[reaction: see text] A novel Cu(I)-catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides with acrylates has been developed. Up to 98/2 exo/endo selectivity and up to 98% enantiomeric excess have been achieved. 相似文献
The kinetics of the exchange between56Mn-labelled manganese dioxide and cations in aqueous solution was studied by measuring the β− activity acquired by the solution. The results of the exchange between a chemical γ MnO2 and a divalent M2+ ion (M=Mn, Co, Cu or Zn) or a trivalent M3+ ion (M=Ga, Fe, In, Rh or Al) indicate a fast initial process followed by a diffusion—controlled exchange. It is assumed that
M2+ ions exchange with Mn2+ ions and M3+ ions exchange with Mn3+ ions in MnO2. The process depends on the radii of the host and substituent ions and on consideration of crystal field stabilisation energies.
It seems that the γ MnO2 studied contains more Mn3+ than Mn2+ ions. The possibility of the exchange between Mn ions and cations of a different charge cannot be ruled out. The exchange
between Co2+ ions and MnO2 was enhanced in presence of pyrophosphate, which stabilises Mn(III) as a complex. The fraction of Mn in different samples
of MnO2 exchanged with a given cation depends on the type and not on the surface area of the sample. 相似文献
Among the bisphosphine ligands, we have previously developed Cn-TunePhos (n = 1-6) as a family of ligands with tunable bite angles. The increase in spacer -CH2- groups in this family of ligands causes changes in ligand dihedral angle, which in turn causes P-Pd-P bite angle variation. Pd-catalyzed asymmetric alkylations and cycloadditions have been tested with Cn-TunePhos ligands. This study aims at a possible correlation between ligand bite angles with enantioselectivity of the Pd-catalyzed asymmetric products. 相似文献
The synergy of the combined use of DMSO and an ionic liquid viz. (bbim)+Br? has brought about a rapid and efficient esterification of sodium carboxylates with acyl and alkyl halides under ambient conditions in excellent isolated yields (90–95%) in short reaction times (12–40 min). 相似文献
A novel synthesis of pyrazole-4-carboxamides is reported. The reaction of N-(3-(dimethylamino)-2-formylacryloyl)formamide, an intermediate obtained by Vilsmeier–Haack formylation of acetonitrile, with
hydrazine hydrate or monosubstituted hydrazines provides such compounds in good yields. This method has advantages over other
methods for construction of such ring systems previously described in the literature. 相似文献
Suzuki-Miyaura cross coupling was successfully used for C5-arylation in 4-amino-2-chloroquinoline-3-carbaldehyde using arylbornic acid and tetrakistriphenylphosphine palladium catalyst in water. Friedländer condensation reaction on 4-amino-2-chloro/2-arylquinoline-3-carbaldehyde and aromatic ketones gave novel aryl and diarylbenzo[h] [1, 6]naphthyridines in good yields. Fluorescence quantum yields were increased by introducing C2 and C5 π donor aryl benzo[h][1, 6]naphthyridines derivatives.