The Vilsmeier–Haack reaction (also called the Vilsmeier reaction) is the

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 a substituted

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it is ...

(1) with

phosphorus oxychloride Phosphoryl chloride (commonly called phosphorus oxychloride) is a colourless liquid with the formula . It hydrolyses in moist air releasing phosphoric acid and fumes of hydrogen chloride. It is manufactured industrially on a large scale from phosp ...

and an

electron-rich In chemistry, electron-rich is jargon that is used in multiple related meanings with either or both kinetic and thermodynamic implications: *with regards to electron-transfer, electron-rich species have low ionization energy and/or are reducing ...

arene Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past grouping ...

(3) to produce an

aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used as ...

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...

(5). The reaction is named after

Anton Vilsmeier Dr. Anton Vilsmeier (12 June 1894 – 12 February 1962) was a German chemist who together with Albrecht Haack discovered the Vilsmeier-Haack reaction. Early life Anton Vilsmeier was born to the mill owner, Wolfgang Vilsmeier, and his wife, Ph ...

and

Albrecht Haack Albrecht ("noble", "bright") is a given name or surname of German language, German origin and may refer to: First name *Albrecht Agthe, (1790–1873), German music teacher *Albrecht Altdorfer, (c. 1480–1538) German Renaissance painter *Albrecht ...

. For example,

benzanilide Benzanilide is the organic compound with the formula C6H5C(O)NHC6H5. It is a white solid. Commercially available, it may be prepared by treating benzoic acid with aniline Aniline is an organic compound with the formula C6 H5 NH2. Consisting ...

and

dimethylaniline ''N'',''N''-Dimethylaniline (DMA) is an organic chemical compound, a substituted derivative of aniline. It consists of a tertiary amine, featuring dimethylamino group attached to a phenyl group. This oily liquid is colourless when pure, but com ...

react with

to produce an unsymmetrical diaryl ketone. Similarly,

anthracene Anthracene is a solid polycyclic aromatic hydrocarbon (PAH) of formula C14H10, consisting of three fused benzene rings. It is a component of coal tar. Anthracene is used in the production of the red dye alizarin and other dyes. Anthracene is ...

is formylated at the 9-position. The reaction of anthracene with ''N''-methylformanilide, also using phosphorus oxychloride, gives 9-anthracenecarboxaldehyde: :

Reaction mechanism

The reaction of a substituted amide with phosphorus oxychloride gives a substituted chloroiminium ion (2), also called the

Vilsmeier reagent The Vilsmeier reagent is an organic compound with the formula CH3)2NCHCll. It is a salt consisting of the N,N-dimethyliminium cation ( CH3)2N=CHClsup>+) and chloride anion. Depending on the particular reaction, the anion can vary. In typical POC ...

. The initial product is an iminium ion (4b), which is

hydrolyze 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 ...

d to the corresponding

during workup. :

References

{{DEFAULTSORT:Vilsmeier-Haack reaction Addition reactions Name reactions Formylation reactions

Reaction mechanism

See also

Further reading

References