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Castro–Stephens Coupling
The Castro–Stephens coupling is a cross coupling reaction between a copper(I) acetylide and an aryl halide in pyridine, forming a disubstituted alkyne and a copper(I) halide. : The reaction was described in 1963 by chemists Castro and Stephens. The reaction is similar to the much older Rosenmund–von Braun synthesis (1914) between aryl halides and copper(I) cyanide and was itself modified in 1975 as the Sonogashira coupling by adding a palladium catalyst and preparing the organocopper compound ''in situ'', allowing copper to also be used catalytically. A typical reaction diphenylacetylene is obtained by the coupling of iodobenzene with Cuphenylacetylene, C2C6H5 in hot pyridine: : Unlike the Sonogashira coupling, the Castro–Stephens coupling can produce heterocyclic compounds when a nucleophilic group is ''arene substitution pattern, ortho'' to the aryl halide, although this typically requires use of dimethylformamide (DMF) as solvent. : References {{DEFAULTSORT:Cas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cross Coupling Reaction
In organic chemistry, a cross-coupling reaction is a reaction where two different fragments are joined. Cross-couplings are a subset of the more general coupling reactions. Often cross-coupling reactions require metal catalysts. One important reaction type is this: : (R, R' = organic fragments, usually aryl; M = main group center such as Li or MgX; X = halide) These reactions are used to form carbon–carbon bonds but also carbon-heteroatom bonds. Cross-coupling reaction are a subset of coupling reactions. Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki were awarded the 2010 Nobel Prize in Chemistry for developing palladium-catalyzed coupling reactions. Mechanism Many mechanisms exist reflecting the myriad types of cross-couplings, including those that do not require metal catalysts. Often, however, cross-coupling refers to a metal-catalyzed reaction of a nucleophilic partner with an electrophilic partner. In such cases, the mechanism generally involves reductive elimin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
