Castro-Stephens coupling

What is Castro-Stephens coupling?

The Castro-Stephens coupling reaction is a method for synthesizing diarylacetylenes. This involves treating aryl iodides with cuprous acetylides in pyridine under a nitrogen, N2,  atmosphere. The reaction results in high yields of the desired product. Moreover, the reaction exclusively converts aryl iodides with ortho-nucleophilic substituents into the corresponding heterocycle.

Castro–Stephens coupling - synthesizing diarylacetylenes
Castro–Stephens coupling
  • X = I, Br, Cl
  • R = alkyl, aryl, vinyl


C.E. Castro, R.D. Stephens, “The Substitution of Aryl Iodides with Cuprous Acetylides. A Synthesis of Tolanes and HeterocyclicsThe Journal of Organic Chemistry, 1963, 28, 12, 3313–3315 (1963)