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. Several reviews have been published. 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 quinoline (5). Variations Halberkann variant Reaction of N-acyl isatins with base gives 2-hydroxy-quinoline-4-carboxylic acids. See also Camps quinoline synthesis Friedländer synthesis Niementowski quinazoline synthesis Talnetant, Cinchocaine References Carbon-carbon bond forming reactions Condensation reactions Quinoline forming reactions Ring expansion reactions Name reactions