23. Finally, treatment with methyllithium resulted in nucleophilic methylation on silicon and opening of the Si-O bond (Scheme 3). 

The hemiketal 12 was easily prepared in high yield (80%) from artemisinin by treatment with trifluoromethyl trimethylsilane (TMSCF3) in the presence of tetrabutylammonium fluoride trihydrate (TBAF, 3H20). Complete desilylation occurred after addition of water (see Scheme 6.5). The reaction was stereoselective, and the a configuration of the CF3 group was unambiguously determined (P-12) [40,44], However, this configuration at C-10 is not the result of an a approach of the CF3 but of a thermodynamic equilibrium of the... 

Irradiation (Vycor filter) of 1,2,3-trimethylsilylated cyclobutenedicarboxylic anhydrides in dichloromethane gave the corresponding trimethylsilyl-substituted bicyclobutane derivative 6, which was partially desilylated with tetrabutylammonium fluoride in chloroform. Complete desilylation to give 7 required treatment with sodium hydroxide for seven days at room temperature and with acetic anhydride. ... 

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. 

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