In
organic chemistry annulation (from the
Latin ''anellus'' for "little ring"; occasionally annelation) is a
chemical reaction in which a new ring is constructed on a molecule.
:
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
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
-
alkene cyclization of ''5-methylenecyclooctanone'' which proceeds through a
ketyl intermediate:
:
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".
upright=1.4, Protonation of Verkade base induces a transannular bonding, giving an atrane.">atrane.html" ;"title="Verkade base induces a transannular bonding, giving an atrane">Verkade base induces a transannular bonding, giving an atrane.
Transannular interaction
A transannular interaction in chemistry is any chemical interaction (favorable or nonfavorable) between different chemical bond, non-bonding molecule, molecular functional group, groups in a large ring or macrocycle.
[
''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
See for an example the molecule
atrane
Atranes are a class of tricyclic molecules with three five-membered rings. It is a heterocyclic structure similar to the propellanes. It has a transannular dative bond from a nitrogen at one bridgehead to a Lewis acidic atom such as silicon o ...
.
References
{{reflist
Organic reactions
Ring forming reactions
