The Gomberg–Bachmann reaction, named for the Russian-American chemist
Moses Gomberg and the American chemist
Werner Emmanuel Bachmann, is an
aryl
In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used ...
-aryl
coupling reaction
In organic chemistry, a coupling reaction is a type of reaction in which two reactant molecules are bonded together. Such reactions often require the aid of a metal catalyst. In one important reaction type, a main group organometallic compound o ...
via a
diazonium
Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide. The parent, compou ...
salt.
:
The
arene compound
Aromatic compounds or arenes are organic compounds "with a chemistry typified by benzene" and "cyclically conjugated."
The word "aromatic" originates from the past grouping of molecules based on odor, before their general chemical properties were ...
(here
benzene
Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...
) is reacted with a
diazonium
Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide. The parent, compou ...
salt in the presence of a base to provide the biaryl through an intermediate
aryl radical An aryl radical in organic chemistry is a reactive intermediate and an arene compound incorporating one free radical carbon atom as part of the ring structure. As such it is the radical counterpart of the arenium ion. The parent compound is the ...
. For example, ''p''-bromo
biphenyl
Biphenyl (also known as diphenyl, phenylbenzene, 1,1′-biphenyl, lemonene or BP) is an organic compound that forms colorless crystals. Particularly in older literature, compounds containing the functional group consisting of biphenyl less one ...
may be prepared from
4-bromoaniline and
benzene
Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...
:
: BrC
6H
4NH
2 + C
6H
6 → BrC
6H
4−C
6H
5
The reaction offers a wide scope for both diazonium component and arene component but yields are generally low following the original procedure (less than 40%), given the many side-reactions of diazonium salts. Several improvements have been suggested. One possibility is to employ diazonium tetrafluoroborates in arene solvent together with a phase-transfer catalyst, another is to use 1-aryl-3,3-dialkyltriazenes.
Pschorr reaction
One
intramolecular variation which gives better results is the
Pschorr cyclization:
:
The group Z can be CH
2, CH
2CH
2, NH and CO (to
fluorenone) to name just a few.
See also
*
Graebe–Ullmann synthesis
*
Meerwein arylation
*
Sandmeyer reaction
The Sandmeyer reaction is a chemical reaction used to synthesize aryl halides from aryl diazonium salts using copper salts as reagents or catalysts.
It is an example of a radical-nucleophilic aromatic substitution. The Sandmeyer reaction provides ...
References
{{DEFAULTSORT:Gomberg-Bachmann reaction
Substitution reactions
Name reactions