Palladium-Catalyzed Intermolecular Trans-Selective Carbofunctionalization of Internal Alkynes to Highly Functionalized Alkenes

A palladium/DPEphos-catalyzed intermolecular trans-selective carbofunctionalization of internal alkynes has been established herein. This method proceeds through a formal anti-carbopalladation, forming trans-alkenyl palladium species, which was trapped by aryl boronic acids to provide all-carbon tetrasubstituted alkenes in 32-92% yields. The trans-selective arylsilylation/remote C-H silylation and hydroarylation/remote C-H borylation of internal alkynes were also achieved using hexamethyldisilane and bis(pinacolato)diboron as trapping reagents, respectively. The reaction features good regio- and stereoselectivity and high functional group tolerance. A preliminary mechanistic study and DFT calculations show that a cis to trans isomerization of cis-alkenyl palladium species was involved in this transformation.