Silyl Ethers - Thieme Chemistry
Silyl Ethers - Thieme Chemistry
Silyl Ethers - Thieme Chemistry
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Scheme 25 Cleavage of Primary and Secondary tert-Butyldimethylsilyl <strong>Ethers</strong> with Tetrabutylammonium<br />
Fluoride [57]<br />
TBDPSO<br />
MeO<br />
TBDMSO<br />
NBoc O<br />
OTBDMS<br />
O<br />
50<br />
O<br />
OMe<br />
O O O<br />
OMe<br />
O<br />
TBAF, THF, rt, 2 h<br />
71%<br />
TBDPSO<br />
MeO<br />
HO<br />
OH<br />
NBoc O<br />
O<br />
51<br />
O<br />
OMe<br />
O O O<br />
More sterically crowded tert-butyldimethylsilyl ethers are sometimes stable toward tetrabutylammonium<br />
fluoride. For example, the tris(silyl ether) 52 undergoes selective cleavage<br />
of only one of the three secondary ether functions with tetrabutylammonium fluoride<br />
to afford hydroxy acid 53 (Scheme 26). [58] A possible explanation for this selectivity<br />
is intramolecular transfer of the most remote tert-butyldimethylsilyl group to the carboxylate<br />
formed when 52 is exposed to the basic fluoride reagent; subsequent acidic<br />
hydrolysis of the silyl ester would lead to 53.<br />
Scheme 26 Selective Cleavage of a tert-Butyldimethylsilyl Ether with Tetrabutylammonium<br />
Fluoride [58]<br />
TBDMSO<br />
FOR PERSONAL USE ONLY<br />
4.4.17 <strong>Silyl</strong> <strong>Ethers</strong> 389<br />
OTBDMS<br />
CO2H O OTBDMS<br />
52<br />
S<br />
N<br />
TBDMSO<br />
TBAF, THF<br />
25 oC, 8 h<br />
78%<br />
OH<br />
CO2H<br />
O OTBDMS<br />
53<br />
OMe<br />
S<br />
N<br />
O<br />
for references see p 410<br />
White, J. D.; Carter, R. G., SOS, (2002) 4, 371. 2002 Georg <strong>Thieme</strong> Verlag KG
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