Tert-Butyldimethylsilyl group

The tert-butyldimethylsilyl group is known to be a particularly useful blocking group, and Ogilvie and Hakimelahi... 

In one remarkable example, Burke and Cobb employed a directed hydroformylation to functionahze regio- and diastereoselectively alkene 24 to provide aldehyde 25 as the major product of a 7.7 0.3 1 1 mixture in 69% yield (Scheme 5.10) [12]. When the ester-directing group was replaced with a tert-butyldimethylsilyl group, a nonselective and inefficient reaction resulted. Aldehyde 25 was converted to the target (-i-)-phyl-lanthocin in just a few additional steps. 

H(34)303]. The tert-butyldimethylsilyl group was found to undergo migration to the carbanionic site and was therefore abandoned [90JCS(Pi)1829], but 5-substituted derivatives have been successfully obtained with all of the other systems (Table III). 

It should be noted that there are some limitations to the use of the tert-butyldimethylsilyl group (and, presumably, other trialkylsilyl groups) for the selective protection of hydroxyl groups. Isomerization between 0-2 and 0-3 occurs with 2 - and 3 -0-(tert-butyldimethyl-silyl) derivatives of nucleosides when they are in prolonged contact with silica gel,309 or when stored in aqueous pyridine, aqueous triethyl-... 

The rate of cleavage is inversely proportional to the bulk of the silyl ether and so trimethylsilyl groups are removed relatively easily whilst tert-butyldimethylsilyl groups are more resistant to removal. 

On the other hand, in the Polonovski reaction of A-oxides using SKA, carbon-carbon bond-forming product was selectively obtained even if the substrate was allowed to react with ferf-butyldimethylsilyl ketene acetal in acetonitrile.28 It has become apparent that the choice of silyl moiety in SKA influences the course of the reaction. Specifically, in the case of SKA bearing a tert-butyldimethylsilyl group, a (methoxycarbonyl) methyl adduct was preferentially converted to a cyanomethyl adduct, whereas in the case of SKA bearing an O-fert-butyldiphenyl-... 

In the present procedure, indole is protected with a tert-butyldimethylsilyl group and further brominated with N-bromosuccinimide in a one-pot reaction. 3-Bromo-1-(tert-butyldimethylsilyl)indole readily undergoes halogen-lithium exchange with tert-... 

The protective strategy is also applicable to methacrylate monomers carrying reactive functional groups, such as OH, C=CH, and =SiOH (Figure 5.7) [105-113]. For example, the hydroxyl group of 2-hydroxyethyl methacrylate (HEMA) was masked with a tert-butyldimethylsilyl group, and the resulting protected monomer subjected to anionic polymerization [105]. Similarly, an acetal protection was... 

Wiberg et al. successfully isolated the first tetrahedrane compound made of four Si elements and stabilized with three-fold electron-donating tri-tert-butylsilyl (named supersilyl) by reacting tetrabromodisilane with tert-butylsilyl Na in THF. Matsumoto et al. chose other bulky and electron donating tert-butyldimethylsilyl groups to produce soluble, air-sensitive octasilacubane by... 

The Danheiser annulation has also been reported to be useful for the preparation of substituted azulene products." For example, treatment of silylallene 58 with tropylium cation 59 at 23 °C produces intermediate cyclopentene dihydroazulene 60, which is not isolated but rather undergoes in situ dehydrogenation with a second equivalent of tropylium cation 59 to provide azulene 61. The use of the tert-butyldimethylsilyl group as opposed to the trimethylsilyl group is necessary since the trimethylsilyl group tends to undergo premature desilylation rather than cyclization to the azulene. Substitution at the 3-position of the allene was also found to significantly... 

The high diastereoselectivity is attributed to the preferential adoption of the tert-butyldimethylsilyl group and the alkyl group of the aldehydes on the opposite side of the transition state (Scheme 6.17) [2]. 

Sauer et al. (1988b) studied the lithiation of terguride. Reaction with tert-butyl lithium afforded bis-lithiated intermediate which was further treated with different electrophiles. Depending on the electrophilic reagent 10a- or 10/ -substituted products or their mixture were obtained—Figure 15. The N-1 position must be protected, most conveniently by tert-butyldimethylsilyl group. 

To examine this hypothesis silicon enolate 85, which has bulky tert-butyldimethylsilyl group, was prepared, to prevent coordination of the a oxygen atom to tin(II). As expected, syn aldol 86 is obtained in high stereoselectivity by reaction of the above-mentioned hindered silicon enolate 85, tin(II) triflate, a chiral diamine 87, and dibutyltin acetate (Eq. (43)) [68]. 

Veysoglu, T., and L. A. Mitcher A Class of New Silylating Reagents. I. A Mild Method for Introduction of the Tert-Butyldimethylsilyl Group. Tetrahedron Lett. 22, 1299 (1981). 

The first 4-silatriafulvene derivative 94 (R = Me) was obtained by Kira s group as a reactive intermediate using the sila-Peterson reaction [52]. By use of the bulky tert-butyldimethylsilyl groups rather than trimethylsilyl (TMS) substituents in 94, the first stable 4-silatriafulvene 95 was synthesized by the same group (Scheme 6.22). An X-ray analysis reveals that 95 has an almost planar skeleton with bond alternation all skeletal carbon and silicon atoms are located almost in a plane and the silicon-carbon double bond length is 1.755 A, which is close to that of tert-butyldimethylsilyl-(trimethylsUyl)adamantylidenesilane 96 (1.741 A) [53]. 

The tert-butyldimethylsilyl groups are less sensitive to hydrolysis than trimeth-ylsilyl groups and allow crystallization of the monomers, but they react easily with the fluoride anions of the catalyst. 

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