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991.
A chiral ligand-controlled conjugate addition reaction of lithium benzyl(trimethylsilyl)amide with tert-butyl enoates gave the corresponding lithium enolates that were then treated with electrophiles, giving anti-alkylation products with high ee up to 98%. The benzyl group on the amino nitrogen was removed by the oxidation of secondary amines to imines and subsequent transoximation to give 3-aminoalkanoates in good yields. The products are the possible key intermediates of otamixaban and premafloxacin. 相似文献
992.
Asymmetric radical addition of ethers to enantiopure aromatic N-p-toluenesulfinyl aldimines has been achieved. The requisite radicals were generated by dimethylzinc-air. Lewis acid activation of the N-p-toluenesulfinyl aldimines followed by radical addition gives a mixture of sulfinamide and sulfonamide products. Subsequent treatment of the mixture with dry m-CPBA affords the sulfonamide product in enantiomerically enriched form. [reaction: see text] 相似文献
993.
In this paper, we review the mass probes used for the derivation of a variety of biomolecules efficiently detected by the electrospray ionization-mass spectrometry and mass probe-assisted ionization method for total analysis and determination by consecutive detection with a single instrument. We describe mass probes for a variety of molecules including proteins, nucleobases, metallic cations, and other small molecules. 相似文献
994.
995.
Hidetaka Tsujimoto Yuichiro Honda Takeshi Maeda Yoshiaki Sakurai 《Journal of luminescence》2010,130(2):217-1978
A new series of heteroleptic cyclometalated platinum(II) complexes Pt-1a-f was synthesized, employing 2-arylpyridine (or 1-arylisoquinoline) (HC∧N-1) and 1,3-bis(3,4-dibutoxyphenyl)propane-1,3-dione (HO∧O-1) for cyclometalation and as ancillary ligands, respectively, and photoluminescent properties were investigated. Focusing on red-shifted phosphorescence, C∧N ligands containing π-extended aromatics and electron-rich heterocycles were examined. All obtained complexes exhibited photoluminescence at ambient temperature, and the emission maxima ranged from green (λPL=518 nm) to far red (λPL=708 nm). The large Stokes shifts of more than 100 nm and sub-microsecond or microsecond emission lifetimes revealed that these complexes are phosphorescent emissive. The quantum yield of Pt-1 ranged from 0.02 to 0.59 at ambient temperature and decreased as the emission maximum was red-shifted. In comparison with the reference platinum(II) complexes, Pt-2 bearing an aliphatic ancillary ligand, such as 2,2,6,6-tetramethylheptane-3,5-dionate (O∧O-2), the ligand O∧O-1 did not significantly affect the photoluminescence emission maxima, indicating that the energy gap between the singlet ground state and the triplet level was predominantly dependent on the C∧N ligand. 相似文献
996.
Yoshitaro Miyashita Satoshi Arai Yasunori Yamada Kiyoshi Fujisawa Ken-ichi Okamoto 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(12):1393-1394
Each of two square-planar PdII ions in the title compound, [Pd2Cl4(μ-Haet-S)2]·2H2O (Haet = 2-ammonioethanethiolate, C2H7NS), which was obtained by rearrangement of [Pd2{Pd(aet-N,S)2}4]4+ in acidic solution, is coordinated by two bridging S atoms from two Haet ligands and by two terminal Cl atoms, forming the dinuclear structure. Since the complex is situated on a center of symmetry, the two monodentate Haet arms are located on opposite sides of the central Pd2S2 square plane, i.e. the present complex is the anti isomer. The S—C—C—N torsion angle is 177.3 (6)° and some intermolecular hydrogen bonds are observed. 相似文献
997.
Yutaka Matsui Kiyoshi Takeuchi 《Proceedings of the American Mathematical Society》2008,136(7):2365-2373
We give a simpler and purely topological proof of Ernström's class formula (1997) for the degree of dual varieties. Our new proof also allows us to obtain a formula describing the degrees of the associated varieties studied by Gelfand, Kapranov and Zelevinsky (1994).
998.
The determination of SO(4)(2-) concentration in individual rain droplets can be achieved using a gelatin film containing 5 mM barium chloride and 5 mM barium nitrate. SO(4)(2-) in droplets reacts with barium chloride in the film to form the characteristic Liesegang rings. The areal ratio of the ring to the droplet print (ARRD) on the film is a good indicator for determining the SO(4)(2-) concentrations in an individual droplet. Interference by NO(3)(-) in determining SO(4)(2-) concentration can be avoided by adding barium nitrate to the gelatin. Measurements of SO(4)(2-) in rainwater samples by this method agreed well with those from ion chromatography. The individual analysis of rain droplets by this method indicated that the concentrations of SO(4)(2-) were largely different with a 5-order magnitude, even among individual rain droplets collected simultaneously, and were higher in smaller rain droplets. 相似文献
999.
Hideyuki Higashimura Kiyoshi Fujisawa Masaaki Kubota Shiro Kobayashi 《Journal of polymer science. Part A, Polymer chemistry》2005,43(9):1955-1962
“Radical‐controlled” oxidative polymerization of phenol (p‐1) by (1,4,7‐triisopropyl‐1,4,7‐triazacyclononane)copper(II) catalyst was performed and compared with that of 4‐phenoxyphenol (p‐2) in detail. Although the coupling selectivity for p‐1 seemed to be controlled by the catalyst, the C? C coupling, which was excluded completely for p‐2, occurred to some extent. The initial reaction rate of p‐1 was much smaller than that of p‐2, leading to the difference of polymerization behavior between p‐1 and p‐2. The rate‐determining step would be the coupling of controlled radicals species from the ESR measurement of the reaction mixture. The polymer resulting from p‐1 consisted mainly of phenylene oxide units, but had no crystallinity in contrast to the crystalline polymer from p‐2. However, the present polymer showed the highest thermal stability in the polymers obtained by oxidative polymerization of p‐1. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1955–1962, 2005 相似文献
1000.
In this paper, we study of Pólya urn model containing balls of (m+1) different labels under a general replacement scheme, which is characterized by an (m+1) × (m+1) addition matrix of integers without constraints on the values of these (m+1)2 integers other than non-negativity. LetX
1,X
2,...,X
n
be trials obtained by the Pólya urn scheme (with possible outcomes: “O”, “1”,...“m”). We consider the multivariate distributions of the numbers of occurrences of runs of different types arising from the various
enumeration schemes and give a recursive formula of the probability generating function. Some closed form expressions are
derived as special cases, which have potential applications to various areas. Our methods for the derivation of the multivariate
run-related distribution are very simple and suitable for numerical and symbolic calculations by means of computer algebra
systems. The results presented here develop a general workable framework for the study of Pólya urn models. Our attempts are
very useful for understanding non-classic urn models. Finally, numerical examples are also given in order to illustrate the
feasibility of our results.
This research was partially supported by the ISM Cooperative Research Program (2003-ISM·CRP-2007). 相似文献