Auwers synthesis

Auwers synthesis

Overview
The Auwers synthesis is a series of organic reaction
Organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis,...

s forming a flavonol from a coumarone. This reaction was first reported by Karl von Auwers
Karl von Auwers
Karl Friedrich von Auwers was a German chemist and the academic adviser of Karl Ziegler and Georg Wittig at the University of Marburg.-Life:...

 in 1908.
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Encyclopedia
The Auwers synthesis is a series of organic reaction
Organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis,...

s forming a flavonol from a coumarone. This reaction was first reported by Karl von Auwers
Karl von Auwers
Karl Friedrich von Auwers was a German chemist and the academic adviser of Karl Ziegler and Georg Wittig at the University of Marburg.-Life:...

 in 1908.

The first step in this procedure is an acid catalyzed
Acid catalysis
In acid catalysis and base catalysis a chemical reaction is catalyzed by an acid or a base. The acid is often the proton and the base is often a hydroxyl ion. Typical reactions catalyzed by proton transfer are esterfications and aldol reactions. In these reactions the conjugate acid of the carbonyl...

 aldol condensation
Aldol condensation
An aldol condensation is an organic reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by a dehydration to give a conjugated enone....

 between benzaldehyde
Benzaldehyde
Benzaldehyde is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. This colorless liquid has a characteristic pleasant almond-like odor...

 and a 3-oxypentanone to an o-hydroxychalcone. Bromination of the alkene
Alkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...

 group gives a dibromo-adduct which rearranges
Rearrangement reaction
A rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another atom in the same molecule...

 to the flavonol by reaction with potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

.

Mechanism


A possible mechanism for the rearrangement step is shown below: