TASF reagent
Encyclopedia
The TASF reagent or tris(dimethylamino)sulfonium difluorotrimethylsilicate is a reagent
in organic chemistry
with structural formula
[((CH3)2N)3S]+[F2Si(CH3)3]-. It is an anhydrous source of fluoride
and is used to cleave silyl ether
protective groups. Many other fluoride reagents are known, but few are truly anhydrous, because of the extraordinary basicity of "naked" F-. In TASF, the fluoride is masked as an adduct with the weak Lewis acid
trimethylsilylfluoride (FSi(CH3)3). The sulfonium
cation ((CH3)2N)3S+ is unusually non-electrophilic due to the electron-donating properties of the three (CH3)2N substituents.
This compound is prepared from sulfur tetrafluoride
:
The colorless salt precipitates from the reaction solvent, diethyl ether
.
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 organic chemistry
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
with structural formula
Structural formula
The structural formula of a chemical compound is a graphical representation of the molecular structure, showing how the atoms are arranged. The chemical bonding within the molecule is also shown, either explicitly or implicitly...
[((CH3)2N)3S]+[F2Si(CH3)3]-. It is an anhydrous source of fluoride
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
and is used to cleave silyl ether
Silyl ether
Silyl ethers are a group of chemical compounds which contain a silicon atom covalently bonded to an alkoxy group. The general structure is R1R2R3Si−O−R4 where R4 is an alkyl group or an aryl group. Silyl ethers are usually used as protecting groups for alcohols in organic synthesis...
protective groups. Many other fluoride reagents are known, but few are truly anhydrous, because of the extraordinary basicity of "naked" F-. In TASF, the fluoride is masked as an adduct with the weak Lewis acid
Lewis acid
]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
trimethylsilylfluoride (FSi(CH3)3). The sulfonium
Sulfonium
A sulfonium ion, also known as sulphonium ion or sulfanium ion, is a positively charged ion featuring three organic substituents attached to sulfur. They have the formula [SR3]+...
cation ((CH3)2N)3S+ is unusually non-electrophilic due to the electron-donating properties of the three (CH3)2N substituents.
This compound is prepared from sulfur tetrafluoride
Sulfur tetrafluoride
Sulfur tetrafluoride is the chemical compound with the formula SF4. This species exists as a gas at standard conditions. It is a corrosive species that releases dangerous HF upon exposure to water or moisture...
:
- 3 (CH3)2NSi(CH3)3 + SF4 → 2 (CH3)3SiF + [((CH3)2N)3S]+[F2Si(CH3)3]-
The colorless salt precipitates from the reaction solvent, diethyl ether
Diethyl ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
.