Carbazole synthesis via an in situ trapping strategy with indolyl enol ethers

Indolyl enol ethers, generated from the alkoxy(indolyl)carbenium tetrafluoroborates 1 by treatment with sodium hydride, can be trapped with dimethyl acetylenedicarboxylate or N-phenylmaleimide to furnish the selectively functionalized carbazoles 3,4,5,9,10 , and 13. In addition, the biaryl derivatives 6 and 11 are produced by a ring-opening reaction of the primarily formed Diels-Alder adduct. In the case of the biaryl derivative 6 , an X-ray crystal structure analysis yields valuable information on constitutions and configurations in the biaryl series. The phenomenon of atropisomerism is discussed for this compound.     

Measurement of the η production in proton-proton collisions with the COSY time-of-flight spectrometer

The reaction pp → ppη was measured at excess energies of 15 and 41 MeV at an external target of the Jülich Cooler Synchrotron COSY with the time-of-flight spectrometer. About 25000 events were measured for the excess energy of 15 MeV and about 8000 for 41 MeV. Both protons of the process ppη were detected with an acceptance of nearly 100% and the η was reconstructed by the missing-mass technique. For both excess energies the angular distributions are found to be nearly isotropic. In the invariant-mass distributions strong deviations from the pure phase space distributions are seen. Received: 24 May 2002 / Accepted: 20 September 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: e.roderburg@fz-juelich.de Communicated by M. Gar?on     

Pyridine Syntheses. II. Condensation Routes Toward Streptonigrin Ring C

Alternative complimentary syntheses of penta-substituted pyridine rings with full regiochemical control of substituents were studied as a method for the synthesis of Streptonigrin ( 1 ). Various α-substituted acetophenones 2 were reacted with enones 3 in acetic acid/ammonium acetate and air to afford penta-substituted pyridines 4 . α-Substituents that could provide a source of exocyclic nitrogen at position 3 of these Steptonigrin ring-C models proved to be the limiting factor. However, an inverse “3+2+1” cyclocondensation of α-cyanochalcone 5c with 2-furyl ethyl ketone ( 6b ) afforded the desired model 6-(2-furyl)-5-methyl2,4-diphenyl-3-pyridinecarbonitrile ( 4g ) in 75% yield.     

Longitudinal wave propagation in bars with variable cross section

Zusammenfassung Eine Störmethode wird angewandt, um die Feldgleichungen für die Wellenausbreitung in Längsrichtung in Balken mit veränderlichem Querschnitt zu entwickeln.

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This work was supported by the United States Atomic Energy Commission and the Engineering Research Institute, Iowa State University.     

Stable elastic waves in anisotropic materials

Zusammenfassung Diese Arbeit befasst sich mit der Fortpflanzung von stabilen Wellen in einem anisotropen Medium infolge einer sich bewegenden Ladung an der Grenze des Materials. Wir behandeln besonders mobile Ladungen, deren Geschwindigkeit höher ist als diejenige der Wellen im Material. Das Problem wird als ebenes Spannungsproblem behandelt.

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This work was supported by the United States Atomic Energy Commission.     

Dominance of α decay from the isoscalar giant quadrupole resonance in 16O

The charged particle (c) decay of the isoscalar giant quadrupole resonance in a ¹⁶O has been studied in a ¹⁶O(α,α'c) coincidence experiment at E_α=155 MeV. The J=2 character of this resonance was established by angular correaltion measurements. Its dominant decay proceeds through the α₁ channel which contains about 40% of the E2 energy weighted sum rule. This explains difficulties of capture reactions to locate the GQR.     

The Hahn-Vitali-Saks and the Uniform Boundedeess Theorem in topological groups

It is shown in this paper that the Theorem of Hahn-Vitali-Saks (Theorem 4) and the Uniform Boundedness Theorem (Theorem 5) hold true for measures with values in a topological group. The proofs given here for these theorems seem to the authors to be more direct than the usual proofs for real valued measures.