Evidence of formation of an exo-pi-allyl complex intermediate in the Pd-0-catalyzed alkylation of a bicyclic allylic diacetate with stabilized carbonnucleophiles

The palladium(0)-catalyzed alkylation of 2,3-bis(acetoxymethyl)bicyclo[2.2. 1]hepta-2,5-diene 1 with malonate-type enolates as nucleophiles is investig ated. A monoalkylated product is formed first, and undergoes (depending on the nucleophile used) a second intramolecular reaction leading to spirocycl opropane-annulated bicyclo[2.2.1]heptene derivatives 5. The formation of en do spirobicyclic cyclopropanes adducts as major isomer is rationalized by a ssuming formation of an intermediate exo-(pi-allyl)palladium complex.