Photocatalytic Generation of N‐Centered Hydrazonyl Radicals: A Strategy for Hydroamination of β,γ‐Unsaturated Hydrazones

A visible‐light photocatalytic generation of N‐centered hydrazonyl radicals has been accomplished for the first time. This approach allows efficient intramolecular addition of hydrazonyl radical to terminal alkenes, thus providing hydroamination and oxyamination products in good yields. Importantly, the protocol involves deprotonation of an N? H bond and photocatalytic oxidation to an N‐centered radical, thus obviating the need to prepare photolabile amine precursors or the stoichiometric use of oxidizing reagents.     

合成生物学展望

近年来,合成生物学快速发展成为一个新兴交叉学科领域,研究重点逐渐由基因线路、简单元件和模块的设计构建转向设计与构建复杂的人工生物系统.本文阐述了合成生物学与化学工程学科的内在联系,并从基因组的人工设计合成与编辑、人工细胞的设计合成、人工合成多细胞体系及其应用等方面展望了未来合成生物学的发展趋势.     

SiBeta负载的VO_x催化剂在丙烷直接脱氢制丙烯中的活性位（英文）

丙烯是一种非常重要的化工基础原料,主要用来生产高价值的化学品,如丙烯腈,异丙醇和甘油等.丙烯的传统来源主要是石油的催化裂化反应,以及石脑油和轻柴油的裂解过程.随着石油资源的减少,丙烷直接脱氢制丙烯技术逐渐成为一条重要的丙烯生产渠道.V基催化剂在丙烷氧化脱氢反应中被广泛研究,但被用于丙烷直接脱氢反应的报道还较少,且V基催化剂在丙烷直接脱氢制丙烯中的活性位目前还没有统一定论,可能是由于V的活性物种与载体性质密切相关,因此研究V基催化剂在不同载体上的活性位具有重要意义.Beta沸石分子筛具有规则微孔结构,高的比表面积以及可调节的酸性,是一种理想的金属催化剂载体.本文采用脱铝后的Beta分子筛作为V催化剂载体,通过调节V的负载量探究丙烷直接脱氢活性和VO_x结构的关系,以及催化剂的酸性对性能的影响.活性测试结果显示,V负载量分别为3wt%,7wt%和10wt%时(催化剂分别命名为3VSiBeta,7VSiBeta和10VSiBeta),三者的催化活性十分接近,此外,这些催化剂还具有较好的循环利用性,但碳沉积,丙烯选择性以及失活率都是随着V负载量的升高而增加.XRD和N2吸附结果揭示,VO_x在SiBeta上呈高度分散状态,并且当V负载量从3wt%升至10wt%时,表面V密度发生明显变化,VO_x物种在3VSiBeta中可基本实现孤立的单分散状态.同时,DRUV-vis,H2-TPR以及Raman测试结果表明,VO_x物种的聚合程度随V负载量的升高逐渐增加.NH^3-TPD结果表明,Beta载体在脱铝后本身的酸性位完全消除,但是负载V后引入了新的酸性位,并且3VSiBeta,7VSiBeta和10VSiBeta三者的酸量基本相当.尽管XPS结果显示,不同VSiBeta催化剂上的V价态分布有差异,但是相似的催化活性说明VSiBeta催化剂的活性位与形成的酸性位数目密切相关,而受V初始价态的影响不大.本文指出,酸性位可能是与V–O–Si键直接相关,V负载量从3wt%增加到10wt%,会逐渐形成无催化活性的V–O–V键,导致活性不能进一步提升.因此,3VSiBeta催化剂中可实现孤立的VO_x物种单层分散在SiBeta载体上,形成了大量的酸性V–O–Si键,从而显示出和高负载量的VSiBeta催化剂相当的活性以及较高的脱氢稳定性.     

Driving Helical Packing of a Cyanine Dye on Dendron Nanofiber: Gel‐Shrinkage‐Triggered Chiral H‐Aggregation and Enhanced Enantiodiscrimination

An intelligent molecular hydrogel with a volume phase transition was constructed to regulate the chiral packing of a well‐known cyanine dye on a dynamically self‐assembled chiral nanofiber by using a pH trigger. During the shrinkage of the gel, the chiral nanofiber hierarchically assembled into a superhelix and simultaneously drove the dye molecules to stack, from a predominantly monomer form, in an unexpected helical H‐aggregation manner. Through such a transformation, the supramolecular chirality of the system was significantly enhanced and a new property of visual discrimination for chiral amines emerged.     

A Dual‐Response Fluorescent Probe Reveals the H2O2‐Induced H2S Biogenesis through a Cystathionine β‐Synthase Pathway

The two signaling molecules H₂S and H₂O₂ play key roles in maintaining intracellular redox homeostasis. The biological relationship between H₂O₂ and H₂S remains largely unknown in redox biology. In this study, we rationally designed and synthesized single‐ and dual‐response fluorescent probes for detecting both H₂O₂ and H₂S in living cells. The dual‐response probe was shown to be capable of mono‐ and dual‐detection of H₂O₂ and H₂S selectively and sensitively. Detailed bioimaging studies based on the probes revealed that both exogenous and endogenous H₂O₂ could induce H₂S biogenesis in living cells. By using gene‐knockdown techniques with bioimaging, the H₂S biogenesis was found to be majorly cystathionine β‐synthase (CBS)‐dependent. Our finding shows the first direct evidence on the biological communication between H₂O₂ (ROS) and H₂S (RSS) in vivo.     

Organic Photocatalytic Cyclization of Polyenes: A Visible‐Light‐Mediated Radical Cascade Approach

A visible‐light‐mediated, organic photocatalytic stereoselective radical cascade cyclization of polyprenoids is described. The desired cascade cyclization products are achieved in good yields and high stereoselectivities with eosin Y as photocatalyst in hexafluoro‐2‐propanol. The catalyst system is also suitable for 1,3‐dicarbonyl compounds, which require only catalytic amounts of LiBr to promote the formation of the corresponding enols.     

The First Introduction of Graphene to Rechargeable Li–CO2 Batteries

The utilization of the greenhouse gas CO₂ in energy‐storage systems is highly desirable. It is now shown that the introduction of graphene as a cathode material significantly improves the performance of Li–CO₂ batteries. Such batteries display a superior discharge capacity and enhanced cycle stability. Therefore, graphene can act as an efficient cathode in Li–CO₂ batteries, and it provides a novel approach for simultaneously capturing CO₂ and storing energy.     

Silver‐Mediated Oxidative Aliphatic CH Trifluoromethylthiolation

The first example of a practical and direct trifluoromethylthiolation reaction of unactivated aliphatic C? H bonds employs a silver‐based reagent. The reaction is operationally simple, scalable, and proceeds under aqueous conditions in air. Furthermore, its broad scope and good functional‐group compatibility were demonstrated by applying this method to the selective trifluoromethylthiolation of natural products and natural‐product derivatives.     

Nature‐Inspired Environmental “Phosphorylation” Boosts Photocatalytic H2 Production over Carbon Nitride Nanosheets under Visible‐Light Irradiation

Inspired by the crucial roles of phosphates in natural photosynthesis, we explored an environmental “phosphorylation” strategy for boosting photocatalytic H₂ production over g‐C₃N₄ nanosheets under visible light. As expected, a substantial improvement was observed in the rate of H₂ evolution to 947 μmol h^?1, and the apparent quantum yield was as high as 26.1 % at 420 nm. The synergy of enhanced proton reduction and improved hole oxidation is proposed to account for the markedly increased activity. Our findings may provide a promising and facile approach to highly efficient photocatalysis for solar‐energy conversion.