bis(trimethylsilyl)acetylene
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 428345929
| ImageFile = Bis(trimethylsilyl)acetylene.png
| ImageSize =
| ImageAlt = Skeletal formula of bis(trimethylsilyl)acetylene
| ImageFile1 = Bis(trimethylsilyl)acetylene-3D-spacefill.png
| ImageAlt1 = Ball-and-stick model of the bis(trimethylsilyl)acetylene molecule
| PIN = Ethynediylbis(trimethylsilane)
| OtherNames = BTMSA
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 14630-40-1
| PubChem = 84564
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = 76286
| SMILES = C(#C[Si](C)(C)C)[Si](C)(C)C
| InChI = 1/C8H18Si2/c1-9(2,3)7-8-10(4,5)6/h1-6H3
| InChIKey = ZDWYFWIBTZJGOR-UHFFFAOYAF
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/C8H18Si2/c1-9(2,3)7-8-10(4,5)6/h1-6H3
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = ZDWYFWIBTZJGOR-UHFFFAOYSA-N
}}
|Section2={{Chembox Properties
| C=8 | H=18 | Si=2
| Appearance = Colorless to white liquid
| Density = 0.791 g/cm3
| MeltingPtC = 26
| MeltingPt_notes =
| BoilingPtC = 134.6 ± 8.0
| Solubility = 0.031 g/L}}
|Section3={{Chembox Hazards
| MainHazards = Flammable, Irritant}}
}}
Bis(trimethylsilyl)acetylene (BTMSA) is an organosilicon compound with the formula Me3SiC≡CSiMe3 (Me = methyl). It is a crystalline solid that melts slightly above room temperature and is soluble in organic solvents. This compound is used as a surrogate for acetylene.
BTMSA is prepared by treating acetylene with butyllithium followed by addition of trimethylsilyl chloride (Me = CH3, Bu = C4H9):{{cite journal|doi=10.1016/S0022-328X(00)89260-8|title=Friedel–Crafts reactions of bis(trimethylsilyl)polyynes with acyl chlorides; a useful route to terminal-alkynyl ketones|year=1972|last1=Walton|first1=D.R.M.|last2=Waugh|first2=F.|journal=Journal of Organometallic Chemistry|volume=37|pages=45–56}}
:HC≡CH + 2 BuLi → LiC≡CLi + 2 BuH
:LiC≡CLi + 2 Me3SiCl → Me3SiC≡CSiMe3 + 2 LiCl
Reactions
BTMSA is used as a nucleophile in Friedel-Crafts type acylations and alkylations and a precursor to lithium trimethylsilylacetylide. The TMS groups can be removed with tetra-n-butylammonium fluoride (TBAF) and replaced with protons. BTMSA is also a useful reagent in cycloaddition reactions. Illustrating its versatility, BTMSA was used in a concise total synthesis of (±)-estrone.{{cite book |doi=10.1002/047084289X.rb209.pub2 |chapter=Bis(trimethylsilyl)acetylene |title=Encyclopedia of Reagents for Organic Synthesis |year=2008 |last1=Curtin |first1=Michael L. |last2=Wang |first2=Cheng |isbn=978-0471936237 }} A key step in this synthesis was the formation of the steroidal skeleton, catalyzed by CpCo(CO)2.
BTMSA also serves as a ligand in organometallic chemistry. For example, it forms stable adducts with metallocenes.{{cite journal|doi=10.1021/om0208570|title=The Titanocene Complex of Bis(trimethylsilyl)acetylene: Synthesis, Structure, and Chemistry|year=2003|last1=Rosenthal|first1=Uwe|last2=Burlakov|first2=Vladimir V.|last3=Arndt|first3=Perdita|last4=Baumann|first4=Wolfgang|last5=Spannenberg|first5=Anke|journal=Organometallics|volume=22|issue=5|pages=884–900}}
: Cp2TiCl2 + Mg + Me3SiC≡CSiMe3 → Cp2Ti(η²-Me3SiC₂SiMe3) + MgCl2