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931.
932.
Donato Donati Stefania Fusi Maria Adelaide Macrip Fabio Ponticelli 《Journal of heterocyclic chemistry》1987,24(2):481-483
Piperidine-pyrrolidine ring contraction of 1-piperideinium bromide ( 1 ) was observed by reaction with aqueous bases, sodium methoxide, phenylhydrazine, (S)-1-phenylethylamine and sodium borohydride, whereas diazomethane addition mainly gave pyrrolo[3,4-b]pyridine derivative 8. Some stereochemical features of these reactions have been investigated. 1 gave back bromine under suitable conditions. 相似文献
933.
Stefania Fioravanti M. Antonietta Loreto Lucio Pellacani Paolo A. Tardella 《Tetrahedron: Asymmetry》1990,1(12):913-930
Thermal reaction of ethyl azidoformate with proline-derived optically active enamines of cyclohexanone, followed by photolysis, proceeds with opposite facial selectivity to that observed using (ethoxycarbonyl)nitrene. A tentative explanation is proposed. The absolute configuration of the main product, 2-(ethoxycarbonylamino)cyclohexanone (6), was deduced by chemical correlation. 相似文献
934.
In this paper we present an extension to SDP of the well known infeasible Interior Point method for linear programming of Kojima, Megiddo and Mizuno (A primal-dual infeasible-interior-point algorithm for Linear Programming, Math. Progr., 1993). The extension developed here allows the use of inexact search directions; i.e., the linear systems defining the search directions can be solved with an accuracy that increases as the solution is approached. A convergence analysis is carried out and the global convergence of the method is proved. 相似文献
935.
We consider a scheme for coherent imaging that exploits the classical correlation of two beams obtained by splitting incoherent thermal radiation. This case is analyzed in parallel with the configuration based on two entangled beams produced by parametric down-conversion, and a precise formal analogy is pointed out. This analogy opens the possibility of using classical beams from thermal radiation for ghost imaging schemes in the same way as entangled beams. 相似文献
936.
Banfi F Giannetti C Ferrini G Galimberti G Pagliara S Fausti D Parmigiani F 《Physical review letters》2005,94(3):037601
Nonlinear photoemission from a silver single crystal is investigated by femtosecond laser pulses in a perturbative regime. A clear observation of above-threshold photoemission in solids is reported for the first time. The ratio between the three-photon above-threshold and the two-photon Fermi edges is found to be 10(-4). This value constitutes the only available benchmark for theories aimed at understanding the mechanism responsible for above-threshold photoemission in solids. 相似文献
937.
Bartolozzi A Pacciani S Benvenuti C Cacciarini M Liguori F Menichetti S Nativi C 《The Journal of organic chemistry》2003,68(22):8529-8533
A nonclassical, totally stereoselective synthesis of orthogonally protected 1,3-disaccharides is reported. Enantiomerically pure beta-keto-delta-lactones, efficiently obtained from glucal and galactal, are transformed into electron-poor heterodienes and chemo-, regio-, and stereoselectively cycloadded to glycals as electron-rich dienophiles, to directly afford 2-thiodisaccharides. The reductive desulfurization of the latter smoothly gave the corresponding 2,2'-dideoxydisaccharides. 相似文献
938.
939.
Riassunto Si prova la rigidità di una certa classe di algebre integre di Cohen-Macaulay.
Lavoro svolto nell'ambito del G.N.S.A.G.A., sez. n. 3, del C.N.R. 相似文献
Summary We prove the rigidity of a certain class of algebras which are Cohen-Macaulay integral domains.
Lavoro svolto nell'ambito del G.N.S.A.G.A., sez. n. 3, del C.N.R. 相似文献
940.
Donato Donati Serena Ferrini Stefania Fusi Fabio Ponticelli 《Journal of heterocyclic chemistry》2004,41(5):761-766
Ring opening with molybdenum hexacarbonyl of functionalized isoxazoles is a valuable synthetic process. Tetrazolopyridine 4 and pyrazolopyridine 9 were obtained from isoxazolopyridines 3 and 6 , respectively, whereas the isoxazole 14 gave ketone 16 through the intermediate 17. 相似文献