A post-modification strategy to precisely construct dual-atom sites for oxygen reduction electrocatalysis

Dual-atom catalysts(DACs) afford promising potential for oxygen reduction electrocatalysis due to their high atomic efficiency and high intrinsic activity.However,precise construction of dual-atom sites remains a challenge.In this work,a post-modification strategy is proposed to precisely fabricate DACs for oxygen reduction electrocatalysis.Concretely,a secondary metal precursor is introduced to the primary single-atom sites to introduce direct metal-metal interaction,which ensures the formation of desired atom pair structure during the subsequent pyrolysis process and allows for successful construction of DACs.The as-prepared FeCo-NC DAC exhibits superior oxygen reduction electrocatalytic activity with a half-wave potential of 0,91 V vs.reversible hydrogen electrode.Zn-air batteries equipped with the FeCo-NC DAC demonstrate higher peak power density than those with the Pt/C benchmark.More importantly,this post-modification strategy is demonstrated universal to achieve a variety of dual-atom sites.This work presents an effective synthesis methodology for precise construction of catalytic materials and propels their applications in energy-related devices.

An altemative synthetic approach towards erythrinan and homoerythrinan alkaloids by tandem semipinacol/intramolecular Schmidt reaction

An alternative construction of A-B-D ring-system of erythrinan and homoerythrinan alkaloids by TiCl4-mediated tandem semipinacol/intramolecular Schmidt reaction of α-siloxyepoxyazide was addressed and the unusual epoxidation stereoselectivity was observed in preparation of the substrate once again.

Synthesis of Spiro Dihydrofurans and 1,8-Dioxo-xanthenes via DABCO Catalyzed Tandem Reaction of Aldehyde with Cyclohexane-1,3-dione and Dimedone

The 1,4-diazabicyclo[2.2.2]octane（DABCO） catalyzed reaction of cyclohexane-1,3-dione or dimedone with various aldehydes in acetonitrile resulted in the polysubstituted tetraketones, spiro dihydrofurans or 1,8-dioxo-xanthenes derivatives as main products respectively according to the structure of reactants and reaction conditions.

Novel Tandem Three Consecutive Reactions: Aza-Wittig, Imine Condensation and Electrophilic Aromatic Substitution Strategy to Indolizine Synthesis

Reaction of ethyl (Z)-3-(heteroaryl/aryl)-2-((triphenyl-λ5-phosphaneylidene) amino) acrylates intermediates with 2,3-thiophenedicarboxaldehyde was used in novel Tandem three consecutive reactions: aza-Wittig, imine condensation and electrophilic heteroaromatic cyclization to obtain a series of indolizines. A tentative mechanism of this reaction is proposed.

SYNTHESIS OF A POTENTIAL ANTIFEEDANT SESOUITERPENE INTERMEDIATE FROM A NEW TERPENOID A, B-RING SYNTHON BY TANDEM NICHAEL REACTION

An efficient synthesis of functionalized 6-decalone 16, starting from a dienolate anion 3a via a tandem Michael reaction, is described. 16 could be used as a potential intermediate for synthesis of drimane related sesquiterpenes.

Synergetic enhancement of selectivity for electroreduction of CO_(2)to C_(2)H_(4)by crystal facet engineering and tandem catalysis over silver-incorporated-cuprous oxides

Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electrosynthesis limits its implementation in industrially interesting processes.Herein,we report a composite structured catalyst composed of Ag and Cu_(2)O with different crystal faces to achieve highly efficient reduction of CO_(2)to C_(2)H_(4).The catalyst composed of Ag and octahedral Cu_(2)O enclosed with(111)facet exhibits the best CO_(2)electroreduction performance,with the Faradaic efficiency(FE)and partial current density reaching 66.8%and 17.8 mA cm2 for C_(2)H_(4)product at-1.2 VRHE in 0.5 M KHCO_(3),respectively.Physical characterization and electrochemical test analysis indicate that the high selectivity for C_(2)H_(4)product stems from the synergistic effect of crystal faces control engineering and tandem catalysis.Specifically,Ag can provide optimal availability of CO intermediate by suppressing hydrogen evolution;subsequently,C-C coupling is promoted on the intimate surface of Cu_(2)O with facetdependent selectivity.The insights gained from this work may be beneficial for designing efficient multicomponent catalysts for improving the selectivity of electrochemical CO_(2)reduction reaction to generate C2þproducts.

ICP-MS/MS测定轻质油中痕量氯含量

基于H_(2)反应模式下的质量转移反应消除干扰,建立电感耦合等离子体串联质谱(ICP-MS/MS)测定轻质油中痕量Cl的分析方法。轻质油经简单稀释后直接采用ICP-MS/MS进行测定,在MS/MS模式下使用H_(2)作为反应气,利用在碰撞/反应池(CRC)中Cl^(+)与H_(2)发生二次H原子转移反应形成的子离子(H_(2)Cl^(+))进行测定,消除所有质谱干扰,获得Cl的灵敏度和检出限(LOD)明显优于O_(2)反应模式,LOD低至7.56μg/kg。通过与扇型磁场ICP-MS(SF-ICP-MS)对比分析标准参考物质NIST SRM 1634c,评价方法的准确可靠性。结果表明,标准参考物质的分析结果与认证值基本一致,相对标准偏差(RSD)为3.1%~4.7%,2种方法的对比分析结果在95%的置信度水平无显著性差异。所建立分析方法的灵敏度、准确度和和精密度高,MS/MS模式和H_(2)质量转移法的结合可无干扰测定轻质油中的Cl,适用于轻质油中痕量Cl的质量控制与评估。

一例三(5-氯苯并噻唑-2-甲基)胺Fe(Ⅱ)配合物的串联合成过程及电催化性质研究

三(芳基甲基)胺由于强配位性,在氧气活化的单/双金属非血红素金属蛋白类似物的合成中起着重要作用,且能够作为加速配体催化Click反应,因而受到广泛关注。本研究以苯并[d]噻唑-2-基甲胺(S1)和5-氯苯并[d]噻唑-2-基)甲醇(L1)为原料,在FeCl_(3)·6H_(2)O的催化下,串联合成得到了一例新颖的三(5-氯苯并噻唑甲基)胺Fe(Ⅱ)配合物1。用X-射线单晶衍射仪、X-射线粉末衍射仪、电喷雾离子化质谱确证了结构,通过晶体学和电喷雾离子质谱相结合,研究了反应过程,检测到了一系列关键中间体片段([i-Cl]^(+)、[ii+H]^(+)、[iii-Cl]^(+)),结合反应过程跟踪提出了可能的反应机理,包括N-烷基化,氧化水解等步骤,实现了3个共价键的连续构筑。对配合物1进行了OER(析氧反应)测试及稳定性性能研究,其中过电势为391 mV,Tafel斜率为95.9 mV·dec^(-1),在电极密度10 mA/cm^(2)下进行了10 h的恒电流电解,在该时间范围内稳定性良好。通过对配合物1的电催化性能研究则为后续该配体的应用领域提供一种新的方向。

UPLC-MS/MS法同时测定蛋白饮料和液体调味品中36种防腐剂

采用提取和净化相结合的前处理方式,建立并优化了同时测定蛋白饮料、液体调味品中36种防腐剂的超高效液相色谱-串联质谱检测方法。样品采用饱和NaCl溶液(用磷酸调节pH=3)净化和乙腈-甲醇(9∶1,体积比)(含体积分数为0.2%的甲酸)提取。采用C18反向色谱柱进行分离,以甲醇和5 mmol/L乙酸铵为流动相梯度洗脱,采用电喷雾离子源正负离子同时扫描,动态多反应监测模式,基质匹配标准曲线,外标法定量。结果表明,36种防腐剂在1~250 ng/mL线性良好(相关系数≥0.999),方法定量限为0.04~0.2 mg/kg;空白样品不同加标水平下的平均加标回收率为75%~119%;相对标准偏差为0.90%~9.8%。建立的高通量检测方法灵敏、快速,准确度高,操作简便且能有效减少基质干扰、降低检测成本,极大提高多种防腐剂的定性定量检测效率。

QuEChERS-超高效液相色谱-串联质谱法测定野生菌中的15种蘑菇毒素

目的基于线性离子阱质谱的多重反应监测-信息依赖采集-增强子离子扫描(multiple reaction monitoring-information dependent acquisition-enhanced product ion scan,MRM-IDA-EPI)二级谱图筛查方法,建立超高效液相色谱-串联质谱法(ultra performance liquid chromatography-tandem mass spectrometry,UPLC-MS/MS)定量检测和定性筛查野生菌中15种蘑菇毒素。方法野生菌样本通过甲酸-甲醇-水-乙腈(1:40:40:19,V:V:V:V)混合溶液超声提取,QuEChERS试剂提取净化,采用UPLC-MS/MS和MRM-IDA-EPI方法对15种蘑菇毒素进行定量分析和定性筛查。结果通过野生菌样本前处理方法和色谱条件优化,对15种蘑菇毒素进行0.04、0.10和0.40 mg/kg三水平加标回收实验,方法准确度为76.6%~109.2%,精密度为0.3%~7.6%;15种蘑菇毒素的线性范围为10~1000μg/L,线性相关系数(r)在0.9980~0.9994之间;其中α-鹅膏毒肽、β-鹅膏毒肽、γ-鹅膏毒肽、光盖伞素和鹅膏蕈氨酸的方法检出限(limits of detection,LODs)和定量限(limits of quantification,LOQs)分别为10μg/kg和30μg/kg,二羟鬼笔毒肽、羧基二羟鬼笔毒肽、羧基三羟鬼笔毒肽、毒蝇碱、蝇蕈醇、甲基裸盖菇素、鹿花菌素、脱磷酸裸盖菇素、奥来毒素和鬼伞菌素的LODs和LOQs分别为20μg/kg和60μg/kg,采用QuEChERS前处理方法对野生菌样本进行处理,样本基质效应系数K值在0.91~1.08之间。结论所建立的野生菌样本前处理方法对15种蘑菇毒素的定量测定无基质干扰,15种蘑菇毒素的UPLC-MS/MS和MRM-IDA-EPI分析方法结果准确、重现性好、灵敏度高,该方法适用于有毒野生菌引起的食源性中毒定量分析和定性筛查。

Metal-Free Synthesis of 2-Aminobenzothiazoles via I2-Catalyzed Tandem Cyclization Reaction of Amines and Carbon Disulfide

Comprehensive Summary,A convenient approach for the construction of 2-aminobenzothiazoles via I2-catalyzed tandem cyclization reaction of amines and carbon disulfide has been developed.The present approach starts from simple and readily available starting materials,affording a series of 2-aminobenzothiazoles in up to 89%yields under metal-free conditions.In this work,C—H/N—H functionalization was achieved and multiple C-hetero bonds were successfully constructed in one pot.

串联反应一锅合成茚酮稠合1,5-苯并二氮杂䓬化合物

以取代的邻苯二胺、1,3-茚满二酮、醛类化合物(苯乙醛,苯丙醛)为原料,无水乙醇为溶剂,对甲苯磺酸为催化剂,应用串联反应一锅合成了8种结构新颖的茚酮稠合1,5-苯并二氮杂䓬化合物.该串联反应经历了两次亲核加成-消除反应过程,形成含烯胺和亚胺结构的活性中间体,再经分子内碳碳偶联环合和质子迁移形成了目标化合物,针对该三组分串联反应提出了合理的反应机制.该方法具有新颖、绿色环保、反应条件温和、底物范围广等诸多优点,为苯并二氮杂䓬化合物的合成提供了高效简便的新思路.

Tandem catalysis of Cu/Ni multi-sites promotes oxygen reduction reaction

The special electronic characteristics and high atom usage efficiency of metal-nitrogen-carbon(M-N-C)materials have made them extremely attractive for oxygen reduction reactions(ORRs).However,it is inevitable that hydrogen peroxide(H_(2)O_(2))will be formed via the two-electron pathway in ORRs.Herein,the Cu nanoparticles(NPs)have been encapsulated into Ni doped hollow mesoporous carbon spheres(Ni-HMCS)to reduce the generation of H_(2)O_(2)in ORR.Electrochemical tests confirm that the introduction of Cu NPs improves the ORR performance greatly.The obtained Cu/Ni-HMCS exhibits a half-wave potential of 0.82 V vs.reversible hydrogen electrode and a limited current density of 5.5 mA cm^(-2),which is comparable with the commercial Pt/C.Moreover,Cu/Ni-HMCS has been used in Zn-air battery,demonstrating a high power density of 161 mW cm^(-2)and a long-term recharge capability(50 h at 5 mA cm^(-2)).The theoretical calculation proposes a tandem catalysis pathway for Cu/Ni multi-sites catalysis,that is,H_(2)O_(2)released from the Ni-N_(4)and Cu-N_(4)sites migrates to the Cu(111)face,on which the captive H_(2)O_(2)is further reduced to H_(2)O.This work demonstrates an interesting tandem catalytic pathway of dual-metal multi-sites for ORR,which provides an insight into the development of effective fuel cell electrocatalysts.

A H_(4)SiW_(12)O_(40)-catalyzed three-component tandem reaction for the synthesis of 3,3-disubstituted isoindolinones

A H_(4)SiW_(12)O_(40)-catalyzed three-component tandem reaction of 2-acylbenzoic acids,primary amines and phosphine oxides to form 3,3-disubstituted isoindolinones was developed.By employing A H_(4)SiW_(12)O_(40)as the catalyst and dimethyl carbonate(DMC)as the solvent,a diverse range of 2-acylbenzoic acid derivatives and primary amines worked well to give the C3-phosphinoyl-functionalized 3,3-disubstituted isoindolinones with the yield range of 61%-87%.Advantages of this transformation include green catalyst and solvent,available starting materials,broad substrate scope,high efficiency and operational simplicity with water as the sole by-product.The strategy achieved an efficient and green molecular fragment assembly to access isoindolinones,which would provide opportunities for the synthesis of potential biologically active molecules in a green manner.

气相色谱-串联质谱法测定化妆品中15种防腐剂类过敏原物质

防腐剂成分大多具有刺激性,容易造成皮肤过敏,国内外对其在化妆品中的使用有明确的禁、限量规定。研究通过气相色谱-串联质谱(GC-MS/MS)同时测定化妆品中15种防腐剂类过敏原物质的含量,建立了基于“两柱保留指数、一个质谱匹配度”的精确鉴定方法,通过外标法定量。样品经过乙腈涡旋超声提取,无水硫酸镁除水后,分别采用DB-5MS和DB-WAX色谱柱分离检测,以电子轰击离子(EI)源为离子源,通过多反应监测模式(MRM)采集数据信息,使用保留指数对15种防腐剂类过敏原物质进行定性。经两次检测,15种防腐剂类过敏原物质在DB-5MS色谱柱上方法的检出限为0.02~0.2 mg/kg,12种防腐剂类过敏原物质在DB-WAX色谱柱上方法的检出限为0.01~20 mg/kg。防腐剂类过敏原物质在DB-5MS和DB-WAX色谱柱上均在一定范围内线性关系良好,相关系数均大于0.99。以水、乳、面膜、膏霜为代表基质,在低、中、高3个加标水平下,15种防腐剂过敏原物质在DB-5MS和DB-WAX色谱柱上的回收率在70.1%~129.8%范围内,相对标准偏差(RSD)均小于15%(n=6)。采用建立的方法对80批实际样品进行检测,在DB-5MS和DB-WAX色谱柱条件下,有两批样品中均检测出禁用防腐剂4-羟基苯甲酸异丙酯;DB-5MS色谱柱条件下,有11种限用防腐剂被检出,DB-WAX色谱柱条件下,10种限用防腐剂被检出。检测结果表明:该方法使用双柱系统,准确性高,能有效避免假阳性和假阴性的检测结果,可用于化妆品中15种防腐剂类过敏原物质的检测,使用保留指数对15种防腐剂类过敏原物质进行定性,为非定向筛查提供了思路,满足监管需求。

Propane dehydro-aromatization reaction over PtFe@S-1 coupling with Zn/ZSM-5 tandem catalysts: the role of Zn species

Unraveling the structure-activity relationship and improving the catalytic performance is paramount in propane dehydro-aromatization reactions. Herein, a tandem catalyst with high propane dehydro-aromatization reaction performance was prepared via coupling the PtFe@S-1 with Zn/ZSM-5 zeolites (PtFe@S-1&1.0Zn/ZSM-5), which exhibits high dehydrogenation activity, aromatics selectivity (~60% at ~78% propane conversion), and stability. The addition of zinc inhibits the cleavage of C_(6)^(=) intermediates on ZSM-5 and promotes the aromatization pathway by weakening zeolite acid strength, significantly improving the selectivity to aromatics. This understanding of the structure-activity relationship in propane dehydro-aromatization reaction helps develop future high-performance catalysts.

A Bioorthogonal Post-modification of N^(6)-Isopentenyl Adenosine i^(6) A RNA in Live Cells

Selective methods for modulating RNA epigenetic modifications within living cells and organisms represent attractive techniques for investigating biological functions and medicinal application.In contrast to enzymatic methods,abiotic chemical modulation offers access to diverse new-to-natural functionalities.We herein report a visible light-assisted bioorthogonal reaction involving flavin mononucleotide,sodium azide,and blue light irradiation.In concert with previous chemical approaches mimicking the demodification pathway,our system functions as a powerful and selective post-modification enzyme that targets N^(6)-prenyl adenosine i^(6) A in RNA and enables the efficient construction of an artificial N^(6)-cyanomethyl adenosine(cnm^(6) A).Notably,most endogenous biomacromolecular functions,including other common RNA epigenetics,remained unaffected.Consequently,we have successfully modified i^(6) A in tRNA to cnm^(6) A in human cells and establish this system as a bona fide bioorthogonal reaction with potential applications in chemical biology and in-cell modulation.

铜(Ⅰ)催化氧化无溶剂合成苯并吖啶二酮衍生物

建立了一种苯并吖啶二酮衍生物的绿色合成方法,以2-(苯基氨基)萘-1,4-二酮类化合物与氰乙酸乙酯为原料,在铜(Ⅰ)与绿色氧化剂过氧叔丁醇的催化氧化体系下,通过无溶剂的自由基串联反应合成9个苯并吖啶二酮衍生物3a~3i,收率72%~79%.该合成策略绿色环保、操作简单(萃取和洗涤,无柱色谱分离)、原料简单易得,为高效合成具有潜在生物活性的苯并吖啶二酮衍生物提供了新的途径.

可见光介导多组分一锅法合成仲胺化合物及其机理探究

将有机光化学领域的前沿研究引入到本科实验教学中,以苯甲醛、苯胺和4-异丙基-1,4-二氢吡啶作为起始原料,在温和条件下进行可见光介导的一锅法串联反应,实现了仲胺化合物的制备。实验具有原料廉价易得、反应条件温和、安全性高、操作简单等特点,同时融入绿色化学理念和有机合成方法学的实验探究过程,适用于本科实验教学,可帮助学生在熟练实验操作的同时,增强对光化学反应、一锅法串联反应、自由基反应等知识的理解。本实验将新的科研成果转化为人才培养内容,有助于提高学生的科研创新与实践能力。

QuEChERS结合大体积进样法测定水产干制品中N-二甲基亚硝胺

目的基于大体积进样(large-volume injections,LVI)系统建立QuEChERS结合气相色谱-串联三重四极杆质谱法测定水产干制品中N-二甲基亚硝胺化合物含量的分析方法。方法称取样品5 g,加5 mL水稀释后加入内标,经乙腈提取,提取液经PLS-A和ProElutQuE 15 mL Tube净化后,得到上机液。在多模式进样口(multi mode injection,MMI)中选择LVI模式进样,采用HP-INNOWAX石英毛细管柱(30 m×0.25 mm,0.25μm)分离,选择多反应监测(multiple reaction monitoring,MRM)模式进行测定,内标法定量。结果N-二甲基亚硝胺在0.1~20.0 ng/mL范围内呈现良好的线性关系,相关系数(r^(2))为0.9994,检出限为0.03μg/kg。在空白基质(不含N-二甲基亚硝胺化合物)样品中分别添加1、3、10μg/kg的3个水平混合标准溶液进行加标回收实验,加标回收率为85.7%~102.3%,相对标准偏差为3.6%~9.8%(n=6)。结论本法称样量少、有机试剂用量少、灵敏度高,能够满足水产干制品中N-二甲基亚硝胺含量的检测分析。