Bis(trimethylsilyl)acetylene explained

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 butyl lithium followed by addition of chlorotrimethylsilane:^[1]

Li₂C₂ + 2 Me₃SiCl → Me₃SiC≡CSiMe₃ + 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.^[2] 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.^[3]

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.

Notes and References

1. 10.1016/S0022-328X(00)89260-8. Friedel-crafts reactions of bis(trimethylsilyl)polyynes with acyl chlorides; a useful route to terminal-alkynyl ketones. 1972. Walton. D.R.M.. Waugh. F.. Journal of Organometallic Chemistry. 37. 45–56.
2. Book: 10.1002/047084289X.rb209.pub2 . Bis(trimethylsilyl)acetylene . Encyclopedia of Reagents for Organic Synthesis . 2008 . Curtin . Michael L. . Wang . Cheng . 978-0471936237 .
3. 10.1021/om0208570. The Titanocene Complex of Bis(trimethylsilyl)acetylene: Synthesis, Structure, and Chemistry†. 2003. Rosenthal. Uwe. Burlakov. Vladimir V.. Arndt. Perdita. Baumann. Wolfgang. Spannenberg. Anke. Organometallics. 22. 5. 884–900.