Functionalization reactions of the refrigerants HFO‐1234yf (2,3,3,3‐tetrafluoropropene) and HFO‐1234ze (1,3,3,3‐tetrafluoropropene) were developed. The selectivity and reactivity towards CF3 groups ...of C−F activation reactions can be controlled by employing either a germane or a silane as the hydrogen source. Unique transformations were designed to accomplish consecutive hydrogermylation and C−F activation steps. This allowed for an unprecedented transformation of an olefinic C−F bond into a C−H bond by heterogeneous catalysis. These reactions are catalyzed by nanoscopic aluminum chlorofluoride (ACF) under very mild conditions.
Functionalizations of tetrafluoropropenes such as HFO‐1234yf were developed. The transformation of the CF3 group into an olefinic CF2 group was achieved at nanoscopic aluminum chlorofluoride (ACF) with silane. Consecutive hydrogermylation and C−F activation steps enabled the transformation of an olefinic C−F into a C−H bond.
The conversion of lignocellulosic biomass into value-added chemicals and biofuels has been attracting the attention of researchers in recent years. Lignin is an abundant, natural polymer and a major ...component of lignocellulose comprising an aromatic structure with ether linkages, methoxy-, and hydroxyl groups. Therefore, it has great potential as a sustainable source to produce basic chemical products. In this study, precious metal-loaded hydrotalcite (HTC) catalysts for the depolymerization of organosolv lignin (OL) were investigated concerning minimizing coke formation and maximizing the value-added lignin oil fraction and lignin tar fraction. The influences of the catalyst support, the platinum loading as well as the loading with a second metal (Cu or Ni) were examined. The resulting depolymerization fractions (lignin oil, lignin tar, aqueous fraction, and coke) were determined gravimetrically. To compare the molecular mass distribution of the lignin oil and lignin tar fractions as well as the purchased OL, gel permeation chromatography (GPC) was used. The lignin oil fractions were analyzed quantitatively and qualitatively by gas chromatography-mass spectroscopy (GC–MS). Regarding the most suitable catalyst system (5%Pt-1%Ni/HTC), a design of experiment (DoE) was prepared to further minimize coke formation and maximize the value-added fractions (lignin oil and lignin tar). This optimization led to 18 wt% lignin oil fraction, 72 wt% lignin tar fraction, and 0.4 wt% coke formation.
•Process optimization for the depolymerization of organosolv lignin using DOE, response surface methodology.•Influences of catalyst support (hydrotalcite, HTC), platinum loading and loading with a second metal (Cu or Ni) were examined.•Maximization of yields of lignin tar and oil product fractions while minimizing coke formation and required catalyst amount.•The yields of value-added products could be increased to about 90% under the optimized process conditions with 5%Pt-1%Ni/HTC.•The depolymerization was carried out in ethanol/water as solvent and H-donor.
Functionalization reactions of the refrigerants HFO‐1234yf (2,3,3,3‐tetrafluoropropene) and HFO‐1234ze (1,3,3,3‐tetrafluoropropene) were developed. The selectivity and reactivity towards CF3 groups ...of C−F activation reactions can be controlled by employing either a germane or a silane as the hydrogen source. Unique transformations were designed to accomplish consecutive hydrogermylation and C−F activation steps. This allowed for an unprecedented transformation of an olefinic C−F bond into a C−H bond by heterogeneous catalysis. These reactions are catalyzed by nanoscopic aluminum chlorofluoride (ACF) under very mild conditions.
Funktionalisierungen von Tetrafluorpropenen wie HFO‐1234yf wurden entwickelt. Die Umwandlung der CF3‐Gruppe in eine olefinische CF2‐Einheit gelang mit nanoskopischem Aluminiumchlorfluorid (ACF) und einem Silan. Aufeinanderfolgende Hydrogermylierung und C‐F‐Aktivierung ermöglichten die Umwandlung der olefinischen C‐F‐Bindung in eine C‐H‐Bindung.
The λ3‐phosphinine derivatives 2,6‐diphenyl‐4‐(p‐tolyl)phosphinine and 2‐(2′‐pyridyl)‐4,6‐diphenylphosphinine were quantitatively converted into the corresponding λ4‐phosphinine anions by reaction ...with phenyllithium. Systematic hydrolysis experiments with H2O and MeOH show that a subtle interplay between the pKa values of the generated 1,2‐dihydrophosphinine derivatives and the pKb value of the formed bases, LiOH and LiOCH3, respectively, leads either to the kinetic or thermodynamic product. The coordination chemistry of the λ4‐phosphinine anions towards RhI was further investigated, and the anions based on 2,6‐diphenyl‐4‐(p‐tolyl)‐phosphinine and 2‐(2′‐pyridyl)‐4,6‐diphenylphosphinine demonstrate different coordination modes. Whereas the former coordinates in an η5 fashion towards the RhI atom, the latter acts as a bidentate chelating ligand with an η1 coordination to the metal center through the phosphorus lone pair.
The λ4‐phosphinine anions of 2,6‐diphenyl‐4‐(p‐tolyl)phosphinine and the structurally related 2‐(2′‐pyridyl)‐4,6‐diphenylphosphinine show a remarkable difference in selectivity towards hydrolysis with water and methanol. Moreover, the presence or absence of an additional nitrogen atom within the ligand framework influences the coordination chemistry of the phosphinine derivatives towards RhI.
Abstract
Selective oxidation of 5‐(hydroxymethyl)furfural (HMF) to 2,5‐diformylfuran (DFF) is an important approach for biobased compound valorization through biorefinery. As there is no large‐scale ...process for this application yet, it is of high importance to find a suitable catalyst system for the production of DFF. In this work, we show that an important step in this direction was taken with a 5 % Ru/Al
2
O
3
catalyst, whereby essentially quantitative selectivities could be obtained in the solvent toluene without the significant formation of over‐oxidation products. A design of experiments approach was used to determine important information about the main process parameters – catalyst amount, oxygen pressure and reaction temperature. By developing an optimised washing method, excellent results were achieved in terms of catalyst reusability, with HMF conversions of over 99.5 % without loss of the catalyst‘s high selectivity after five cycles. Upscaling experiments were performed with the catalyst in a 5‐L reactor at different reactor fill rates, where complete conversion of HMF to DFF was achieved, with a 25 % longer reaction time to achieve full conversion compared to a smaller scale reactor setup.
Heterogeneous catalytic oxidation of 5‐hydroxymethylfurfural (HMF) with molecular oxygen to 2,5‐diformylfuran (DFF) was performed on aluminium oxide‐supported ruthenium catalysts (Ru/Al2O3). The ...ruthenium catalysts were analyzed by pH and Brunauer‐Emett‐Teller (BET) measurement, and potential side products measured by HPLC‐UV. High catalyst activity with near‐quantitative DFF yield (>99.9 %) was achieved in toluene under moderate reaction conditions (90 °C, 0.2 MPa O2). Various Al2O3 supports were screened for optimal catalyst activity and selectivity for DFF, and the most effective was chosen for a Design of Experiments (DoE). With a central composite design based on a response‐surface model, the effects of reaction parameters (i. e., catalyst amount, oxygen pressure and temperature) on the reaction rate were investigated, and the selected model tested by analysis of variance (ANOVA). The modeling showed that catalyst amount had the highest relative impact on the reaction rate, and afforded in‐depth knowledge about the chemical space investigated.
In this study, various Ru/Al2O3 catalysts were used for the aerobic heterogeneous oxidation of 5‐(hydroxymethl)furfural to 2,5‐diformylfuran. With the help of the design of experiment approach, high catalyst activities with excellent product selectivity could be achieved under relatively moderate reaction conditions.
The selective activation of CCl bonds of hydrochlorofluoromethanes and chloromethanes at moderate reaction conditions using ACF in a combination with Et3GeH is presented. The reactions of the ...chloromethanes (CH3Cl, CH2Cl2, CHCl3 and CCl4) in the presence of Et3GeH and ACF as catalyst led to the activation of only one CCl bond resulting in the hydrodechlorination. Friedel-Crafts reactions with benzene as solvent are suppressed by Et3GeH. A selective hydrodechlorination of hydrochlorofluoromethanes was achieved, because a transformation of a CF bond into a CH bond by the combination of ACF with Et3GeH did not occur. Supporting PulseTA® experiments illustrated the interaction between the solid catalyst and Et3GeH, the solvent benzene or CH2Cl2.
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•Selective monohydrodechlorination reactions of polychlorinated alkanes were achieved.•Hydrodechlorination of CHCl2F and CHClF2 occurs with selectivity towards C−Cl activation.•Heterogeneous catalytic reactions were developed.•PTA studies give information about the interaction between the substrates at ACF · Et3GeH.
•Radiotherapy of brain tumors may cause dose-dependent side-effects.•HipPro Pilot study using structural MRI and comprehensive neurocognitive evaluation.•Hippocampal thickness or objective memory ...performance did not change.•Subjective memory impairment was associated with symptoms of depression.•Future studies of memory impairment should assess depressive symptoms.
Radiotherapy in patients with primary brain tumors may affect hippocampal structure and cause dyscognitive side-effects.
Using structural MRI and comprehensive neurocognitive evaluation, we investigated associations between hippocampal structure and memory deficits in 15 patients with WHO grade 3 and grade 4 gliomas receiving standard radio(chemo)therapy.
We did not find changes in hippocampal thickness or cognitive abilities three months after completing radiotherapy. However, subjective memory impairment was associated with symptoms of depression, but not with objective memory performance, cortical thickness of the hippocampus or radiation dose.
Irrespective of whether there is a bidirectional relationship between affective changes and subjective cognitive dysfunction in these patients, depressive symptoms remain a target for intervention to improve their quality of life. The results of our pilot study highlight that future assessment of side effects of radiotherapy concerning memory should include assessments of depressive symptoms.
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