Ethers as protective groups

Silyl Ethers as Protective Groups for Alcohols. Oxidative Deprotection and Stability Under Alcohol Oxidation Conditions, Muzart. J. Synthesis. 1993, 11... 

R Gigg. The allyl ether as protecting group in carbohydrate chemistry. Part II. The 3-methyIbut-2-enyl ( Prenyl") group, J. Chem. Soc. Perkin TYans. 7 738 (1980) and references therein. 

The synthetic potential of silyl ethers as protecting groups for hydroxyls is based on the fact that they can be easily introduced and cleaved under mild conditions and their relative stability can be tuned by varying the substituents on silicon. In carbohydrate chemistry, the tert-butyl-dimethylsilyl (TBDMS), terl-butyldiphenylsilyl (TBDPS) and triethyl-silyl (TES) ethers are the most often applied silicon-based protecting groups (Scheme 2.9).23... 

TBS- vs. TIPS- ethers as protecting groups in the anomeric iithiation of giycais... 

General problems, as compared to the formation of 0-glycosides, are the incompatibility between catalytic hydrogenolysis and sulfur functions, which complicates the use of benzyl ethers as protecting groups, although Birch reduction might be an alternative, and the easy formation of disulfides from thiols, irrespective of if they are used as donors or acceptors. 

The hrst synthesis of pelargonidin chloride used methyl ethers as protecting groups for the phenolic hydroxyls during the Grignard addition step."" ... 

The suitability of tritylone ethers as protecting groups for alcohols has been explored, with cholesterol among model alcohols.The ether (134) was formed from tritylone alcohol and cholesterol under acidic conditions with azeotropic... 

Silyl Ethers.—Examples of the usefulness of t-butyldimethylsilyl ethers as protecting groups are nicely illustrated in Schemes 17 and 19. Methyl a-D-gluco-pyranoside reacted with a molar equivalent of t-butyldimethylsilyl chloride in pyridine to give the 6-0-(t-butyldimethylsilyl) derivative in virtually quantitative yield, and sucrose reacted with 3.5 molar equivalents of the silylating reagent to give almost exclusively r,6,6 -tri-0-(t-butyldimethylsilyl)sucrose and traces of mono- and di-substituted products. In the presence of an excess of sucrose, a mixture of 6 -, 6,6 -di-, and r,6,6 -tri-0-(t-butyldimethylsilyl)sucroses was obtained. 

This isomerization is a basis of using allyl ethers as protecting groups for alcohols [Eq. (139) (Corey and Suggs, 1973)]. 

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