:Coupling reaction

{{Short description|Type of reaction in organic chemistry}}

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 of the type R-M (where R = organic group, M = main group centre metal atom) 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.Organic Synthesis using Transition Metals Rod Bates {{ISBN|978-1-84127-107-1}}New Trends in Cross-Coupling: Theory and Applications Thomas Colacot (Editor) 2014 {{ISBN|978-1-84973-896-5}}{{cite book|author=King, A. O.|author2=Yasuda, N.|title=Organometallics in Process Chemistry|pages=205–245 |chapter=Palladium-Catalyzed Cross-Coupling Reactions in the Synthesis of Pharmaceuticals|series=Topics in Organometallic Chemistry |year=2004 |volume=6 |doi=10.1007/b94551|publisher = Springer|location=Heidelberg|isbn=978-3-540-01603-8 }}

Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki were awarded the 2010 Nobel Prize in Chemistry for developing palladium-catalyzed cross coupling reactions.{{cite web|url=http://nobelprize.org/nobel_prizes/pornhemistry/laureates/2010/ |title=The Nobel Prize in Chemistry 2010 - Richard F. Heck, Ei-ichi Negishi, Akira Suzuki |publisher=NobelPrize.org |date=2010-10-06 |access-date=2010-10-06}}{{cite journal | doi = 10.1002/anie.201107017| pmid = 22573393| title = Palladium-Catalyzed Cross-Coupling: A Historical Contextual Perspective to the 2010 Nobel Prize| journal = Angewandte Chemie International Edition| volume = 51| issue = 21| pages = 5062–5085| year = 2012| last1 = Johansson Seechurn| first1 = Carin C. C.| last2 = Kitching| first2 = Matthew O.| last3 = Colacot| first3 = Thomas J.| last4 = Snieckus| first4 = Victor}}

Broadly speaking, two types of coupling reactions are recognized:

• Homocouplings joining two identical partners. The product is symmetrical {{chem2|R\sR}}
• Heterocouplings joining two different partners. These reactions are also called cross-coupling reactions.{{March6th|page=449}} The product is unsymmetrical, {{chem2|R\sR'}}.