Reagent for Introduction of the TTMSS Group

Chlorotris(trimethylsilyl)silane (1) is a reagent for the introduction of tris(trimethylsilyl)silyl group (TTMSS group) as a protecting group. 1 reacts with primary or secondary alcohols in the presence of DMAP to give the corresponding TTMSS ethers in high yields.¹⁾ TTMSS ethers are stable to Grignard reagents, oxidation and acidic conditions. They are also stable to CsF, conditions under which cleavage of silyl ethers is often observed. TTMSS ethers can be cleaved with photolysis (254 nm) or by the action of TBAF.
Furthermore, in the Mukaiyama cross-aldol reaction²⁾ and the [2+2] cyclization with acrylates³⁾ using silyl enol ethers, the corresponding products can be obtained in high yields with high diastereoselectivity by the introduction of TTMSS group.

Typical Procedure: Protection of the Alcohol¹⁾
To a stirring solution of the alcohol (1 mmol) and 4-dimethylaminopyridine (DMAP) (1.20 mmol) in CH₂Cl₂ is added a solution of chlorotris(trimethylsilyl)silane (1–1.2 mmol) in CH₂Cl₂ (1 M). The solution is stirred overnight at room temperature under N₂. Water is added and the aqueous layer is extracted with CH₂Cl₂. The organic layer is dried over anhydrous sodium sulfate, filtered and the solvent is removed under reduced pressure. Separation by flash chromatography gives the products in 80–90% yields.