Silyl Ethers - Thieme Chemistry

imine used for the elaboration of the aziridine 49 from á,â-unsaturated ketone 48
(Scheme 24).
Scheme 24 Migration of a tert-Butyldimethylsilyl Group to a Secondary Alcohol [56]
HO
TBDMSO
O
Ph 2S NH H 2O
CH2Cl 2, rt, 16 h
60%
TBDMSO
HO
MeO
H
MeO
48 49
4-(tert-Butyldimethylsiloxy)-1,1,1-trifluorobutan-2-ol (47): [55]
A 0.5 M soln of alcohol 46 in a mixed solvent of THF and DMF (1:4) was reacted with t-
BuOK (1.1 equiv) at ±788C. After stirring for 4 h at that temperature, the reaction was
quenched with aq NH 4Cl and extracted with Et 2O (3 ”). The combined extracts were dried
(MgSO 4), filtered, concentrated in vacuo, and purified by column chromatography
(EtOAc/hexanes 14:86) to afford 47 in quantitative yield.
(+)-(1S,8S,9S,10S,12R)-12-(tert-Butyldimethylsiloxy)-1-hydroxy-9,10-imino-8-methoxybicyclo[7.3.1]tridec-4-ene-2,6-diyn-11-one
(49): [56]
To a soln of ketol 48 (59 mg, 0.16 mmol) in dry CH 2Cl 2 (5 mL) was added S,S-diphenylsulfilimine
monohydrate (359 mg, 1.64 mmol), and the resulting suspension was stirred at rt
for 16 h. The reaction was quenched with sat. NaHCO 3 and extracted with CH 2Cl 2 (3 ”).
The combined organics were washed with H 2O (2 ”) and brine (1 ”), dried (Na 2SO 4), filtered,
and concentrated. The resulting crude material was subjected to flash chromatography
(Et 2O/heptane 1:1) to give aziridine 49 as white needles; yield: 36 mg (60%).
Cleavage
FOR PERSONAL USE ONLY
388 Science of Synthesis 4.4 Silicon Compounds
4.4.17.3.4 Method 4:
Cleavage of tert-Butyldimethylsilyl Ethers with
Tetrabutylammonium Fluoride
The most general method for cleaving tert-butyldimethylsilyl ethers is with tetrabutylammonium
fluoride in tetrahydrofuran. Unhindered silyl ethers of this class are transformed
quite readily to their respective alcohols with this reagent at room temperature.
[46] Conversion of the bis(tert-butyldimethylsilyl ether) 50 into diol 51 illustrates this
cleavage and demonstrates that a tert-butyldiphenylsilyl ether can be retained intact under
these conditions (Scheme 25). [57]
White, J. D.; Carter, R. G., SOS, (2002) 4, 371. 2002 Georg Thieme Verlag KG
O
HN
H