Bis(trimethylsilyl)acetylene

Bis(trimethylsilyl)acetylene (BTMSA) is an organosilicon compound with the formula C2(Si(CH3)3)2. It is a colorless liquid that is soluble in organic solvents. This compound is used as a surrogate for acetylene.

Bis(trimethylsilyl)acetylene
Names
IUPAC name
Bis(trimethylsilyl)acetylene
Other names
BTMSA
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.035.141
Properties
C8H18Si2
Molar mass 170.402 g·mol−1
Appearance Colorless to white Liquid
Density 0.791 g/cm3
Melting point 26 °C (79 °F; 299 K)
Boiling point 134.6 ± 8.0 °C
0.031 g/L
Hazards
Main hazards Flammable, Irritant
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

BTMSA is prepared by treating acetylene with butyl lithium followed by addition of chlorotrimethylsilane:[1][2]

Li2C2 + 2 (CH3)3SiCl → [(CH3)3Si]2C2 + 2 LiCl

Applications

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.[3] 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.[4]

Cp2TiCl2 + Mg + Me3SiC≡CSiMe3 → Cp2Ti[(CSiMe3)2] + MgCl2

BTMSA is also used in the total synthesis of epibatidine (and analogs), and also in the synthesis of iclaprim.

References
  1. Holmes, A.; Sporikou, C.; Org. Synth. 1993, Coll. Vol. 8, 606.
  2. Walton, D. R. M.; Waugh, F., J. Organomet. Chem. 1972, 37, 45. doi:10.1016/S0022-328X(00)89260-8
  3. Curtain, M. L.; Wang, C. Bis(trimethylsilyl) acetylene. e-EROS.
  4. Rosenthal, U.; Burlakov, V. V.; Arndt, P.; Baumann, W.; Spannenberg, A. Organometallics 2003, 22, 884. doi:10.1021/om0208570
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