2-trimethylsilylethyl

Methyl Carbamate 5. 9-Fluorenylmethyl Carbamate 8. 2,2,2-Trichloroethyl Carbamate 11. 2-Trimethylsilylethyl Carbamate 16. 1,1-Dimethylpropynyl Carbamate 20. 1-Methyl-1-phenylethyI Carbamate 22. 1-Methyl-l-(4-biphenylyl)ethyl Carbamate 24. 1,1 -Dimethy 1-2-haloethyl Carbamate 26. l,l-Dimethyl-2-cyanoethyl Carbamate 28. r-Butyl Carbamate... 

The parent alcohol can be obtained in a straightforward manner from chloromethyltrimethylsilane (Chapter 16). The protection afforded is naturally related to the functionality involved, and liberation is achieved using either fluoride ion or a Lewis acid. For example, 2-trimethylsilylethyl esters (Chapter 16) are stable to a wide variety of conditions such as those used in peptide synthesis, but are readily cleaved by fluoride ion (14,15). 

PPTS, Pyridinium p - toluene s u I fo n ate SE, 2-Trimethylsilylethyl TBDMS, ferf-Butyl-dimethylsilyl TBDPS, ferf-Butyldiphenylsilyl TEMPO, 2,6,6-Tetramethyl-l-piperidi-nyloxy Tf, Trifluoromethanesulfonyl THF, Tetrahydrofuran THP, Tetrahydropyran TIPDS, l,l,3,3-Tetraisopropyl-l,3-disiloxanyl TMS, Trimethylsilyl. 

The observation that sterically less demanding nitrogen sources exhibit superior reactivity and give higher enantioselectivity has led to the new nitrogen source/oxidant 2-trimethylsilylethyl /V-chloro-/V-sodiocarbamate (TeoCNCINa).81 This TeoCNCINa can be prepared by reacting NaOH/... 

We attempted to by-pass the above reductive amination by preparing alternative glycosides, namely the allyl- and 2-trimethylsilylethyl- -D-xylopyrano-sides, 57 and 58, respectively. However, to date, we have not been able to convert either 57 or 58 into the enantiomer of 52 or its expected precursor 59 [41]. 

Sharpless also described the use of 2-trimethylsilylethyl carbamate 36 in the AA. This reagent leads to a product with a protective group that is easily removed by fluoride. Enantiose-lectivities in aminohydroxylation with 36 remain comparable with those obtained with benzyl carbamate 35 [78]. 

In 2-trimethylsilylethyl 4-phenylbenzoate 44, the C—Si and C—O ester bonds are in an antiperiplanar conformation, and the C—O ester bond is significantly longer than expected for an alkyl ester bond at a primary centre. This is consistent with a oq si T c o interaction in the ground state. In /raw.v-2-(di methyl phenyl si ly I )cyclohexyl-3,5-dinitrobcnzoate 45, the dihedral angle between the C—Si and C—O ester bonds is found to be just over 60°, and there appears to be little lengthening of the C—O bond. 

Hi. pSilyl-substituted tertiary benzyl cations. Earlier attempts to prepare the 1,1-diphenyl-2-trimethylsilylethyl cation 345 by ionization of l,l-diphenyl-2-trimethylsilyl-ethanol in FS03H/S02C1F at both -78 °C and -140 °C failed and led only to the formation of 1,1-diphenylethyl cation 298 along with trimethylsilyl fluorosulphate113. 

Cleavage of 2-bromoethyl esters. These esters can be cleaved by treatment with Still s reagent in THF and then with tetra-n-butylammonium fluoride (cf. cleavage of 2-trimethylsilylethyl esters, 8, 510). 

Deblocking of the anomeric position, protected as the 2-trimethylsilylethyl ether, has been achieved in high yields in examples drawn from mono-, di-, and trisaccharide chemistry [112]. An example is shown in Eq. (66). In the absence of acetic anhydride, the product with a free anomeric hydroxy group is obtained. 

More specific anomeric protecting groups are the 2-trimethylsilylethyl (TMSE) [25] and p-methoxyphenyl glycosides [26], both introduced by glycosylation reactions on protected derivatives (Scheme 3.5). The former is cleaved by treatment with BF3-etherate conditions in which TBDMS ethers survive. p-Methoxyphenyl glycosides are cleaved by CAN-oxidation similarly to p-methoxybenzyl ethers. 

PyBOP (benzotriazol-l-yloxy)tripyrrolidinophosphonium hexafluorophosphate SE 2-trimethylsilylethyl... 

Acyl chlorides may be replaced with imidazolides, which react with sodium azide to give acyl azides. In the reaction shown in equation (34), 2-trimethylsilylethanol is used for trapping the isocyanate. The resulting 2-trimethylsilylethyl ester is easily cleaved with tetra-n-butylammonium fluoride. 

A mechanistically related and mild fragmentation is that of 2-trimethylsilylethyl esters (Tmse esters). The Tmse residue is a selectively cleavable carboxy-protecting group (see Volume 6, Chapter 3.2) Examples are known for the synthesis, via these esters, of peptides, macrolides such as curvularin and macrocyclic trichothecenes like verrucinol (Scheme 54). °... 

Fluoride-promoted fragmentation of 2,3-bis(2-trimethylsilylethyl)cyclopropenethione resulted in elimination of fluorotrimcthylsilane and ethenc to give the tetrabutylammonium salt of 3-thioxocycloprop-1 -cne-1,2-dithiolate, which, by addition of sodium perchlorate solution, was converted into the sodium salt in 62% yield.The reaction of 2,3-bis(/ert-butylsulfanyl)cyclo-propenethione with two equivalents of phenyllithium in tetrahydrofuran at — 80 C for three hours gave 2-(tect-butylsulfanyl)-3-phcnylcyclopropenethionc in 85% yield. 

Trimethylsilylethyl, 81 2-(Benzylthio)ethyl, 81 2-(Phenylselenyl)ethyl, 82 f-Butyl, 82 Cyclohexyl, 84... 

Trichloroethyl, 718 2-Trimethylsilylethyl, 719 (2-Phenyl-2-trimethylsilyl)ethyl, 721 2-Phenylethyl, 722 2-Chloroethyl, 722... 

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