tert-Butyldimethylsilyl chloride

Chemical Properties

tert-Butyldimethylsilyl chloride is a colorless or white solid that is soluble in many organic solvents but reacts with water and alcohols.It is an organosilicon compound that can be used as a versatile protecting reagent for alcohols, amines, amides, and various carboxylic acids.

Uses

tert-Butyldimethylchlorosilane is used to protect hydroxyl group in organic synthesis. It finds application in the synthesis of prostaglandin. It is also used as an auxiliary material for hypolipaemics such as lovastatin and simvastatin. It plays an important role in the preparation of isoxazolines N-oxides from alpha-bromonitroalkanes. It acts as a versatile protecting reagent for amines, amides and alcohols.

Definition

ChEBI: Tert-butyldimethylsilyl chloride is a silyl chloride consisting of a central silicon atom covalently bound to one chloro, one tert-butyl and two methyl groups. tert-Butyldimethylsilyl chloride is a derivatisation agent used in gas chromatography/mass spectrometry applications. It has a role as a chromatographic reagent.

Preparation

tert-butyldimethylsilyl chloride (TBSCI) was synthesized by the reaction of tert-butyllithium with dichlorodimethylsilane.
The pentane solution of dichlorodimethylsilane was cooled to 0°C, and the pentane solution of tert-butyllithium was added dropwise with stirring under nitrogen. The temperature was maintained at 0 °C, stirred for 1.5 h and then heated to 25 °C, and the reaction was continued for 48 h. Distillation, collect 125 ℃ (97.5kPa) fractions, stand to solidify, and obtain tert-butyldimethylsilyl chloride. Yield 70%.

Application

Tert-butyldimethylsilyl chloride is a sterically hindered organosilicon protective agent, which is widely used in the synthesis of original drugs. It is used as a protective group for hydroxyl in the synthesis of ribonucleosides, and is also an oxidant and decyanide.
t-Butyldimethylchlorosilane is useful as an anion trapping reagent. For example, TBDMSCl was found to be an efficient trap of the lithio α-phenylthiocyclopropane anion.When dichlorothiophene was treated with 2 equiv of n-butyllithium followed by 2 equiv of TBDMSCl the di-TBDMS-thiophene was isolated. The lithium anions of primary (eq 1) and secondary (eq 2) nitriles were trapped with TBDMSCl to give C,N-disilyl- and Nsilylketenimines in excellent yields.

Silyl stannanes have been prepared by trapping tin anions with TBDMSCl or other silyl chlorides. Alkynes treated with silyl stannanes and catalytic tetrakis(triphenylphosphine)palladium(0) give cis-silyl stannylalkenes in good yields.

Reactions

tert-Butyldimethylsilyl chloride reacts with alcohols in the presence of base to give tert-butyldimethylsilyl ethers:
(Me3C)Me2SiCl + ROH → (Me3C)Me2SiOR + HCl
These silyl ethers hydrolyze much more slowly than the trimethylsilyl ethers.

Hazard

Moderately toxic.

Flammability and Explosibility

Flammable

Synthesis

Example 3: To a 500 mL four-necked flask equipped with a reflux condenser, a dosing funnel, a thermometer, and a mechanical stirrer was added 12.2 g (0.5 mol) of magnesium powder under nitrogen protection. After drying, tert-butyl Grignard reagent was prepared by adding 250 mL of anhydrous tetrahydrofuran and 46.3 g (0.5 mol) of chlorotert-butane under stirring. At room temperature, 0.34 g (0.004 mol) of sodium thiocyanate was added to the reaction system as a catalyst, followed by the slow dropwise addition of 64.5 g (0.5 mol) of dimethyldichlorosilane. The reaction was exothermic and the system temperature was raised to 60°C. After maintaining reflux stirring for 3 h, the reaction mixture was diluted by adding 100 mL of hexane and filtered to remove insoluble material. The solvent was removed from the filtrate by distillation under reduced pressure, followed by distillation at atmospheric pressure to give 59 g (78% yield) of the colorless liquid product tert-butyldimethylchlorosilane.

Purification Methods

Fractionally distil it at atmospheric pressure. [Sommer & Tyler J Am Chem Soc 76 1030 1954, Corey & Venkateswarlu J Am Chem Soc 94 6190 1972, Beilstein 4 IV 4076.]

References

[1] Patent: US5068386, 1991, A
[2] Tetrahedron Letters, 1989, vol. 30, # 46, p. 6393 - 6394