Chemical reaction constructing a new ring on a molecule
In organic chemistry , annulation (from Latin anellus 'little ring'; occasionally annelation ) is a chemical reaction in which a new ring is constructed on a molecule.[1]
Examples are the Robinson annulation , Danheiser 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) iodide induced ketone - alkene cyclization of 5-methylenecyclooctanone which proceeds through a ketyl intermediate:[2]
Benzannulation
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:
In contemporary chemical literature, the term benzannulation also means "construction of benzene rings from acyclic precursors".[3]
Protonation of Verkade base induces a transannular bonding, giving an atrane .[4]
Transannular interaction
A transannular interaction in chemistry is any chemical interaction (favorable or nonfavorable) between different non-bonding molecular groups in a large ring or macrocycle .[5] See for example atranes .
References
^ IUPAC , Compendium of Chemical Terminology , 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "annulation ". doi :10.1351/goldbook.A00367 IUPAC , Compendium of Chemical Terminology , 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "annelation ". doi :10.1351/goldbook.A00365.html
^ 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
^ Swami, Bhawna; Yadav, Deepak; Menon, Rajeev S. (January 2022). "Benzannulation Reactions: A Case for Perspective Change From Arene Decoration to Arene Construction" . The Chemical Record . 22 (1): e202100249. doi :10.1002/tcr.202100249 . ISSN 1527-8999 . PMID 34796605 . S2CID 244403005 .
^ Verkade, John G.; Urgaonkar, Sameer; Verkade, John G.; Urgaonkar, Sameer (2012). "Proazaphosphatrane". Encyclopedia of Reagents for Organic Synthesis . doi :10.1002/047084289X.rn00702.pub2 . ISBN 978-0471936237 .
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Experimental evidence in support of transannular interactions in diketones Kata Mlinaric-Majerski, Marijana Vinkovic, Danko Škare, Alan P. Marchand Arkivoc DS-339E 2002 Online Article Archived 2006-05-04 at the Wayback Machine