Search

Abstract In this study, a novel approach for the tertiary α‐alkylation of ketones using alkanes with electron‐deficient C─H bonds is presented, employing a synergistic catalytic system combining inexpensive copper salts with aminocatalysis. This methodology addresses the limitations of traditional alkylation methods, such as the need for strong metallic bases, regioselectivity issues, and the risk of over alkylation, by providing a high reactivity and chemoselectivity without the necessity for pre‐functionalized substrates. The dual catalytic strategy enables the direct functionalization of C(sp3)─H bonds, demonstrating remarkable selectivity in the presence of conventional C(sp3)─H bonds that are adjacent to heteroatoms or π systems, which are typically susceptible to single‐electron transfer processes. The findings contribute to the advancement of alkylation techniques, offering a practical and efficient route for the construction of C(sp3)─C(sp3) bonds, and paving the way for further developments in the synthesis of complex organic molecules.

In order to improve the corrosion resistance of anticorrosive coatings and expand the application scope of Iranian rock asphalt, solentless Iranian rock asphalt anticorrosive coatings were prepared throuth a two-component process using the matrix asphalt, Iranian rock asphalt and epoxy resin as film - forming materials with the addtion of fillers, various additives and other components. The anti - corrosion properties of such coatings were studied through AC impedance test and acid, alkali and salt corrosion resistance test. Results showed that when the content of Iranian rock asphalt was 15%, the comprehensive properties of modified asphalt were best. The corrosion resistance of the prepared Iranian rock asphalt anticorrosive coating was much better than that of the petroleum asphalt anticorrosive coating. The corrosion resistance time to acid, alkali and salt immersion was prolonged by more than 10 days. The viscosity of Iranian rock asphalt anticorrosive coating was large at room temperature, and good coating effect was achieved when the coating temperature was about 60 ℃.

In this study, a novel approach for the tertiary α‐alkylation of ketones using alkanes with electron‐deficient C─H bonds is presented, employing a synergistic catalytic system combining inexpensive copper salts with aminocatalysis. This methodology addresses the limitations of traditional alkylation methods, such as the need for strong metallic bases, regioselectivity issues, and the risk of over alkylation, by providing a high reactivity and chemoselectivity without the necessity for pre‐functionalized substrates. The dual catalytic strategy enables the direct functionalization of C(sp3)─H bonds, demonstrating remarkable selectivity in the presence of conventional C(sp3)─H bonds that are adjacent to heteroatoms or π systems, which are typically susceptible to single‐electron transfer processes. The findings contribute to the advancement of alkylation techniques, offering a practical and efficient route for the construction of C(sp3)─C(sp3) bonds, and paving the way for further developments in the synthesis of complex organic molecules. [ABSTRACT FROM AUTHOR]

Quasicrystals have aroused great interest and argument among researchers due to their unique atomic configurations. In this paper, based on the Stroh formalism and Barnett-Lothe matrices, we investigate the problems of two-dimensional piezoelectric quasicrystal composite wedges and spaces subjected to different loadings, such as line force and line dislocation. The special cases of the semi-infinite spaces, infinite spaces, and bi-material composite spaces are also taken into consideration. We derive the analytical expressions of displacements and stresses by considering the continuities of the displacements and surface tractions on the radial plane. After that, the comparative study regarding the infinite space problem, between solutions from Green's function and solutions from our method, is performed to verify the accuracy of the formulation and numerical results. Numerical examples are given to present the mechanical behaviors of quasicrystal under different loadings. The results prove that line force affects phonon displacement more clearly than phason displacement, but line dislocation affects stresses and electric displacement little. [ABSTRACT FROM AUTHOR]

In the framework of thermo-electro-elasticity, the present paper investigates the singular behaviors of interface corners, interface cracks, composite wedges and spaces for one-dimensional hexagonal quasicrystal. The stress function and temperature variation can be described as the exponential form with a view to stress and heat flux singularities. Based on the Stroh formalism, the analytical expressions of singular orders of stress and heat flux are easily established by simple multiplication of the crucial matrix. Numerical examples of the singular orders are given for some general cases including single, bi-material, and tri-material wedges and spaces under different boundary conditions. Numerical results show that the geometry structures, material properties, boundary conditions, and heat conduction coefficients have great influences on singularities, but thermal moduli have no effect on singularities. [ABSTRACT FROM AUTHOR]

Research has been conducted on the Hib pili from Haemophilus influenzae type b. The structure of this pili has been investigated via the use of electron microscopy and image processing and results provide the basis for understanding bacterial strategies that facilitate H. influenzae type b survival.