1,283 research outputs found

    One-step transformation of 2-oxa-3-azabicyclo[2.2.1]hept-5-ene and methyl 2,3-diazabicyclo[2.2.1]heptane-2-carboxylate to ion uptake systems

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    Linker generated duplexes of the title compounds- prepared from cyclopentadiene- with possibility for positioning of four oxygen in the cavity, are shown to be excellent ion uptake systems. Mass spectrometric doping studies with lithium, sodium, potassium and silver ions, show a clear preference for lithium complexation. The lithium salts of the best examples have been prepared and characterized

    Ytterbium triflate (and trimethylsilyl triflate) catalyzed isomerization of glycidic esters to α-hydroxy-β,γ-unsaturated esters and their conversion into cyclopentanoids using Johnson-Claisen rearrangement

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    A variety of glycidic esters undergo smooth isomerization to the corresponding α-hydroxy-β, γ-unsaturated esters upon reaction with Yb(OTf)3 or TMSOTf. These α-hydroxy-β, γ-unsaturated esters undergo Johnson-Claisen rearrangement to appropriately substituted diesters, some of which are converted into cyclopentanoids

    Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

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    The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum
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