Castro–Stephens coupling

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Castro–Stephens coupling
Named after Charles E. Castro
Robert D. Stephens
Reaction type Coupling reaction
Identifiers
RSC ontology ID RXNO:0000525

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.[1][2]

General scheme for Castro-Stephens coupling

The reaction was described in 1963 by chemists Castro and Stephens.[1][2] The reaction is similar to the much older Rosenmund–von Braun synthesis (1914)[3][4] 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.[5][6]

A typical reaction diphenylacetylene is obtained by the coupling of iodobenzene with CuC2C6H5 in hot pyridine:[1]

Application of Castro–Stephens coupling with phenyliodide.

Unlike the Sonogashira coupling, the Castro–Stephens coupling can produce heterocyclic compounds when a nucleophilic group is ortho to the aryl halide, although this typically requires use of dimethylformamide (DMF) as solvent.[7][8]

Application of Castro-Stephens coupling with o-iodobenzoic acid to produce an isocoumarin.

References

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