烯胺酮α-官能团化反应的研究进展

烯胺酮是一类非常重要的有机合成砌块,具有易获得、储存方便、反应多样性等优点.更重要的是,烯胺酮是许多杂环化合物的重要前体.最近,通过C—H活化对烯胺酮进行过渡金属催化或无过渡金属的α-官能团化反应已成为构建官能化烯胺酮或杂环化合物的一种更为原子和步骤经济的策略,并引起了许多有机化学家的关注.根据成键类型,该综述分为五个部分:C—C键的形成、C—O键的形成、C—N键的形成和C—X键的形成以及C—S/C—Se键的形成.主要对烯胺酮α位官能团化反应进行了综述,从反应机理、反应体系、底物范围等角度系统地综述了烯胺酮α位官能团化反应的进展.     

B(C6F5)3催化不饱和烃的硅化反应

有机硅化合物由于其独特的性质,在合成化学、药物化学、高分子化学和有机光电材料等领域具有广泛的应用.不饱和化合物的硅化反应是获得有机硅化合物的重要途径之一,因此引起了化学家的关注并取得了令人瞩目的进展.B(C₆F₅)₃作为一类独特的非金属路易斯酸,近年来,其催化不饱和烃的硅化取得了重要的研究进展,详细介绍了不饱和烃的硅化反应及机理研究.     

苯乙烯及其衍生物的生物氨羟化反应用于β-氨基醇的高效合成（英文）

氨基醇是非常重要的手性砌块,广泛用于药物、天然产物、氨基酸及其手性助剂的合成.迄今为止,超过300000种含有此类结构单元的化合物已被报道,其中包括2000多种天然产物、80多种已获批准的药物以及超过100种候选药物.鉴于β-氨基醇的重要作用,对映选择性高效合成β-氨基醇具有非常重大的意义.过去几十年,研究人员一直致力于β-氨基醇高效合成方法的开发.其中,通过利用过量的胺作为胺供体直接与环氧化物进行氨解反应,是合成β-氨基醇最为实用和认可的方法之一.此外,科学家也开发了使用各种路易斯酸或在不同有机溶剂中反应的化学法来提高环氧化物氨解反应的效率.然而,这些方法普遍存在反应温度高、催化剂用量大、催化剂对水敏感以及有机溶剂危害大等缺陷.为了解决这些问题,研究人员进一步开发出了水溶液体系中不依赖催化剂的环氧化物氨解反应,用于氨基醇高效合成.但该方法仍然需要以高反应活性的环氧化物作为起始原料,导致其在选择性控制和后期应用方面存在一定的问题.此外,环氧化物(尤其是手性环氧化物)难以制备,通常需要金属催化剂在苛刻的反应条件下进行.相比之下,以廉价易得的烯烃作为底物,通过Sharpless不对称胺羟化...     

捕捉环加成反应中的有机亚铜中间体构筑氮杂环化合物研究进展

铜(I)盐催化的环加成反应,如叠氮-炔[3+2]环加成(Cu AAC)、不饱和化合物与异氰基化合物的[3+2]环加成、硝酮-炔的环加成(Kinugasa反应)是构建多类氮杂环的高效合成方法,被广泛应用于有机合成的各个领域.近年来,针对几类环加成反应中产生的有机亚铜中间体的多样性转化吸引了国内外很多课题组的注意,基于对这些环加成反应中有机亚铜中间体的捕捉,多类串联及多组分反应得以发展,从而成功实现了一系列多取代杂环或稠环结构的高效构建.本综述总结了这一领域的研究进展,按照所经历的有机亚铜中间体的类型进行分类,包括:(1)Cu AAC反应中产生的三氮唑亚铜中间体;(2)炔烃与异氰化合物[3+2]环加成反应中产生的2H-吡咯基亚铜中间体;(3) Kinugasa反应中产生的烯醇亚铜中间体.期望此综述能够有助于研究者了解有机亚铜中间体捕捉策略的发展、应用现状及不足之处,进一步推动铜催化转化的发展.     

钯催化不对称烯丙基化/去对称化反应合成无保护基的2-喹啉酮骨架环状氨基酸（英文）

作为一类重要的含氮杂环化合物, 3-氨基-2-二氢喹啉酮结构存在于一些药物和生物活性分子中.目前还没有手性催化的方法直接合成无保护基的此类结构.在过渡金属的催化作用下,乙烯基苯并噁嗪酮脱除一分子二氧化碳,生成的两性离子中间体可以参与多种反应合成含氮杂环化合物.我们设想乙烯基苯并噁嗪酮和2-氨基丙二酸酯直接发生不对称烯丙基化反应/去对称化反应,则可直接实现无保护基2-喹啉酮骨架环状氨基酸的手性合成.然而2-氨基丙二酸酯作为亲核试剂时,如何实现碳选择性进攻而不是固有的氮选择性进攻将成为此反应中一个重要挑战.本文通过钯催化的不对称烯丙基化/去对称化反应合成具有2-喹啉酮骨架的环状氨基酸.采用手性膦配体与钯作为催化剂,成功实现了乙烯基苯并噁嗪酮与2-氨基丙二酸酯的不对称α-烯丙基取代反应.随后无需提纯,烯丙基取代产物直接在三氟乙酸的作用下,发生分子内的去对称化内酰胺化反应,最终生成具有无保护基的2-喹啉酮骨架环状氨基酸产物.该催化方法反应条件温和,催化体系简单高效(钯催化剂负载量可降低至1 mol%,非对映选择性可高达15/1,对映选择性高达96%ee),并且具有良好的官能团兼容性.经盐酸处理...     

用于电解水制氢的过渡金属有机骨架基催化剂

金属有机骨架(MOFs)材料因具有无机和有机的杂合性质、高度有序的多孔性、结构可修饰性、比表面积大和孔隙率高等特点,在催化领域具有广阔的应用前景。本文从氢能的开发利用角度出发,在纯MOFs、MOFs复合及衍生材料三个方面对近十年来过渡金属MOFs基催化剂在电解水制氢方面的重要研究进展进行了综述,着重针对材料的合成进行了探讨,以及在基础研究和产业应用的角度指出当前过渡金属MOFs基制氢催化剂面临的挑战和机遇,对其应用前景进行展望。     

P修饰提高Fe-N-C的氧反应活性用于高稳定的锌-空气电池（英文）

生物质碳基材料具有可调的微观结构、丰富的表面活性中心、优良的导电和导热性能以及较大的比表面积,已经成为新能源领域的重要基础材料.然而,应用于锌-空气电池中时,碳基材料高电位下的碳腐蚀问题严重影响了电池的稳定性,因此,开发具有低过电位的析氧反应(OER)催化剂来降低充电电压是解决该问题的关键.本课题组采用一种低温磷化策略制备了具有低OER过电位的P修饰的Fe₃O₄/Fe₂N和生物质碳复合催化剂(P-Fe₃O₄/Fe₂N@NPC),其具有较好的双功能氧反应活性,氧还原反应(ORR)的半波电位为0.86 V,仅需要280 m V的OER过电位就可以达到10 m Acm^-2的电流密度.以P-Fe₃O₄/Fe₂N@NPC作为正极组装的锌-空气电池表现出低的充放电电压差和长期稳定性,在目前报道的碳基催化剂应用于锌-空气电池中具有很大优势.此外,采用X射线光电子能谱(XPS)、拉曼光...     

利用空间位阻和氢溢流协同作用促进5-羟甲基糠醛选择性加氢制备5-甲基糠醛

Selective hydrogenation is a vital class of reaction. Various unsaturated functional groups in organic compounds, such as aromatic rings, alkynyl (C≡C), carbonyl (C＝O), nitro (-NO₂), and alkenyl (C＝C) groups, are typical targets in selective hydrogenation. Therefore, selectivity is a key indicator of the efficiency of a designed hydrogenation reaction. 5-(Hydroxymethyl)furfural (HMF) is an important platform compound in the context of biomass conversion, and recently, the hydrogenation of HMF to produce fuels and other valuable chemicals has received significant attention. Controlling the selectivity of HMF hydrogenation is paramount because of the different reducible functional groups (C＝O, C-OH, and C＝C) in HMF. Moreover, the exploration of new routes for hydrogenating HMF to valuable chemicals is becoming attractive. 5-Methylfurfural (MF) is also an important organic compound; thus, the selective hydrogenation of HMF to MF is an essential synthetic route. However, this reaction has challenging thermodynamic and kinetic aspects, making it difficult to realize. Herein, we propose a strategy to design a highly efficient catalytic system for selective hydrogenation by exploiting the synergy between steric hindrance and hydrogen spillover. The design and preparation of the Pt@PVP/Nb₂O₅ catalyst (PVP = polyvinyl pyrrolidone; Nb₂O₅ = niobium(V) oxide) were also conducted. Surprisingly, HMF could be converted to MF with 92% selectivity at 100% HMF conversion. The reaction pathway was revealed through the combination of control experiments and density functional theory calculations. Although PVP blocked HMF from accessing the surface of Pt, hydrogen (H₂) could be activated on the surface of Pt due to its small molecular size, and the activated H₂ could migrate to the surface of Nb₂O₅ through a phenomenon called H₂ spillover. The Lewis acidic surface of Nb₂O₅ could not adsorb the C＝O group but could adsorb and activate the C-OH group of HMF; therefore, when HMF was adsorbed on Nb₂O₅, the C-OH groups were hydrogenated by the spilled over H₂ to form MF. The high selectivity of this reaction was realized because of the unique combination of steric effects, hydrogen spillover, and tuning of the electronic states of the Pt and Nb₂O₅ surfaces. This new route for producing MF has great potential for practical application owing to its discovered advantages. We believe that this novel strategy can be used to design catalysts for other selective hydrogenation reactions. Furthermore, this study demonstrates a significant breakthrough in selective hydrogenation, which will be of interest to researchers working on the utilization of biomass, organic synthesis, catalysis, and other related fields.      

纳米SiC基光催化剂研究进展

Industrialization undoubtedly boosts economic development and improves the standard of living; however, it also leads to some serious problems, including the energy crisis, environmental pollution, and global warming. These problems are associated with or caused by the high carbon dioxide (CO₂) and sulfur dioxide (SO₂) emissions from the burning of fossil fuels such as coal, oil, and gas. Photocatalysis is considered one of the most promising technologies for eliminating these problems because of the possibility of converting CO₂ into hydrocarbon fuels and other valuable chemicals using solar energy, hydrogen (H₂) production from water (H₂O) electrolysis, and degradation of pollutants. Among the various photocatalysts, silicon carbide (SiC) has great potential in the fields of photocatalysis, photoelectrocatalysis, and electrocatalysis because of its good electrical properties and photoelectrochemistry. This review is divided into six sections: introduction, fundamentals of nanostructured SiC, synthesis methods for obtaining nanostructured SiC photocatalysts, strategies for improving the activity of nanostructured SiC photocatalysts, applications of nanostructured SiC photocatalysts, and conclusions and prospects. The fundamentals of nanostructured SiC include its physicochemical characteristics. It possesses a range of unique physical properties, such as extreme hardness, high mechanical stability at high temperatures, a low thermal expansion coefficient, wide bandgap, and superior thermal conductivity. It also possesses exceptional chemical characteristics, such as high oxidation and corrosion resistance. The synthesis methods for obtaining nanostructured SiC have been systematically summarized as follows: Template growth, sol-gel, organic precursor pyrolysis, solvothermal synthesis, arc discharge, carbon thermal reduction, and electrospinning. These synthesis methods require high temperatures, and the reaction mechanism involves SiC formation via the reaction between carbon and silicon oxide. In the section of the review involving the strategies for improving the activity of nanostructured SiC photocatalysts, seven strategies are discussed, viz., element doping, construction of Z-scheme (or S-scheme) systems, supported co-catalysts, visible photosensitization, construction of semiconductor heterojunctions, supported carbon materials, and construction of nanostructures. All of these strategies, except element doping and visible photosensitization, concentrate on enhancing the separation of holes and electrons, while suppressing their recombination, thus improving the photocatalytic performance of the nanostructured SiC photocatalysts. Regarding the element doping and visible photosensitization strategies, element doping can narrow the bandgap of SiC, which generates more holes and electrons to improve photocatalytic activity. On the other hand, the principle of visible photosensitization is that photo-induced electrons move from photosensitizers to the conduction band of SiC to participate in the reaction, thus enhancing the photocatalytic performance. In the section on the applications of nanostructured SiC, photocatalytic H₂ production, pollutant degradation, CO₂ reduction, photoelectrocatalytic, and electrocatalytic applications will be discussed. The mechanism of a photocatalytic reaction requires the SiC photocatalyst to produce photo-induced electrons and holes during irradiation, which participate in the photocatalytic reaction. For example, photo-induced electrons can transform protons into H₂, as well as CO₂ into methane, methanol, or formic acid. Furthermore, photo-induced holes can convert organic waste into H₂O and CO₂. For photoelectrocatalytic and electrocatalytic applications, SiC is used as a catalyst under high temperatures and highly acidic or basic environments because of its remarkable physicochemical characteristics, including low thermal expansion, superior thermal conductivity, and high oxidation and corrosion resistance. The last section of the review will reveal the major obstacles impeding the industrial application of nanostructured SiC photocatalysts, such as insufficient visible absorption, slow reaction kinetics, and hard fabrication, as well as provide some ideas on how to overcome these obstacles.      

高分子材料的生物降解性能表征

生物降解能够使高分子材料回归自然界物质循环,被认为是解决塑料污染的一大重要途径.高分子材料的生物降解性能表征对相关材料开发、改性和产业应用十分重要.本文针对高分子材料的需氧生物降解,从降解产物和降解残留材料两个方面介绍常用表征方法 .降解产物的表征主要从CO2生成量、O2消耗量和小分子产物三方面开展,降解残留材料的表征围绕其组成结构变化和性能变化.介绍了各表征方法的简单原理和典型案例,并对未来发展进行了展望.