Reversible C-CN Bond Cleavage by a Formal Dinickel(I) Hydride Cation.

An N-heterocyclic carbene (NHC) ligand supports a stable [NiH] core, formally dinickel(I). This diamagnetic cation complex features a bent hydride bridge and a Ni···Ni distance, 2.9926(5) Å, larger than two covalent radii.

Decarboxylative Cross-Coupling Enabled by Fe and Ni Metallaphotoredox Catalysis.

Decarboxylative cross-coupling of carboxylic acids and aryl halides has become a key transformation in organic synthesis to form C(sp)-C(sp) bonds. In this report, a base metal pairing between Fe and Ni has been developed with complementary reactivity to the well-established Ir and Ni metallaphotoredox reactions. Utilizing an inexpensive FeCl cocatalyst along with a pyridine carboxamidine Ni catalyst, a range of aryl iodides can be preferentially coupled to carboxylic acids over boronic acid esters, triflates, chlorides, and even bromides in high yields.

N-Halogenation by Vanadium-Dependent Haloperoxidases Enables 1,2,4-Oxadiazole Synthesis.

Nitrogen-containing compounds are valuable synthetic intermediates and targets in nearly every chemical industry. While methods for nitrogen-carbon and nitrogen-heteroatom bond formation have primarily relied on nucleophilic nitrogen atom reactivity, molecules containing nitrogen-halogen bonds allow for electrophilic or radical reactivity modes at the nitrogen center. Despite the growing synthetic utility of nitrogen-halogen bond-containing compounds, selective catalytic strategies for their synthesis are largely underexplored.

Halide Abstraction-Mediated Synthesis of a Highly Twisted Amide.

Highly strained [3.2.1] bicyclic twisted amide and corresponding amidium were synthesized for the first time through Ag(I)-mediated halide abstraction.

D-Symmetric Dirhodium Tetrakis(binaphthylphosphate) Catalysts for Enantioselective Functionalization of Unactivated C-H Bonds.

Dirhodium tetrakis(2,2'-binaphthylphosphate) catalysts were successfully developed for asymmetric C-H functionalization with trichloroethyl aryldiazoacetates as the carbene precursors. The 2,2'-binaphthylphosphate (BNP) ligands were modified by introduction of aryl and/or chloro functionality at the 4,4',6,6' positions. As the BNP ligands are C-symmetric, the resulting dirhodium tetrakis(2,2'-binaphthylphosphate) complexes were expected to be D-symmetric, but X-ray crystallographic and computational studies revealed this is not always the case because of internal T-shaped CH-π and aryl-aryl interactions between the ligands.

Michael Addition-Elimination Ring-Opening Polymerization.

A cyclic thioenone system capable of controlled ring-opening polymerization (ROP) is presented that leverages a reversible Michael addition-elimination (MAE) mechanism. The cyclic thioenone monomers are easy to access and modify and for the first time incorporate the dynamic reversibility of MAE with chain-growth polymerization. This strategy features mild polymerization conditions, tunable functionalities, controlled molecular weights (), and narrow dispersities.

Investigating the Effect of Trace Levels of Manganese Ions During Solvothermal Synthesis of Massey University Framework-16 on CO Uptake Capacity.

The effects of impurities on reaction precursors for metal-organic framework (MOF) synthesis have not been studied in extensive detail. The impact of these impurities can be an important factor while considering scale-up of these materials. In this work, we study the apparently positive impact of the presence of manganese ions for the synthesis of a Co-based MOF, Massey University Framework-16 (MUF-16).

Rhodium(II)-Catalyzed Asymmetric Cyclopropanation and Desymmetrization of [2.2]Paracyclophanes.

Chiral [2.2]paracyclophane derivatives are of considerable interest because of their potential in asymmetric catalysis and the development of chiral materials. This study describes the scope of rhodium-catalyzed reactions of aryldiazoacetates with [2.

A tetrahedral neptunium(V) complex.

Neptunium is an actinide element sourced from anthropogenic production, and, unlike naturally abundant uranium, its coordination chemistry is not well developed in all accessible oxidation states. High-valent neptunium generally requires stabilization from at least one metal-ligand multiple bond, and departing from this structural motif poses a considerable challenge. Here we report a tetrahedral molecular neptunium(V) complex ([Np(NPC)][B(ArF)], 1-Np) (NPC = [NPBu(pyrr)]; Bu = C(CH); pyrr = pyrrolidinyl (N(CH)); B(ArF) = tetrakis(2,3,4,5,6-pentafluourophenyl)borate).

Stereoelectronic interactions are too weak to explain the molecular conformation in solid state of -2--butyl-5-(-butylsulfonyl)-1,3-dioxane.

-2--Butyl-5-(-butylsulfonyl)-1,3-dioxane (-1) exhibits a high degree of eclipsing in the H-C5-S-C segment in the solid state, the origin of which remains unexplained. The eclipsed conformation that corresponds to an energetic minimum in the solid state practically corresponds to a rotational transition state in solution, which allows an approach to understand transitions states. The difference in the enthalpy of sublimation Δ between -1 and the more stable -1 is 8.

Intervalence Charge Transfer in Nonbonding, Mixed-Valence, Homobimetallic Ytterbium Complexes.

There are several reports of compounds containing lanthanide ions in two different formal oxidation states; however, there are strikingly few examples of intervalence charge transfer (IVCT) transitions observed for these complexes, with those few occurrences limited to extended solids rather than molecular species. Herein, we report the synthesis, characterization, and computational analysis for a series of ytterbium complexes including a mixed-valence Yb complex featuring a remarkably short Yb···Yb distance of 2.9507(8) Å.

Convergent and Efficient Total Synthesis of (+)-Heilonine Enabled by C-H Functionalizations.

We report a convergent and efficient total synthesis of the C- D- steroidal alkaloid (+)-heilonine with a hexacyclic ring system, nine stereocenters, and a -hydrindane moiety. Our synthesis features four selective C-H functionalizations to form key C-C bonds and stereocenters, a Stille carbonylative cross-coupling to connect the AB ring system with the DEF ring system, and a Nazarov cyclization to construct the five-membered C ring. These enabling transformations significantly reduced functional group manipulations and delivered (+)-heilonine in 11 or 13 longest linear sequence (LLS) steps.

Structural distortion by alkali metal cations modulates the redox and electronic properties of Ce imidophosphorane complexes.

A series of Ce complexes with counter cations ranging from Li to Cs are presented. Cyclic voltammetry data indicate a significant dependence of the oxidation potential on the alkali metal identity. Analysis of the single-crystal X-ray diffraction data indicates that the degree of structural distortion of the secondary coordination sphere is linearly correlated with the measured oxidation potential.

Catalytic C-H Trifluoromethylation of Arenes and Heteroarenes via Visible Light Photoexcitation of a Co(III)-CF Complex.

A cobalt photocatalyst for direct trifluoromethylation of (hetero)arene C(sp)-H bonds is described and shown to operate via visible light activation of a Co-CF intermediate, which functions as a combined chromophore and organometallic reaction center. Chemical oxidations of previously reported (OCO)Co complexes containing a redox-active [OCO] pincer ligand afford a Co-CF complex two oxidation states above Co(II). Computational and spectroscopic studies are consistent with formulation of the product as [(OCO)Co(CF)(THF)(OTf)] () containing an open-shell [OCO] radical ligand bound to a = 0 Co(III) center.

Ant Venom-Based Ceramide Therapy Is Effective Against Atopic Dermatitis In Vivo.

Background: Atopic dermatitis (AD) is a common skin condition with relatively few therapeutic alternatives. These include corticosteroids, which address inflammation but not superinfection, and Januse kinase (JAK) inhibitors, which have a US Food and Drug Administration (FDA) black box for potential carcinogenicity.

Methods: We demonstrate that S14, a synthetic derivative of ant venom-derived solenopsin, has potent anti inflammatory effects on the OVA murine model of atopic dermatitis.

Diruthenium Tetracarboxylate-Catalyzed Enantioselective Cyclopropanation with Aryldiazoacetates.

A series of chiral bowl-shaped diruthenium(II,III) tetracarboxylate catalysts were prepared and evaluated in asymmetric cyclopropanations with donor/acceptor carbenes derived from aryldiazoacetates. The diruthenium catalysts self-assembled to generate -symmetric bowl-shaped structures in an analogous manner to their dirhodium counterparts. The optimum catalyst was found to be Ru(-TPPTTL)·BAr [-TPPTTL = ()-2-(1,3-dioxo-4,5,6,7-tetraphenylisoindolin-2-yl)-3,3-dimethylbutanoate, BAr = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate], which resulted in the cyclopropanation of a range of substrates in up to 94% ee.

Evaluating the Effectiveness of Tethered Bis(urazolyl) Diradicals as Molecular Building Blocks for Dynamic Covalent Chemistry.

Dynamic covalent chemistry (DCvC) is a powerful means by which to rapidly prepare complex structures from simple molecular building blocks. Effective DCvC behavior is contingent upon the reversibility of covalent bond formation. Stabilized radical species, therefore, have been effectively used for these applications.

Divergent Stabilities of Tetravalent Cerium, Uranium, and Neptunium Imidophosphorane Complexes.

The study of the redox chemistry of mid-actinides (U-Pu) has historically relied on cerium as a model, due to the accessibility of trivalent and tetravalent oxidation states for these ions. Recently, dramatic shifts of lanthanide 4+/3+ non-aqueous redox couples have been established within a homoleptic imidophosphorane ligand framework. Herein we extend the chemistry of the imidophosphorane ligand (NPC=[N=P Bu(pyrr) ] ; pyrr=pyrrolidinyl) to tetrahomoleptic NPC complexes of neptunium and cerium (1-M, 2-M, M=Np, Ce) and present comparative structural, electrochemical, and theoretical studies of these complexes.

Design, Synthesis, and Evaluation of Extended C4-Symmetric Dirhodium Tetracarboxylate Catalysts.

The synthesis and evaluation of six C-symmetric bowl-shaped dirhodium tetracarboxylate catalysts are described. These elaborate high symmetry catalysts are readily generated by means of the self-assembly of four C-symmetric ligands around the dirhodium core. These catalysts are capable of highly site-selective, diastereoselective and enantioselective C-H functionalization reactions by means of donor/acceptor carbene-induced C-H insertions.

Synthesis, structure, in vitro pharmacology, and in vivo activity of trans-3,4-dichloro-N-[[1-(dimethylamino)-4-phenylcyclohexyl]methyl]-benzamide (AP01; 4-phenyl-AH-7921), a novel mixed μ-/κ-opioid.

Analogs of non-fentanyl novel synthetic opioids (NSO) with modifications that fall outside of established structure-activity relationships (SARs) for that class of drugs create the question whether or not it should be considered an analog, as defined by 21 U.S.C.

Ligand Control of Oxidation and Crystallographic Disorder in the Isolation of Hexavalent Uranium Mono-Oxo Complexes.

The development of high-valent transuranic chemistry requires robust methodologies to access and fully characterize reactive species. We have recently demonstrated that the reducing nature of imidophosphorane ligands supports the two-electron oxidation of U to U and established the use of this ligand to evaluate the inverse-trans-influence (ITI) in actinide metal-ligand multiple bond (MLMB) complexes. To extend this methodology and analysis to transuranic complexes, new small-scale synthetic strategies and lower-symmetry ligand derivatives are necessary to improve crystallinity and reduce crystallographic disorder.

Conformationally Preorganized High-Affinity Ligands for Copper Biology with Hinged and Rigid Thiophene Backbones.

Copper-selective ligands are essential tools for probing the affinity of cuproproteins or manipulating the cellular copper availability. They also harbor significant potential as antiangiogenic agents in cancer therapy or as therapeutics to combat copper toxicity in Wilson's disease. To achieve the high Cu(I) affinities required for competing effectively with cellular cuproproteins, we recently devised a ligand design based on phosphine-sulfide-stabilized phosphine (PSP) donor motifs.

Ground-State Spin Dynamics in Kagome-Lattice Titanium Fluorides.

Many quantum magnetic materials suffer from structural imperfections. The effects of structural disorder on bulk properties are difficult to assess systematically from a chemical perspective due to the complexities of chemical synthesis. The recently reported S = 1/2 kagome lattice antiferromagnet, (CHNH)NaTiF, , with highly symmetric kagome layers and disordered interlayer methylammonium cations, shows no magnetic ordering down to 0.

Elemental chalcogen reactions of a tetravalent uranium imidophosphorane complex: cleavage of dioxygen.

Herein we report the first example of a mononuclear uranium complex, [U(NP(pip))] (1-U), that selectively reduces dioxygen to produce a terminal oxo complex, [UO(NP(pip))] (2-U; [NP(pip)] is tris(piperidinyl)imidophosphorane). Reactions between 1-U and the heavier elemental chalcogens, S or Se, result in six-coordinate U(VI) complexes, [U(κ-E)(NP(pip))] (E = S (3-U) or Se (4-U)).