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81.
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83.
Fedor I. Zubkov Julya D. Ershova Mykola D. Obushak Ekaterina A. Sokolova Alexey V. Varlamov 《Tetrahedron letters》2010,51(52):6822-6824
1-(2-Furyl)-3,4-dihydroisoquinolines, easily prepared from readily available phenethylamines, undergo tandem alkylation/[4+2]-cycloaddition with allyl halides. The reaction proceeds via 2-allyl-1-furyl-3,4-dihydroisoquinolinium salt formation and subsequent intramolecular exo-Diels-Alder reaction of furan with the allyl fragment (IMDAF reaction). The adducts formed include the basic structural element of the isoindolo[1,2-a]isoquinoline alkaloids jamtine and hirsutine. 相似文献
84.
Naumkin FY 《Physical chemistry chemical physics : PCCP》2006,8(38):4402-4404
Charge-transfer in combination with geometric features induces a pentavalent state of the carbon atom in metastable super-fluorinated alkali-metal compounds, M:C2F7 (M = K to Cs). 相似文献
85.
Sarkisov OM Gostev FE Shelaev IV Novoderezhkin VI Gopta OA Mamedov MD Semenov AY Nadtochenko VA 《Physical chemistry chemical physics : PCCP》2006,8(48):5671-5678
The pulsed excitation of electronic levels coupled to specific nuclear modes by a 26 fs laser pulse at 706 nm creates a wavepacket in the nuclear space of photopystem I (PS I) of Synechocystis sp. strain PCC 6803 both in the ground state and in the one-exciton manifold. Fourier transform of transient decay curves shows several low frequency peaks. The most prominent Power Spectral Density (PSD) peaks are at omega = 49 cm(-1) and omega = 88 cm(-1). The peculiarity of the coherent wavepacket in the PS I of S. sp. strain PCC 6803 is the unique, long-lived 49 cm(-1) and 88 cm(-1) oscillations with decay times up to 10 ps. It was suggested that such a long-lived coherence is determined by a contribution of the ground state wavepacket. The dependence of these two PSD peaks on the probe wavelength resembles the profile of the transient absorption spectra of PS I. The pump-probe signal in the Soret region reflects the dynamics of the ground state wavepacket created by pulsed excitation of the Q(y)-band. It was shown that the multimode Brownian oscillator model allows a quantitative fit of the oscillatory patterns of the pump-probe signal to be obtained. 相似文献
86.
Experimental evidence for the formation of HXeCCH: the first hydrocarbon with an inserted rare-gas atom 总被引:1,自引:0,他引:1
Feldman VI Sukhov FF Orlov AY Tyulpina IV 《Journal of the American Chemical Society》2003,125(16):4698-4699
Combined FTIR and EPR studies of acetylene irradiated with fast electrons in a solid xenon matrix provide experimental evidence for the formation of HXeCCH, a novel-type organic molecule with an inserted rare-gas atom. The new species resulting from the reaction of H atoms with CCH radicals in xenon was characterized by an intense IR absorption at 1486.0 cm(-1) corresponding to Xe-H stretching. 相似文献
87.
Vladimir V. Kouznetsov Fedor I. Zubkov Eugenia V. Nikitina 《Tetrahedron letters》2004,45(9):1981-1984
An unprecedented intramolecular Friedel-Crafts ipso-alkylation at the ortho-alkyl group of the N-arylamino moiety of 1-allyl-1-N-arylaminocycloalkanes to give alkyl substituted dihydrospiro[(1H) quinoline-2,1′-cycloalkanes] is reported. Unexpected results were explained in the context of intramolecular ipso-substitution of alkyl groups and their 1,2-rearrangement. A plausible mechanism for this type of Friedel-Crafts alkylation by an alkene moiety promoted by a Brönsted acid (H2SO4) is proposed. 相似文献
88.
89.
Zubkov FI Nikitina EV Turchin KF Aleksandrov GG Safronova AA Borisov RS Varlamov AV 《The Journal of organic chemistry》2004,69(2):432-438
The reactions of 3-acetyl-3-aza-11-oxatricyclo[6.2.1.0(1,6)]undec-9-ene and its 9,10-epoxy derivative with bromine and Ac(2)O/BF(3).OEt(2) under different conditions were studied. Unusual products of Wagner-Meerwein rearrangement bearing the olefin fragment (5-aza-2-oxatricyclo[6.2.1.0(3,9)]undecen-3-enes) were isolated and characterized by X-ray analysis. 相似文献
90.
The oriented diameter of a bridgeless connected undirected (bcu) graph G is the smallest diameter among all the diameters of strongly connected orientations of G. We study algorithmic aspects of determining the oriented diameter of a chordal graph. We (a) construct a linear‐time approximation algorithm that, for a given chordal bcu graph G, finds a strongly connected orientation of G with diameter at most one plus twice the oriented diameter of G; (b) prove that, for every k ≥ 2 and k # 3, to decide whether a chordal (split for k = 2) bcu graph G admits an orientation of diameter k is NP‐complete; (c) show that, unless P = NP, there is neither a polynomial‐time absolute approximation algorithm nor an α‐approximation algorithm that computes the oriented diameter of a bcu chordal graph for α < . © 2004 Wiley Periodicals, Inc. J Graph Theory 45: 255–269, 2004 相似文献