A dearomatization reaction is an
organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical rea ...
which involves
arenes
Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past grouping ...
as reactants and in which the reaction products have permanently lost their
aromaticity
In chemistry, aromaticity is a chemical property of cyclic (ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to sat ...
.
This reaction type is of some importance in synthetic organic chemistry for the organic synthesis of new building blocks
and in
total synthesis
Total synthesis is the complete chemical synthesis of a complex molecule, often a natural product, from simple, commercially-available precursors. It usually refers to a process not involving the aid of biological processes, which distinguishes i ...
.
Several methods for the dearomatization of carbocyclic arenes exist: hydrogenation (
Birch reduction
The Birch reduction is an organic reaction that is used to convert arenes to cyclohexadienes. The reaction is named after the Australian chemist Arthur Birch and involves the organic reduction of aromatic rings in an amine solvent (traditional ...
), alkylative dearomatization, photochemical dearomatization, thermal dearomatization, oxidative dearomatization, dearomatization with transition metals and enzymatic dearomatization.
Photochemical dearomatization
Examples of photochemical reactions are those between certain arenes and alkenes forming
+2and
+4cycloaddition
In organic chemistry, a cycloaddition is a chemical reaction in which "two or more unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity". ...
adducts.
Enzymatic dearomatization
Examples of enzymes capable of arene dearomatization
are toluene dixoyhydrogenase, naphthalene dixoyhydrogenase and benzoyl CoA reductase.
Transition-metal assisted dearomatization
A classic example of transition-metal assisted dearomatization is the
Buchner ring expansion
The Buchner ring expansion is a two-step organic C-C bond forming reaction used to access 7-membered rings. The first step involves formation of a carbene from ethyl diazoacetate, which cyclopropanates an aromatic ring. The ring expansion occ ...
Catalytic asymmetric dearomatization reactions (CADA) are used in
enantioselective synthesis
Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecul ...
.
References
{{reflist, colwidth=50em
, refs=
[Pigge, F. C. (2015) ''Dearomatization Reactions, in Arene Chemistry: Reaction Mechanisms and Methods for Aromatic Compounds'' (ed J. Mortier), John Wiley & Sons, Inc, Hoboken, NJ. {{doi, 10.1002/9781118754887.ch15]
[Roche, S. P. and Porco, J. A. (2011), ''Dearomatization Strategies in the Synthesis of Complex Natural Products.'' Angew. Chem. Int. Ed., 50: 4068–4093. {{doi, 10.1002/anie.201006017]
[''Dearomatizing Benzene Ring Reductases'' Boll M. J Mol Microbiol Biotechnol 2005;10:132–142 {{doi, 10.1159/000091560]
[''Anaerobic degradation of homocyclic aromatic compounds via arylcarboxyl-coenzyme A esters: organisms, strategies and key enzymes''. Boll M, Löffler C, Morris BE, Kung JW. Environ Microbiol. 2014 Mar;16(3):612-27. {{doi, 10.1111/1462-2920.12328]
[Zhuo, C.-X., Zhang, W. and You, S.-L. (2012), ''Catalytic Asymmetric Dearomatization Reactions''. Angew. Chem. Int. Ed., 51: 12662–12686. {{doi, 10.1002/anie.201204822]
Organic reactions