EXAMPLE OF THERMODYNAMIC CONTROL IN PALLADIUM-CATALYZED ALLYLIC ALKYLATION - EVIDENCE FOR PALLADIUM-ASSISTED ALLYLIC C-C BOND-CLEAVAGE

Pd(0)-catalyzed reactions of a number of dienyl acetates with dialkyl malonates show that the regiochemistry of the reaction is very dependent on the reaction conditions. At low temperature and short reaction times the reaction is under kinetic control, but at elevated temperature and longer reaction times the reaction is under thermodynamic control. Under the latter conditions it was demonstrated that the kinetic allylic malonate rearranged to its thermodynamically more stable regioisomer in the presence of the Pd(0) catalyst. The results strongly support the cleavage of an allylic C-C bond by Pd(0), and thus the dialkyl malonate anion has acted as a leaving group.