Dehydrogenative TEMPO‐Mediated Formation of Unstable Nitrones: Easy Access to N‐Carbamoyl Isoxazolines

N‐carbamoyl nitrones represent an important class of reagents for the synthesis of a variety of natural and biologically active compounds. These compounds are generally converted into valuable 4‐isoxazolines upon cyclization reaction with dipolarophiles. However, these types of N‐protected nitrones are highly unstable, which limits their synthesis, storage and practical use, enforcing alternative lengthy or elaborated synthetic routes. In this work, a 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO)‐mediated formal “dehydrogenation” of N‐protected benzyl‐, allyl‐ and alkyl‐substituted hydroxylamines followed by in situ trapping of the generated unstable nitrones into N‐carbamoyl 4‐isoxazolines is presented. A plausible mechanism is also proposed, in which the dipolarophile shows an important assistant role in the generation of the active nitrone intermediate. This simple protocol avoids the problematic isolation of N‐carbamoyl protected nitrones, providing new synthetic possibilities in isoxazoline chemistry.     

A measurement of single electrons,electron pairs,and associated phenomena,in proton-proton collisions at the CERN ISR

Measurements of single-electron production in proton-proton collisions at the CERN ISR are presented for five centre-of-mass energies √s = 23.5, 30.6, 44.8, 52.7, and 62.4 GeV. The invariant cross sections for single electrons with transverse momenta of 0.60 to 4.7 GeV/c are given. Measurements of electron-positron pairs and measurements of charged hadrons produced in association with the single electrons, are also reported.     

Ko and λ production at the CERN ISR

Transverse momentum distributions of $\text{λ}{}^{\mathrm{o}}\text{,}\text{λ}{}^{\mathrm{o}}$, and K^o, produced in pp collisions at x = 0, have obtained at the CERN ISR. The K^o yield is in agreement with published K⁺, K^? results, obtained at this centre-of-mass energy (√s≈44 GeV). The results on $\text{λ}{}^{\mathrm{o}}\text{and}\text{λ}{}^{\mathrm{o}}$ production obtained in this experiment are compared with results obtained at lower centre-of-mass energies.     

A study of high transverse momentum η and π0 mesons at the CERN ISR

The production of high transverse momentum η mesons from proton-proton collisions has been studied at the CERN ISR. The decay η→γγ was identified in an array of lead-glass ?erenkov counters. The preliminary results, obtained at a total centre-of-mass energy √s=52.7 GeV, show an η signal, which amounts to approximately one half of the π⁰ cross-section for centre-of-mass transverse momenta between 3 and 5 GeV/c. The production of high transverse momentum π⁰'s was also measured and compared with previous results.     

Observation of high transverse momentum electrons at the CERN ISR

A search for high transverse momentum electrons directly produced in proton-proton collisions has been performed at the CERN ISR. The apparatus included a magnetic spectrometer with wire spark chambers, a lead-glass counter array, and a threshold gas ?erenkov counter. At a centre-of-mass energy √s = 52.7 GeV, a signal has been observed in the range $\text{1.6<p}{}_{\mathrm{T}}{}^1\text{<4.7}\text{GeV}\text{/c}$. The signal occurs at a level of approximately 10^?4 of the inclusive pion cross-section.     

Neutrino production of dimuons

Neutrino interactions with two muons in the final state have been studied using the Fermilab narrow band beam. A sample of 18v _μ like sign dimuon events withP _μ>9 GeV/c yields 6.6±4.8 events after backgroud subtraction and a prompt rate of (1.0±0.7)×10^?4 per single muon event. The kinematics of these events are compared with those of the non-prompt sources. A total of 437v _μ and 31 \(\bar v_\mu \) opposite sign dimuon events withP _μ>4.3 GeV/c are used to measure the strange quark content of the nucleon: \(\kappa = {{2s} \mathord{\left/ {\vphantom {{2s} {\left( {\bar u + \bar d} \right) = 0.52_{ - 0.15}^{ + 0.17} \left( {or\eta _s \frac{{2s}}{{u + d}} = 0.075 \pm 0.019} \right) for 100< E_v< 230 GeV\left( {\left\langle {Q^2 } \right\rangle = {{23 GeV^2 } \mathord{\left/ {\vphantom {{23 GeV^2 } {c^2 }}} \right. \kern-0em} {c^2 }}} \right)}}} \right. \kern-0em} {\left( {\bar u + \bar d} \right) = 0.52_{ - 0.15}^{ + 0.17} \left( {or\eta _s \frac{{2s}}{{u + d}} = 0.075 \pm 0.019} \right) for 100< E_v< 230 GeV\left( {\left\langle {Q^2 } \right\rangle = {{23 GeV^2 } \mathord{\left/ {\vphantom {{23 GeV^2 } {c^2 }}} \right. \kern-0em} {c^2 }}} \right)}}\) using a charm semileptonic branching ratio of (10.9±1.4)% extracted from measurements ine ⁺ e ^? collisions and neutrino emulsion data.     

Observation of high mass electron-positron pairs produced in proton-proton collisions at the CERN ISR

In an experiment performed at the CERN Intersecting Storage Rings (ISR), 11 e⁺e^? pairs of high invariant mass value (> 2.5 GeV/c²) have been observed. Of these events, 9 can be interpreted as arising from the reaction p + p → J (3.1) + anything. the cross-section for this reaction is estimated and compared with the result obtained at lower centre-of-mass energies.     

Correlations between two large transverse momentum πO mesons at the CERN ISR

The correlations between two π^O's of high transverse momentum were studied at the CERN ISR at a centre-of-mass energy $\text{s}\text{= 52.7}\text{GeV}$. Results are presented for two π^O's detected with an azimuthal separation near 180° and also near 0°. Angular and p_⊥ correlations are discussed, as well as invariant mass plots. The observations are compared with some theoretical models of high p_⊥ phenomena. The most striking feature of the data is a strong correlation in the transverse momentum of the two π^O's.     

In Situ Formation of a MoS2‐Based Inorganic–Organic Nanocomposite by Directed Thermal Decomposition

Nanocomposites based on molybdenum disulfide (MoS₂) and different carbon modifications are intensively investigated in several areas of applications due to their intriguing optical and electrical properties. Addition of a third element may enhance the functionality and application areas of such nanocomposites. Herein, we present a facile synthetic approach based on directed thermal decomposition of (Ph₄P)₂MoS₄ generating MoS₂ nanocomposites containing carbon and phosphorous. Decomposition at 250 °C yields a composite material with significantly enlarged MoS₂ interlayer distances caused by in situ formation of Ph₃PS bonded to the MoS₂ slabs through Mo?S bonds and (Ph₄P)₂S molecules in the van der Waals gap, as was evidenced by ³¹P solid‐state NMR spectroscopy. Visible‐light‐driven hydrogen generation demonstrates a high catalytic performance of the materials.     

Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

Invariant cross-sections are presented for the inclusive reaction p + p → π^o + anything, Measurements of large transverse momentum π^o's (2.5 GeV/c<p_⊥<9 GeV/c) were made near 90° at the CERN ISR at five centre-of-mass energies (√s = 23.5, 30.6, 44.8, 52.7 and 62.4 GeV. At large p_⊥, the invariant cross-sections are seem to vary with s and p_⊥, in good agreement with a fit of the form Ap_⊥^?nF(p_⊥/√s), with n≈8 and F(p_⊥/√s)≈exp(?26p_⊥/√s).