β-Olefination of 2-Alkynoates Leading to Trisubstituted 1,3-Dienes

A phosphine-mediated olefination of 2-alkynoates with aldehydes forming 1,3-dienes with high E-selectivity and up to 88% yield is described. Reaction conditions are optimized and reactions are demonstrated for,various aryl, alkyl, and alkenyl aldehydes and for ethyl 2-alkynoates with different substituents in the delta-position. Proof of concept is shown for the generation of a beta,gamma-unsaturated lactone by intramolecular olefination, and furthermore the use of the generated 1,3-dienes in the Diels-Alder reaction has been demonstrated.