Substrate-Dependent Mechanisms for the Gold(I)-Catalyzed Cycloisomerization of Silyl-Tethered Enynes: A Computational Study

The gold­(I)-catalyzed alkenyl-, allyl-, and arylsilylation reactions of silyl-tethered enynes discovered by Murakami et al. provide efficient methods for the facile constructions of 1-silaindene derivatives. A comprehensive mechanistic DFT study of these reactions was carried out to better understand the experimental outcomes, and divergent and substrate-dependent mechanisms for the formations of 1-silaindene derivatives were uncovered based on the computational results. From cationic gold­(I) π-alkyne complexes, the <i>endo</i>-dig cyclization pathway may lead possibly to both C₂- and C₃-group-substituted (group = alkenyl, allyl, or aryl) 1-silaindene products, and the regioselectivity will be finally determined by the 1,2-group migration of the gold carbenoid intermediate. On the other hand, the <i>exo</i>-dig cyclization pathway leads only to C₃-group-substituted (group = alkenyl, allyl, or aryl) 1-silaindene, in which a notable promoting effect of the bistriflimide counterion on the rearrangement of the silyl cation intermediate was disclosed. The results reported herein provide insights into aspects of regioselective cyclization, silyl-involved skeletal rearrangements, chemoselective 1,2-migration in gold carbenoids, and the dramatic counterion effect in the reactions concerned

PDE1A polymorphism contributes to the susceptibility of nephrolithiasis

We here provide evidence for a monogenic cause of nephrolithiasis, or kidney stones, based on an association of a polymorphism in the <i>PDE1A</i> gene. This variant was detected through whole-exome analysis of ten members of an affected family, as well as a case–control study of a validation cohort including over 2000 patients at our hospital

Noninnocent Counterion Effect on the Rearrangements of Cationic Intermediates in a Gold(I)-Catalyzed Alkenylsilylation Reaction

A mechanistic DFT study of the gold(I)-catalyzed alkenylsilylation reaction of a silyl-tethered 1,6-enyne system is reported. A novel pathway involving bistriflimide counterion-assisted rearrangements of carbocation and silyl cation intermediates corroborates the experimental observations. The results suggest the important role of the counterion in modulating the reactivity of cationic intermediates in gold catalysis

Mechanistic Understanding of the Aryl-Dependent Ring Formations in Rh(III)-Catalyzed C–H Activation/Cycloaddition of Benzamides and Methylenecyclopropanes by DFT Calculations

The divergence between Rh­(III)-catalyzed C–H activation/cycloaddition of phenyl- and 2-furanyl-containing benzamides with methylenecyclopropanes (MCP) was studied by DFT calculations. Calculations found that the C–H activation via a CMD mechanism is the most difficult step of the reaction involving phenyl. In contrast, the C–H activation of the 2-furanyl-containing substrate is kinetically easier but the formed five-membered rhodacycle is relatively unstable, making the following MCP insertion more difficult. Thus, different KIE data was obtained in experiments. The MCP insertion forms a seven-membered-ring rhodacycle intermediate, from which the chemoselectivity of the whole reaction is determined by the competitive pivalate migration (path I) and β-C elimination (path II). While the β-C elimination is lower in energy when a furanylene is contained in the intermediate, a reversed preference of pivalate migration was predicted for the phenylene counterpart. Structural analysis suggested that the unfavorable β-C elimination in the phenylene case should be attributed to the obviously increased ring strain in the corresponding transition state, instead of the difference in electronic properties between the aryl groups. This accounts for why aryl-dependent chemoselectivity was observed. In addition, the results indicated that for both paths I and II the generation of a Rh­(V)–nitrenoid intermediate from pivalate migration is crucial for the final C–N bond formation. This explains why no reaction occurred when the N–OPiv moiety was replaced with an N–OMe group, as no Rh­(V) intermediate could be formed in this system

Selective Metallization Induced by Laser Activation: Fabricating Metallized Patterns on Polymer via Metal Oxide Composite

Recently, metallization on polymer substrates has been given more attention due to its outstanding properties of both plastics and metals. In this study, the metal oxide composite of copper–chromium oxide (CuO·Cr₂O₃) was incorporated into the polymer matrix to design a good laser direct structuring (LDS) material, and the well-defined copper pattern (thickness =10 μm) was successfully fabricated through selective metallization based on 1064 nm near-infrared pulsed laser activation and electroless copper plating. We also prepared polymer composites incorporated with CuO and Cr₂O₃; however, these two polymer composites both had very poor capacity of selective metallization, which has no practical value for LDS technology. In our work, the key reasons causing the above results were systematically studied and elucidated using XPS, UV–vis–IR, optical microscopy, SEM, contact angle, ATR FTIR, and so on. The results showed that 54.0% Cu²⁺ in the polymer composite of CuO·Cr₂O₃ (the amount =5 wt %) is reduced to Cu⁰ (elemental copper) after laser activation (irradiation); however, this value is only 26.8% for the polymer composite of CuO (the amount =5 wt %). It was confirmed that to achieve a successful selective metallization after laser activation, not only was the new formed Cu⁰ (the catalytic seeds) the crucial factor, but the number of generated Cu⁰ catalytic seeds was also important. These two factors codetermined the final results of the selective metallization. The CuO·Cr₂O₃ is very suitable for applications of fabricating metallic patterns (e.g., metal decoration, circuit) on the inherent pure black or bright black polymer materials via LDS technology, which has a prospect of large-scale industrial applications

Specifications of equivalent circuit of the Battery/Supercapacitor HESS in Boost mode.

<p>Specifications of equivalent circuit of the Battery/Supercapacitor HESS in Boost mode.</p

Equivalent circuit of the Battery/Supercapacitor HESS in Boost mode.

<p>Equivalent circuit of the Battery/Supercapacitor HESS in Boost mode.</p

Adaptive fractional order sliding mode control for Boost converter in the Battery/Supercapacitor HESS - Fig 3

<p><b>Simulation results of the FASMC and ASMC strategy for the Battery/supercapacitor HESS:</b> (a) The turn-on voltage of the FASMC; (b) The inductor current of the FASMC; (c)The turn-on voltage of the ASMC; (d) The inductor current of the ASMC.</p

Simulated output voltage responses due to the different λ by AFSMC.

<p>Simulated output voltage responses due to the different λ by AFSMC.</p

Prevalence of hypertension according to different category.

<p>Prevalence of hypertension according to different category.</p