Solvent Directed Diastereodivergent Synthesis of Spiro-Oxindoles with Quaternary Carbon Center Forming

An efficient method has been developed for the solvent-directed diastereodivergent cyclization reactions with quaternary center formation. Various spiro-oxindole diastereoisomers were synthesized with good yields (up to >99 %) and moderate to high diastereoselectivities (up to >20 : 1). Further study on NMR studies indicates that the key to this approach lies in different interactions between the substrate and organocatalyst across diverse solvents. This methodology may have significant implications for switchable, solvent-directed diastereodivergent synthesis.     

Radical Arylaminoformylation of Activated Alkenes to Amides Containing All-Carbon Quaternary Stereocenters

Herein we report an Ag⁺/S₂O₈²⁻ inducted measure for functionalized succinyl diamides bearing an all-carbon quaternary stereocenter via a radical aminoformylation/aryl-migration/desulfonylation cascade. The improved process is developed employing readily available and inexpensive oxalic monoamide as a carbamoyl radical precursor through radical Smiles rearrangement. Additionally, the tolerance to oxygen and water, operational simplicity, convenient reagents, as well as scalability, enhance the practical value of the proposed synthesis strategy.     

Brønsted Base-Catalyzed Enantioselective α-Functionalization of Carbonyl Compounds Involving π-Extended Enolates

Chiral Brønsted base (BB) catalyzed asymmetric transformations constitute an important tool for synthesis. A meaningful fraction of these transformations proceeds through transiently generated enolate intermediates, which display quite versatile reactivity against a variety of electrophiles. Some years ago, our group became interested in developing BB-catalyzed asymmetric reactions of enolizable carbonyl substrates that involve π-extended enolates in which, besides control of reaction diastereo and enantioselectivity, the site-selectivity control is an additional issue in most cases. In the examples covered in this account the opportunities deployed, and the challenges posed, by these methods are illustrated, with a focus on the generation of quaternary carbon stereocenters. In the way, new bifunctional BB catalysts as well as achiral templates were developed that may find further applications.     

Hyperbranched Polymer Induced Antibacterial Tree-Like Nanofibrous Membrane for High Effective Air Filtration

The air filtration materials with high efficiency, low resistance, and extra antibacterial property are crucial for personal health protection. Herein, a tree-like polyvinylidene fluoride (PVDF) nanofibrous membrane with hierarchical structure (trunk fiber of 447 nm, branched fiber of 24.7 nm) and high filtration capacity is demonstrated. Specifically, 2-hydroxypropyl trimethyl ammonium chloride terminated hyperbranched polymer (HBP-HTC) with near-spherical three-dimensional molecular structure and adjustable terminal positive groups is synthesized as an additive for PVDF electrospinning to enhance the jet splitting and promote the formation of branched ultrafine nanofibers, achieving a coverage rate of branched nanofibers over 90% that is superior than small molecular quaternary ammonium salts. The branched nanofibers network enhances mechanical properties and filtration efficiency (99.995% for 0.26 µm sodium chloride particles) of the PVDF/HBP-HTC membrane, which demonstrates reduced pressure drop (122.4 Pa) and a quality factor up to 0.083 Pa⁻¹ on a 40 µm-thick sample. More importantly, the numerous quaternary ammonium salt groups of HBP-HTC deliver excellent antibacterial properties to the PVDF membranes. Bacterial inhibitive rate of 99.9% against both S. aureus and E. coli is demonstrated in a membrane with 3.0 wt% HBP-HTC. This work provides a new strategy for development of high-efficiency and antibacterial protection products.     

Asymmetric S-Michael Reaction: Synthesis of CF2H−Containing S-Ether Compounds through Isosteric Replacement

Optical pharmaceutical important compounds which bring CF₂H to mimic the role of –SH were synthesized through the asymmetric S-Michael addition reaction in the presence of quinine–a derived squaramide catalyst. Various sulfhydryl compounds including Benzyl mercaptan, phenthiol, alkyl thiophenol, mercaptoacetate, methyl 3-mercaptoacrylate, and 1,4-dithiane-2,5-diol were tested. The broad substrate scope, good functional group tolerance, and easy derivatization make this synthesis method very attractive.     

Comparative analysis of molecular interactions in quaternary fluid system performed by classical and ab initio molecular dynamics

Molecular interactions in the quaternary fluid system acetic acid–n-propanol–n-propyl acetate–water were analyzed by classical and ab initio molecular dynamics methods. It was shown that ab initio molecular dynamics simulation can reproduce the molecular mobility tendency and structural features of a multicomponent system without empirical parameters.     

四元体系Na~ ,K~ ∥CO_3~(2-),B_4O_7~(2-)H_2O 298K相平衡研究

采用等温溶解平衡法研究了四元体系Na K ∥CO32-B4O72-H2O298K时的相关系。该四元体系298K时的溶解度等温图含有5个相区Na2B4O7·10H2OK2B4O7·4H2ONa2CO3·10H2OK2CO3·3/2H2O和复盐Na2CO3·K2CO3·H2O7条单变量曲线和3个共饱点其中Na2CO3·K2CO3·H2O K2CO3·3/2H2O K2B4O7·4H2O为相称共饱点。体系中发现了一种新的复盐Na2CO3·K2CO3·H2O这种复盐同时存在于含Na K ∥CO32-H2O三元体系的其它四元或高元体系中。