Stereoselective synthesis of tetrasubstituted olefins via palladium-catalyzed three-component coupling of aryl iodides, internal alkynes, and arylboronic acids in supercritical carbon dioxide

The Pd-catalyzed three-component coupling of readily available aryl iodides, internal alkynes, and arylboronic acids provides a convenient, one-step route to tetrasubstituted olefins in good to excellent yields in scCO2 using CsOAc as base. The final optimized reaction conditions for the three-component coupling in scCO2 was determined to be aryl iodides (0.5 mmol), internal alkynes (0.25 mmol), and arylboronic acids (0.5 mmol) in the presence of PdCl2 (2 mol%) and CsOAc (0.75 mmol) in scCO2 ( P C O 2 = 7.5   MPa ) at 100 °C for 24 h. The presence of scCO2 generally substantially improved this Pd-catalyzed system and increased the yields of the desired tetrasubstituted olefins. The reaction involves full cis-addition of internal alkynes and this system in scCO2 is an effective and environmental friendly alternative to the previous methods involving organic solvent.