Fischer's indole synthesis
The Fischer indole synthesis (also Fischer indole synthesis ) is a name reaction of organic chemistry , which was first described in 1883 by Emil Fischer . The synthesis is used to produce indoles . It does this by heating hydrazines and ketones (or aldehydes ) in the presence of an acidic catalyst :
Reaction mechanism
The mechanism first described by GM Robinson and R. Robinson consists of several steps. In the first step, phenylhydrazine 1 reacts with a ketone (or aldehyde). The phenylhydrazone 6 is formed with elimination of water. 6 and the enamine 7 are in a tautomeric equilibrium. This is followed by a [3,3] sigmatropic rearrangement. This causes a CC bond to form with the formation of the quinoid compound 8 . This is followed by rearomatization, producing an aromatic amine 9 . An aminal 10 is formed after an internal, nucleophilic attack . After ammonia is split off by acid catalysis and deprotonated , the desired indole 13 is formed .
literature
- Emil Fischer, Friedrich Jourdan: About the hydrazines of pyruvic acid . In: Reports of the German Chemical Society . tape 16 , no. 2 , July 1883, p. 2241–2245 , doi : 10.1002 / cber.188301602141 ( digitized on Gallica ).
- Gertrude Maud Robinson, Robert Robinson: A new synthesis of tetraphenylpyrrole . In: Journal of the Chemical Society, Transactions . tape 113 , 1918, pp. 639-645 , doi : 10.1039 / CT9181300639 .
- Theophil Eicher , Siegfried Hauptmann : The Chemistry of Heterocycles . 2nd, Wiley-VCH, Weinheim 2005, p. 106.
Web links
- chemiestudent.de: Name reactions and example of the Fischer indole synthesis
- organic-chemie.ch: name reactions and current literature examples
Individual evidence
- ^ László Kürti , Barbara Czakó: Strategic Applications of Named Reactions in Organic Synthesis ; Elsevier Academic Press, Burlington-San Diego-London 2005, 1st edition; ISBN 0-12-369483-3 .
- ↑ J. Clayden, N. Greeves, S. Warren, P. Wothers: Organic Chemistry . Oxford University Press, 2001.