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In the presence of CuCN, reaction of γ,γ-dialkoxyallylic zirconium species 1 with imines proceeded at the γ-position of 1 to give gem-dialkoxyhomoallylic amines 3 in high yield. In this reaction, γ,γ-dialkoxyallylic zirconium species 1 acts as an α,β-unsaturated acyl anion equivalent. 相似文献
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A nontransmetalation reaction pathway for anionic four-electron donor-based (Type I) palladacycle-catalyzed addition reactions of arylborons with aldehydes is described. This new reaction pathway offers new catalysis opportunities for Type I palladacycle-catalyzed addition reactions such as the exceptionally low catalyst loading catalysis, with the catalyst loading as low as 0.0005 mol %. This new pathway may be applicable for other transition metal-catalyzed addition reactions and might lead to the development of new reactions including sequential/tandem reactions. 相似文献
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The mechanism is investigated for CptBuRh(OH)2-catalyzed annulation of 2-biphenylboronic acid with three activated alkenes using M06-2X functional. The reaction comprises transmetalation via two steps and following C-H activation producing reactive Rh-biphenyl complex with two Rh—C σ bonds. After the coordination/insertion of alkenes, respective fused or bridged cyclic products are yielded depending on different alkenes accompanied by the release of CptBuRh. The promotion of CptBuRh(OH)2 lies in the barrier decrease of transmetalation and C-H activation ready for coordination/insertion ensuring the smooth progress of common rate-limiting reductive elimination. The stereoselective transfer and ring rotation are specific for benzoquinone and cyclopropenone. The role of Rh(III) catalyst and release of Rh(I) is supported by Multiwfn analysis on frontier molecular orbital(FMO) of specific transiton states(TSs) and Mayer bond order(MBO) value of vital bonding, breaking. 相似文献
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Akella Sivaramakrishna 《Journal of organometallic chemistry》2007,692(23):5125-5132
The synthesis, characterization and chemistry of novel η3-allyl metal complexes (M = Ir, Rh) are described. The structures of compounds (C5Me4H)Ir(PPh3)Cl2 (1), (C5Me4H)Ir(PPh3)(η3-1-methylallyl)Br (3a), (C5Me4H)Ir(η4-1,3,5-hexatriene) (8), and (C5Me5)Rh(η3-1-ethylallyl)Br (5d) have been determined by X-ray crystallography. Structural comparisons among these complexes are discussed. It is found that the neutral metal allylic complex [Cp∗IrCl(η3-methylallyl)] (5) ionizes in polar solvents to give [Cp∗Ir(η3-methylallyl)]+Cl− (6) and reaches equilibrium (5 ? 6) at room temperature. Addition of tertiary phosphine ligands to neutral complexes such as [Cp∗Ir(η3-methylallyl)Cl], results in the formation of stable ionic phosphine adducts. Factors such as solvent, length of carbon chain, temperature and light are discussed with respect to the formation, stability and structure of the allyl complexes. 相似文献
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A sterically hindered metallocene catalyst, Cp ZrCl2 activated with methylaluminoxane (MAO), is found to polymerize ethene at temperatures up to 60° with a good propagation rate constant but low number of active sites, and with negligible β‐hydride elimination or β‐hydride transfer to monomer. Moreover, transmetalation to Al is found to be effectively irreversible for alkyl groups larger than Me. With the major mechanisms for chain transfer and termination suppressed, one might expect a living polymerization. The bulk polymerization of ethene was indeed found to be quasi‐living even when performed at well above room temperature, and furthermore provided rate constants which agreed remarkably well with those from the mass‐spectrometric study. 相似文献
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Yasushi Nishihara Masanori Okamoto Yoshiaki Inoue Mikihiro Miyazaki Mitsuru Miyasaka Kentaro Takagi 《Tetrahedron letters》2005,46(50):8661-8664
Alkynylboronates are employed as a practical and versatile precursor for a variety of π-conjugated organic compounds. In the presence of a Cu(I) or Cu(II) salt, transformation of alkynylboronates into the corresponding 1,3-diynes upon exposure to air takes place readily in aprotic polar solvents such as DMI. 相似文献
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Yu Chen Xiao Zhang Fang Liu Gucheng He Ju Zhang K. N. Houk Amos B. Smith III Yong Liang 《中国化学快报》2021,32(1):441-444
Experiments indicate that a catalytic amount of Cul plays an important role in the siloxane-mediated Pd-catalyzed cross-coupling reactions with the direct use of organolithium reagents.Addition of organolithium to the siloxane transfer agent generates an organosilicon intermediate.DFT calculations indicate that Cul initially accelerates the Si-Pd(Ⅱ) transmetalation of the organosilicon intermediate by the formation of CuI2-.Subsequently,CuI2-works as a shuttle between the Si-Cu(Ⅰ) and Cu(Ⅰ)-Pd(Ⅱ)transmetalation processes. 相似文献
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《Journal of Coordination Chemistry》2012,65(7):1236-1248
A new series of ruthenium(II) N-heterocyclic carbene complexes [RuL1,2,3(p-cymene)Cl2] (3a–c) (where L is a N-heterocyclic carbene), have been synthesized via transmetalation. The new ruthenium(II)-NHC complexes were applied to transfer hydrogenation of acetophenone derivatives and aldehydes using 2-propanol as a hydrogen source and KOH as a co-catalyst. The results show that the corresponding alcohols could be obtained in good yield with high catalyst activity (up to 100%) under mild conditions. [RuL1(p-cymene)Cl2] (3a) is much more active than the other complexes in transfer hydrogenation. Reactions, catalyzed by 3a–c, showed the highest reaction rates and yields of alcohol when the substrates bear more electron-withdrawing substituents. All new compounds were characterized by IR, elemental analysis, LC–MS (ESI), and NMR spectroscopy. 相似文献