Aromatization (chemistry)

Aromatization refers to the reaction of an unsaturated cyclic chemical compound to an aromatic compound . Since the oxidation level of the previously unsaturated ring atoms increases, it is an oxidation . The aromatization is usually energetically favorable, since a low-energy, mesomeric - stabilized aromatic system is created.

Aromatizations are often the last reaction steps in the synthesis of heteroaromatics , for example in common pyridine , quinoline , isoquinoline or indole syntheses.

Aromatization of dehydroquinoline to quinoline by oxidation with nitrobenzene

In the case of electrophilic aromatic substitutions , aromatizations occur as the last reaction step by splitting off a proton . Since in this case an aromatic was already present as a starting material ( 1 ) and the aromatic system is only broken up intermediately ( 2b ), this is referred to as rearomatization .

Mechanism of electrophilic aromatic substitution. The intermediate non-aromatic σ-complex ( 2b ) is rearomatized by splitting off a proton.

Individual evidence

1. ↑ Entry on aromatic compounds. In: Römpp Online . Georg Thieme Verlag, accessed on December 28, 2014.
2. ^ ^{A b} Hans Beyer and Wolfgang Walter : Textbook of Organic Chemistry , 24th Edition, S. Hirzel Verlag, Stuttgart 2004, ISBN 3-7776-1221-9 .
3. ↑ DT Davies: Basistexte Chemie: Aromatic Heterocyclen , 1st edition, Wiley-VCH, Weinheim 1995, ISBN 3-527-29289-6 .
4. ↑ JA Joules, K. Mills: Heterocyclic Chemistry , 5th Edition, pp. 125-141, Blackwell Publishing, Chichester, 2010, ISBN 978-1-4051-9365-8 .