A method for the coupling of aryl chlorides and thiophenols using an air-stable nickel(0) catalyst is described. This thioetherification procedure can be effectively applied to a range of ...electronically diverse aryl/heteroaryl chlorides without more expensive metal catalysts such as palladium, iridium, or ruthenium. This investigation also illustrates both, a variety of thiol coupling partners and, in certain cases, the use of Cs2CO3.
The thymus supports multiple αβ T cell lineages that are functionally distinct, but mechanisms that control this multifaceted development are poorly understood. Here we examine medullary thymic ...epithelial cell (mTEC) heterogeneity and its influence on CD1d-restricted iNKT cells. We find three distinct mTEC
subsets distinguished by surface, intracellular and secreted molecules, and identify LTβR as a cell-autonomous controller of their development. Importantly, this mTEC heterogeneity enables the thymus to differentially control iNKT sublineages possessing distinct effector properties. mTEC expression of LTβR is essential for the development thymic tuft cells which regulate NKT2 via IL-25, while LTβR controls CD104
CCL21
mTEC
that are capable of IL-15-transpresentation for regulating NKT1 and NKT17. Finally, mTECs regulate both iNKT-mediated activation of thymic dendritic cells, and iNKT availability in extrathymic sites. In conclusion, mTEC specialization controls intrathymic iNKT cell development and function, and determines iNKT pool size in peripheral tissues.
Bridged or caged polycyclic hydrocarbons have rigid structures that project substituents into precise regions of 3D space, making them attractive as linking groups in materials science and as ...building blocks for medicinal chemistry. The efficient synthesis of new or underexplored classes of such compounds is, therefore, an important objective. Herein, we describe the silver(I)-catalyzed rearrangement of 1,4-disubstituted cubanes to cuneanes, which are strained hydrocarbons that have not received much attention since they were first described in 1970. The synthesis of 2,6-disubstituted or 1,3-disubstituted cuneanes can be achieved with high regioselectivities, with the regioselectivity being dependent on the electronic character of the cubane substituents. A preliminary assessment of cuneanes as scaffolds for medicinal chemistry suggests cuneanes could serve as isosteric replacements of trans-1,4-disubstituted cyclohexanes and 1,3-disubstituted benzenes. An analogue of the anticancer drug sonidegib was synthesized, in which the 1,2,3-trisubstituted benzene was replaced with a 1,3-disubstituted cuneane.
The enantioselective
synthesis of pharmacologically important 14-hydroxy-6-oxomorphinans is described. 4,5-Desoxynaltrexone and 4,5-desoxynaloxone were prepared using this route and their biological ...activities against the opioid receptors were measured.
The dirhodium(II)-catalyzed synthesis of a range of C2-substituted 2,3-dehydropiperazines using 1-mesyl-1,2,3-triazoles and β-haloalkylcarbamates is reported. The reaction is proposed to proceed ...through an α-imino rhodium carbene 1,3-insertion into N–H followed by a base-mediated cyclization. C-Substituted dehydropiperazines can also be conducted directly from terminal alkynes in a three-step, one-pot operation, forming the triazole in situ. This methodology has also been expanded to afford several 2,5-disubstituted 2,3-dehydropiperazines as well as a larger 4,5,6,7-tetrahydro-1H-1,4-diazepine derivative.
Herein, we report a Rh(II)-catalyzed reaction between 1-tosyl-1,2,3-triazoles and halohydrins to provide 2,6-substituted 3,4-dihydro-2H-1,4-oxazines under basic conditions. The reaction is proposed ...to undergo a rhodium carbenoid 1,3-insertion into O–H followed by an annulation. The scope includes phenyl or alkenyl C4-substituted triazoles and a range of halohydrins using catalytic Rh2Oct4 and K2CO3. A synthesis of the antimicrobial natural product (±)-chelonin C is also reported using this novel methodology.
Image contrast is often limited by background autofluorescence in steady‐state bioimaging microscopy. Upconversion bioimaging can overcome this by shifting the emission lifetime and wavelength beyond ...the autofluorescence window. Here we demonstrate the first example of triplet‐triplet annihilation upconversion (TTA‐UC) based lifetime imaging microscopy. A new class of ultra‐small nanoparticle (NP) probes based on TTA‐UC chromophores encapsulated in an organic–inorganic host has been synthesised. The NPs exhibit bright UC emission (400–500 nm) in aerated aqueous media with a UC lifetime of ≈1 μs, excellent colloidal stability and little cytotoxicity. Proof‐of‐concept demonstration of TTA‐UC lifetime imaging using these NPs shows that the long‐lived anti‐Stokes emission is easily discriminable from typical autofluorescence. Moreover, fluctuations in the UC lifetime can be used to map local oxygen diffusion across the subcellular structure. Our TTA‐UC NPs are highly promising stains for lifetime imaging microscopy, affording excellent image contrast and potential for oxygen mapping that is ripe for further exploitation.
A new class of ultra‐small nanoparticle (NP) probes based on triplet‐triplet annihilation upconversion (TTA‐UC) chromophores in an organic–inorganic ureasil host have been prepared and used to stain living cells as a proof‐of‐concept demonstration of TTA‐UC lifetime imaging for the first time. Fluctuations of the UC lifetime in the stained cells indicate the NPs can be used to map local oxygen diffusion across the subcellular structure.
Understanding and eliminating degradation of the electrolyte solution is arguably the major challenge in the development of high energy density lithium–air batteries. The use of acetonitrile provides ...cycle stability comparable to current state‐of‐the‐art glyme ethers and, while solvent degradation has been extensively studied, no mechanism for acetonitrile degradation has been proposed. Through the application of in situ pressure measurements and ex situ characterization to monitor the degradation of acetonitrile in the lithium–air battery, a correlation between H2O concentration within the cell and deviation from the idealized electron/oxygen ratio is revealed. Characterization of the cycled electrolyte solution identifies acetamide as the major degradation product under both cell and model conditions. A new degradation pathway is proposed that rationalizes the formation of acetamide, identifies the role of H2O in the degradation process, and confirms lithium hydroperoxide as a critical antagonistic species in lithium–air cells for the first time. These studies highlight the importance of considering the impact of atmospheric gases when exploring lithium–air cell chemistry and suggest that further exploration of the impact of hydroperoxide species on the degradation in lithium–air cells may lead to identification of more effective electrolyte solvents.
A new degradation pathway for acetonitrile in the lithium–air battery is proposed, which leads to the formation of acetamide and implicates hydroperoxide, formed from H2O in the cell, as a critical antagonistic species for the first time. These studies highlight the importance of considering the impact of atmospheric gases when exploring lithium–air cell chemistry.
Herein, we report the synthesis and characterization of a new class of hybrid Wells–Dawson polyoxometalate (POM) containing a diphosphoryl group (P2O6X) of the general formula P2W17O57(P2O6X)6− (X=O, ...NH, or CR1R2). Modifying the bridging unit X was found to impact the redox potentials of the POM. The ease with which a range of α‐functionalized diphosphonic acids (X=CR1R2) can be prepared provides possibilities to access diverse functionalized hybrid POMs. Compared to existing phosphonate hybrid Wells–Dawson POMs, diphosphoryl‐substituted POMs offer a wider tunable redox window and enhanced hydrolytic stability. This study provides a basis for the rational design and synthesis of next‐generation hybrid Wells–Dawson POMs.
The synthesis and characterization of a new class of hybrid diphosphoryl Wells–Dawson polyoxometalate (POM) is described. The covalent tethering of diphosphoryl compounds to the inorganic cluster gives redox‐active materials with enhanced hydrolytic stability compared to the corresponding phosphonate analogues. These readily modifiable precursors provide a platform for structural and electronic modulation of the POM, enabling the rational design and synthesis of next‐generation hybrid Wells–Dawson POMs.
A multi-component coordination compound, in which ruthenium antenna complexes are connected to a polyoxotungstate core is presented. This hybrid cluster effectively promotes the electrochemical ...conversion of CO2 to C1 feedstocks, the selectivity of which can be controlled by the acidity of the media.
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