Trimethylsilylacetylene

Silican-protected group

Trimethylsilylacetylene is a silican-protected group, also known as trimethylethynylsilane, trimethylethynyl silicon and ethynyltrimethylsilane. It is a colorless transparent liquid at room temperature. It could be used to synthesize parazole by the addition of 1,3-bipolar ring of acetylene diazide. It is also the substrate of nickel catalyzed reaction and benzonitrile coupling reaction.

Application

• Common intermediate for asymmetric synthesis
• Silica reagent

Chemical Properties

CLEAR COLORLESS LIQUID

Physical properties

bp 53 °C; d 0.695 g cm3.

Uses

Ethynyltrimethylsilane was used in: microwave-assisted, one-pot, three-step Sonogashira cross-coupling-desilylation-cycloaddition reaction for the preparation of 1,4-disubstituted 1,2,3-triazoles synthesis of poly(ethynyltrimethylsilane) containing Pd (II) coordination sites pyrazole synthesis via 1,3-dipolar cycloaddition of diazo compounds to acetylenes

Uses

Trimethylsilylacetylene is a valuable reagent used in ethynylation by palladium(0)-catalyzed coupling/condensation with aryl and vinyl halides and triflates, or by nucleophilic attack of the corresponding acetylide on electrophilic centers; reacts with alkyl iodides, tin hydrides,6 and dichloroketene in a regioselective and stereoselective manner, participating in the following synthesis reactions: Ethynylations, Palladium(0)-Catalyzed Coupling Reactions,Reaction of Trimethylsilylacetylides with Electrophiles, Radical-Initiated and Transition Metal-Catalyzed Additions, Cycloaddition Reactions, Ethynylations, Cycloaddition Reactions, Further Transformations etc.

Uses

(Trimethylsilyl)acetylene is used in the preparation of trimethylsilanyl-propiolic acid ethyl ester by reacting with carbonochloridic acid ethyl ester as well as in the synthesis of iodoalkenes by radical addition of perfluoroalkyl iodides. It is used as a nucleophile in Friedel-Crafts type acylations and alkylations reactions, as a ligand in organometallic chemistry and an useful reagent in cycloaddition reactions. It acts as a precursor to lithium trimethylsilylacetylide It finds application in the synthesis of (±)-estrone.

General Description

Laser-induced polymerization of gaseous ethynyltrimethylsilane was used for efficient chemical vapour deposition of polycarbosilane films. Ethynyltrimethylsilane acts as substrate for nickel-catalyzed cross-coupling with benzonitriles.

Reactivity Profile

Trimethylsilylacetylene is a versatile two carbon building block of considerable utility. Unlike acetylene, which is a gas at room temperature and potentially dangerous, this mono-protected synthon is an easily handled liquid. In many instances, the introduction of the ethynyl group is facilitated by the use of TMS-acetylene. It can be used in many types of synthetic procedures without the need for specialized equipment. Trimethylsilylacetylene (TMSA) has found tremendous utility in the ethynylation of aromatic, heteroaromatics and olefinic compounds via the palladium-catalyzed coupling with halides and triflates. It has become a significant method for the introduction of terminal acetylene into organic molecules. Other synthetic uses of TMSA include alkylation via Grignard or alkali metal reagents, hydroboration and hydrosilation.

Synthesis

A solution of chlorotrimethylsilane (152 mL, 130 g, 1.197 mol) in dry THF (100 mL) is placed in the 1-L dropping funnel. It is added (20 min) to the cooled and stirred solution of ethynylmagnesium chloride at a rate sufficient to maintain a reaction temperature of about 15–20°C. Finally, the dropping funnel is replaced by an efficient double-surface condenser and calcium chloride drying tube, and the reaction mixture is heated under reflux for 1 hr. The reflux condenser is replaced by a distillation head, and a double-surface condenser is connected to a receiver flask, which is cooled in an ice bath. The reaction mixture is distilled under nitrogen with stirring until all the azeotrope of trimethylsilylacetylene and THF (700–800 mL, bp ca. 66°C) has been distilled. The distillate is washed with ice–water portions (10 × 500 mL) to remove the THF. Washing is continued until the organic layer stays constant in volume. Distillation of the organic layer under an atmosphere of nitrogen through a short Vigreux column gives trimethylsilylacetylene, bp 50–52°C/760mm, nD20 1.391.

Purification Methods

Distil it through an efficient column. The IR has bands at max 2041 (CC) and 3289 (C-H) cm-1. [Kr.hnke & Goss Chem Ber 92 30 1959, Beilstein 4 IV 3937.]