trimethylsilyl chloride

TMSCl is prepared on a large scale by the direct process, the reaction of methyl chloride with a silicon-copper alloy. The principal target of this process is dimethyldichlorosilane, but substantial amounts of the trimethyl and monomethyl products are also obtained.{{Ullmann | author = Röshe, L.; John, P.; Reitmeier, R. | title = Organic Silicon Compounds | doi = 10.1002/14356007.a24_021}} The relevant reactions are (Me = methyl, {{chem2|CH3}}):

$$x\backslash \; \backslash ce\{MeCl\; +\; Si\}\; \backslash longrightarrow\; \backslash begin\{cases\}$$

\ce{Me3SiCl}, \\[2pt]

\ce{Me2SiCl2}, \\[2pt]

\ce{MeSiCl3},\\[2pt]

\text{etc.}

\end{cases}

Typically about 2–4% of the product stream is the monochloride, which forms an azeotrope with {{chem2|MeSiCl3}}.

TMSCl is reactive toward nucleophiles, resulting in the replacement of the chloride. In a characteristic reaction of TMSCl, the nucleophile is water, resulting in hydrolysis to give the hexamethyldisiloxane:

$$\backslash ce\{2\; Me3SiCl\; +\; H2O\; ->\; Me3Si-O-SiMe3\; +\; 2\; HCl\}$$

The related reaction of trimethylsilyl chloride with alcohols can be exploited to produce anhydrous solutions of hydrochloric acid in alcohols, which find use in the mild synthesis of esters from carboxylic acids and nitriles as well as, acetals from ketones. Similarly, trimethylsilyl chloride is also used to silanize laboratory glassware, making the surfaces more lipophilic.Such as in {{OrgSynth | title =The use of polystyrylsulfonyl chloride resin as a solid supported condensation reagent for the formation of esters: Synthesis of N-[(9-fluorenylmethoxy)carbonyl]-L-aspartic acid; α tert-butyl ester, β-(2-ethyl[(1E)-(4-nitrophenyl)azo]phenyl]amino]ethyl ester | volume = 81 | pages = 235 | year = 2005 | prep = v81p0235 | author = Norbert Zander and Ronald Frank}}

By the process of silylation, polar functional groups such as alcohols and amines readily undergo reaction with trimethylsilyl chloride, giving trimethylsilyl ethers and trimethylsilyl amines. These new groups "protect" the original functional group by removing the labile protons and decreasing the basicity of the heteroatom. The lability of the {{chem2|Me3Si\sO}} and {{chem2|Me3Si\sN}} groups allow them to be easily removed afterwards ("deprotected"). Trimethylsilylation can also be used to increase the volatility of a compound, enabling gas chromatography of normally nonvolatile substances such as glucose.

Trimethylsilyl chloride also reacts with carbanions to give trimethylsilyl derivatives.{{cite journal|author1=Stephanie Ganss|author2 =Julia Pedronl|author3 =Alexandre Lumbroso|author4= Günther Leonhardt-Lutterbeck|author5 =Antje Meißner|author6 =Siping Wei|author7 =Hans-Joachim Drexler|author8= Detlef Heller|author9 = Bernhard Breit|title=Rhodium-Catalyzed Addition of Carboxylic Acids to Terminal Alkynes towards Z-Enol Esters|journal=Org. Synth.|year=2016|volume= 93|pages= 367–384|doi=10.15227/orgsyn.093.0367|doi-access=free}} Lithium acetylides react to give trimethylsilylalkynes such as bis(trimethylsilyl)acetylene. Such derivatives are useful protected forms of alkynes.

In the presence of triethylamine and lithium diisopropylamide, enolisable aldehydes, ketones and esters are converted to trimethylsilyl enol ethers.{{OrgSynth|author=Yoshihiko Ito, Shotaro Fujii, Masashi Nakatuska, Fumio Kawamoto, and Takeo Saegusa | year = 1979 | title = One-Carbon Ring Expansion of Cycloalkanones to Conjugated Cycloalkenone: 2-Cyclohepten-1-one | volume = 59 | pages = 113 | collvol = 1 | collvolpages = 327 | prep = CV6P0327 }} Despite their hydrolytic instability, these compounds have found wide application in organic chemistry; oxidation of the double bond by epoxidation or dihydroxylation can be used to return the original carbonyl group with an alcohol group at the alpha carbon. The trimethylsilyl enol ethers can also be used as masked enolate equivalents in the Mukaiyama aldol addition.

Dehydration of metal chlorides with trimethylsilyl chloride in THF gives the solvate as illustrated by the case of chromium trichloride:{{cite book|chapter=Solvated and Unsolvated Anhydrous Metal Chlorides from Metal Chloride Hydrates|journal=Inorg. Synth.|volume=29|author=Philip Boudjouk |author2=Jeung-Ho So |title=Inorganic Syntheses |year=1992|pages=108–111|doi=10.1002/9780470132609.ch26|isbn=978-0-470-13260-9}}

$$\backslash ce\{CrCl3\; *\; 6\; H2O\; +\; 12\; Me3SiCl\; ->\; CrCl3(THF)3\; +\; 6\; (Me3Si)2O\; +\; 12\; HCl\}$$

Trimethylsilyl chloride is used to prepare other trimethylsilyl halides and pseudohalides, including trimethylsilyl fluoride, trimethylsilyl bromide, trimethylsilyl iodide, trimethylsilyl cyanide, trimethylsilyl azide,{{OrgSynth | volume = 50 | pages = 107 | collvol = 6 | collvolpages = 1030 | year = 1970 | prep = cv6p1030 | author = L. Birkofer and P. Wegner | title = Trimethylsilyl azide}} and trimethylsilyl trifluoromethanesulfonate (TMSOTf). These compounds are produced by a salt metathesis reaction between trimethylsilyl chloride and a salt of the (pseudo)halide (MX):

$$\backslash ce\{MX\; +\; Me3Si-Cl\; ->\; MCl\; +\; Me3Si-X\}$$

TMSCl, lithium, and nitrogen molecule react to give tris(trimethylsilyl)amine, under catalysis by nichrome wire or chromium trichloride:

$$\backslash ce\{3\; Me3SiCl\; +\; 3\; Li\}\; +\; \backslash tfrac\{1\}\{2\}\; \backslash ,\; \backslash ce\{N2\; ->\; (Me3Si)3N\; +\; 3\; LiCl\}$$

Using this approach, atmospheric nitrogen can be introduced into organic substrate. For example, tris(trimethylsilyl)amine reacts with α,δ,ω-triketones to give tricyclic pyrroles.{{ cite book | last = Brook | first = Michael A. | title = Silicon in Organic, Organometallic, and Polymer Chemistry | year = 2000 | publisher = John Wiley & Sons | location = New York | pages = 193–194 }}

Reduction of trimethylsilyl chloride give hexamethyldisilane:

$$\backslash ce\{2\; Me3SiCl\; +\; 2\; Na\; ->\; 2\; NaCl\; +\; Me3Si-SiMe3\}$$

{{reflist}}

{{DEFAULTSORT:Trimethylsilyl Chloride}}

Category:Reagents for organic chemistry

Category:Trimethylsilyl compounds

Category:Organochlorosilanes