Silicon protecting group

Scheme 12.6). Stereoselective reduction and chromatographic separation afforded diastereomerically pure derivative 32 in 94% ee. Removal of the silicon protecting group, followed by acetylation of the two secondary alcohols, set the stage for an elegant palladium-catalyzed allylic transposition that provided compound 33 with...

Trialkylsilyl protection of carboxylic acids and amines is rare owing to hydrolytic lability. Nevertheless, synthetically useful silicon protecting groups have been developed for these functional groups in which the requisite stability is achieved by incorporating the silicon atom into a 2-(trimethylsilyl)ethyl substituent. The principle is illustrated [Scheme 1.9] by the reaction of 2-(trimethylsilyl)ethyl esters with tetrabutylammonium fluoride the pentavalent siliconate intermediate fragments with loss of ethylene and fluorotrimethylsilane14-15 to liberate a carboxylic arid as its tetrabutylammonium salt. 

We invoke 7c-stacking of the alkene with a phenyl moiety on the silicon protecting group (since this high degree of selectivity was only observed for TBDPS and not with TBS), in the precursor to explain this remarkable selectivity (Figure 1). Lewis acid induced reduction of the epoxide with sodium cyanoborohydride led regioselectively to the 1,3-diol (11) the hydride attacks the more substituted position via an S 2 mechanism. ... 

Fig. 10 Alkylations of aniline using a silicon protecting group to prevent nitrogen complexa-tion...

A new approach to the synthesis of 2,4-disubstituted furans involves protection of the 2-position in 3-substituted furans such as furan-3-carboxylic acid <91SL33,9iJCS(Pl)2600> and 3-furylmethanol <94TL5335> as the 2-/-butyldimethylsilyl-derivatives. Metallation at low temperature followed by reaction with an electrophile and removal of the silicon protecting group then gives the required... 

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