Alkynes as Stille Reaction Pseudohalides: Gold- and Palladium-Cocatalyzed Synthesis of Tri- and Tetra-Substituted Olefins

A Stille-type reaction that employs alkynes as pseudohalides provides access to the catalytic chemistry of palladium−carbon σ-bonds starting from π-systems. The synthesis of a variety of tri- and tetra-substituted olefins by addition of sp 2 - and sp-hybridized stannanes across mono- and diester alkynes was accomplished with complete regioselectivity and high stereoselectivity. The reaction is proposed to proceed via a bimetallic mechanism where the Lewis acidic Au(I) activates the alkyne toward oxidative addition across Pd(0).