PALLADIUM-CATALYZED REGIOSELECTIVE BETA-ACETONATION ALPHA-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 a t room temperature gave the corresponding beta-acetonated alpha-allyla ted double addition products 6 regioselectively in good to excellent y ields. The nature of the electron-withdrawing group in activated olefi ns affected significantly the reactivity of substrates; at least one o f two electron-withdrawing groups of 4 should be a CN group. A propose d mechanism for this unprecedented three-component coupling reaction i nvolves oxa-pi-allyl-pi-allylpalladium intermediate 3a (or its synthet ic equivalents 3b-d). The in situ generation of activated olefins 4, f rom the aldehyde 11 and malononitrile 12, followed by the palladium-ca talyzed reaction with allyl acetoacetate 5 also worked well, producing the corresponding three-component coupling products in good yields. F urthermore, allyltributylstannane 13 and alpha-chloro acetone 14 could be used as the alpha-allylation and beta-acetonation components, resp ectively, instead of allyl acetoacetate 5. The scope and limitations o f palladium-catalyzed regioselective beta-acetonation-alpha-allylation reaction of activated olefins are described.