A coupling reaction in
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J ...
is a general term for a variety of reactions where two fragments are joined together with the aid of a metal
catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
. In one important reaction type, a main group
organometallic compound
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and s ...
of the type R-M (R = organic fragment, M = main group center) reacts with an organic halide of the type R'-X with formation of a new
carbon-carbon bond in the product R-R'. The most common type of coupling reaction is the
cross coupling reaction
In organic chemistry, a cross-coupling reaction is a reaction where two fragments are joined together with the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (R = organic fragment, M ...
.
Richard F. Heck
Richard Frederick Heck (August 15, 1931 – October 9, 2015) was an American chemist noted for the discovery and development of the Heck reaction, which uses palladium to catalyze organic chemical reactions that couple aryl halides with alkenes ...
,
Ei-ichi Negishi, and
Akira Suzuki were awarded the 2010
Nobel Prize in Chemistry
)
, image = Nobel Prize.png
, alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "M ...
for developing
palladium-catalyzed cross coupling reactions.
Broadly speaking, two types of coupling reactions are recognized:
*Heterocouplings combine two different
partners, such as in the
Heck reaction
The Heck reaction (also called the Mizoroki–Heck reaction) is the chemical reaction of an unsaturated halide (or triflate) with an alkene in the presence of a base and a palladium catalyst (or palladium nanomaterial-based catalyst) to form a s ...
of an
alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond.
Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic ...
(RC=CH) and an
alkyl halide (R'-X) to give a substituted alkene, or the
Corey–House synthesis The Corey–House synthesis (also called the Corey–Posner–Whitesides–House reaction and other permutations) is an organic reaction that involves the reaction of a lithium diorganylcuprate (R_CuLi) with an organic pseudohalide (R'-X) to form ...
of an
alkane
In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in wh ...
by the reaction of a
lithium
Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense soli ...
diorganylcuprate (R
2CuLi) with an
organyl (pseudo)halide (R'X). Heterocouplings are also called
cross-coupling
In organic chemistry, a cross-coupling reaction is a reaction where two fragments are joined together with the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (R = organic fragment, M = ...
s.
*Homocouplings couple two identical partners, as in the
Glaser coupling
The Glaser coupling is a type of coupling reaction. It is by far the oldest acetylenic coupling and is based on cuprous salts like copper(I) chloride or copper(I) bromide and an additional oxidant like oxygen. The base in its original scope is amm ...
of two
acetylide
In organometallic chemistry, acetylide refers to chemical compounds with the chemical formulas and , where M is a metal. The term is used loosely and can refer to substituted acetylides having the general structure (where R is an organic side c ...
s (RC≡CH) to form a dialkyne (RC≡C-C≡CR).
Homo-coupling types
Coupling reactions are illustrated by the famous Ullmann reaction:
Cross-coupling types
An illustrative cross-coupling reaction is the Heck coupling of an alkene and an aryl halide:
Applications
Coupling reactions are routinely employed in the preparation of pharmaceuticals.
[ Conjugated polymers are prepared using this technology as well.]
References
{{DEFAULTSORT:Coupling Reaction
Organometallic chemistry
Carbon-carbon bond forming reactions
Catalysis