Efficient sulfonylation of ketones with sodium sulfinates for the synthesis of β-keto sulfones

The oxidative sulfonylation of ketones with sodium sulfinates as the sulfone source and DMSO as the oxidant is reported. A series of β-keto sulfones were obtained in good to excellent yields. The advantages of this efficient protocol include the low cost of DMSO and HBr, and a broad scope.     

Preparation of mesoporous crack-free Sb-SnO2 xerogels through ambient-pressure drying and its application as three-dimensional electrode

Journal of Sol-Gel Science and Technology - Ambient-pressure-dried (APD) crack-free Sb-SnO2 xerogel has been developed through a facile sol-gel approach. Propylene oxide was added into the tin and...     

Long Time Well-Posedness of the MHD Boundary Layer Equation in Sobolev Space

In this paper, we study the long time well-posedness of 2-D MHD boundary layer equation. It was proved that if the initial data satisfies■,then the life span of the solution is at least of order ε~(2-η) for η 0.     

Dynamics and isotherms of water vapor sorption on mesoporous silica gels modified by different salts

The mesoporous silica gels impregnated with different metal salts were prepared and studied. The pore structure and specific surface area of adsorbents were evaluated using nitrogen adsorption. Then, the sorption isotherms and dynamics of water vapor were carried out at 303 K and different relative humidity (RH). The temperature programmed desorption experiments were conducted to estimate the activation energy (E _d) of water desorption on the silica gels. The results showed that the sorption capacity for water decreased with the increase of the ionic radius (except the calcium ion) and that CaCl₂ and LiCl were particularly suitable for use in modification of the mesoporous silica gel to improve their sorption rates and capacities for water vapor at the lower and medium RH (RH < 80%). The larger the average pore diameter and pore volume of the initial silica gels, higher the accrual rates of the water vapor sorption rate and capacity were after modification with hygroscopic salts. The activation energy of the water desorption on the mesoporous silica gel modified by CaCl₂ were much higher than that on the silica gel modified by LiCl, because the polarizability of the Ca²⁺ was higher than that of Li⁺.     

Preparative isolation and purification of 12 main antioxidants from the roots of Polygonum multiflorum Thunb. using high‐speed countercurrent chromatography and preparative HPLC guided by 1,1′‐diphenyl‐2‐picrylhydrazyl‐HPLC

A hyphenated strategy by off‐line coupling of 1,1′‐diphenyl‐2‐picrylhydrazyl‐high‐performance liquid chromatography, high‐speed countercurrent chromatography, and preparative high‐performance liquid chromatography was established to screen and separate antioxidants from ethyl acetate fraction of the roots of Polygonum multiflorum. Under the targeted guidance of 1,1′‐diphenyl‐2‐picrylhydrazyl‐high‐performance liquid chromatography experiment, 12 compounds were identified as potential antioxidants and readily isolated by high‐speed counter‐current chromatography and preparative high‐performance liquid chromatography. Ultraviolet spectroscopy, mass spectrometry, and ¹H NMR spectroscopy were employed to identify their structures, which were assigned as gallic acid ( 1 , 6.2 mg, 98.28%), catechin ( 2 , 8.8 mg, 90.69%), epicatechin ( 3 , 4.1 mg, 96.71%), polydatin ( 4 , 5.3 mg, 94.91%), 2,3,5,4′‐tetrahydroxy stilbene‐2‐Ο‐β‐D‐glucoside ( 5 , 20.2 mg, 95.23%), piceatannol ( 6 , 5.3 mg, 96.85%), rutin ( 7 , 5.4 mg, 97.92%), resveratrol ( 8 , 5.2 mg, 96.94%), isorhapontigenin ( 9 , 11.4 mg, 94.81%), hyperoside ( 10 , 9.7 mg, 98.52%), rhein ( 11 , 4.9 mg, 97.46%), and emodin ( 12 , 8.2 mg, 95.74%). Notably, compounds 6 and 9 were isolated from Polygonum multiflorum for the first time. In addition, antioxidant activity of compounds 1–12 were evaluated, and compounds 1–8 and 10 exhibited stronger antioxidant activity than ascorbic acid (positive control). These results indicated that the proposed method is a highly efficient strategy to screen and isolate antioxidants from complex natural products.     

Core–Shell Structured Nanocomposites for Photocatalytic Selective Organic Transformations

Core–shell structured nanocomposites, a type of talented functional materials with unique microstructure and properties, have shown great promise as photocatalysts for various applications, including photocatalytic degradation of pollutants, water splitting for hydrogen production, and selective organic transformations. The synthesis and utilization of efficient core–shell nanoarchitectured photocatalysts for selective organic synthesis are at the center of our research efforts and the focus of this minireview. Specifically, semiconductor‐based core–shell nanocomposites, including metal–semiconductor, semiconductor–semiconductor, semiconductor–shell (graphene and SiO₂) as photocatalysts/cocatalysts for selective oxidation of alcohols, reduction of nitro organics and carbon dioxide for synthesis of fine chemicals, and redox‐combined selective synthesis of pipecolinic acid are summarized. It is hoped that this minireview can make a contribution to catalyzing the development of smart core–shell nanostructures in the field of photocatalytic selective organic transformations for solar energy conversion.     

Estimates of Invariant Metrics on Pseudoconvex Domains Near Boundaries with Constant Levi Ranks

Estimates of the Bergman kernel and the Bergman and Kobayashi metrics on pseudoconvex domains near boundaries with constant Levi ranks are given. As a consequence, a characterization of Levi-flatness in terms of boundary behavior of the Bergman and Kobayashi metrics is obtained.     

Nickel-Catalyzed Amination of (Hetero)aryl Halides Facilitated by a Catalytic Pyridinium Additive

An efficient and operationally simple Ni-catalyzed amination protocol has been developed. This methodology features a simple Ni^II salt, an organic base and catalytic amounts of both a pyridinium additive and Zn metal. A diverse number of (hetero)aryl halides were coupled successfully with primary and secondary alkyl amines, and anilines in good to excellent yields. Similarly, benzophenone imine gave the corresponding N-arylation product in an excellent yield.     

Research Progress of the Biosynthesis of Natural Bio-Antibacterial Agent Pulcherriminic Acid in Bacillus

Pulcherriminic acid is a cyclic dipeptide found mainly in Bacillus and yeast. Due to the ability of pulcherriminic acid to chelate Fe³⁺ to produce reddish brown pulcherrimin, microorganisms capable of synthesizing pulcherriminic acid compete with other microorganisms for environmental iron ions to achieve bacteriostatic effects. Therefore, studying the biosynthetic pathway and their enzymatic catalysis, gene regulation in the process of synthesis of pulcherriminic acid in Bacillus can facilitate the industrial production, and promote the wide application in food, agriculture and medicine industries. After initially discussing, this review summarizes current research on the synthesis of pulcherriminic acid by Bacillus, which includes the crystallization of key enzymes, molecular catalytic mechanisms, regulation of synthetic pathways, and methods to improve efficiency in synthesizing pulcherriminic acid and its precursors. Finally, possible applications of pulcherriminic acid in the fermented food, such as Chinese Baijiu, applying combinatorial biosynthesis will be summarized.