- Pfitzinger reaction
The Pfitzinger reaction (also known as the Pfitzinger-Borsche reaction) is the
chemical reaction ofisatin with base and acarbonyl compound to give substitutedquinoline -4-carboxylic acid s. [Pfitzinger, W. "J. Prakt. Chem. " 1886, "33", 100.] [Pfitzinger, W. "J. Prakt. Chem. " 1888, "38", 582.]Several reviews have been published. [Manske, R. H. "
Chem. Rev. " 1942, "30", 126. (Review)] [Bergstrom, F. W. "Chem. Rev. " 1944, "35", 152. (Review)] [Shvekhgeimer, M. G.-A. "Chemistry of Heterocyclic Compounds" 2004, "40", 257-294. (Review, DOI|10.1023/B:COHC.0000028623.41308.e5)]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. Aketone (oraldehyde ) will react with the aniline to give theimine (3) and theenamine (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 acid s. [Halberkann, J. "Ber. " 1921, "54", 3090.]References
ee also
*
Camps quinoline synthesis
*Friedländer synthesis
*Niementowski quinazoline synthesis
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