Conrad-Limpach quinoline synthesis
The Conrad-Limpach quinoline synthesis is a name reaction from the field of organic chemistry and was observed in 1887 by Max Conrad (1848–1920) and Leonhard Limpach (1852–1933). This takes place with elimination of water and alcohol, a condensation of aniline with a β- keto ester to form a Hydroxi quinoline .
Overview reaction
The Conrad Limpach quinoline synthesis is carried out in acidic , aqueous solution .
The atoms drawn in gray leave the molecule during the reaction and the connection drawn in blue stands for the newly established bond between the aniline and the β-ketoester to form a multi-ringed heterogeneous aromatic, a quinoline derivative. The radical R can stand for an organic radical .
Possible mechanism
The following mechanism of the Conrad Limpach quinoline synthesis is explained using aniline and β-propanoethyl ester and hydrogen chloride (HCl).
The aniline (1) attacks the keto group of the β- propanoethyl ester (2) nucleophilically , while the keto group is protonated . This creates the cation 3 . Cation 4 is created through internal rearrangement of the proton and subsequent elimination of water . The intermediate product 5k is formed by deprotonation on nitrogen . The carbonyl group tautomerizes to the alcohol group through the keto-enol tautomerism and the molecule thus to the enol 5e . Electron migrations create a ring closure to intermediate 6 . After splitting off of methanol , the intermediate product 7 is formed , which is aromatized by renewed internal rearrangement of the proton and thus the end product 4-hydroxy-2-methyl-quinoline (8) is formed.
application
Since the Conrad-Limpach quinoline synthesis initially only produces a quinoline derivative, the process is a preparation for the quinoline synthesis.
literature
- Bradford P. Mundy, Michael G. Ellerd, Frang G. Favaloro Jr .: Name Reactions and Reagents in Organic Synthesis . 2nd Edition. John Wiley & Sons, New York 2005, ISBN 0-471-22854-0 , pp. 134-135.
- Martha Windholz: The Merck Index. 9th edition. Merck & Co., New Jersey 1976, ISBN 0-911910-26-3 , p. 19.
Individual evidence
- ↑ Bradford P. Mundy, Michael G. Ellerd, Frang G. Favaloro JR .: Name Reactions and Reagents in Organic Synthesis . Second Edition, John Wiley & Sons, New York 2005, p. 166.
- ↑ Bradford P. Mundy, Michael G. Ellerd, Frang G. Favaloro Jr .: Name Reactions and Reagents in Organic Synthesis . 2nd Edition. John Wiley & Sons, New York 2005, p. 167.