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Liebeskind-Srogl Coupling |

An extremely useful coupling
reaction has recently been developed. Known as Liebeskind-Srogl
coupling, this reaction involves the coupling of a boronic acid
with a thiol ester to form ketones (J. Am. Chem. Soc. 2000,
122,11260-11261). This reaction is also mechanistically
interesting in that the reaction does not use palladium, but uses
stoichiometric copper(I) thiophenecarboxylate (CuTC) as a
mediator. The reaction is extremely general and even works with
base-sensitive functional groups.
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Kumada coupling is a
well-established method for forming carbon-carbon bonds with a
Grignard reagent and a aryl, vinyl, or alkyl halide. The
Kumada reaction is less general simply because it is not
compatible with any functional groups that react with Grignards.
However, the reaction has the advantage that nickel catalysts can
often be used. Despite it's limitations, the Kumada reaction
is a very powerful and inexpensive method of forming simple
biaryls.
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Hiyama coupling is the coupling of
organosilanes and organohalides. This method is similar to
the Suzuki reaction. An activating agent such as fluoride is
often required. This reaction has been expanded by the DeShong
group to work with siloxanes.
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When most cross coupling reactions
are performed under a CO atmosphere, the reaction produces a
ketone by incorporation of CO. Carbonylative coupling is general
nomenclature referring to this type of reaction. Recent
publications
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In this reaction an alkyne is
coupled to an aromatic halide. A base and Cu(I) are
required. This reaction is quite general and is an extremely
useful method of forming alkynes. Recent
publications
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All of the above cross-coupling
methods have been used in combinatorial chemistry. In fact, the
combinatorial arena as probably the largest growth area. The mild
conditions and functional group tolerance of cross-coupling
reactions make them perfect methodologies for forming C-C
bonds. With cross-coupling, difficult and divers molecules
can be rapidly and reliably synthesized. Recent
publications in combichem.
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