Allan-Robinson condensation

Färber-Wau ( Reseda luteola ) contains luteolin both as an aglycon and as a glycoside .

The Allan-Robinson condensation , also known as Allan-Robinson's flavonoids synthesis , Allan-Robinson synthesis or Allan-Robinson reaction is a name reaction in organic chemistry . It was named after the English chemist Robert Robinson and the chemist James Allan . The reaction is used for the synthesis of flavones or isoflavones , these belong to the class of flavonoids that - like luteolin - occur in nature, e.g. B. in Färber-Wau.

Overview reaction

In this condensation reaction between an aromatic ortho- hydroxy ketone (R ¹ = hydrogen or any organic radical, e.g. alkyl radical ) and an aromatic acid anhydride (R ² = aryl radical , e.g. phenyl ), in the presence of the sodium salt of the acid bicyclic heterocycle :

mechanism

One possible reaction mechanism is as follows:

The ketone 1 has an enol form 2 which reacts with the acid anhydride to form the alcoholate anion 3 , with elimination of a proton . By shifting electrons, a carboxylate anion is split off and the ketone 4 is formed . The ketone 4 also has an enol form 5 . The hydroxyl group on the benzene ring of 5 is deprotonated by the carboxylate anion, the alcoholate 6 is formed , which then cyclizes to the isomeric alcoholate 7 . The action of a carboxylic acid creates the protonated form 8 , which reacts to a flavone or isoflavone 9 through proton-catalyzed splitting of water .

Individual evidence

↑ Albert Gossauer : Structure and reactivity of biomolecules. An introduction to organic chemistry. Verlag Helvetica Chimica Acta et al., Zurich et al. 2006, ISBN 3-906390-29-2 , p. 422.
^ ^A ^b Zerong Wang: Comprehensive Organic Name Reactions and Reagents. Volume 1. John Wiley & Sons, Hoboken NJ 2009, ISBN 978-0-471-70450-8 , p. 64.
↑ Martha Windholz (Ed.): The Merck Index. An Encyclopedia of Chemicals and Drugs. 9th edition. Merck & Co., Rahway NJ 1976, ISBN 0-911910-26-3 , p. ON-03.
↑ Bradford P. Mundy, Michael G. Ellerd, Frank G. Favaloro Jr .: Name Reactions and Reagents in Organic Synthesis. 2nd edition. John Wiley & Sons, Hoboken NJ 2005, ISBN 0-471-22854-0 , pp. 32-33.
^ Zerong Wang: Comprehensive Organic Name Reactions and Reagents. Volume 1. John Wiley & Sons, Hoboken NJ 2009, ISBN 978-0-471-70450-8 , p. 65.

Web links

Commons : Allan – Robinson reaction - collection of pictures, videos and audio files

[Gossauer-1] Albert Gossauer : Structure and reactivity of biomolecules. An introduction to organic chemistry. Verlag Helvetica Chimica Acta et al., Zurich et al. 2006, ISBN 3-906390-29-2 , p. 422.

[Wang_1477-2] A ^b Zerong Wang: Comprehensive Organic Name Reactions and Reagents. Volume 1. John Wiley & Sons, Hoboken NJ 2009, ISBN 978-0-471-70450-8 , p. 64.

[Windholz_1477-3] Martha Windholz (Ed.): The Merck Index. An Encyclopedia of Chemicals and Drugs. 9th edition. Merck & Co., Rahway NJ 1976, ISBN 0-911910-26-3 , p. ON-03.

[Mundy-4] Bradford P. Mundy, Michael G. Ellerd, Frank G. Favaloro Jr .: Name Reactions and Reagents in Organic Synthesis. 2nd edition. John Wiley & Sons, Hoboken NJ 2005, ISBN 0-471-22854-0 , pp. 32-33.

[Wang-5] Zerong Wang: Comprehensive Organic Name Reactions and Reagents. Volume 1. John Wiley & Sons, Hoboken NJ 2009, ISBN 978-0-471-70450-8 , p. 65.