Pfitzinger reaction

Pfitzinger reaction
Named after W. Pfitzinger
Reaction type ring-condensation
Reaction
ketone or aldehyde
+
isatin
+
potassium hydroxide
↓
quinoline-4-carboxylic acid
+
water
Conditions
Typical solvents protic

The Pfitzinger reaction (also known as the Pfitzinger-Borsche reaction) is the chemical reaction of isatin with base and a carbonyl compound to yield substituted quinoline-4-carboxylic acids.[1][2]

Several reviews have been published.[3][4][5]

Reaction mechanism

The reaction of isatin with a base such as potassium hydroxide hydrolyses the amide bond to give the keto-acid 2. This intermediate can be isolated, but is typically not. A ketone (or aldehyde) will react with the aniline to give the imine (3) and the enamine (4). The enamine will cyclize and dehydrate to give the desired quiniline (5).

Variations

Halberkann variant

Reaction of N-acyl isatins with base gives 2-hydroxy-quinoline-4-carboxylic acids.[6]

See also

References

  1. ↑ Pfitzinger, W. (1886). "Chinolinderivate aus Isatinsäure". J. Prakt. Chem. 33: 100. doi:10.1002/prac.18850330110.
  2. ↑ Pfitzinger, W. (1888). "Chinolinderivate aus Isatinsäure". J. Prakt. Chem. 38: 582. doi:10.1002/prac.18880380138.
  3. ↑ Manske, R. H. (1942). Chem. Rev. 30: 126. doi:10.1021/cr60095a006. Missing or empty |title= (help)
  4. ↑ Bergstrom, F. W. (1944). "Heterocyclic Nitrogen Compounds. Part IIA. Hexacyclic Compounds: Pyridine, Quinoline, and Isoquinoline". Chem. Rev. 35 (2): 152. doi:10.1021/cr60111a001.
  5. ↑ Shvekhgeimer, M. G.-A. (2004). "The Pfitzinger Reaction". Chemistry of Heterocyclic Compounds 40 (3): 257. doi:10.1023/B:COHC.0000028623.41308.e5.)
  6. ↑ Halberkann, J. (1921). "Abkömmlinge der Chininsäure". Chemische Berichte 54 (11): 3090. doi:10.1002/cber.19210541118.
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