Copper(I)-catalyzed homocoupling reaction of terminal alkynes in supercritical CO2

An efficient method for CuCl-catalyzed homocoupling reaction of terminal alkynes in the synthesis of symmetric 1,3-diynes has been developed in supercritical CO 2 (ScCO 2 ) without organic solvent. Homocoupling of various terminal alkynes (solid or liquid) could afford the corresponding products in moderate to excellent yields. In addition, ScCO 2 play the role of reactive solvent, and DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) acts as the key additive for homocoupling reactions of terminal alkynes, which enhanced the reaction rate and the solubility of copper(I) catalyst in ScCO 2 .