Silyl ether

Trimethylsilyl ether and trimethylsilyl enol ether

Structural formula of a trimethylsilyl ether, where R is an organyl radical (alkyl radical, aryl radical, arylalkyl radical, etc.), but not a hydrogen atom.

General structural formula of a trimethylsilyl enol ether, R 1 to R 3 being organyl radicals (alkyl radicals, aryl radicals, arylalkyl radicals, etc.) or a hydrogen atom.

Silyl ethers are chemical compounds that belong to the group of ethers and contain a silicon atom and an alkoxy group , which are linked to one another by an atomic bond . An important subgroup are the silyl enol ethers, which are used as intermediates in synthetic organic chemistry.

The basic structure is R ¹ R ² R ³ Si − O − R ⁴ , where R ^{4 represents} an alkyl or aryl group .

Commonly used silyl ethers are:

• Trimethylsilyl derivatives (TMS)
• tert -Butyldiphenylsilyl derivatives (TBDPS)
• tert -Butyldimethylsilyl derivatives (TBS / TBDMS)
• Triisopropylsilyl derivatives (TIPS)

Silyl ethers are used as protective groups in organic syntheses , which prevent functional groups present in the course of a multi-stage synthesis from reacting with the reagents used . The special thing about protecting groups is the possibility of reversibly adding them and removing them again without great effort.

education

Several methods are known for the formation of silyl ethers, two of which are particularly common:

• The reaction of the alcohol with a silyl chloride and an amine at room temperature
• The reaction of the alcohol with a silyl triflate and an amine base at low temperature

An example is the formation of silyl ethers with the help of chlorotrimethylsilane .

Silyl enol ethers can be obtained analogously by reacting silyl chloride with the carbonyl function of aldehydes and ketones in the presence of an amine base.

The cleavage can take place with the aid of fluoride ions (e.g. hexafluorosilicic acid or tetrabutylammonium fluoride in a polar aprotic solvent such as THF ).

Web links

• Description of silyl ethers and their production

Individual evidence

1. ↑ House HO, Czuba LJ, Gall M, Olmstead HD (1969): "Chemistry of carbanions. XVIII. Preparation of trimethylsilyl enol ethers", J. Org. Chem. , P. 2324, doi: 10.1021 / jo01260a018 .