Palladium-free synthesis of conjugated enynes by direct olefination of terminal alkynes using vinyl bromides
A series of conjugated enynes were successfully synthesized by the direct copper-catalyzed coupling reaction of vinyl bromides and alkynes. The reaction proceeds smoothly in DMF at 110 °C to give the corresponding products in good to excellent yields. The protocol is tolerant to a broad range of functional groups on the substrates. Moreover, the products were furnished as specific E isomers, as the stereochemistry of the vinyl bromides was retained.