Regio- and Stereoselective Route to Tetrasubstituted Olefins by the Palladium-Catalyzed Three-Component Coupling of Aryl Iodides, Internal Alkynes, and Arylboronic Acids

The Pd-catalyzed three-component coupling of readily available aryl iodides, internal alkynes, and arylboronic acids provides a convenient, one-step, regio- and stereoselective route to tetrasubstituted olefins in good to excellent yields, although electron-poor aryl iodides and dialkylalkynes normally afford only low yields under our standard reaction conditions. The proper combination of substrates and reaction conditions is important for high yields. The presence of water generally substantially increases the yields of the desired tetrasubstituted olefins. The reaction involves cis-addition of the aryl group from the aryl iodide to the less hindered or more electron-rich end of the alkyne, while the aryl group from the arylboronic acid adds to the other end. A modified, room-temperature procedure has also been successfully developed, which works very well for some substrates. Tamoxifen and its derivatives are synthesized in a concise, regio- and stereoselective manner by applying our synthetic protocol.