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The enantioselective vinylogous Mannich reaction of ketimines derived from isatins with acyclic vinylketene silyl acetals has been developed using a chiral bis(imidazoline)-Cu(II) catalyst. A series of chiral 3-aminooxindole derivatives bearing tetra-substituted stereogenic centers with an α,β-unsaturated ester moiety were obtained in excellent yields (up to 99%) with high enantioselectivities (up to 98% ee). Enantioselective bisvinylogous Mannich reaction to ketimines derived from isatins also afforded product with high enantioselectivity. Based on the experimental investigations, a possible transition state has been proposed to explain the origin of the asymmetric induction.Static plasmonic metal-insulator-nanohole (MIN) cavities have been shown to create high chromaticity spectral colors for display applications. While on-off switching of said devices has been demonstrated, introducing active control over the spectral color of a single cavity is an ongoing challenge. Electrochromic oxides such as tungsten oxide (WO3) offer the possibility to tune their refractive index (2.1-1.8) and extinction (0-0.5) upon ion insertion, allowing active control over resonance conditions for MIN based devices. In combination with the dynamic change in the WO3 layer, the utilization of a plasmonic superstructure allows creation of well-defined spectral reflection of the nanocavity. Here, we employ inorganic, electrochromic WO3 as the tunable dielectric in a MIN nanocavity, resulting in a theoretically achievable resonance wavelength modulation from 601 to 505 nm, while maintaining 35% of reflectance intensity. Experimental values for the spectral modulation result in a 64 nm shift of peak wavelength with high reproducibility and fast switching speed. Remarkably, the introduced device shows electrochemical stability over 100 switching cycles while most of the intercalated charge can be regained (91.1%), leading to low power consumption (5.6 mW/cm-2).The cross-coupling of N,N-dialkyl aniline and aminonaphthalenes with phenols and naphthols using a Cr-salen catalyst under aerobic conditions was developed. Notably, air serves as an effective oxidant affording products in high selectivity. Initial mechanistic studies suggest an outer-sphere oxidation of the aniline/aminonaphthalene partner, followed by nucleophilic attack of the phenol/naphthol. Single products were observed in most cases, whereas mixtures of C-C and C-O coupled products arose from reactions involving aminonapthalene and sterically unencumbered phenols.An efficient gold-catalyzed cyclization of 2-alkynylaldehyde cyclic acetals has been developed for the synthesis of indenone derivatives. A wide variety of functionalized indenone derivatives can be obtained in good-to-excellent yields. HMBC and NOESY NMR analyses and mechanistic elucidation experiments revealed that the cyclization occurs via a 1,5-H shift. The cyclic acetal group promoted the 1,5-H shift by activating the benzylic C-H bond and preventing the migration of the alkoxy group by tethering both alkoxy groups.We combine state-of-the-art ultrafast photoluminescence and absorption spectroscopy and nonadiabatic molecular dynamics simulations to investigate charge-carrier cooling in CsPbBr3 nanocrystals over a very broad size regime, from 0.8 to 12 nm. Contrary to the prevailing notion that polaron formation slows down charge-carrier cooling in lead-halide perovskites, no suppression of carrier cooling is observed in CsPbBr3 nanocrystals except for a slow cooling (over ∼10 ps) of "warm" electrons in the vicinity (within ∼0.1 eV) of the conduction band edge. At higher excess energies, electrons and holes cool with similar rates, on the order of 1 eV ps-1 carrier-1, increasing weakly with size. Our ab initio simulations suggest that cooling proceeds via fast phonon-mediated intraband transitions driven by strong and size-dependent electron-phonon coupling. The presented experimental and computational methods yield the spectrum of involved phonons and may guide the development of devices utilizing hot charge carriers.The total synthesis of a potent multi-drug-resistant reverser, dysoxylacatam A (1), was achieved in a highly efficient and stereocontrolled fashion. The highlights of the strategy enlisted an iterative combination of lithiation-borylation tactics including Aggarwal homologation and Matteson homologation, Brown crotylation, Krische allylation, and ring-closing metathesis to forge the macrocycle.The development of a strategy for the assembly of nanoscale building blocks, in particular, anisotropic nanoparticles, into desired structures is important for the construction of functional materials and devices. However, control over the orientation of rod-shaped nanoparticles on a substrate for integration into solid-state devices remains challenging. Here, we report a strategy for the fabrication of finely aligned gold nanorod (GNR) arrays using polymer (DNA) brushes as a nanoscale template. The gold nanorods modified with cationic surface ligands were electrostatically adsorbed onto the DNA brush substrates under various conditions. The orientational behavior of the GNRs was examined by spectral analyses and transmission electron microtomography (TEMT). As a result, we found several important factors, such as moderate interaction between GNRs and polymers and polymer densities on the substrate, related to the vertical alignment of GNRs on the substrates. We also developed a purification method to remove the undesired adsorption of GNRs onto the arrays. Anti-infection chemical Finally, we have succeeded in the fabrication of extensive vertical GNR arrays of high quality via the easy bottom-up process.The aggregation-induced emission (AIE) mechanism of restriction of double-bond rotation (RDBR) was utilized to design an excellent solid emitter and sensor for the first time. Thus, cis-tetraphenylethylene (TPE) macrocycle diammoniums were synthesized and bound to a DNA chain by its two ammonium arms. The formed TPE dicycle at the cis position restricted the rotation of the double bond in both the ground and excited states, resulting in AIE enhancement, chiroptical performance enhancement, and sensing enhancement.
Homepage: https://www.selleckchem.com/products/ll37-human.html
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