Pfitzinger Reaction
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The Pfitzinger reaction (also known as the Pfitzinger-Borsche reaction) is the
chemical reaction A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...
of
isatin Isatin, also known as tribulin, is an organic compound derived from indole with formula C8H5NO2. The compound was first obtained by Otto Linné Erdman and Auguste Laurent in 1840 as a product from the oxidation of indigo dye by nitric acid and ...
with base and a
carbonyl In organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double bond, double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such a ...
compound to yield substituted
quinoline Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only sl ...
-4-
carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...
s. Several reviews have been published.


Reaction mechanism

The reaction of isatin with a base such as
potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...
hydrolyses 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 ...
the amide bond to give the keto-acid 2. This intermediate can be isolated, but is typically not. A
ketone In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...
(or
aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...
) will react with the aniline to give the
imine In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bon ...
(3) and the
enamine An enamine is an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine. Enamines are versatile intermediates. The word "enamine" is derived from the affix ''en''-, used as the suffix of alkene, and the r ...
(4). The enamine will cyclize and dehydrate to give the desired quinoline (5).


Variations


Halberkann variant

Reaction of ''N''-
acyl In chemistry, an acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an organyl group () or hydrogen in the case of formyl grou ...
isatins with base gives 2- hydroxy-
quinoline Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only sl ...
-4-
carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...
s.


See also

* Camps quinoline synthesis * Friedländer synthesis *
Niementowski quinazoline synthesis The Niementowski quinazoline synthesis is the chemical reaction of anthranilic acids with amides to form 4-oxo-3,4-dihydroquinazolines (3''H''-quinazolin-4-ones). Uses Research has demonstrated that the Niementowski quinazoline synthesis could ...
*
Doebner reaction The Doebner reaction is the chemical reaction of an aniline with an aldehyde and pyruvic acid to form quinoline-4-carboxylic acids. The reaction serves as an alternative to the Pfitzinger reaction. Reaction mechanism The reaction mechanism is ...
* Talnetant,
Cinchocaine Cinchocaine ( INN/ BAN) or dibucaine ( USAN) is an amide local anesthetic. Among the most potent and toxic of the long-acting local anesthetics, current use of cinchocaine is generally restricted to spinal and topical anesthesia. It is sold under ...


References

{{Reflist Carbon-carbon bond forming reactions Condensation reactions Quinoline forming reactions Ring expansion reactions Name reactions