The Staudinger reaction is a

chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breakin ...

of an

organic azide An organic azide is an organic compound that contains an azide (–) functional group. Because of the hazards associated with their use, few azides are used commercially although they exhibit interesting reactivity for researchers. Low molecular ...

with a phosphine or

phosphite The general structure of a phosphite ester showing the lone pairs on the P In organic chemistry, a phosphite ester or organophosphite usually refers to an organophosphorous compound with the formula P(OR)3. They can be considered as esters of ...

produces an iminophosphorane. The reaction was discovered by and named after Hermann Staudinger. The reaction follows this stoichiometry: :R₃P + R'N₃ → R₃P=NR' + N₂

Staudinger reduction

The Staudinger reduction is conducted in two steps. First phosphine imine-forming reaction is conducted involving treatment of the azide with the phosphine. The intermediate, e.g. triphenylphosphine phenylimide, is then subjected to hydrolysis to produce a

phosphine oxide Phosphine oxides are phosphorus compounds with the formula OPX3. When X = alkyl or aryl, these are organophosphine oxides. Triphenylphosphine oxide is an example. An inorganic phosphine oxide is phosphoryl chloride (POCl3). Structure and bonding ...

and an

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent suc ...

: :R₃P=NR' + H₂O → R₃P=O + R'NH₂ The overall conversion is a mild method of reducing an azide to an amine.

Triphenylphosphine Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to P Ph3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists ...

tributylphosphine Tributylphosphine is the organophosphorus compound with the formula P(CH). Abbreviated or PBu, it is a tertiary phosphine. It is an oily liquid at room temperature, with a nauseating odor. It reacts slowly with atmospheric oxygen, and rapidly w ...

are most commonly used, yielding tributylphosphine oxide or triphenylphosphine oxide as a side product in addition to the desired amine. An example of a Staudinger reduction is the

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

of the pinwheel compound 1,3,5-tris(aminomethyl)-2,4,6-triethylbenzene.

Reaction mechanism

The reaction mechanism centers around the formation of an iminophosphorane through

nucleophilic addition In organic chemistry, a nucleophilic addition reaction is an addition reaction where a chemical compound with an electrophilic double or triple bond reacts with a nucleophile, such that the double or triple bond is broken. Nucleophilic additions d ...

of the aryl or alkyl phosphine at the terminal nitrogen atom of the organic azide and expulsion of

diatomic Diatomic molecules () are molecules composed of only two atoms, of the same or different chemical elements. If a diatomic molecule consists of two atoms of the same element, such as hydrogen () or oxygen (), then it is said to be homonuclear. Ot ...

nitrogen. The iminophosphorane is then hydrolyzed in the second step to the amine and a phosphine oxide byproduct. staudinger_mechanism2

Staudinger ligation

Of interest in

chemical biology Chemical biology is a scientific discipline spanning the fields of chemistry and biology. The discipline involves the application of chemical techniques, analysis, and often small molecules produced through synthetic chemistry, to the study and m ...

is the Staudinger ligation, which has been called one of the most important bioconjugation methods. Two versions of the Staudinger ligation have been developed. Both begin with the classic iminophosphorane reaction. In classical Staudinger ligation, the organophosphorus compound becomes incorporated into the peptide. Typically, appended to the organophosphorus component are reporter groups such as fluorophores. In traceless Staudinger ligation, the organophosphorus group dissociates giving a phosphorus-free bioconjugate. NontracelessStaudinger

References

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External links

Staudinger Reaction at organic-chemistry.org
accessed 060906.
Julia-Staudinger Reaction
Organic redox reactions Carbohydrate chemistry Name reactions