Bis(trimethylsilyl)acetylene
Encyclopedia
Bisacetylene (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
.
BTMSA is prepared by treating acetylene with butyl lithium
followed by addition of chlorotrimethylsilane:
in Friedel-Crafts
type acylation
s and alkylation
s 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
. 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 adduct
s with metallocene
s.
Organosilicon
Organosilicon compounds are organic compounds containing carbon silicon bonds. Organosilicon chemistry is the corresponding science exploring their properties and reactivity.Like carbon, the organically bound silicon is tetravalent and tetrahedral...
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
Acetylene
Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...
.
BTMSA is prepared by treating acetylene with butyl lithium
Butyl lithium
Butyllithium may refer to one of three isomeric organolithium reagents used in chemical synthesis:*n-Butyllithium, abbreviated BuLi or nBuLi*sec-Butyllithium, abbreviated sec-BuLi or sBuLi...
followed by addition of chlorotrimethylsilane:
- Li2C2 + 2 (CH3)3SiCl → [(CH3)3Si]2C2 + 2 LiCl
Applications
BTMSA is used as a nucleophileNucleophile
A nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...
in Friedel-Crafts
Friedel-Crafts reaction
The Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877. There are two main types of Friedel–Crafts reactions: alkylation reactions and acylation reactions. This reaction type is a form of electrophilic aromatic substitution...
type acylation
Acylation
In chemistry, acylation is the process of adding an acyl group to a compound. The compound providing the acyl group is called the acylating agent....
s and alkylation
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...
s and a precursor to lithium trimethylsilylacetylide. The TMS groups can be removed with tetra-n-butylammonium fluoride
Tetra-n-butylammonium fluoride
Tetra-n-butylammonium fluoride or TBAF is a quaternary ammonium salt with the chemical formula 4N+F-. It is commercially available as the trihydrate and as a solution in tetrahydrofuran....
(TBAF) and replaced with protons. BTMSA is also a useful reagent
Reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...
in cycloaddition
Cycloaddition
A cycloaddition is a pericyclic chemical reaction, in which "two or more unsaturated molecules combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity." The resulting reaction is a cyclization reaction.Cycloadditions are usually described by the...
reactions. Illustrating its versatility, BTMSA was used in a concise total synthesis of (±)-estrone
Estrone
Estrone is an estrogenic hormone secreted by the ovary as well as adipose tissue.Estrone is one of several natural estrogens, which also include estriol and estradiol...
. A key step in this synthesis was the formation of the steroidal skeleton, catalyzed by CpCo(CO)2
Cyclopentadienylcobalt dicarbonyl
Cyclopentadienylcobalt dicarbonyl is an organocobalt compound with formula Co2, abbreviated CpCo2. It is an example of a half-sandwich complex. It is a dark red air sensitive liquid. This compound features one cyclopentadienyl ring that is bound in an η5-manner and two carbonyl ligands...
:
BTMSA also serves as a ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
in organometallic chemistry
Organometallic chemistry
Organometallic chemistry is the study of chemical compounds containing bonds between carbon and a metal. Since many compounds without such bonds are chemically similar, an alternative may be compounds containing metal-element bonds of a largely covalent character...
. For example, it forms stable adduct
Adduct
An adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species...
s with metallocene
Metallocene
A metallocene is a compound typically consisting of two cyclopentadienyl anions bound to a metal center in the oxidation state II, with the resulting general formula 2M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride, vanadocene dichloride...
s.
- Cp2TiCl2 + Mg + Me3SiC≡CSiMe3 → Cp2Ti[(CSiMe3)2] + MgCl2