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.
Ruthenium-Catalyzed Decarboxylative Insertion of Electrophiles
作者:Chao Wang、Jon A. Tunge
DOI:10.1021/ol050466s
日期:2005.5.1
A ruthenium complex, Cp*Ru(bipyridyl)CI, has been developed as a catalyst for the first regioselective tandem Michael addition-allylic alkylation of activated Michael acceptors. The net transformation is the decarboxylative insertion of Michael acceptors into allyl beta-ketoesters.
Air-tolerant C–C bond formation via organometallic ruthenium catalysis: diverse catalytic pathways involving (C5Me5)Ru or (C5H5)Ru are robust to molecular oxygen
carbon pronucleophiles, various [2+2+2] cycloadditions, and addition of a diazocompound to an alkyne are shown to proceed in the presence of air. Notably diverse catalytic manifolds remain supported under conditions generally regarded as prohibitive. Building on rare reports from the literature we show that a range of organometallic transformations based on reaction intermediates derived from (C5Me5)Ru
碳原子亲核试剂的钌催化取代,各种[2 + 2 + 2]环加成反应以及重氮化合物向炔烃的加成反应均在空气存在下进行。值得注意的是,各种催化歧管在通常被认为是禁止的条件下仍保持支撑。基于文献的稀有报道,我们表明基于衍生自(C 5 Me 5)Ru或(C 5 H 5)Ru部分的反应中间体的一系列有机金属转化是与空气相容的。