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171.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. 相似文献
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An in situ‐generated catalytic system based on PdCl2 and primary amine‐based ligand exhibited excellent activity (up to 98% isolated yield) in the Suzuki–Miyaura cross‐coupling reactions of aryl bromides with arylboronic acids in water, at room temperature, without any additive. The efficiencies of the ligands follow the order: (C6H5)3CNH2 > C6H5CH2 NH2 > C6H5 NH2 > C6H11 NH2, which is in accordance with the palladacycle forming capacity of the respective ligands. Moderate‐to‐good yields (up to 78% isolated yield) of the coupling products were also obtained with less reactive aryl chlorides as substrates at room temperature in isopropanol using an alternative protocol based on Pd(OAc)2 and (C6H5)3CNH2. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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3-Amino-2-oxindoles bearing tetra-substituted stereocenter are very important constituents of many bioactive and pharmaceutical agents. In the last few years, asymmetric organocatalysis emerged as an excellent approach for the synthesis of optically active 3-substituted-3-amino-2-oxindoles. This review describes the various organocatalytic enantioselective strategies for the synthesis of 3-substituted 3-amino-2-oxindole frameworks. 相似文献
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The reaction of p‐(N,N‐dimethylaminophenyl)diphenylphosphine [PPh2(p‐C6H4NMe2)] with [Fe3(CO)12], [Rh(CO)2Cl]2 and PdCl2 resulted in three new mononuclear complexes, {Fe(CO)4[η1‐(P)‐PPh2(p‐C6H4NMe2)]} ( 1a ), trans‐{Rh(CO)Cl[η1‐(P)‐PPh2(p‐C6H4NMe2)]2} ( 2 ) and trans‐{PdCl2[η1‐(P)‐PPh2(p‐C6H4NMe2)]2} ( 3 ), respectively. A small amount of dinuclear nonmetal‐metal bonded complex, {Fe2(CO)8[µ‐(P,N)‐PPh2(p‐C6H4NMe2)]} ( 1b ), was also isolated as a side product in the reaction of [Fe3(CO)12]. The complexes were characterized by elemental analyses, mass, IR, UV–vis, 1H, 13C (except 1b) and 31P{1H} NMR spectroscopy. The Pd complex 3 effectively catalyzes the Suzuki–Miyaura cross‐coupling reactions of aryl halides with arylboronic acids in water–isopropanol (1:1) at room temperature. Excellent yields (up to 99% isolated yield) were achieved. The effects of different solvents, bases, catalyst quantities were also evaluated. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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We study a well-known regenerative machine tool vibration model (a delay differential equation) near a codimension 2 Hopf bifurcation point. The method of multiple scales is used directly, bypassing a center manifold reduction. We use a nonstandard choice of expansion parameter that helps understand practically relevant aspects of the dynamics for not-too-small amplitudes. Analytical expressions are then obtained for the double Hopf points. Both sub- and supercritical bifurcations are predicted to occur near the reference point; and analytical conditions on the parameter variations for each type of bifurcation to occur are obtained as well. Analytical approximations are supported by numerics. 相似文献