Trimethylsilyl cyanide
Encyclopedia
Trimethylsilyl cyanide is the chemical compound
with the formula
(CH3)3SiCN. This volatile liquid consists of a cyanide
group, that is CN, attached to a trimethylsilyl
group. The molecule is used in organic synthesis
as the equivalent of hydrogen cyanide. It is prepared by the reaction of lithium cyanide and trimethylsilyl chloride:
In its principal reaction, it adds across carbon-oxygen double bonds, for example in an aldehyde
:
The product is an O-silylated cyanohydrin
.
One use of this reagent is to convert pyridine
-N-oxide
s into 2-cyanopyridine. This transformation is best done in dichloromethane
solution using dimethyl carbamoyl chloride as the activating electrophile
. It is possible to use benzoyl chloride
but the yields and regioselectivity
of the addition of the cyano group are lower.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
(CH3)3SiCN. This volatile liquid consists of a cyanide
Cyanide
A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....
group, that is CN, attached to a trimethylsilyl
Trimethylsilyl
A trimethylsilyl group is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom [−Si3], which is in turn bonded to the rest of a molecule...
group. The molecule is used in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
as the equivalent of hydrogen cyanide. It is prepared by the reaction of lithium cyanide and trimethylsilyl chloride:
- LiCN + (CH3)3SiCl → (CH3)3SiCN + LiCl
In its principal reaction, it adds across carbon-oxygen double bonds, for example in an aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
:
- RCHO + (CH3)3SiCN → RCH(CN)OSi(CH3)3
The product is an O-silylated cyanohydrin
Cyanohydrin
A cyanohydrin is a functional group found in organic compounds. Cyanohydrins have the formula R2CCN, where R is H, alkyl, or aryl. Cyanohydrins are industrially important precursors to carboxylic acids and some amino acids...
.
One use of this reagent is to convert pyridine
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...
-N-oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
s into 2-cyanopyridine. This transformation is best done in dichloromethane
Dichloromethane
Dichloromethane is an organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is miscible with many organic solvents...
solution using dimethyl carbamoyl chloride as the activating electrophile
Electrophile
In general electrophiles are positively charged species that are attracted to an electron rich centre. In chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile...
. It is possible to use benzoyl chloride
Benzoyl chloride
Benzoyl chloride, also known as benzenecarbonyl chloride, is an organochlorine compound with the formula C6H5COCl. It is a colourless, fuming liquid with an irritating odour...
but the yields and regioselectivity
Regioselectivity
In chemistry, regioselectivity is the preference of one direction of chemical bond making or breaking over all other possible directions. It can often apply to which of many possible positions a reagent will affect, such as which proton a strong base will abstract from an organic molecule, or where...
of the addition of the cyano group are lower.
Safety
Trimethylsilyl cyanide is treated with care since it hydrolyzes to give hydrogen cyanide:- 2 (CH3)3SiCN + H2O → (CH3)3SiOSi(CH3)3 + 2 HCN