Synthesis of Biindene Derivatives via Pd-Catalyzed Alkene Difunctionalization Reactions.

The palladium-catalyzed cross-coupling of 2-allylphenyl triflate and related electrophiles with substituted indenes affords biindene derivatives in moderate to good yields with high selectivity for thermodynamically preferred alkene isomers. The transformations involve alkene nucleopalladation with indenyl anions, and we also demonstrate that 2-allylphenyl triflates can be transformed to indenes under similar conditions. The scope of this transformation, along with the mechanism of formation of both indene and biindene products, is described.