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The tetraaryl μ‐hydridodiborane(4) anion [2H]− possesses nucleophilic B−B and B−H bonds. Treatment of K[2H] with the electrophilic 9‐H‐9‐borafluorene (HBFlu) furnishes the B3 cluster K[3], with a triangular boron core linked through two BHB two‐electron, three‐center bonds and one electron‐precise B−B bond, reminiscent of the prominent [B3H8]− anion. Upon heating or prolonged stirring at room temperature, K[3] rearranges to a slightly more stable isomer K[3 a]. The reaction of M[2H] (M+=Li+, K+) with MeI or Me3SiCl leads to equimolar amounts of 9‐R‐9‐borafluorene and HBFlu (R=Me or Me3Si). Thus, [2H]− behaves as a masked [:BFlu]− nucleophile. The HBFlu by‐product was used in situ to establish a tandem substitution‐hydroboration reaction: a 1:1 mixture of M[2H] and allyl bromide gave the 1,3‐propylene‐linked ditopic 9‐borafluorene 5 as sole product. M[2H] also participates in unprecedented [4+1] cycloadditions with dienes to furnish dialkyl diaryl spiroborates, M[R2BFlu].
Certain electron-rich 1,4-diborabenzene derivatives efficiently activate single, double, and triple bonds and thereby increasingly compete with transition metals in homogeneous catalysis. This review compares the activation of three model substrates (H2, H2C=CH2, CO2) by (i) 9,10-dihydro-9,10-diboraanthracene dianions, (ii) their neutral carbene-stabilized congeners, (iii) 1,3,2,5-diazadiborinines, and (iv) 1,4,2,5-diazadiborinines. Distinct structure-properties relationships become apparent, the most influential factors being (i) the steric demands of the B-bonded substituents, (ii) the charges on the B-doped (hetero)arenes, (iii) charge polarization as a result of additional N-doping, and (iv) the energies and nodal structures of the frontier orbitals. The observed reactions are explained by a transition metal-like activation mechanism. If the two boron atoms are chemically inequivalent, contributions of a B(+I)/B(+III) mixed-valence state determine the observed regioselectivities when polar substrates are added. The lessons learned from the conversions of the model substrates are subsequently used to rationalize the behavior of the B2 heterocycles also toward more sophisticated substrate molecules. Finally, catalytic cycles based on H2- and H−-transfers, hydroboration reactions, and CO2 reductions will be covered.
SixGey alloys are emerging materials for modern semiconductor technology. Well-defined model systems of the bulk structures aid in understanding their intrinsic characteristics. Three such model clusters have now been realized in the form of the SixGey heteroadamantanes [0], [1], and [2] through selective one-pot syntheses starting from Me2GeCl2, Si2Cl6, and [nBu4N]Cl. Compound [0] contains six GeMe2 and four SiSiCl3 vertices, whereas one and two of the GeMe2 groups are replaced by SiCl2 moieties in compounds [1] and [2], respectively. Chloride-ion-mediated rearrangement quantitatively converts [2] into [1] at room temperature and finally into [0] at 60 °C, which is not only remarkable in view of the rigidity of these cage structures but also sheds light on the assembly mechanism.
Vicinally diiodinated polycyclic aromatic hydrocarbons (I2‐PAHs) are accessible from the corresponding diborylated B2‐PAHs through boron/iodine exchange. The B2‐PAHs have been prepared via twofold electrophilic borylation reactions templated by a vicinally disilylated benzene. Our protocol is applicable to fluorenes, acenes, annulated acenes, oligoaryls, and even [5]helicene. Using B2‐naphthalene as the example, we have shown that the reaction scope can, in principle, be expanded to include the synthesis of vicinally dibrominated and dihydroxylated PAHs. The usefulness of the building blocks provided by our method in the field of optoelectronic materials was demonstrated by the successful conversion of I2‐fluoranthene to the analogous doubly alkynylated fluoranthene emitter.
Two subvalent, redox-active diborane(4) anions, [3]4− and [3]2−, carrying exceptionally high negative charge densities are reported: Reduction of 9-methoxy-9-borafluorene with Li granules without stirring leads to the crystallization of the B(sp3)−B(sp2) diborane(5) anion salt Li[5]. [5]− contains a 2,2′-biphenyldiyl-bridged B−B core, a chelating 2,2′-biphenyldiyl moiety, and a MeO substituent. Reduction of Li[5] with Na metal gives the Na+ salt of the tetraanion [3]4− in which two doubly reduced 9-borafluorenyl fragments are linked via a B−B single bond. Comproportionation of Li[5] and Na4[3] quantitatively furnishes the diborane(4) dianion salt Na2[3], the doubly boron-doped congener of 9,9′-bis(fluorenylidene). Under acid catalysis, Na2[3] undergoes a formal Stone–Wales rearrangement to yield a dibenzo[g,p]chrysene derivative with B=B core. Na2[3] shows boron-centered nucleophilicity toward n-butyl chloride. Na4[3] produces bright blue chemiluminescence when exposed to air.
SixGey alloys are emerging materials for modern semiconductor technology. Well-defined model systems of the bulk structures aid in understanding their intrinsic characteristics. Three such model clusters have now been realized in the form of the SixGey heteroadamantanes [0], [1], and [2] through selective one-pot syntheses starting from Me2GeCl2, Si2Cl6, and [nBu4N]Cl. Compound [0] contains six GeMe2 and four SiSiCl3 vertices, whereas one and two of the GeMe2 groups are replaced by SiCl2 moieties in compounds [1] and [2], respectively. Chloride-ion-mediated rearrangement quantitatively converts [2] into [1] at room temperature and finally into [0] at 60 °C, which is not only remarkable in view of the rigidity of these cage structures but also sheds light on the assembly mechanism.
Treatment of hexachloropropene (Cl2C[double bond, length as m-dash]C(Cl)–CCl3) with Si2Cl6 and [nBu4N]Cl (1 : 4 : 1) in CH2Cl2 results in a quantitative conversion to the trisilylated, dichlorinated allyl anion salt [nBu4N][Cl2C[double bond, length as m-dash]C(SiCl3)–C(SiCl3)2] ([nBu4N][1]). Tetrachloroallene Cl2C[double bond, length as m-dash]C[double bond, length as m-dash]CCl2 was identified as the first intermediate of the reaction cascade. In the solid state, [1]− adopts approximate Cs symmetry with a dihedral angle between the planes running through the olefinic and carbanionic fragments of [1]− of C[double bond, length as m-dash]C–Si//Si–C–Si = 78.3(1)°. One-electron oxidation of [nBu4N][1] with SbCl5 furnishes the distillable blue radical 1˙. The neutral propene Cl2C[double bond, length as m-dash]C(SiCl3)–C(SiCl3)2H (2) was obtained by (i) protonation of [1]− with HOSO2CF3 (HOTf) or (ii) H-atom transfer to 1˙ from 1,4-cyclohexadiene. Quantitative transformation of all three SiCl3 substituents in 2 to Si(OMe)3 (2OMe) or SiMe3 (2Me) substituents was achieved by using MeOH/NMe2Et or MeMgBr in CH2Cl2 or THF, respectively. Upon addition of 2 equiv. of tBuLi, 2Me underwent deprotonation with subsequent LiCl elimination, 1,2-SiMe3 migration and Cl/Li exchange to afford the allenyl lithium compound Me3Si(Li)C[double bond, length as m-dash]C[double bond, length as m-dash]C(SiMe3)2 (Li[4]), which is an efficient building block for the introduction of Me, SiMe3, or SnMe3 (5) groups. The trisilylated, monochlorinated allene Cl3Si(Cl)C[double bond, length as m-dash]C[double bond, length as m-dash]C(SiCl3)2 (6), was obtained from [nBu4N][1] through Cl−-ion abstraction with AlCl3 and rearrangement in CH2Cl2 (1˙ forms as a minor side product, likely because the system AlCl3/CH2Cl2 can also act as a one-electron oxidant).
Colorectal carcinoma (CRC) is a major cause of morbidity and mortality in Western countries. It has so far been molecularly defined mainly by alterations of the Wnt pathway. We show here for the first time that aberrant activities of the signal transducer and activator of transcription STAT3 actively contribute to this malignancy and, thus, are a potential therapeutic target for CRC. Constitutive STAT3 activity was found to be abundant in dedifferentiated cancer cells and infiltrating lymphocytes of CRC samples, but not in non-neoplastic colon epithelium. Cell lines derived from malignant colorectal tumors lost persistent STAT3 activity in culture. However, implantation of colon carcinoma cells into nude mice resulted in restoration of STAT3 activity, suggesting a role of an extracellular stimulus within the tumor microenvironment as a trigger for STAT activation. STAT3 activity in CRC cells triggered through interleukin-6 or through a constitutively active STAT3 mutant promoted cancer cell multiplication, whereas STAT3 inhibition through a dominant-negative variant impaired IL-6-driven proliferation. Blockade of STAT3 activation in CRCderived xenograft tumors slowed down their development, arguing for a contribution of STAT3 to colorectal tumor growth.
Nanoplastics (NP) and microplastics (MP) accumulate in our environment as a consequence of the massive consumption of plastics. Huge knowledge-gaps exist regarding uptake and fate of plastic particles in micro- and nano-dimensions in humans as well as on their impact on human health.
This study investigated the transport and effects of 50 nm and 0.5 μm COOH-modified polystyrene (PS) particles, as representatives for NP and MP, in different biological models in vitro. Acute toxicity and potential translocation of the particles were studied at the human intestinal and placental barrier using advanced in vitro co-culture models. Furthermore, embryotoxicity and genotoxicity were investigated as highly sensitive endpoints.
Polystyrene was not acutely toxic in both sizes (nano- and microparticles). No transport across the intestinal and placental barrier but a cellular uptake and intracellular accumulation of PS nano- and microparticles were determined. The particles were identified as weak embryotoxic and non-genotoxic.
In contrast to single-organ studies, this multi-endpoint study is providing a data-set with the exact same type of particles to compare organ-specific outcomes. Our study clearly shows the need to investigate other types of plastics as well as towards long-term or chronic effects of plastic particles in different biological models in vitro.
Background: Rare diseases are, by definition, very serious and chronic diseases with a high negative impact on quality of life. Approximately 350 million people worldwide live with rare diseases. The resulting high disease burden triggers health information search, but helpful, high-quality, and up-to-date information is often hard to find. Therefore, the improvement of health information provision has been integrated in many national plans for rare diseases, discussing the telephone as one access option. In this context, this study examines the need for a telephone service offering information for people affected by rare diseases, their relatives, and physicians.
Methods: In total, 107 individuals participated in a qualitative interview study conducted in Germany. Sixty-eight individuals suffering from a rare disease or related to somebody with rare diseases and 39 health care professionals took part. Individual interviews were conducted using a standardized semi-structured questionnaire. Interviews were analysed using the qualitative content analysis, triangulating patients, relatives, and health care professionals. The fulfilment of qualitative data processing standards has been controlled for.
Results: Out of 68 patients and relatives and 39 physicians, 52 and 18, respectively, advocated for the establishment of a rare diseases telephone service. Interviewees expected a helpline to include expert staffing, personal contact, good availability, low technical barriers, medical and psychosocial topics of counselling, guidance in reducing information chaos, and referrals. Health care professionals highlighted the importance of medical topics of counselling—in particular, differential diagnostics—and referrals.
Conclusions: Therefore, the need for a national rare diseases helpline was confirmed in this study. Due to limited financial resources, existing offers should be adapted in a stepwise procedure in accordance with the identified attributes.
Background: Recently, public and political interest has focused on people living with rare diseases and their health concerns. Due to the large number of different types of rare diseases and the sizable number of patients, taking action to improve the life of those affected is gaining importance. In 2013, the federal government of Germany adopted a national action plan for rare diseases, including the call to establish a central information portal on rare diseases (Zentrales Informationsportal über seltene Erkrankungen, ZIPSE).
Objective: The objective of this study, therefore, was to conduct scientific research on how such a portal must be designed to meet the needs of patients, their families, and medical professionals, and to provide high-quality information for information seekers.
Methods: We chose a 3-step procedure to develop a needs-based prototype of a central information portal. In the first step, we determined the information needs of patients with rare diseases, their relatives, and health care professionals by means of qualitative interviews and their content-analytical evaluation. On the basis of this, we developed the basic structure of the portal. In the second step, we identified quality criteria for websites on rare diseases to ensure that the information linked with ZIPSE meets the quality demands. Therefore, we gathered existing criteria catalogs and discussed them in an expert workshop. In the third step, we implemented and tested the developed prototypical information portal.
Results: A portal page was configured and made accessible on the Web. The structure of ZIPSE was based on the findings from 108 qualitative interviews with patients, their relatives, and health care professionals, through which numerous information needs were identified. We placed particularly important areas of information, such as symptoms, therapy, research, and advisory services, on the start page. Moreover, we defined 13 quality criteria, referring to factors such as author information, creation date, and privacy, enabling links with high-quality information. Moreover, 19 users tested all the developed routines based on usability and comprehensibility. Subsequently, we improved the visual presentation of search results and other important search functions.
Conclusions: The implemented information portal, ZIPSE, provides high-quality information on rare diseases from a central point of access. By integrating the targeted groups as well as different experts on medical information during the construction, the website can assure an improved search for information for users. ZIPSE can also serve as a model for other Web-based information systems in the field of rare diseases.
Registered Report Identifier: RR1-10.2196/7425.
The signal transducer and activator of transcription 5 (STAT5) regulates differentiation, survival, proliferation and transformation of hematopoietic cells. Upon cytokine stimulation, STAT5 tyrosine phosphorylation (pYSTAT5) is transient, while in diverse neoplastic cells persistent overexpression and enhanced pYSTAT5 are frequently found. Post-translational modifications might contribute to enhanced STAT5 activation in the context of transformation, but the strength and duration of pYSTAT5 are incompletely understood. We found that O-GlcNAcylation and tyrosine phosphorylation act together to trigger pYSTAT5 levels and oncogenic transcription in neoplastic cells. The expression of a mutated hyperactive gain-of-function (GOF) STAT5 without O-GlcNAcylation resulted in decreased tyrosine phosphorylation, oligomerization and transactivation potential and complete loss of oncogenic transformation capacity. The lack of O-GlcNAcylation diminished phospho-ERK and phospho-AKT levels. Our data show that O-GlcNAcylation of STAT5 is an important process that contributes to oncogenic transcription through enhanced STAT5 tyrosine phosphorylation and oligomerization driving myeloid transformation. O-GlcNAcylation of STAT5 could be required for nutrient sensing and metabolism of cancer cells.
The intriguing (μ-hydrido)diboranes(4) with their prominent pristine representative [B2H5]− have mainly been studied theoretically. We now describe the behavior of the planarized tetraaryl (μ-hydrido)diborane(4) anion [1H]− in cycloaddition reactions with the homologous series of heterocumulenes CO2, iPrNCO, and iPrNCNiPr. We show that a C=O bond of CO2 selectively activates the B−B bond of [1H]−, while the μ-H ligand is left untouched ([2H]−). The carbodiimide iPrNCNiPr, in contrast, neglects the B−B bond and rather adds the B-bonded H− ion to its central C atom to generate a formamidinate bridge across the B2 pair ([3]−). As a hybrid, the isocyanate iPrNCO combines the reactivity patterns of both its congeners and gives two products: one of them ([4H]−) is related to [2H]−, the other ([5]−) is an analog of [3]−. We finally propose a mechanistic scenario that rationalizes the individual reaction outcomes and combines them to a coherent picture of B–B vs. B–H bond activation.
TRIANNI mice carry an entire set of human immunoglobulin V region gene segments and are a powerful tool to rapidly isolate human monoclonal antibodies. After immunizing these mice with DNA encoding the spike protein of SARS-CoV-2 and boosting with spike protein, we identified 29 hybridoma antibodies that reacted with the SARS-CoV-2 spike protein. Nine antibodies neutralize SARS-CoV-2 infection at IC50 values in the subnanomolar range. ELISA-binding studies and DNA sequence analyses revealed one cluster of three clonally related neutralizing antibodies that target the receptor-binding domain and compete with the cellular receptor hACE2. A second cluster of six clonally related neutralizing antibodies bind to the N-terminal domain of the spike protein without competing with the binding of hACE2 or cluster 1 antibodies. SARS-CoV-2 mutants selected for resistance to an antibody from one cluster are still neutralized by an antibody from the other cluster. Antibodies from both clusters markedly reduced viral spread in mice transgenic for human ACE2 and protected the animals from SARS-CoV-2-induced weight loss. The two clusters of potent noncompeting SARS-CoV-2 neutralizing antibodies provide potential candidates for therapy and prophylaxis of COVID-19. The study further supports transgenic animals with a human immunoglobulin gene repertoire as a powerful platform in pandemic preparedness initiatives.
The title compound, di-μ3-chlorido-tetra-μ2-chlorido-tetrakis(diethyl ether-κO)bis(1,1-dimethylethyl)tetramagnesium, [Mg4(C4H9)2Cl6(C4H10O)4], features an Mg4Cl6 open-cube cluster. The two four-coordinate Mg2+ ions show an almost tetrahedral coordination, whereas the two six-coordinate Mg2+ ions have their ligands in an octahedral environment. The Mg—Cl bond lengths differ depending on the coordination number (2 or 3) of the bridging μ-Cl− ligands. There are few comparable structures deposited in the Cambridge Structural Database.
Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the R3B/LAND setup with incident beam energies in the range of 300–450 MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type AO(p,2p)A−1N have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry.
The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process β-decay chains. These nuclei are attributed to the p and rp process.
For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections.
The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.
The neutron-unbound isotope 13Be has been studied in several experiments using different reactions, different projectile energies, and different experimental setups. There is, however, no real consensus in the interpretation of the data, in particular concerning the structure of the low-lying excited states. Gathering new experimental information, which may reveal the 13Be structure, is a challenge, particularly in light of its bridging role between 12Be, where the N = 8 neutron shell breaks down, and the Borromean halo nucleus 14Be. The purpose of the present study is to investigate the role of bound excited states in the reaction product 12Be after proton knockout from 14B, by measuring coincidences between 12Be, neutrons, and γ rays originating from de-excitation of states fed by neutron decay of 13Be. The 13Be isotopes were produced in proton knockout from a 400 MeV/nucleon 14B beam impinging on a CH2 target. The 12 Be-n relative-energy spectrum d σ /d Ef n was obtained from coincidences between 12Be(g.s.) and a neutron, and also as threefold coincidences by adding γ rays, from the de-excitation of excited states in 12Be. Neutron decay from the first 5/2+ state in 13Be to the 2+ state in 12Be at 2.11 MeV is confirmed. An energy independence of the proton-knockout mechanism is found from a comparison with data taken with a 35 MeV/nucleon 14B beam. A low-lying p-wave resonance in 13Be(1/2−) is confirmed by comparing proton- and neutron-knockout data from 14B and 14Be.
2,5-Diformylbenzene-1,4-diol (5) is a well-suited starting compound for the preparation of ditopic hydroquinone-based ligands. Here, we report an optimized synthesis of 5 which improves the overall yield from published 7% to 42 %. Three new ditopic Schiff base ligands, 2,5-[iPr2N(CH2)2N=CH]2 - 1,4-(OH)2-C6H2 (8), 2,5-(pyCH2N=CH)2-1,4-(OH)2-C6H2 (9), and 2,5-[py(CH2)2N=CH]2-1,4- (OH)2-C6H2 (10), have been synthesized from 5 and structurally characterized by X-ray crystal structure analysis (py = 2-pyridyl).
Supersilylated tetrachlorodigermane (tBu3Si)Cl2GeGeCl2(SitBu3) and trigermoxetane (tBu3Si)3Ge3Cl3O
(2004)
In contrast to the tetrachlorodigermane (tBu3Si)Cl2Ge-GeCl2(SitBu3), the cis,transcyclotrigermane (tBu3SiGeCl)3 is sensitive to oxygen. Its treatment with O2 at ambient temperature leads to the trigermoxetane (tBu3Si)3Ge3Cl3O. According to an X-ray structure analysis of single crystals consisting of cocrystallized (tBu3Si)3Ge3Cl3O and (tBu3Si)Cl2Ge-GeCl2(SitBu3) the trigermaoxetane contains an almost planar Ge3O-ring while the tetrachlorodigermane (tBu3Si)Cl2Ge- GeCl2(SitBu3) possesses a Si-Ge-Ge-Si chain which is exactly all trans,
The thermolabile triazenides M[tBu3SiNNNSiMetBu2] (M = Li, Na) are accessible from the reaction of tBu2MeSiN3 with the silanides MSitBu3 (M = Li, Na) at −78 °C in THF. At r. t. N2 elimination from the triazenides M[tBu3SiNNNSiMetBu2] (M = Li, Na) takes place with the formation of M[N(SiMetBu2)(SitBu3)] (M = Li, Na). X-Ray quality crystals of Li(THF)[N(SiMetBu2)(SitBu3)] (orthorhombic, Pna21) are obtained from a benzene solution at ambient temperature. In contrast to the structures of the unsolvated silanides MSitBu3 (M = Li, Na), the THF adduct Li(THF)3SitBu3 is monomeric in the solid state (orthorhombic, Pna21).
The supersilylated ethene trans-(tBu3Si)HC=CH(SitBu3) (triclinic, P ī) is accessible from the reaction of tBu3SiCHBr2 with nBuLi at −78 °C in THF or Et2 O. The reaction of Li(H2NCH2CH2NH2)C≡CH with tBu3SiBr leads to the formation of (tBu3Si)C≡CH and (tBu3Si)C≡C(SitBu3). X-Ray quality crystals of (tBu3Si)C≡C(SitBu3) (triclinic, P ī) were obtained by recrystallization from hexane. In contrast to the structures of the disilane tBu3Si-SitBu3 and the disiloxane tBu3Si-O-SitBu3, the sterically crowded ethene trans-(tBu3Si)HC=CH(SitBu3) and ethyne (tBu3Si)C≡C(SitBu3) feature dihedral angles of 60° in the solid-state structures.
Pyrazolyl-substituted 1,4-dihydroxybenzene and 1,4-dihydroxynaphthene derivatives have been synthesized by reaction of 1,4-benzoquinone and 1,4-naphthoquinone, respectively, with pyrazole. Cyclovoltammetric measurements have shown that 1,4-benzoquinone possesses the potential to oxidize 2-(pyrazol-1-yl)- and 2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene. The 2,5-bis(pyrazol-1-yl)- 1,4-dihydroxybenzene reacts with air to give quantitatively black insoluble 2,5-bis(pyrazol-1-yl)-1,4- quinhydrone. Black crystals of 2,5-bis(pyrazol-1-yl)-1,4-quinhydrone suitable for X-ray diffraction were grown from methanol at ambient temperature (monoclinic C2/c). The poor yields of pyrazolylsubstituted 1,4-dihydroxybenzene and 1,4-dihydroxynaphthene derivatives can be explained by the formation of insoluble black quinhydrons in the reaction of benzoquinone and naphthoquinone with pyrazole. The dianions of 2-(pyrazol-1-yl)- and 2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene react with oxygen to give the corresponding semiquinone anions. 2,5-Bis(pyrazol-1-yl)-1,4-benzoquinone shows two reversible one-electron reduction processes in cyclovoltammetric measurements, whereas pyrazolyl-substituted 1,4-dihdroxybenzene and -naphthene derivatives undergo irreversibile electrontransfer processes.
To examine their luminescence behavior, two air-stable BN addition compounds were synthesized by the reaction of 5-fluoro-2-(2′-pyridyl)indole with 1,4- and 1,3-bis(bromo(methyl)boryl)benzene, respectively. Both BN adducts are luminescent. Their emission maxima (1,3-substituted BN adduct: 495 nm; 1,4-substituted BN adduct: 497 nm) are comparable with the value (490 nm) of the related mono-borylated benzene species, which is composed of a BPh2 fragment and a 5-fluoro-2-(2′-pyridyl) indole unit. The starting materials 1,4- and 1,3-bis(bromo(methyl)boryl)benzene were accessible by treatment of 1,4- or 1,3-bis(dibromoboryl)benzene with two equivalents of SnMe4. In addition, the results of the X-ray structure analyses of the B,B′-bis-5-fluoro-2-(2′-pyridyl)indolyl-complexed meta-bismethylborylbenzene fragment (9, triclinic, P1̅) as well as of 5-chloro-2-(2′-pyridyl)indole (2, monoclinic, P21/c) and 5-fluoro-2-(2′-pyridyl)indole (1, orthorhombic, Pca21) are reported. The pyridylindole derivatives of this approach were synthesized by an optimized two-step procedure from 2-acetylpyridine and 4-fluoro- or 4-chlorophenylhydrazine hydrochloride.
Single crystals suitable for X-ray diffraction of (tBu2P)3Ga (monoclinic, space group Cc) were obtained from GaCl3 and two equivalents of Li[PtBu2] at room temperature in benzene. The phosphanylgallane (tBu2P)3Ga was also produced via a one-pot approach by reaction of GaCl3 with three or more than three equivalents of Li[PtBu2]. However, treatment of one equivalent of GaCl3 with one equivalent of Li[PtBu2] and subsequent protolysis yielded [tBu2PH2][tBu2P(GaCl3)2 - Li(Cl3Ga)2PtBu2]. Single crystals of this phosphonium salt (monoclinic, space group Cc) were obtained from benzene at room temperature.
Double reduction of the THF adduct of 9H-9-borafluorene (1⋅THF) with excess alkali metal affords the dianion salts M2[1] in essentially quantitative yields (M=Li–K). Even though the added charge is stabilized through π delocalization, [1]2− acts as a formal boron nucleophile toward organoboron (1⋅THF) and tetrel halide electrophiles (MeCl, Et3SiCl, Me3SnCl) to form B−B/C/Si/Sn bonds. The substrate dependence of open-shell versus closed-shell pathways has been investigated.
Subvalent boron compounds contain boron atoms with oxidation numbers lower than +III. Over the last decades, the development of isolable derivatives has relied heavily on the use of specially designed ligands capable of stabilizing the electron‐rich boron centers electronically or through steric protection. Herein, we are exclusively reviewing anionic organo(hydro)boranes largely devoid of stabilizing ligands or heteroatom substituents. The restriction to these subvalent species is intended to minimize the risk of ligand artifacts being included when carving out the characteristic properties of the respective boron centers, such as nucleophilic or carbenoid behavior. The scope of this review encompasses triorganoborane radical monoanions ([·BR3]–) along with closed‐shell dianions ([:BR3]2–), boryl anions ([:BR2]–), as well as B–B single‐bonded diborane(6) dianions ([R3B–BR3]2–) and diborane(5) monoanions ([R2B–BR3]–), and finally B=B double‐bonded diborane(4) dianions ([R2B=BR2]2–). We are showing how these species are related to each other and comment on their bonding situations from an experimentalist's perspective.
The donor-free silanimines tBu2Si=N-SiRtBu2 (R = tBu, Ph), which are prepared from tBu2ClSiN3 and NaSiRtBu2 at −78 ◦C inBu2O, decompose in benzene at room temperature with the formation of isobutene. Products of ene reactions of isobutene and tBu2Si=N-SiRtBu2 (R = tBu, Ph) are formed. X-Ray quality crystals of H2C=C(CH2SitBu2-NH-SiPhtBu2)2 (monoclinic, space group C2/c, Z = 4) were grown from a benzene solution at ambient temperature, whereas single crystals of H2C=C(CH2SitBu2-NH-SitBu3)2 (monoclinic, space group P21, Z = 2) were obtained by recrystallization from THF.
The bis(trimethyl)silylamido complex Na(THF){Fe[N(SiMe3)2]3} and the disilane tBu3SiSitBu3 were obtained from the reaction of Fe[N(SiMe3)2]3 with the sodium silanide Na(THF)2[SitBu3] in a mixture of benzene and THF. Single crystals of Na(THF){Fe[N(SiMe3)2]3} suitable for X-ray diffraction were grown from the reaction solution at ambient temperature (orthorhombic, C2221, Z = 4). The solid-state structure features a contact-ion pair with two short N-Na contacts. The THF adducts {M(THF)2[N(SiMe3)2]2} reacted with 2,2´-bipyridine to give the corresponding complexes {M(2,2´bipy)[N(SiMe3)2]2} (M= Mn; Fe). Their structures (M= Fe: orthorhombic, Pca21, Z = 8; M = Mn: orthorhombic, Pbca, Z = 8) feature monomeric units. The cyclic voltammogram of Fe[N(SiMe3)2]3 revealed a reversible redox transition with the potential of -0;523 V (E½), which was assigned to the Fe(III)[N(SiMe3)2]3 → Fe(II)[N(SiMe3)2]-3 redox transition, whereas the compounds {Fe(THF)2[N(SiMe3)2]2} (Eox = -0;379 V) and {Fe(2,2´bipy)[N(SiMe3)2]2} (Eox = -0;436 V) featured irreversible oxidation waves. The related manganese bis(trimethylsilyl)amido complexes {Mn(THF)2[N(SiMe3)2]2} (Eox = -0;458 V) and {Mn(2,2´bipy)[N(SiMe3)2]2} (Eox = -0513 V) also underwent irreversibile electron transfer processes.
Treatment of relapse after allogeneic hematopoietic stem cell transplantation (alloHSCT) remains a great challenge. Aiming to evaluate the combination of venetoclax and hypomethylating agents (HMAClax) for the treatment of relapse of myeloid malignancies after alloHSCT, we retrospectively collected data from 32 patients treated at 11 German centers. Venetoclax was applied with azacitidine (n = 13) or decitabine (n = 19); 11 patients received DLI in addition. HMAClax was the first salvage therapy in 8 patients. The median number of cycles per patient was 2 (1–19). All but 1 patient had grade 3/4 neutropenia. Hospital admission for grade 3/4 infections was necessary in 23 patients (72%); 5 of these were fatal. In 30 evaluable patients, overall response rate (ORR) was 47% (14/30, 3 CR MRDneg, 5 CR, 2 CRi, 1 MLFS, 3 PR). ORR was 86% in first salvage patients versus 35% in later salvage patients (p = 0.03). In 6 patients with molecular relapse (MR), ORR was 67% versus 42% in patients with hematological relapse (HR) (n = 24, p = n.s.). After a median follow-up of 8.4 months, 25 patients (78%) had died and 7 were alive. Estimated median overall survival was 3.7 months. Median survival of patients with HMAClax for first versus later salvage therapy was 5.7 and 3.4 months (p = n.s.) and for patients with MR (not reached) compared to HR (3.4 months, p = 0.024). This retrospective case series shows that venetoclax is utilized in various different combinations, schedules, and doses. Toxicity is substantial and patients who receive venetoclax/HMA combinations for MR or as first salvage therapy derive the greatest benefit.
We measured the Coulomb dissociation of 16O into 4He and 12C at the R3B setup in a first campaign within FAIR Phase 0 at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The goal was to improve the accuracy of the experimental data for the 12C(α,γ)16O fusion reaction and to reach lower center-ofmass energies than measured so far.
The experiment required beam intensities of 109 16O ions per second at an energy of 500 MeV/nucleon. The rare case of Coulomb breakup into 12C and 4He posed another challenge: The magnetic rigidities of the particles are so close because of the same mass-to-charge-number ratio A/Z = 2 for 16O, 12C and 4He. Hence, radical changes of the R3B setup were necessary. All detectors had slits to allow the passage of the unreacted 16O ions, while 4He and 12C would hit the detectors' active areas depending on the scattering angle and their relative energies. We developed and built detectors based on organic scintillators to track and identify the reaction products with sufficient precision.