Bis(trimethylsilyl)acetylene (BTMSA) is an organosilicon compound with the formula Me<sub>3</sub>SiCâ¡CSiMe<sub>3</sub> (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 = CH<sub>3</sub>, Bu = C<sub>4</sub>H<sub>9</sub>):
An alternative source is the reaction of dimethyl acetylenedicarboxylate and 3,4-bis(trimethylsilyl)furan.
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 (ñ)-estrone. A key step in this synthesis was the formation of the steroidal skeleton, catalyzed by CpCo(CO)<sub>2</sub>.
BTMSA also serves as a ligand in organometallic chemistry. For example, it forms stable adducts with metallocenes.