Annulation (derived from annular, occasionally annelation) in organic chemistry is a chemical reaction in which a new ring is constructed on another molecule (often another ring). [GoldBookRef|title=annulation|url= GoldBookRef|title=annelation|url=]


Examples are the Robinson annulation and certain cycloadditions. Annular molecules are constructed from side-on condensed cyclic segments, for example helicenes and acenes. In transannulation a bicyclic molecule is created by intramolecular carbon-carbon bond formation in a large monocyclic ring. An example is the samarium(II) chloride induced ketone - alkene cyclization of "5-methylenecyclooctanone" which proceeds through a ketyl intermediate ["Construction of Bicyclic Ring Systems via a Transannular SmI2-Mediated Ketone-Olefin Cyclization Strategy"Gary A. Molander, Barbara Czakó, and Michael Rheam J. Org. Chem.; 2007; 72(5) pp 1755 - 1764; (Article) DOI|10.1021/jo062292d] :



The term benzannulated compounds refers to derivatives of cyclic compounds (usually aromatic) which are fused to a benzene ring. Examples are listed in the table below:


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  • annulation — [ anylasjɔ̃ ] n. f. • 1320, repris fin XVIIIe; lat. ecclés. adnulatio ♦ Dr. Décision judiciaire ou administrative déclarant sans effet un acte contrevenant à un commandement ou à une défense de la loi. ⇒ abrogation, 1. cassation, infirmation,… …   Encyclopédie Universelle

  • Annulation — An nu*la tion, n. A circular or ringlike formation; a ring or belt. Nicholson. [1913 Webster] …   The Collaborative International Dictionary of English

  • annulation — [an΄yo͞o lā′shən, an΄yəlā′shən] n. 1. formation of rings 2. a ring or ringlike structure * * * an·nu·la·tion (ăn yə lāʹshən) n. 1. The act or process of forming rings. 2. A ringlike structure, segment, or part. * * * …   Universalium

  • annulation — ANNULATION. s. fémin. Action d annuller …   Dictionnaire de l'Académie Française 1798

  • annulation — [an΄yo͞o lā′shən, an΄yəlā′shən] n. 1. formation of rings 2. a ring or ringlike structure …   English World dictionary

  • Annulation — Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom. Annulation en informatique Annulation rétroactive Recours en annulation Annulation de mariage Voir aussi Nullité Catégorie  …   Wikipédia en Français

  • ANNULATION — s. f. Action d annuler. L annulation d un acte, d un marché …   Dictionnaire de l'Academie Francaise, 7eme edition (1835)

  • ANNULATION — n. f. Action d’annuler. L’annulation d’un acte, d’un marché …   Dictionnaire de l'Academie Francaise, 8eme edition (1935)

  • annulation — (a nnu la sion) s. f. Action d annuler. ÉTYMOLOGIE    Provenç. anullatio ; espagn. anulacion ; ital. annullazione (voy. annuler). SUPPLÉMENT AU DICTIONNAIRE    ANNULATION. Ajoutez : HIST. XVe s. •   Lequel a esté à l encontre du bien commun, l… …   Dictionnaire de la Langue Française d'Émile Littré

  • annulation — noun Date: 1829 a ringlike anatomical structure …   New Collegiate Dictionary

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