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COUPLING REACTIONS
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Coupling Reactions
Coupling reactions occur between organometallic with organic halide with the aid of a metal containing catalyst.
Coupling reactions can be divided into two main classes, cross couplings in which two different molecules react to form one new molecule.
The other type of coupling is homocoupling, in this reaction two similar molecules coupling together to form a new molecule.
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Main features
Common metal used in this field is Pd, in addition to Zn, Ni, Cu, B, and Sn.
Most of coupling reactions are air and water sensitive ??
But, some coupling reactions can be carried out in aqueous solutions.
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Some thing about Palladium
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Reaction Year Reactant 1 Reactant 2 Catalyst
Kumada 1972 R-MgBr RX Pd or Ni
Heck 1972 Alkene RX Pd
Sonogashira 1973 Alkyne RX Pd or Cu
Nigishi 1977 R-Zn-X RX Pd or Ni
Stille 1977 R-Sn-R3` RX Pd
Suzuki 1979 R-B(OR)2 RX Pd
Hyiama 1988 R-Si-R3 RX Pd
Buchwald-Hartwig 1994 R2-N-R RX Pd
Important coupling reactions
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Kumada coupling reaction
Cross coupling between aryl or alkyl Grignard with aryl or vinyl halocarbon.
The first Pd or Ni catalysed coupling reaction
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Kumada coupling
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Kumada coupling
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Heck coupling
Pd catalyzed coupling between aryl or vinyl halides with activated alkene in basic media.
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Heck coupling
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Sonogashira coupling
Terminal alkynes with aryl or vinyl halides (triflate).
Pd as a catalyst, Cu as co-catalyst and an amine as a base.
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Sonogashira coupling
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Sonogashira coupling
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Nigishi coupling
Pd or Ni catalyzed coupling organozinc compounds with aryl, vinyl, benzyl halids.
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Nigishi coupling
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Stille coupling
Using tin (stannes) alkyl compounds, wide range of R groups, but?????
Less polar, more toxic???
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Stille coupling
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Suzuki coupling
Using boronic acids or esters B(OR)3 . Needs base to activate boron species
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Suzuki coupling
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Suzuki coupling
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Hyiama coupling
Organosilanes (Si), with organohalids.Needs base or fluoride ion to activate Fluorinated, methoxyleted silanes more
reactive than alkyl ones.
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Hyiama coupling
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Buchwald-Hartwig coupling
Pd catalyzed synthesis of aryl secondry or tertiary amines.
Using primary or secondry amins and aryl halides (or triflates)
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Buchwald-Hartwig coupling
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Buchwald-Hartwig coupling
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Fukuyama Coupling*
Pd catalyzed coupling of organozinc with thioesters to form ketones.