Kostanecki-Robinson reaction

The Kostanecki-Robinson reaction or also known as Kostanecki acylation is a name reaction in organic chemistry . The reaction is named after the Polish explorer Stanislaus von Kostanecki and is used to produce coumarin or chromones . The reaction 1 → 2 is an Allan-Robinson condensation and 1 → 3 is a Kostanecki reaction.

Overview reaction

The coumarin or chromone is produced by an ortho- acylation with a subsequent aldol condensation . An ortho -hydroxyacetophenone (or a similar o -hydroxyarylalkyl ketone) and an aliphatic carboxylic acid anhydride , in the presence of the associated sodium salt , are required:

The radicals R ¹ and R ² can be hydrogen atoms , alkyl radicals or aryl radicals .

Reaction mechanism

The possible reaction mechanism is divided into three paragraphs for better illustration, in the first part it goes up to an intermediate stage, from which either a coumarin or a chromone can arise. Then there is a continuation for each intermediate level.

The hydroxy group from alcohol 1 attacks a carbonyl carbon atom of acetic anhydride . This creates 2 . 2 is deprotonated by the acetate anion and the alcoholate anion 3 is formed . With elimination of an acetate ion, the carboxylic acid ester 4 is formed. Here, an intermediate stage is formed at which it decides whether it will be a coumarin or a chromone . The split off acetate ion can now deprotonate the carbon in the α-position to the carbonyl group. Since there are two carbonyl groups, the carbanions 5a and 5b are formed .

The carbanion 5a attacks the carbon atom of the other carbonyl group. This creates the alcoholate anion 6a . The acetic acid further protonates the alcoholate anion 6a to form an oxonium ion 7a . Chromone 8a is formed by splitting off protonated water .

The reaction mechanism is analogous with coumarin: The carbanion 5b attacks the carbon atom of the other carbonyl group. This creates the alcoholate anion 6b . The acetic acid further protonates the alcoholate anion 6b to form an oxonium ion 7b . The coumarin 8b is formed by splitting off protonated water .

Individual evidence

↑ Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 2 Volume Set . John Wiley & Sons, Hoboken, NJ 2009, ISBN 978-0-470-28663-0 , p. 1679.
↑ St. v. Kostanecki, A. Różycki: About a mode of formation of chromone derivatives . In: Reports of the German Chemical Society . 34, 1901, p. 102. doi : 10.1002 / cber.19010340119 .
↑ JJ Li, Name Reactions , 4th edition, p. 322. doi : 10.1007 / 978-3-642-01053-8_142
↑ ^a ^b Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 2 Volume Set . John Wiley & Sons, Hoboken, NJ 2009, ISBN 978-0-470-28663-0 , p. 1680.

[Wang_1477-1] Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 2 Volume Set . John Wiley & Sons, Hoboken, NJ 2009, ISBN 978-0-470-28663-0 , p. 1679.

[2] St. v. Kostanecki, A. Różycki: About a mode of formation of chromone derivatives . In: Reports of the German Chemical Society . 34, 1901, p. 102. doi : 10.1002 / cber.19010340119 .

[3] JJ Li, Name Reactions , 4th edition, p. 322. doi : 10.1007 / 978-3-642-01053-8_142

[Wang-4] Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 2 Volume Set . John Wiley & Sons, Hoboken, NJ 2009, ISBN 978-0-470-28663-0 , p. 1680.