二甲基亚砜参与的烯烃的氧化碘羟化反应

利用原位生成碘正离子的策略,基于在酸性条件下二甲基亚砜具备氧化碘负离子的能力,研究了烯烃分子的氧化碘羟化反应.在温和条件下,以中等到优良的收率合成了碘代醇衍生物.并通过亲核性醇类溶剂的加入,实现了烯烃的碘醚化反应.     

Research Progress of Lithium Plating on Graphite Anode in Lithium‐Ion Batteries

Lithium plating on graphite anode is triggered by harsh conditions of fast charge and low temperature, which significantly accelerates SOH (state of health) degradation and may cause safety issues of lithium ion batteries (LIBs). This paper has reviewed recent research progress of lithium plating on graphite anode. Firstly, we summarize the forming mechanisms of Li plating with corresponding influence factors, the detecting methods and hazard of Li plating. Then, approaches to suppress Li plating are discussed, including anode surface modification, electrolyte composition optimization and development of optimal charge strategies. Finally, we conclude and propose the remaining challenges and prospects in terms of mechanism research, detecting approaches, and suppressing methods of Li plating. This review highlights the development of Li plating research and plays a guiding rule of further study on Li plating in LIBs.     

γ-和δ-酮酸衍生物均相催化氢化研究进展

γ-和δ-酮酸衍生物是最重要的双官能团生物质平台化合物之一,如何高效地催化这些酮酸类化合物转化成相应的单一精细化学品是当今研究的难点.我们综述了金属有机配合物均相催化氢化γ-和δ-酮酸的最新进展,重点介绍了用于催化生产γ-和δ-羟基酸、酯、内酯、环醚等的均相催化剂的结构、活性、选择性和反应机理.     

Heterogeneous Hydrogenation with Hydrogen Spillover Enabled by Nitrogen Vacancies on Boron Nitride-Supported Pd Nanoparticles

Heterogeneous hydrogenation with hydrogen spillover has been demonstrated as an effective route to achieve high selectivity towards target products. More effort should be paid to understand the complicated correlation between the nature of supports and hydrogenation involving hydrogen spillover. Herein, we report the development of the hydrogenation system of hexagonal boron nitride (h-BN)-supported Pd nanoparticles for the hydrogenation of aldehydes/ketones to alcohols with hydrogen spillover. Nitrogen vacancies in h-BN determine the feasibility of hydrogen spillover from Pd to h-BN. The hydrogenation of aldehydes/ketones with hydrogen spillover from Pd proceeds on nitrogen vacancies on h-BN. The weak adsorption of alcohols to h-BN inhibits the deep hydrogenation of aldehydes/ketones, thus leading to high catalytic selectivity to alcohols. Moreover, the hydrogen spillover-based hydrogenation mechanism makes the catalyst system exhibit a high tolerance to CO poisoning.     

Stereoselective Synthesis of Enamides through Palladium-Catalyzed Oxidative Amidation of Conjugated Olefins with 2-Pyridones

A palladium-catalyzed oxidative amidation of conjugated olefin with 2-pyridone is described. A series of E-Enamides were synthesized in a highly stereocontrolled manner. The reaction also accommodates other cyclic and acyclic amides. Z-Enamides were predominantly prepared for primary amides probably due to the presence of an intramolecular hydrogen bond. Gram-scale synthesis of enamide and the following oxidative annulation with diphenylacetylene demonstrates the synthetic utility of this reaction.     

Sulfur Poisoning and Self-Recovery of Single-Site Rh1/Porous Organic Polymer Catalysts for Olefin Hydroformylation

Sulfur poisoning and regeneration are global challenges for metal catalysts even at the ppm level. The sulfur poisoning of single-metal-site catalysts and their regeneration is worthy of further study. Herein, sulfur poisoning and self-recovery are first presented on an industrialized single-Rh-site catalyst (Rh₁/POPs). A decreased turnover frequency of Rh₁/POPs from 4317 h⁻¹ to 318 h⁻¹ was observed in a 1000 ppm H₂S co-feed for ethylene hydroformylation, but it self-recovered to 4527 h⁻¹ after withdrawal of H₂S, whereas the rhodium nanoparticles demonstrated poor activity and self-recovery ability. H₂S reduced the charge density of the single Rh atom and lowered its Gibbs free energy with the formation of inactive (SH)Rh(CO)(PPh₃-frame)₂, which could be regenerated to active HRh(CO)(PPh₃-frame)₂ after withdrawing H₂S. The mechanism and the sulfur-related structure–activity relationship were highlighted. This work provides an understanding of heterogeneous ethylene hydroformylation and sulfur-poisoned regeneration in the science of single-atom catalysts.     

Acidic Media Impedes Tandem Catalysis Reaction Pathways in Electrochemical CO2 Reduction

Electrochemical CO₂ reduction (CO₂R) in acidic media with Cu-based catalysts tends to suffer from lowered selectivity towards multicarbon products. This could in principle be mitigated using tandem catalysis, whereby the *CO coverage on Cu is increased by introducing a CO generating catalyst (e.g. Ag) in close proximity. Although this has seen significant success in neutral/alkaline media, here we report that such a strategy becomes impeded in acidic electrolyte. This was investigated through the co-reduction of ¹³CO₂/¹²CO mixtures using a series of Cu and CuAg catalysts. These experiments provide strong evidence for the occurrence of tandem catalysis in neutral media and its curtailment under acidic conditions. Density functional theory simulations suggest that the presence of H₃O⁺ weakens the *CO binding energy of Cu, preventing effective utilization of tandem-supplied CO. Our findings also provide other unanticipated insights into the tandem catalysis reaction pathway and important design considerations for effective CO₂R in acidic media.     

铁苯基膦配合物均相催化乙酰丙酸乙酯与甲酸反应转化为γ-戊内酯的分子机制

本文基于密度泛函理论,计算了Fe(CF3SO3)2/PP3催化乙酰丙酸乙酯与甲酸反应转化为γ-戊内酯的反应机理。分析了单重态和三重态反应路径的热力学和动力学性质,结果表明除了预催化剂活化出现势能面交叉外,反应主要在三重态势能面上进行,包括以下几个步骤：甲酸盐配位方式重置,β-H消除得到活性催化剂[FeH(PP3)]+,接着乙酰丙酸乙酯的羰基碳和羰基氧接连被质子化得到中间体4-羟基戊酸乙酯,最后质子化的反离子CF3SO3H作为氢转移梭子协助分子内脱醇—关环生成目标产物γ-戊内酯。进一步探讨不同金属苯基膦配合物的催化活性,证实金属适宜的配位能力是筛选催化剂的关键。理论计算结果为优化设计高性能的生物质转化催化剂提供一定的理论指导。     

Frenkel Defect-modulated Anti-thermal Quenching Luminescence in Lanthanide-doped Sc2(WO4)3

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc₂(WO₄)₃:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back-transfer the stored excitation energy to Ln³⁺ upon heating. Therefore, except routine anti-thermal quenching, thermally enhanced 415-fold downshifting and 405-fold upconversion luminescence are even obtained in Sc₂(WO₄)₃:Yb/Er, which has set a record of both the Yb³⁺-Er³⁺ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high-temperature luminescence.     

Separation and purification of quinolyridine alkaloids from seeds of Thermopsis lanceolata R. Br. by conventional and pH-zone-refining counter-current chromatography

In this work, the preparative separation of quinolyridine alkaloids from seeds of T. lanceolata by conventional and pH-zone-refining counter-current chromatography. Traditional counter-current chromatography separation was performed by a flow-rate changing strategy with a solvent system of ethyl acetate-n-butanol-water (1:9:10, v/v) and 200 mg sample loading. Meanwhile, the pH-zone-refining mode was adopted for separating 2.0 g crude alkaloid extracts with the chloroform-methanol-water (4:3:3, v/v) solvent system using the stationary and mobile phases of 40 mM hydrochloric acid and 10 mM triethylamine. Finally, six compounds, including N-formylcytisine (two conformers) ( 1 ), N-acetycytisine (two conformers) ( 2 ), (-)-cytisine ( 3 ), 13-β-hydroxylthermopsine ( 4 ), N-methylcytisine ( 5 ), and thermopsine ( 6 ) were successfully obtained in the two counter-current chromatography modes with the purities over 96.5%. Moreover, we adopted nuclear magnetic resonance and mass spectrometry for structural characterization. Based on the obtained findings, the pH-zone-refining mode was the efficient method to separate quinolyridine alkaloids relative to the traditional mode.