Combining Organocatalysis with Central‐to‐Axial Chirality Conversion: Atroposelective Hantzsch‐Type Synthesis of 4‐Arylpyridines

Suitably substituted enantioenriched 4‐aryl‐1,4‐dihydro‐pyridines prepared by an organocatalytic enantioselective Michael addition were oxidized with MnO₂ into axially chiral 4‐arylpyridines with central‐to‐axial chirality conversion. Moderate to complete percentages (cp) were observed, and a model for the conversion of chirality is discussed.     

Copper Salt‐Controlled Divergent Reactivity of [Cu]CF2PO(OEt)2 with α‐Diazocarbonyl Derivatives

Herein, we report a copper salt‐controlled divergent reactivity toward α‐diazocarbonyl compounds. By a simple change of the copper counteranion under identical reaction conditions, the reported method allowed an easy access to either (Z)‐α‐fluorovinylphosphonate or alkyl‐SCF₂PO(OEt)₂ derivatives in good yields. Mechanistic studies were performed and suggested two different pathways to explain the formation of these products.     

Light induced gradient refractive index materials

Controlled and patterned variation of refractive index (wavefront) across a lens surface was obtained via the use of “phase mask”. Gradient interpenetrating network was selected to screen the acrylate and epoxy monomer to obtain necessary refractive index change over the lens surface. The best photoinitiator system was determined to give a stable and transparent wavefront as a mixture of 2 wt% Irgacure 250 (I 250), 1 wt% Isopropylthoxanthone (ITX) and 0.5 wt Irgacure 184 (I 184). It is found that a dipropylene glycol diacrylate (SR 508) and a triethylene glycol dimethacrylate (TGDM) improved the stability of the transparent wavefront because of higher Tg of the network. Haze problem, a consequence of diffusion of one monomer to other network because of the rate differences, was eliminated with IPN composed of TGDM (an acrylate with slow polymerization rate) and bis (3,4‐epoxy cyclohexylmethyl)adipate (BECMA, an epoxy with fast polymerization rate). A high refractive index additive, bromonaphthalene, resulted the best wavefront with lens power when incorporated into BECMA and TGDM IPN. Copyright © 2015 John Wiley & Sons, Ltd.     

Highly Enantioselective Iridium‐Catalyzed Hydrogenation of Cyclic Enamides

The MaxPHOX–Ir catalyst system provided the highest selectivity ever reported for the reduction of cyclic enamides derived from α‐ and β‐tetralones. This result indicates that iridium catalysts are also proficient in reducing alkenes bearing metal‐coordinating groups. In the present system, selectivity was pressure‐dependent: In most cases, a decrease in the H₂ pressure to 3 bar resulted in an increase in enantioselectivity. Moreover, the process can be carried out in environmentally friendly solvents, such as methanol and ethyl acetate, with no loss of selectivity.     

Reducing complexity of algebraic multigrid by aggregation

A typical approach to decrease computational costs and memory requirements of classical algebraic multigrid methods is to replace a conservative coarsening algorithm and short‐distance interpolation on a fixed number of fine levels by an aggressive coarsening with a long‐distance interpolation. Although the quality of the resulting algebraic multigrid grid preconditioner often deteriorates in terms of convergence rates and iteration counts of the preconditioned iterative solver, the overall performance can improve substantially. We investigate here, as an alternative, a possibility to replace the classical aggressive coarsening by aggregation, which is motivated by the fact that the convergence of aggregation methods can be independent of the problem size provided that the number of levels is fixed. The relative simplicity of aggregation can lead to improved solution and setup costs. The numerical experiments show the relevance of the proposed combination on both academic and benchmark problems in reservoir simulation from oil industry. Copyright © 2016 John Wiley & Sons, Ltd.     

From Tethered to Freestanding Stabilizers of 14-3-3 Protein-Protein Interactions through Fragment Linking

Small-molecule stabilization of protein-protein interactions (PPIs) is a promising strategy in chemical biology and drug discovery. However, the systematic discovery of PPI stabilizers remains a largely unmet challenge. Herein we report a fragment-linking approach targeting the interface of 14-3-3 and a peptide derived from the estrogen receptor alpha (ERα) protein. Two classes of fragments—a covalent and a noncovalent fragment—were co-crystallized and subsequently linked, resulting in a noncovalent hybrid molecule in which the original fragment interactions were largely conserved. Supported by 20 crystal structures, this initial hybrid molecule was further optimized, resulting in selective, 25-fold stabilization of the 14-3-3/ERα interaction. The high-resolution structures of both the single fragments, their co-crystal structures and those of the linked fragments document a feasible strategy to develop orthosteric PPI stabilizers by linking to an initial tethered fragment.     

Encapsulation of Microperoxidase-8 into MIL-101(Cr/Fe) Nanoparticles: A New Biocatalyst for the Epoxidation of Styrene

A new biocatalyst MP8@MIL-101(Cr/Fe) was prepared by immobilization of a heme octapeptide, Microperoxidase 8 (MP8) within a mixed metal MOF, MIL-101(Cr/Fe). Both MIL-101(Cr/Fe) and MP8@MIL-101(Cr/Fe) were characterized by PXRD, FTIR spectroscopy and TGA. The catalytic activity of MP8@MIL-101(Cr/Fe) for the oxidation of styrene by H₂O₂ and tBuOOH was then examined under various reaction conditions (nature of the co-solvent and of the oxidant, concentration of the oxidant and of the substrate, time, pH) and compared to that of MP8 alone. Under the best conditions used, MP8@MIL-101(Cr/Fe) was then shown to catalyze the oxidation of styrene about 3 times more efficiently than MP8 alone with approximately 50 % selectivity for styrene oxide.     

Amorphous oxide as a novel efficient catalyst for direct selective oxidation of methanol to dimethoxymethane

We report for the first time the use of an amorphous oxide catalyst for the selective oxidation of methanol in the gas phase, leading at 553 K to the production of dimethoxymethane with a selectivity as high as 90% at high methanol conversion (68%).