Powerful relativistic jets are one of the main ways in which accreting black holes provide kinetic feedback to their surroundings. Jets launched from or redirected by the accretion flow that powers ...them are expected to be affected by the dynamics of the flow, which for accreting stellar-mass black holes has shown evidence for precession
due to frame-dragging effects that occur when the black-hole spin axis is misaligned with the orbital plane of its companion star
. Recently, theoretical simulations have suggested that the jets can exert an additional torque on the accretion flow
, although the interplay between the dynamics of the accretion flow and the launching of the jets is not yet understood. Here we report a rapidly changing jet orientation-on a time scale of minutes to hours-in the black-hole X-ray binary V404 Cygni, detected with very-long-baseline interferometry during the peak of its 2015 outburst. We show that this changing jet orientation can be modelled as the Lense-Thirring precession of a vertically extended slim disk that arises from the super-Eddington accretion rate
. Our findings suggest that the dynamics of the precessing inner accretion disk could play a role in either directly launching or redirecting the jets within the inner few hundred gravitational radii. Similar dynamics should be expected in any strongly accreting black hole whose spin is misaligned with the inflowing gas, both affecting the observational characteristics of the jets and distributing the black-hole feedback more uniformly over the surrounding environment
.
The first (3+3)‐annulation process of donor–acceptor cyclopropanes using synergistic catalysis is reported. The Rh2(OAc)4‐catalyzed decomposition of diazo carbonyl compounds generated carbonyl ylides ...in situ. These 1,3‐dipoles were converted with donor–acceptor cyclopropanes, activated by Lewis acid catalysis, to afford multiply substituted pyran scaffolds in high yield and diastereoselectivity. Extensive optimization studies enabled access to 9‐oxabicyclo3.3.1nonan‐2‐one and 10‐oxabicyclo4.3.1decen‐2‐ol cores, exploiting solvent effects on intermediate reactivity.
Best of both worlds: A synergistic catalytic approach for the construction of multiply substituted pyrans is reported. It merges cyclopropane with carbene chemistry. The synthesis of 3.3.1‐ and 4.3.1‐core structures under mild conditions in moderate to excellent yields is demonstrated and a plausible mechanism is suggested.
D–A cyclopropanes bearing a simple cyclopropyl group as donor are shown to undergo a variety of 3+n-cycloaddition reactions (n = 2–4). This behavior contrasts sharply with that of common D–A ...cyclopropanes with aliphatic donors. Kinetic experiments demonstrate that, in terms of donor ability, the cyclopropyl substituent lies between electron-rich and electron-neutral aryl donors.
The kinetics of (3+2) cycloaddition reactions of 18 different donor–acceptor cyclopropanes with the same aldehyde were studied by in situ NMR spectroscopy. Increasing the electron density of the ...donor residue accelerates the reaction by a factor of up to 50 compared to the standard system (donor group=phenyl), whereas electron‐withdrawing substituents slow down the reaction by a factor up to 660. This behavior is in agreement with the Hammett substituent parameter σ. The obtained rate constants from the (3+2) cycloadditions correlate well with data from additionally studied (3+n) cycloadditions with a nitrone (n=3) and an isobenzofuran (n=4). A comparison of the kinetic data with the bond lengths in the cyclopropane (obtained by X‐ray diffraction and computation), or the 1H and 13C NMR shifts, revealed no correlation. However, the computed relaxed force constants of donor–acceptor cyclopropanes proved to be a good indicator for the reactivity of the three‐membered ring.
Who is faster? The reactivity of donor–acceptor cyclopropanes was investigated in (3+n) cycloaddition reactions with an aldehyde, a nitrone, and an isobenzofuran by NMR and in operando IR spectroscopy. The obtained reaction rates were compared with the structural and electronic properties of the donor–acceptor cyclopropanes.
The first ring‐opening reaction of donor–acceptor cyclopropanes to give diamines is reported. For this reaction, a 1,3‐bisfunctionalization was developed using cyclopropanes, triazinanes, and ...Sc(OTf)3 as the catalyst, followed by treatment with acid. The reaction proceeds under very mild conditions and tolerates many functional groups. Moreover, a library of various 1,3‐diazepanes, which arise as intermediates of the first formal aza‐4+3‐cycloaddition reaction with donor–acceptor cyclopropanes, was synthesized.
Double Amination: Donor–acceptor cyclopropanes can be selectively opened with triazinanes to give diamines under scandium catalysis and mild acidic conditions. Moreover, a library of various 1,3‐diazepanes, which arise as intermediates of these formal aza‐4+3‐cycloaddition reactions, was synthesized.
We describe the first electrochemical activation of D–A cyclopropanes and D–A cyclobutanes leading after C(sp3)−C(sp3) cleavage to the formation of highly reactive radical cations. This concept is ...utilized to formally insert molecular oxygen after direct or DDQ‐assisted anodic oxidation of the strained carbocycles, delivering β‐ and γ‐hydroxy ketones and 1,2‐dioxanes electrocatalytically. Furthermore, insights into the mechanism of the oxidative process, obtained experimentally and by additional quantum‐chemical calculations are presented. The synthetic potential of the reaction products is demonstrated by diverse derivatizations.
The first electrochemical activation of donor–acceptor (D–A) cyclopropanes and D–A cyclobutanes has been applied for the formal insertion of molecular oxygen into these compounds. C(sp3)−C(sp3) cleavage of the ring moieties was achieved either by direct anodic electrolysis or by utilizing a DDQ‐assisted electrochemical strategy. Quantum‐chemical calculations and supportive experiments provided mechanistic understanding of the electrocatalytic process.
Horizontal gene transfer (HGT) can radically alter the genomes of microorganisms, providing the capacity to adapt to new lifestyles, environments, and hosts. However, the extent of HGT between ...eukaryotes is unclear. Using whole-genome, gene-by-gene phylogenetic analysis we demonstrate an extensive pattern of cross-kingdom HGT between fungi and oomycetes. Comparative genomics, including the de novo genome sequence of Hyphochytrium catenoides, a free-living sister of the oomycetes, shows that these transfers largely converge within the radiation of oomycetes that colonize plant tissues. The repertoire of HGTs includes a large number of putatively secreted proteins; for example, 7.6% of the secreted proteome of the sudden oak death parasite Phytophthora ramorum has been acquired from fungi by HGT. Transfers include gene products with the capacity to break down plant cell walls and acquire sugars, nucleic acids, nitrogen, and phosphate sources from the environment. Predicted HGTs also include proteins implicated in resisting plant defense mechanisms and effector proteins for attacking plant cells. These data are consistent with the hypothesis that some oomycetes became successful plant parasites by multiple acquisitions of genes from fungi.
A fundamental, highly fluorescent, and easily accessible scaffold derived from the BODIPY core is reported. The use of benzimidazole as a bridging ligand at the meso position enables the binding of ...two BF2 units to provide sufficient rigidity and enhanced electron‐withdrawing strength. Absorption and emission events thus take place in the red (λ≈600 nm); the fluorescence quantum yields can reach unity (0.96) and show little dependence on solvent polarity. The synthetic route was shortened to two steps starting from commercially available precursors while the preparation is modular and tolerates various pyrrole and benzimidazole moieties. Fluoride replacement by propynyl groups, various halogenations, as well as Knoevenagel‐type condensations were applied to extend the versatility of these new photostable fluorophores, which we termed BOIMPYs.
A convenient leap into the red: Two synthetic steps provide access to a new family of highly fluorescent fluorophores termed BOIMPYs. Two BF2 units enable the efficient exploitation of the meso position and lead to absorption at λ≈600 nm. Owing to the structural similarity to well‐studied BODIPY dyes, common modes of post‐functionalization can be easily transferred to the new motif.
Five series of thiourea derivatives bearing benzothiazole moiety (20 compounds) were efficiently synthesized and evaluated for antimicrobial and anticancer activities. The results indicated that the ...compounds possessed a broad spectrum of activity against the tested microorganisms and showed higher activity against fungi than bacteria. Compounds
1b,
2b,
3b,
4b and
5b exhibited the greatest antimicrobial activity. Preliminary study of the structure–activity relationship revealed that electronic factors in benzothiazole rings had a great effect on the antimicrobial activity of these compounds. In preliminary MTT cytotoxicity studies, the thiourea derivatives (
2d,
5c and
5d) were found most potent. In MCF-7 and HeLa cells, the IC
50 values were observed in the range of 18–26 μM and 38–46 μM, respectively.
In this communication, we have described a novel procedure for the synthesis of thiourea derivatives using tetrabutyl ammonium bromide (TBAB) as phase transfer catalyst (PTC).
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An intramolecular Pd‐catalyzed cascade reaction is presented that consists of a formal anti‐carbopalladation of a C−C triple bond followed by C−H activation. As a result, oligocyclic ring systems ...with an embedded tetrasubstituted double bond are formed. The key to success in affording the trans geometry of the emerging double bond are alkyne units with residues that must not undergo β‐hydride elimination (e.g., t‐butyl or silyl groups). Silyl groups proved to be a perfect handle to further convert the tetrasubstituted alkenes. The evaluation of kinetic data with a deuterium‐labeled compound and X‐ray analyses of trapped intermediates provided additional insight into the catalytic cycle.
Meet in the middle: The trans‐carbocarbonation of internal alkynes enables the formation of two new carbon–carbon bonds through a formal anti‐carbopalladation/C−H activation cascade catalyzed by Pd. Highlights of the cascade include a completely regioselective reaction and the use of aryl and heteroaryl groups for C−H activation.
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