Pfitzinger reaction

The Pfitzinger reaction or Borsche Pfitzinger reaction refers to the synthesis of quinoline -4-carboxylic acids from isatin and a carbonyl compound under the action of a base. She goes to the German organic chemist Wilhelm Pfitzinger ( University of Leipzig, 1886, 1888) and Walther Borsche ( 1877-1950; Georg- August -Universität Göttingen, 1914) back.

There have been published several reviews.

Reaction mechanism

The reaction of isatin with a base such as potassium hydroxide, the amide bond is hydrolyzed and the keto acid is 2 This intermediate may be isolated but this is generally avoided. A ketone or aldehyde (R1 = H) then condensed with the aniline to the imine 3, which lies with the enamine 4 in equilibrium, then produced in a cyclocondensation the quinoline 5

Half Can - variant

The reaction of N - acylisatinen with base gives 2- hydroxyquinoline - 4-carboxylic acids. The German pharmacist Philipp Josef Half Can (1880-1952) discovered this reaction variant.