129 research outputs found
Search for pair-produced resonances decaying to quark pairs in proton-proton collisions at root s=13 TeV
Get PDFA general search for the pair production of resonances, each decaying to two quarks, is reported. The search is conducted separately for heavier resonances (masses above 400 GeV), where each of the four final-state quarks generates a hadronic jet resulting in a four-jet signature, and for lighter resonances (masses between 80 and 400 GeV), where the pair of quarks from each resonance is collimated and reconstructed as a single jet resulting in a two-jet signature. In addition, a b-tagged selection is applied to target resonances with a bottom quark in the final state. The analysis uses data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb(-1), from proton-proton collisions at a center-of-mass energy of 13 TeV. The mass spectra are analyzed for the presence of new resonances, and are found to be consistent with standard model expectations. The results are interpreted in the framework of R-parity-violating supersymmetry assuming the pair production of scalar top quarks decaying via the hadronic coupling lambda ''(312) or lambda ''(323) and upper limits on the cross section as a function of the top squark mass are set. These results probe a wider range of masses than previously explored at the LHC, and extend the top squark mass limits in the (t) over tilde -> qq' scenario.Peer reviewe
Synthesis of Pyrroles through a 4π-Electrocyclic Ring-Closure Reaction of 1-Azapentadienyl Cations
No full text1-Azapenta-1,4-diene-3-ols <b>4a</b>–<b>m</b> are easily accessible from 1-azapenta-1,4-dien-3-ones <b>3a</b>–<b>i</b> and organolithium compounds. Treatment
of
the compounds <b>4a</b>–<b>m</b> with strong acid
(triflic acid) generates 1-azapentadienyl cations in situ upon protonation
at the hydroxyl oxygen atom and subsequent water elimination. The
intermediate cations undergo facile 4π-electrocyclization under
ambient condition to give diversely substituted pyrroles <b>6a</b>–<b>m</b> in moderate to good yield. The product pyrrole <b>6k</b> could be characterized by X-ray diffraction. Quantum chemical
calculations were performed to elucidate the mechanism of this reaction
with respect to starting compounds, transition states, and products.
They support the proposed mechanism of a 4π-conrotatory Möbius-type
electrocyclic ring-closure reaction
Synthesis of Pyrroles through a 4π-Electrocyclic Ring-Closure Reaction of 1-Azapentadienyl Cations
No full text1-Azapenta-1,4-diene-3-ols <b>4a</b>–<b>m</b> are easily accessible from 1-azapenta-1,4-dien-3-ones <b>3a</b>–<b>i</b> and organolithium compounds. Treatment
of
the compounds <b>4a</b>–<b>m</b> with strong acid
(triflic acid) generates 1-azapentadienyl cations in situ upon protonation
at the hydroxyl oxygen atom and subsequent water elimination. The
intermediate cations undergo facile 4π-electrocyclization under
ambient condition to give diversely substituted pyrroles <b>6a</b>–<b>m</b> in moderate to good yield. The product pyrrole <b>6k</b> could be characterized by X-ray diffraction. Quantum chemical
calculations were performed to elucidate the mechanism of this reaction
with respect to starting compounds, transition states, and products.
They support the proposed mechanism of a 4π-conrotatory Möbius-type
electrocyclic ring-closure reaction
Reactions of Modified Intermolecular Frustrated P/B Lewis Pairs with Dihydrogen, Ethene, and Carbon Dioxide
No full textIn this contribution, we discuss the reactivity of different
phosphanes
(XPhos (<b>1a</b>), <i><sup>t</sup></i>BuXPhos (<b>1b</b>), and Mes<sub>2</sub>PEt (<b>1c</b>)) and tris(pentafluorophenyl)borane
(and in one case, EtB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>) against
small molecules. <b>1a</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>, <b>1b</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>, and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> split
dihydrogen heterolytically to yield the phosphonium borate salts <b>2a</b>, <b>2b</b>, and <b>2c</b>, respectively. Control
experiments with D<sub>2</sub> gave the respective deuterated phosphonium
borates <b>2a</b>-D<sub>2</sub>, <b>2b</b>-D<sub>2</sub>, and <b>2c</b>-D<sub>2</sub>. The FLP systems <b>1b</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> underwent 1,2-addition reactions
with ethene, resulting in the generation of the ethylene-bridged phosphonium
borates <b>3b</b> and <b>3c</b>. As well, the Lewis pair
EtB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> and Mes<sub>2</sub>PEt
reacted with ethene to yield the corresponding 1,2-addition product <b>3d</b>. At low temperature, the FLP systems <b>1a</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> coordinated carbon dioxide (<b>4a</b>, <b>4c</b>). The new compounds <b>2a</b>, <b>2b</b>, <b>3b</b>, <b>3c</b>, <b>3d</b>, <b>4a</b>, and <b>4c</b> were characterized by X-ray crystal structure
analyses
Reactions of Modified Intermolecular Frustrated P/B Lewis Pairs with Dihydrogen, Ethene, and Carbon Dioxide
No full textIn this contribution, we discuss the reactivity of different
phosphanes
(XPhos (<b>1a</b>), <i><sup>t</sup></i>BuXPhos (<b>1b</b>), and Mes<sub>2</sub>PEt (<b>1c</b>)) and tris(pentafluorophenyl)borane
(and in one case, EtB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>) against
small molecules. <b>1a</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>, <b>1b</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>, and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> split
dihydrogen heterolytically to yield the phosphonium borate salts <b>2a</b>, <b>2b</b>, and <b>2c</b>, respectively. Control
experiments with D<sub>2</sub> gave the respective deuterated phosphonium
borates <b>2a</b>-D<sub>2</sub>, <b>2b</b>-D<sub>2</sub>, and <b>2c</b>-D<sub>2</sub>. The FLP systems <b>1b</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> underwent 1,2-addition reactions
with ethene, resulting in the generation of the ethylene-bridged phosphonium
borates <b>3b</b> and <b>3c</b>. As well, the Lewis pair
EtB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> and Mes<sub>2</sub>PEt
reacted with ethene to yield the corresponding 1,2-addition product <b>3d</b>. At low temperature, the FLP systems <b>1a</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> coordinated carbon dioxide (<b>4a</b>, <b>4c</b>). The new compounds <b>2a</b>, <b>2b</b>, <b>3b</b>, <b>3c</b>, <b>3d</b>, <b>4a</b>, and <b>4c</b> were characterized by X-ray crystal structure
analyses
Reactions of Modified Intermolecular Frustrated P/B Lewis Pairs with Dihydrogen, Ethene, and Carbon Dioxide
No full textIn this contribution, we discuss the reactivity of different
phosphanes
(XPhos (<b>1a</b>), <i><sup>t</sup></i>BuXPhos (<b>1b</b>), and Mes<sub>2</sub>PEt (<b>1c</b>)) and tris(pentafluorophenyl)borane
(and in one case, EtB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>) against
small molecules. <b>1a</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>, <b>1b</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>, and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> split
dihydrogen heterolytically to yield the phosphonium borate salts <b>2a</b>, <b>2b</b>, and <b>2c</b>, respectively. Control
experiments with D<sub>2</sub> gave the respective deuterated phosphonium
borates <b>2a</b>-D<sub>2</sub>, <b>2b</b>-D<sub>2</sub>, and <b>2c</b>-D<sub>2</sub>. The FLP systems <b>1b</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> underwent 1,2-addition reactions
with ethene, resulting in the generation of the ethylene-bridged phosphonium
borates <b>3b</b> and <b>3c</b>. As well, the Lewis pair
EtB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> and Mes<sub>2</sub>PEt
reacted with ethene to yield the corresponding 1,2-addition product <b>3d</b>. At low temperature, the FLP systems <b>1a</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> coordinated carbon dioxide (<b>4a</b>, <b>4c</b>). The new compounds <b>2a</b>, <b>2b</b>, <b>3b</b>, <b>3c</b>, <b>3d</b>, <b>4a</b>, and <b>4c</b> were characterized by X-ray crystal structure
analyses
Reactions of Modified Intermolecular Frustrated P/B Lewis Pairs with Dihydrogen, Ethene, and Carbon Dioxide
No full textIn this contribution, we discuss the reactivity of different
phosphanes
(XPhos (<b>1a</b>), <i><sup>t</sup></i>BuXPhos (<b>1b</b>), and Mes<sub>2</sub>PEt (<b>1c</b>)) and tris(pentafluorophenyl)borane
(and in one case, EtB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>) against
small molecules. <b>1a</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>, <b>1b</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>, and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> split
dihydrogen heterolytically to yield the phosphonium borate salts <b>2a</b>, <b>2b</b>, and <b>2c</b>, respectively. Control
experiments with D<sub>2</sub> gave the respective deuterated phosphonium
borates <b>2a</b>-D<sub>2</sub>, <b>2b</b>-D<sub>2</sub>, and <b>2c</b>-D<sub>2</sub>. The FLP systems <b>1b</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> underwent 1,2-addition reactions
with ethene, resulting in the generation of the ethylene-bridged phosphonium
borates <b>3b</b> and <b>3c</b>. As well, the Lewis pair
EtB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> and Mes<sub>2</sub>PEt
reacted with ethene to yield the corresponding 1,2-addition product <b>3d</b>. At low temperature, the FLP systems <b>1a</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> and <b>1c</b>/B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> coordinated carbon dioxide (<b>4a</b>, <b>4c</b>). The new compounds <b>2a</b>, <b>2b</b>, <b>3b</b>, <b>3c</b>, <b>3d</b>, <b>4a</b>, and <b>4c</b> were characterized by X-ray crystal structure
analyses
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