Stereoconvergent palladium-catalyzed carbonylation of both E and Z isomersof a 2-trifloxy-1,3-butadiene

Carbonylation of the illustrated Z-tetrasubstituted enol triflate followed by tandem silyloxy-Cope rearrangement leads to the CP-263,114 core ring sys tem with the all-carbon quaternary stereocenter intact in 46% yield. Subjec tion of the corresponding E isomer to the same conditions gives the same pr oduct in 56% yield. This observation is explained by a mechanism involving isomerization of a pi-allyl palladium species involving an allenic intermed iate.