Catalytic alkylation of benzylic C-H bonds with 1,3-dicarbonyl compounds utilizing oxygen as terminal oxidant

The oxidative alkylation of benzylic C-H bonds with 1,3-dicarbonyl compounds was developed using oxygen as the terminal oxidant in the presence of catalytic amounts of FeCl₂, CuCl and NHPI.     

Infrared transmission equations in a five media system: gas and liquid

Equations are proposed for transmission cells in the presence of multiple reflections and absorption which generate unwanted fringes. These influence adversely band intensity measurements. The infrared (IR) spectra generated with these equations are compared successfully with experimental spectra obtained with BaF₂, ZnSe, and Si windows in parallel mount formation having μm range air gaps. Equations are extended for integration of a variable path length such as in wedge shaped cells that are used to mitigate fringe formations but generate other odd problems such as path length determination. These equations allow the evaluation of the transmission obtained from boxcar cells whose parallelism is a little offset. This phenomenon modifies the fringe intensities. The proposed equations were used to calculate the IR spectra of pure liquid D₂O between BaF₂ and ZnSe windows with path lengths of around 25 μm and compared with experimental spectra. Since the fit was very good it indicates that the proposed equations give better optical properties of pure liquids than that presently available. This is important for liquid used as standards and in particular water used here as reference.     

Quantifying time-varying coordination of multimodal speech signals using correlation map analysis

This paper demonstrates an algorithm for computing the instantaneous correlation coefficient between two signals. The algorithm is the computational engine for analyzing the time-varying coordination between signals, which is called correlation map analysis (CMA). Correlation is computed around any pair of points in the two input signals. Thus, coordination can be assessed across a continuous range of temporal offsets and be detected even when changing over time due to temporal fluctuations. The correlation algorithm has two major features: (i) it is structurally similar to a tunable filter, requiring only one parameter to set its cutoff frequency (and sensitivity), (ii) it can be applied either uni-directionally (computing correlation based only on previous samples) or bi-directionally (computing correlation based on both previous and future samples). Computing instantaneous correlation for a range of time offsets between two signals produces a 2D correlation map, in which correlation is characterized as a function of time and temporal offset. Graphic visualization of the correlation map provides rapid assessment of how correspondence patterns progress through time. The utility of the algorithm and of CMA are exemplified using the spatial and temporal coordination of various audible and visible components associated with linguistic performance.     

Mechanism of W(CO)6 sonolysis in diphenylmethane

The present work analyses the mechanism of W₂C/C nanocomposite formation during sonolysis of W(CO)₆ in diphenylmethane (DPhM) solutions. Carbon supported WC_x nanoparticles attract much interest as an alternative fuel cell electrocatalysts. Sonolysis of neat DPhM under the effect of 20 kHz power ultrasound in argon at 80 °C yields a sonopolymer as a solid product and acetylene, hydrogen, methane, diacetylene and benzene as gaseous products. Diacetylene is formed due to the secondary sonochemical dimerisation of acetylene obtained at the primary stage of DPhM sonolysis. FTIR and μ-Raman studies show that the sonopolymer consists of a mixture of some polymeric partially oxidized aromatic species, and disordered carbon. Sonolysis of W(CO)₆ in diphenylmethane solutions follows the first order kinetics. This process yields monodispersed 2-3 nm X-ray amorphous WC_x nanoparticles embedded in amorphous sonopolymer. The annealing of air sensitive as-prepared solids in an inert atmosphere at 600 °C causes formation of stable W₂C/C nanocomposite with W₂C average particle size in the range of 4-7 nm and hexagonal carbon fine particles with the average size of 30-40 nm. Kinetic study revealed that tungsten carbide is formed inside the cavitation bubble due to the reaction of tungsten nanoparticles originated from primary sonolysis of W(CO)₆ with acetylene produced as a result of diphenylmethane sonochemical degradation.     

An introduction to variational quantum algorithms for combinatorial optimization problems

4OR - Noisy intermediate-scale quantum computers (NISQ computers) are now readily available, motivating many researchers to experiment with Variational Quantum Algorithms (VQAs). Among them, the...     

Structurally Diverse Bench-Stable Nickel(0) Pre-Catalysts: A Practical Toolkit for In Situ Ligation Protocols**

A flurry of recent research has centered on harnessing the power of nickel catalysis in organic synthesis. These efforts have been bolstered by contemporaneous development of well-defined nickel (pre)catalysts with diverse structure and reactivity. In this report, we present ten different bench-stable, 18-electron, formally zero-valent nickel–olefin complexes that are competent pre-catalysts in various reactions. Our investigation includes preparations of novel, bench-stable Ni(COD)(L) complexes (COD=1,5-cyclooctadiene), in which L=quinone, cyclopentadienone, thiophene-S-oxide, and fulvene. Characterization by NMR, IR, single-crystal X-ray diffraction, cyclic voltammetry, thermogravimetric analysis, and natural bond orbital analysis sheds light on the structure, bonding, and properties of these complexes. Applications in an assortment of nickel-catalyzed reactions underscore the complementary nature of the different pre-catalysts within this toolkit.