Trimethylsilyl protecting group

The trimethylsilyl protecting group can be removed by routine deprotection with triethylamine -hydrogen fluoride complex. 

Scheme 203 provides a methodology for the conversion of aryl bromides onto 4-aryl-l,2,3-triazoles. In the given example, palladium-copper catalyzed substitution of the bromine atom in indole 1226 by trimethylsilylacetylene provides intermediate 1227. Hydrolysis of the trimethylsilyl protecting group releases terminal alkyne 1228, isolated... 

Chlorotrimethylsilane, (CH3)3SiCl Reacts with alcohols to add the trimethylsilyl protecting group (Section 17.8). 

The masked disilene procednre was nsed by Saknrai and co-workers to synthesize two samples of diblock copolymers of 1,1-dimethyl-2,2-dihexylsilane (MHS) and 2-(trimethylsilyloxy)ethyl methacrylate, which differed only in the relative lengths of their blocks. Hydrolysis of the trimethylsilyl protecting groups gave the corresponding amphiphilic diblock copolymers, poly(l,l-dimethyl-2,2-dihexyldisilene)-fe-poly(2-hydroxyethyl methacrylate) (PMH S-fc-PHEMA), depicted in Pig. 22 [48]. 

PTFE poly(tetrafluoroethylene) (Teflon) TMS trimethylsilyl protecting group... 

J. T. Fletcher, et al., Organometallics, 27 (21), 5430-5433 (2008). In this approach, the trimethylsilyl protecting group is removed in situ (replaced with a hydrogen) with H20/t-BuOH. Write the product. 

Removal of the trimethylsilyl protecting group from (49), regenerating pristinamycin 11, was shown to occur under mild acidic conditions. 

Two Sonogashira coupling reactions can be used to make unsymmetrical diaryl alkynes by first using trimethylsilylacetylene. The trimethylsilyl protecting group can be removed by addition of fluoride (usually tetrabutylammonium fluoride, see Section 11.6). Show how such a sequence of reactions can be used to construct the following product when one reactant is phenyl iodide. 

FIGURE 3.23 Trimethylsilyl protecting group for the formation of monolayers. 

Hydroorganosilane transfers its hydride ion, together with a proton, from an acid to the acceptor molecule, and thus reduces the latter. If trimethylsilyl enol ethers have been used, their carbonyl groups are protected against attack by reactants. Later, the trimethylsilyl protective groups may be removed by hydrolysis. 

An alternate method of preparing the azetidinone sulfenic acid was developed by initially trapping the sulfenic acid as its trimethylsilyl ester (32) (Chou et al., 1976). Careful cleavage of the trimethylsilyl protecting group with methanol afforded the sulfenic acid (31) (Chou et al., 1974). 

Another recently approved compound is the cholesterol absorption inhibitor Ezetimibe (Zetia ) (Figure 15.3) discovered and initially produced by Schering-Plough, with a linear synthesis of seven steps [21-23]. The commercial process toward the synthesis of Ezetimibe (Zetia) starts with a CBS reduction (5% catalyst load) of ketone 41, affording chiral alcohol 42 in 95% yield. Judicious choice of the trimethylsilyl protecting group allowed clean in situ protection of both the benzylic and phenolic... 

Triethylsilyl are preferred to trimethylsilyl protecting groups in the polyacetylene series (n > 3) owing to the relatively greater resistance of the former to base-catalysed cleavage from a polyacetylene chain in the pH range 7-9. 

An important feature of the trimethylsilyl protecting group is that it may both be introduced and removed under very mild conditions. A large number of methods have been described [40] for the trimethylsilylation of alcohols but the most common, which are inreaction between the substrate and (a) trimethylchlorosilane in the presence of base, (b) hexamethyldisilazane alone, and (c) hexamethyldisilazane in the presence of an acid catalyst (often trimethylchlorosilane in pyridine solution). The trimethylsilyl group is generally removed [40] by heating a solution of the protected intermediate in aqueous alcohol, under reflux. 

Where the phenolic product is labile towards acid the trimethylsilyl ether may be used. Riemann circumvented [39] the final difficult dealkylation step [40] in the synthesis of hydroxystilbenes (42) by use of the trimethylsilyl protecting group—first to prepare the ylid (40) and secondly in the condensation step (e.g., 41). Removal of the trimethylsUyl ether grouping was then achieved by refluxing in aqueous methanol. 

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