Terr-butyldimethylsilyl ethers

Scheme 21). Scheme 22 illustrates an example of kinetic resolution of a racemic allylic alcohol with a 1,3-hydrogen shift. When racemic 4-hydroxy-2-cyclopentenone is exposed to a cationic (/ )-BINAP-Rh complex in THF, the S enantiomer is consumed five times faster than the R isomer (32). The slow-reacting stereoisomer purified as the crystalline terr-butyldimethylsilyl ether is an intermediate in prostaglandin synthesis (35). These isomerizations may occur via initial Rh-olefinic bond interaction (34). 

Potassium carbonate in methanol or HOAc-H20-THF (3 1 1) at room temperature is sufficient to cleave even terr-butyldimethylsilyl esters. The esters cleave faster than the corresponding ethers [Scheme 6.105].235 Their high base lability allows removal of rerr-butyldimethylsilyl esters in the presence of tert-butyldimethylsilyl ethers [Scheme 6,106].236 The dwerf-butylmethylsilyl group is sufficiently stable to allow selective removal of a tetrahydropyranyl group using pyridinium p-toluenesulfonate in warm ethanol.237... 

The naphthalene-diene compounds (-)-22 and (+)-23 were also derived directly from halenaquinol dimethyl ether (+)-17 by the reduction and subsequent terr-butyldimethylsilylation (Scheme 3). Diketone (-i-)-17 was reduced and then treated with hydrochloric acid, as in the case of ketone (+)-19 of Scheme 2, giving rranj-methoxy alcohol (-)-24 and cj j-methoxy alcohol (-)-25, respectively. Each alcohol was then converted to its /ert-butyldimethylsilyl ether, which was identical with the authentic sample derived from compound (+)-19. 

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