Annulation

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Examples of fused compounds. Top row: thiophene (left) and the benzo [ b ] thiophene derived from it by annulation . Bottom row: Cyclohexane (left) and the decalin derived from it by annulation .

Anellation (from Latin: anellus = small ring), also condensation , in English also fusion , is in chemistry the name for the addition of a further ring to one or more existing rings of a cyclic molecule . At the joint, at least two (of the original) rings share one and the same atomic bond .

Bridged molecules and spiro compounds are not fused systems . In spiro compounds, only one ring atom is part of two rings. In bridged connections such as For example, norbornanes or phanes , the atoms that share two rings are not adjacent - they are bridgeheads .

The spelling “Annelierung” and “Annellierung” is wrong according to German spelling, but often found.

synthesis

The possibilities of producing fused products are numerous. The formation is possible via inter- (type C in the scheme) and intramolecular reactions (types A and B), (type B is a transannular cyclization).

Strategies for the synthesis of fused compounds

The annulation reactions include cycloadditions - [2 + 2] cycloadditions and the Diels-Alder reaction -, condensations with maleic anhydride and the Robinson reaction , others are the Danheiser benzannulation , Dötz reaction (benzoannulation), Eder -Sauer-Wiechert reaction ( enantioselective Robinson annulation), Larock indole synthesis (palladium-catalyzed annulation).

Fused ring systems are often also called fused ring systems.

See also

literature

  • Heinz GO Becker, Werner Berger, Günter Domschke, Egon Fanghänel, Jürgen Faust, Mechthild Fischer, Fritjof Gentz, Karl Gewald, Reiner Gluch, Roland Mayer, Klaus Müller, Dietrich Pavel, Hermann Schmidt, Karl Schollberg, Klaus Schwetlick, Erika Seiler and Günter Zeppenfeld: Organikum , 19th edition, Johann Ambrosius Barth Verlag, 1993, ISBN 3-335-00343-8 .

Individual evidence

  1. ↑ a b Entry on condensed ring systems. In: Römpp Online . Georg Thieme Verlag, accessed on November 15, 2013.
  2. ↑ a b Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 1: A-Cl. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1979, ISBN 3-440-04511-0 , pp. 205-206.
  3. ^ Brockhaus ABC Chemie , VEB FA Brockhaus Verlag Leipzig 1965, p. 85.

Web links

Wiktionary: annealing  - explanations of meanings, word origins, synonyms, translations
Wiktionary: annellate  - explanations of meanings, word origins, synonyms, translations