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The positional isomerization of C═C double bonds is a powerful strategy for the interconversion of alkene regioisomers. However, existing methods provide access to thermodynamically more stable isomers from less stable starting materials. Here, we report the discovery of a dual catalyst system that promotes

The recognition of latent symmetry in delavatine A has enabled a short synthesis of the natural product starting from 3,5-dibromo-2-pyrone. The concise synthetic route features a cascade process involving a 6π electrocyclization to construct the indane core of delavatine A. In addition, we have conducted detailed experimental and computational studies to gain an in-depth understanding of the mechanism of the observed site-selective cross-coupling of 3,5-dibromo-2-pyrone. This insight may provide new avenues to achieve the selective cross-coupling of multiply halogenated heteroarenes.

Vinylene-bridged covalent organic frameworks (COFs) have shown great potential for advanced applications because of their high chemical stability and intriguing semiconducting properties. Exploring new functional monomers available for the reticulation of vinylene-bridged COFs and establishing effective reaction conditions are extremely desired for enlarging the realm of this kind of material. In this work, a series of vinylene-bridged two-dimensional (2D) COFs are synthesized by Knoevenagel condensation of tricyanomesitylene with ditopic or tritopic aromatic aldehydes. With use of appropriate secondary amines as catalysts, high-crystalline vinylene-bridged COFs were achieved, exhibiting long-range ordered structures, well-defined nanochannels, high surface areas (up to 1231 m2 g-1), and excellent photophysical properties. Under a low loading amount and short reaction time, they enable aerobic photocatalytic transformation of arylboronic acids to phenols with high efficiency and excellent recyclability. This work demonstrates a new functional monomer, tricyanomesitylene, feasible for the general synthesis of vinylene-bridged COFs with potential application in photocatalytic organic transformation, which instigates further research on such kind of material.

Metal–organic frameworks (MOFs) provide highly designable platforms to construct complex coordination architectures for targeted applications. Herein, we demonstrate that trans-coordinated metal centers with exposed equatorial positions can be placed in a MOF matrix. A Zr-based MOF, namely, PCN-160, was initially synthesized as a scaffold structure. Postsynthetic linker labilization was subsequently implemented to partially remove the original dicarboxylate linkers and incorporate pyridinecarboxylates. A pair of neighboring pyridyl groups was arranged at proper proximity within the framework to form trans-binding sites that accommodate different metal cations including Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Pd2+. Furthermore, the trans-coordinated Ni2+ sites in porous frameworks can be readily accessed by substrates along the equatorial plane, facilitating the catalysis as manifested by the superior activity in ethylene dimerization over that observed for a cis-chelated catalyst.

Two different boron layers, flat (graphene-like) and puckered (phosphorene-like), found in the crystal structure of Mo2B4 show drastically different activities for hydrogen evolution, according to Gibbs free energy calculations of H-adsorption on Mo2B4. The graphene-like B layer is highly active, whereas the phosphorene-like B layer performs very poorly for hydrogen evolution. A new Sn-flux synthesis permits the rapid single-phase synthesis of Mo2B4, and electrochemical analyses show that it is one of the best hydrogen evolution reaction active bulk materials with good long-term cycle stability under acidic conditions. Mo2B4 compensates its smaller density of active sites if compared with highly active bulk MoB2 (which contains only the more active graphene-like boron layers) by a 5-times increase of its surface area.

We report here reactions of alkyl sulfides with benzynes thermally generated by the hexadehydro-Diels-Alder (HDDA) cycloisomerization. The initially produced 1,3-betaine (o-sulfonium/aryl carbanion) undergoes intramolecular proton transfer to generate a more stable S-aryl sulfur ylide. This can react in various manners, including engaging weak acids (HA) in the reaction medium. This can produce transient ion pairs ArSR2(+)A(-) that proceed to the products ArSR + RA. When cyclic sulfides are used, A(-) opens the ring and is incorporated into the product, an outcome that constitutes a versatile, three-component coupling process.

Two different boron layers, flat (graphene-like) and puckered (phosphorene-like), found in the crystal structure of Mo

The electrochemistry, spectroscopy, and electrogenerated chemiluminescence (ECL) of a variety of 2- and 4-fold anthracene-functionalized tetraarylbimesityls, AB1-4, were investigated. AB1-4 compounds contain a bimesityl core with 2- and 4-fold anthracene functionalities, which generate a rigid D(2d)-symmetric structure. Cyclic voltammetry of AB1 and AB2 showed two reversible, closely spaced one-electron transfers for both oxidation and reduction, and that of AB3 and AB4 showed four reversible, closely spaced one-electron transfers for oxidation and reduction in a benzene/acetonitrile solution. The multielectron transfer properties of all four compounds were confirmed by chronoamperometric experiments with an ultramicroelectrode and digital simulations. These serve as models to probe how interacting groups on a molecule affect the energies of successive electron transfers. AB1-4 compounds are highly fluorescent in nonaqueous solvents and display blue-green emission. They produce very strong ECL with emission at 480 nm, near that of the photoluminescence spectra that can be assigned to emission by direct formation of the singlet via the S-route.

The coordination-driven self-assembly of an anthracene-functionalized ditopic pyridyl donor and a tetracene-based dinuclear Ru(II) acceptor resulted in an interlocked metalla[2]catenane, [M2L2]2, in methanol and a corresponding monorectangle, [M2L2], in nitromethane. Subsequently, guest template, solvent, and concentration effects allowed the self-assembly to be reversibly fine-tuned among monorectangle and catenane structures.

The unique structural attributes inherent to D(2d)-symmetric rigid tetraarylbimesityls render their close packing in the solid state difficult. We have exploited the indisposed tendency of such modules based on the bimesityl scaffold toward crystallization to design a novel class of amorphous functional materials with high glass transition temperatures and thermal stability (T(d)400 degrees C). It is shown that a variety of 2- and 4-fold anthracene-functionalized bimesityls, 1-7, that exhibit excellent amorphous properties (T(g) = ca. 190-330 degrees C) can be readily prepared via facile Pd(0)-mediated cross-coupling strategies. As the communication between the bimesityl core and the anchored anthracenes is negligible or only marginal, the trends observed for luminescence of model constituent anthracenes are reproduced in the condensed-phase photoluminescence and electroluminescence of 1-7. In other words, the emission characteristics, i.e., lambda(max) and quantum yields, are readily modulated via appropriate modification of the fluorophores. The functional behavior of this unique class of amorphous materials based on the bimesityl scaffold is demonstrated by fabrication of OLED devices. The 2-fold functionalized derivatives 1 and 2 lend themselves to sublimation techniques, so that the electroluminescence is captured with high efficiencies at low turn-on voltages (3.5-6.5 V). The device ITO/NPB (400 A)/1% 2:MADN (400 A)/TPBI (400 A)/LiF (10 A)/Al (1500 A) for 2 yields the highest luminance of approximately 13,900 cd/m(2) at 17.5 V, a maximum luminance efficiency of approximately 7.4 cd/A at 4.5 V, and a power efficiency of approximately 5.3 lm/W at 4.0 V. Further, at a brightness of 800 cd/m(2) and a current density of 13.8 mA/cm(2), the device is found to exhibit excellent luminance efficiency of 5.8 cd/A, external quantum efficiency of 4.3% with a power efficiency of 2.2 lm/W, and pure blue light with a CIE(x,y) (x = 0.13, y = 0.18). The performance characteristics of the devices fabricated for 1 and 2 are remarkable. Although the 4-fold functionalized systems did not permit sublimation leading to spin-coating as a means for device fabrication, the observed electroluminescence for 4 and 5 attests to a broader scope and applicability of this new category of amorphous molecules for application in OLEDs.

Nepheline group materials obtained by a thermal treatment of K2CO3-supported nanosized sodalite are identified as cost-effective materials which show promising activity and durability toward diesel soot combustion.