33 research outputs found
In Vivo Functional Adaptive Immune Responses in Mice Subjected to Allogeneic Umbilical Cord Blood Cell Transplantation
Palladium/IzQO-Catalyzed Coordination–Insertion Copolymerization of Ethylene and 1,1-Disubstituted Ethylenes Bearing a Polar Functional Group
Coordination–insertion copolymerization
of ethylene with
1,1-disubstituted ethylenes bearing a polar functional group, such
as methyl methacrylate (MMA), is a long-standing challenge in catalytic
polymerization. The major obstacle for this process is the huge difference
in reactivity of ethylene versus 1,1-disubstituted ethylenes toward
both coordination and insertion. Herein we report the copolymerization
of ethylene and 1,1-disubstituted ethylenes by using an imidazo[1,5-<i>a</i>]quinolin-9-olate-1-ylidene-supported palladium catalyst.
Various types of 1,1-disubstituted ethylenes were successfully incorporated
into the polyethylene chain. In-depth characterization of the obtained
copolymers and mechanistic inferences drawn from stoichiometric reactions
of alkylpalladium complexes with methyl methacrylate and ethylene
indicate that the copolymerization proceeds by the same coordination–insertion
mechanism that has been postulated for ethylene
Synthesis and Reactivity of Methylpalladium Complexes Bearing a Partially Saturated IzQO Ligand
A saturated
N-heterocyclic carbene–phenolate bidentate ligand,
3,3a,4,5-tetrahydroimidazo[1,5-<i>a</i>]quinolin-9-olate-1-ylidene
(SIzQO), was synthesized and characterized. The SIzQO ligand was then
treated with PdClMe(pyridine)<sub>2</sub> and [Pd(μ-Cl)Me(2,6-lutidine)]<sub>2</sub>, which afforded <i>C</i>,<i>C</i>-<i>cis</i>-(SIzQO)PdMe(pyridine) and the thermodynamically unstable <i>trans</i> isomer <i>C</i>,<i>C</i>-<i>trans</i>-(SIzQO)PdMe(2,6-lutidine), respectively. The latter
isomerizes at 40 °C into the corresponding <i>cis</i> isomer via a dissociative mechanism. These palladium/SIzQO complexes
catalyze the polymerization of ethylene at 100–120 °C,
although the catalytic activity is lower than that of a previously
reported palladium/imidazo[1,5-<i>a</i>]quinolin-9-olate-1-ylidene
(IzQO) system
Palladium/IzQO-Catalyzed Coordination–Insertion Copolymerization of Ethylene and 1,1-Disubstituted Ethylenes Bearing a Polar Functional Group
Coordination–insertion copolymerization
of ethylene with
1,1-disubstituted ethylenes bearing a polar functional group, such
as methyl methacrylate (MMA), is a long-standing challenge in catalytic
polymerization. The major obstacle for this process is the huge difference
in reactivity of ethylene versus 1,1-disubstituted ethylenes toward
both coordination and insertion. Herein we report the copolymerization
of ethylene and 1,1-disubstituted ethylenes by using an imidazo[1,5-<i>a</i>]quinolin-9-olate-1-ylidene-supported palladium catalyst.
Various types of 1,1-disubstituted ethylenes were successfully incorporated
into the polyethylene chain. In-depth characterization of the obtained
copolymers and mechanistic inferences drawn from stoichiometric reactions
of alkylpalladium complexes with methyl methacrylate and ethylene
indicate that the copolymerization proceeds by the same coordination–insertion
mechanism that has been postulated for ethylene
Synthesis and Reactivity of Methylpalladium Complexes Bearing a Partially Saturated IzQO Ligand
A saturated
N-heterocyclic carbene–phenolate bidentate ligand,
3,3a,4,5-tetrahydroimidazo[1,5-<i>a</i>]quinolin-9-olate-1-ylidene
(SIzQO), was synthesized and characterized. The SIzQO ligand was then
treated with PdClMe(pyridine)<sub>2</sub> and [Pd(μ-Cl)Me(2,6-lutidine)]<sub>2</sub>, which afforded <i>C</i>,<i>C</i>-<i>cis</i>-(SIzQO)PdMe(pyridine) and the thermodynamically unstable <i>trans</i> isomer <i>C</i>,<i>C</i>-<i>trans</i>-(SIzQO)PdMe(2,6-lutidine), respectively. The latter
isomerizes at 40 °C into the corresponding <i>cis</i> isomer via a dissociative mechanism. These palladium/SIzQO complexes
catalyze the polymerization of ethylene at 100–120 °C,
although the catalytic activity is lower than that of a previously
reported palladium/imidazo[1,5-<i>a</i>]quinolin-9-olate-1-ylidene
(IzQO) system
The Intermediary Roles of Public Health Nurses (PHNs) in Utilizing Communication Robots (CRs) in Community Health Care Practice
Combined angiotensin receptor blocker and ACE inhibitor on myocardial fibrosis and left ventricular stiffness in dogs with heart failure
Nationwide Survey of Pediatric Inpatients With Hand, Foot, and Mouth Disease, Herpangina, and Associated Complications During an Epidemic Period in Japan: Estimated Number of Hospitalized Patients and Factors Associated With Severe Cases
Helper T cell-dominant tertiary lymphoid structures are associated with disease relapse of advanced colorectal cancer
Tertiary lymphoid structures (TLSs), clusters of immune cells found around tumor tissue, have been shown to be associated with anti-tumor immunity, but the cellular composition within each TLS and whether the cellular composition of a TLS affects a patient’s prognosis are poorly understood. In the present study, each TLS was categorized according to its cellular composition determined by a system of multiplex immunohistochemical staining and quantitative analysis, and the correlation between the category and prognosis was examined. Sixty-seven patients with curatively resected stage II/III colorectal cancer (CRC) were enrolled. A TLS, consisting of germinal center B cells, follicular dendritic cells, T helper (Th) cells, B cells, cytotoxic T cells, and macrophages, was confirmed in the tumor tissue of 58 patients (87%). The densities of Th cells and macrophages were significantly higher in relapsed patients than in not-relapsed patients (p = .043 and p = .0076). A higher ratio of Th cells was the most significant independent risk factor for disease relapse on multivariate analysis. The subset increasing in Th cells was GATA3+ Th2. A total of 353 TLSs was divided into five clusters according to immune cell composition. Among them, the Th-rich type TLS was significantly increased (p = .0009) in relapsed patients. These data suggest the possibility that Th cell-dominant composition might disturb the anti-tumor immune response, and the function of each TLS might differ depending on its composition
Elucidating the Key Role of Phosphine−Sulfonate Ligands in Palladium-Catalyzed Ethylene Polymerization: Effect of Ligand Structure on the Molecular Weight and Linearity of Polyethylene
The
mechanism of linear polyethylene formation catalyzed by palladium/phosphine−sulfonate
and the effect of the ligand structure on the catalytic performance,
such as linearity and molecular weight of the polyethylene, were reinvestigated
theoretically and experimentally. We used dispersion-corrected density
functional theory (DFT-D3) to study the entire mechanism of polyethylene
formation from (R<sub>2</sub>PC<sub>6</sub>H<sub>4</sub>SO<sub>3</sub>)PdMe(2,6-lutidine) (R = Me, <i>t-</i>Bu) and elucidated
the key steps that determine the molecular weight and linearity of
the polyethylene. The alkylpalladium ethylene complex is the key intermediate
for both linear propagation and β-hydride elimination from the
growing polymer chain. On the basis of the key species, the effects
of substituents on the phosphorus atom (R = <i>t-</i>Bu, <i>i</i>-Pr, Cy, Men, Ph, 2-MeOC<sub>6</sub>H<sub>4</sub>, biAr)
were further investigated theoretically to explain the experimental
results in a comprehensive manner. Thus, the experimental trend of
molecular weights of polyethylene could be correlated to the ΔΔ<i><i>G</i></i><sup>⧧</sup> value between (i)
the transition state of linear propagation and (ii) the transition
state of the path for ethylene dissociation leading to β-hydride
elimination. Moreover, the experimental behavior of the catalysts
under varied ethylene pressure was well explained by our computation
on the small set of key species elucidated from the entire mechanism.
In our additional experimental investigations, [<i>o</i>-Ani<sub>2</sub>PC<sub>6</sub>H<sub>4</sub>SO<sub>3</sub>]PdH[P(<i>t</i>-Bu)<sub>3</sub>] catalyzed a hydrogen/deuterium exchange
reaction between ethylene and MeOD. The deuterium incorporation from
MeOD into the main chain of polyethylene, therefore, can be explained
by the incorporation of deuterated ethylene formed by a small amount
of Pd–H species. These insights into the palladium/phosphine−sulfonate
system provide a comprehensive understanding of how the phosphine−sulfonate
ligands function to produce linear polyethylene