Castro–Stephens coupling

The Castro–Stephens coupling is a cross coupling reaction between a copper(I) acetylide and an aryl halide forming a disubstituted alkyne and a copper(I) halide.

The reaction was discovered in 1963 by University of California, Riverside chemists Castro and Stephens[1][2] and is used as a tool in the organic synthesis of organic compounds. The reaction has similarities with the much older Rosenmund–von Braun synthesis (1916) between aryl halides and copper(I) cyanide and was itself modified in 1973 with 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 is the coupling of iodobenzene with the copper acetylide of phenylacetylene in refluxing pyridine to diphenylacetylene:

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 DMF as solvent.[3][4]

References

  1. ↑ The Substitution of Aryl Iodides with Cuprous Acetylides. A Synthesis of Tolanes and Heterocyclics R. D. Stephens and C. E. Castro J. Org. Chem.; 1963; 28(12); pp 3313–15; doi:10.1021/jo01047a008
  2. ↑ D. C. Owsley and C. E. Castro.Organic Syntheses, Coll. Vol. 6, p.916 (1988); Vol. 52, p.128 (1972) Link.
  3. ↑ Synthesis of natural isocoumarins, artemidin and 3-propylisocoumarin G. Batu, R. Stevenson J. Org. Chem.; 1980; 45(8); pp 1532–34; doi:10.1021/jo01296a044
  4. ↑ Copper (I) Substitutions. Scope and Mechanism of Cuprous Acetylide Substitutions C. E. Castro, R. Havlin, V. K. Honwad, A. Malte, and Steve Moje J. Am. Chem. Soc.;1969; 91(23); pp 6464–6470; doi:10.1021/ja01051a049
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