R-butyldimethylsilyl

Me3SiCH2CH=CH2i TsOH, CH3CN, 70-80°, 1-2 h, 90-95% yield. This silylating reagent is stable to moisture. Allylsilanes can be used to protect alcohols, phenols, and carboxylic acids there is no reaction with thiophenol except when CF3S03H is used as a catalyst. The method is also applicable to the formation of r-butyldimethylsilyl derivatives the silyl ether of cyclohexanol was prepared in 95% yield from allyl-/-butyldi-methylsilane. Iodine, bromine, trimethylsilyl bromide, and trimethylsilyl iodide have also been used as catalysts. Nafion-H has been shown to be an effective catalyst. 

Rexyn 101 (polystyrene sulfonic acid), 80-91% yield.This method does not cleave the r-butyldimethylsilyl ether. 

DMSO, H2O, dioxane, reflux, 12 h, 65-99% yield.These conditions cleave a dimethyl ketal in the presence of a r-butyldimethylsilyl ether. 

AC2O, FeCl3, It, <30 min, 60-93% yield. These conditions will selectively protect an aldehyde in the presence of a ketone. This combination also converts r-butyldimethylsilyl (TBDMS) ethers to acetates. 

Bu4N F, THF, 0°, 1 h, 52-95% yield.A primary alcohol protected as the r-butyldimethylsilyl ether is cleaved under these conditions, but a similarly protected secondary alcohol is stable. 

Pyrroles and indoles can be protected with the r-butyldimethylsilyl group by treatment with TBDMSCl and n-BuLi or NaH. Triisopropylsilyl chloride (NaH, DMF, 0°-rt, 73% yield) has been used to protect the pyrrole nitrogen in order to direct electrophilic attack to the 3-position.It has also been used to protect an indole.This derivative can be prepared from the silyl chloride and The silyl protective group is cleaved with Bu4N F , THF, rt or with CF3COOH. 

If the chifdl duxilidry in Eq 4 96 is modified by changing MeO into more bulky groups such dS trityl (Tr or r-butyldimethylsilyl (TBS group, an improved asymmetric nitro-olefinddon of ct-alkyl- /- and 5-lactones is possible fEq 4 97) ... 

In their outcomes, similar, but mechanistically different, coupling reactions were observed in the zincation of (tert-butyldimethylsilyl)(2-pyridinemethyl)amine (Scheme 75), which produced methylzinc(/ r/-butyldimethylsilyl) (2-pyridylmethyl)amide 113. Thermolysis of 113, or its treatment with one additional equivalent of dimethylzinc, yielded the C-G coupled dimer [l,2-bis(/ / -butyldimethylsilylamido)-l,2-dipyridylethane]bis(methylzinc) 114.170... 

Protonolysis of 114 with acetamide yielded the free ligand in racemic form, namely as (1, 2 )- and (1R,ZR)-1,2-dipyridyl-l,2-bis (/ r/-butyldimethylsilyl)amino ethane.173... 

The same research group also showed that the r-butyldimethylsilyl (TBDMS)-protected 4-substitued 4,5-dihydro-l,2,4-oxadiazol-5-one 192 afforded the alcohol 193 on treatment with ethanolic HC1. Mesylation and treatment of the intermediate with sodium iodide gave the iodofluoroalkenyl-substituted 4,5-dihydro-l,2,4-oxadiazol-5-one 194 (Scheme 26) <2004T10907>. 

Reduction of a-methyl-fi-hydroxy ketones,2 The r-butyldimethylsilyl ethers of these ketones, in which chelation is difficult, are reduced by lithium aluminum hydride with a high degree of 1,2-anri-selectivity. This reaction can therefore afford either aM ,a/iri-l,3-diols or anti,syn- 1,3-diols with high selectivity. 

Hoye described an RCM-based total synthesis of the 20-membered marine macrolide dactylolide 288 and its subsequent conversion to the natural carbinolamide zampanolide 289 (Scheme 56), both feature a common highly unsaturated macrolide core, bridging a m-2,6-disubstituted 4-methylene tetrahydropyran unit. When the polyunsaturated acyclic lactone 286 (1 1 epimeric mixture around the /i r/-butyldimethylsilyl (TBS)-protected carbinol center) was in situ protected with bis-trimethylsilylacetamide (BSA) and then treated with catalyst G in benzene at 60 °C, each diastereomer smoothly cyclized to the corresponding cycloalkene 287 with exclusive ( )-geometry at the newly formed double bond. 

As(III) and As(V) compounds. Comparison with T-ECgTLtMgBr derivatization with A-r-butyldimethylsilyl-A-methyltrifluoroacetamide with 1% r-butyldimethylchlorosilane. ... 

In the latest development of his elegant work with hydrazone derivatives, Andrew Myers of Harvard reports (J. Am. Chem. Soc. 2004,126, 5436) that Sc(OTf), catalyzes the addition of l,2-bis(r-butyldimethylsilyl)hydrazine, to aldehydes and ketones to form the t-butyldimethylsilylhydrazones. Addition of tBuOH/tBuOK in DMSO to the crude hydrazone effects low temperature Wolff-Kishner reduction. Alternatively, halogenation of ketone hydrazones can lead to vinyl halides such as 11, or the 1,1-dihalo derivatives, depending on conditions. Halogenation of aldehyde hydrazones provides the 1,1-dihalo derivatives such as 13. 

P-D-glucopyranoside with 2,3,4-tri-0-benzyl-6-0-r-butyldimethylsilyl-p-D-glucopyranosyl 2-thiopyridylcarbonate 461... 

To a mixture cooled at 0°C containing 2.34 g (8.15 mmol) of 3-methoxy-2-pyridyI p-D-glucopyranoside in 50 mL of dry pyridine was added dropwise 2.1 mL (8.97 mmol) of r-butyldimethylsilyl Inflate over 15 min. The resulting mixture was stirred at 0°C for another 15 min at which time TLC indicated the silylation was completed. After 3.1 mL (27... 

A solution of 2,3,4-tri-O-benzyl-a-D-glucopyranosyl azide 16 (21 mg, 0.044 mmol) in 0.6 mL of dichloromethane was stirred in the presence of powdered 4-A molecular sieves and 24 mg (0.067 mmol) of Cu(OTf)2. After 10 min, a solution of 100 mg (0.067 mmol) of 3-methoxy-2-pyridyl 2,3,4-tri-O-benzyl-6-0-r-butyldimethylsilyl-a-D-glucopyranosyl-(1—>6)-2,3,4-tri-0-benzoyl-0-D-glucopyranoside 10 in 1.6 mL of dichloromethane was added dropwise over 5 h. A few drops of pyridine were added, the solvent was evaporated, and the residue was chromatographed with CCl4-acetone (10 1) as eluant to give the title compound (44 mg, 66%). 

Detritylation Trityl ethers are cleaved by reaction with formic acid in ether in high yield in 7-45 minutes. Under these conditions isopropylidene and benzyl-idene acetals and r-butyldimethylsilyl ethers are not affected, but tetrahydropyranyl ethers are partially cleaved. 

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