Palladium catalyzed regioselective β-acetonation α-allylation of activated olefins in one shot

The reaction of certain activated olefins 4 with allyl acetoacetate 5 in the presence of catalytic amounts of Pd(PPh3)(4) (5 mol %) in THF at room temperature gave the corresponding beta-acetonated alpha-allylated double addition products 6 regioselectively in good to excellent yields. The nature of the electron-withdrawing group in activated olefins affected significantly the reactivity of substrates; at least one of two electron-withdrawing groups of 4 should be a CN group. A proposed mechanism for this unprecedented three-component coupling reaction involves oxa-pi-allyl-pi-allylpalladium intermediate 3a (or its synthetic equivalents 3b-d). The in situ generation of activated olefins 4, from the aldehyde 11 and malononitrile 12, followed by the palladium-catalyzed reaction with allyl acetoacetate 5 also worked well, producing the corresponding three-component coupling products in good yields. Furthermore, allyltributylstannane 13 and alpha-chloro acetone 14 could be used as the alpha-allylation and beta-acetonation components, respectively, instead of allyl acetoacetate 5. The scope and limitations of palladium-catalyzed regioselective beta-acetonation-alpha-allylation reaction of activated olefins are described.