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 break ...

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 w ...

with a

phosphine Phosphine ( IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotti ...

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 Hermann Staudinger (; 23 March 1881 – 8 September 1965) was a German organic chemist who demonstrated the existence of macromolecules, which he characterized as polymers. For this work he received the 1953 Nobel Prize in Chemistry. He is also ...

. 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 Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological 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 su ...

: :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 ...

or tributylphosphine 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 In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs. A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage o ...

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 ...

of the aryl or alkyl

at the terminal nitrogen atom of the organic azide and expulsion of diatomic

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seve ...

. 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 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