联二萘酚酰基硫脲催化下吲哚衍生物的高效合成

研究了多种多功能氢键型手性催化剂联二萘酚酰基硫脲在吲哚与硝基烯烃的不对称Friedel-Crafts烷基化反应中的应用。结果显示:该类催化剂中联二萘酚独特的空间结构和强的氢键催化作用使合成的吲哚衍生物具有良好的化学产率(高达91%)和对映选择性(高达93%ee)。该工艺操作简单、反应条件温和、催化剂高效且用量少、底物具有很好的官能团耐受性。

基于探究式教学模式对预阳极化前后的玻碳电极测定对乙酰氨基酚的伏安图差异的分析及机理讨论

基于电极反应活化能,预阳极化前后玻碳电极表面结构变化及氢键催化作用,以探究式教学模式讨论了预阳极化前后的玻碳电极测定对乙酰氨基酚的伏安图差异形成的原因。这种教学模式不仅有利于提高实验课教学质量,也会促进教师自身业务能力的提高。

Superposition of dual electric fields in covalent organic frameworks for efficient photocatalytic hydrogen evolution

Covalent organic frameworks(COFs)are promising materials for converting solar energy into green hydrogen.However,limited charge separation and transport in COFs impede their application in the photocatalytic hydrogen evolution reaction(HER).In this study,the intrinsically tunable internal bond electric field(IBEF)at the imine bonds of COFs was manipulated to cooperate with the internal molecular electric field(IMEF)induced by the donor-acceptor(D-A)structure for an efficient HER.The aligned orientation of IBEF and IMEF resulted in a remarkable H_(2) evolution rate of 57.3 mmol·g^(-1)·h^(-1)on TNCA,which was approximately 520 times higher than that of TCNA(0.11 mmol·g^(-1)·h^(-1))with the opposing electric field orientation.The superposition of the dual electric fields enables the IBEF to function as an accelerating field for electron transfer,kinetically facilitat-ing the migration of photogenerated electrons from D to A.Furthermore,theoretical calculations indicate that the inhomogeneous charge distribution at the C and N atoms in TNCA not only pro-vides a strong driving force for carrier transfer but also effectively hinders the return of free elec-trons to the valence band,improving the utilization of photoelectrons.This strategy of fabricating dual electric fields in COFs offers a novel approach to designing photocatalysts for clean energy synthesis.

离子液体反应体系的氢键作用

离子液体是由有机阳离子和无机/有机阴离子组成的一类低温熔融盐,具有高度的功能可设计性.氢键作用广泛存在于离子液体体系中,由于静电作用影响,其作用远强于分子体系的氢键作用,因此在化学反应中显示出独特的性能.氢键作用一方面可催化化学反应,实现一系列无金属催化的绿色反应路线;另一方面,可调控反应选择性,高收率地获得单一化学品.本文总结了近年来关于离子液体体系的氢键作用研究成果,及其催化和调控化学反应的研究进展,并对发展前景进行了展望.

Direct oxidation of the C_(sp3)-H bonds of N-heterocyclic compounds to give the corresponding ketones using a reusable heterogeneous MnO_x-N@C catalyst

Novel reusable MnOx‐N@C catalyst has been developed for the direct oxidation of N‐heterocycles under solvent‐free conditions using TBHP as benign oxidant to give the corresponding N‐heterocyclic ketones. The catalytic system exhibited a broad substrate scope and excellent regi‐oselectivity, as well as being amenable to gram‐scale synthesis. This MnOx‐N@C catalyst also showed good reusability and was successfully recycled six times without any significant loss of activity.

The Role of Hydrogen Bond in Catalytic Triad of Serine Proteases

In order to investigate the origin of catalytic power for serine proteases,the role of the hydrogen bond in the catalytic triad was studied in the proteolysis process of the peptides chymotrypsin inhibitor 2(CI2),MCTI-A,and a hexapeptide(SUB),respectively.We first calculated the free energy profile of the proton transfer between His and Asp residues of the catalytic triad in the enzyme-substrate state and transition state by employing QM/MM molecular dynamics simulations.The results show that a low-barrier hydrogen bond(LBHB)only forms in the transition state of the acylation of CI2,while it is a normal hydrogen bond in the acylation of MCTI-A or SUB.In addition,the change of the hydrogen bond strength is much larger in CI2 and SUB systems than in MCTI-A system,which decreases the acylation energy barrier significantly for CI2 and SUB.Clearly,a LBHB formed in the transition state region helps accelerate the acylation reaction.But to our surprise,a normal hydrogen bond can also help to decrease the energy barrier.The key to reducing the reaction barrier is the increment of hydrogen bond strength in the transition state state,whether it is a LBHB or not.Our studies cast new light on the role of the hydrogen bond in the catalytic triad,and help to understand the catalytic triad of serine proteases.

Light-driven activation of carbon-halogen bonds by readily available amines for photocatalytic hydrodehalogenation

A straightforward protocol using readily available aromatic amines,N,N,N',N'-tetramethyl-p-phenylenediamine or N,N,N',N'-tetramethylbenzidine,as photocatalysts was developed for theefficient hydrodehalogenation of organic halides,such as 4'-bromoacetophenone,polyfluoroarenes,cholorobenzene,and 2,2',4,4'-tetrabromodiphenyl ether(a resistant and persistent organic pollu-tant).The strongly reducing singlet excited states of the amines enabled diffusion-controlled disso-ciative electron transfer to effectively cleave carbon-halogen bonds,followed by radical hydrogena-tion.Diisopropylethylamine served as the terminal electron/proton donor and regenerated theamine sensitizers.

Proposal of an Amide-Directed Carbocupration Mechanism for Copper-Catalyzed meta-Selective C-H Arylation of Acetanilides by Diaryliodonium Salts

We examined the puzzling mechanism for Cu-catalyzed meta-C-H arylation reaction of anilides by diaryliodonium salts through systematic theoretical analysis. The previously proposed anti-oxy-cupration mechanism featuring anti-1,2- or anti-1,4-addition of cuprate and oxygen to the phenyl ring generating a meta-cuprated intermediate was excluded due to the large activation barriers. Alternatively, a new amide-directed carbocupration mechanism was proposed which involves a critical rate- and regio-determining step of amide-directed addition of the Cu（III）-aryl bond across the phenyl C2=C3 double bond to form an orthocuprated, meta-arylated intermediate. This mechanism is kinetically the most favored among several possible mechanisms such as ortho-or para-cupration/migration mechanism, direct meta C-H bond cleavage mediated by Cu（III） or Cu（I）, and Cu（III）-catalyzed ortho-directed C-H bond activation mechanism this mechanism has been shown to Furthermore, the predicted regioselectivity based on favor the meta-arylation that is consistent with the experimental observations.

Effects of indium on Ni/SiO_2 catalytic performance in hydrodeoxygenation of anisole as model bio-oil compound: Suppression of benzene ring hydrogenation and C–C bond hydrogenolysis

SiO2‐supported monometallic Ni and bimetallic Ni‐In catalysts were prepared and used for hydrodeoxygenation of anisole,which was used as a model bio‐oil compound,for BTX(benzene,toluene,and xylene)production.The effects of the Ni/In ratio and Ni content on the structures and performances of the catalysts were investigated.The results show that In atoms were incorporated into the Ni metal lattice.Although the Ni‐In bimetallic crystallites were similar in size to those of monometallic Ni at the same Ni content,H2uptake by the bimetallic Ni‐In catalyst was much lower than that by monometallic Ni because of dilution of Ni atoms by In atoms.Charge transfer from In to Ni was observed for the bimetallic Ni‐In catalysts.All the results indicate intimate contact between Ni and In atoms,and the In atoms geometrically and electronically modified the Ni atoms.In the hydrodeoxygenation of anisole,although the activities of the Ni‐In bimetallic catalysts in the conversion of anisole were lower than that of the monometallic Ni catalyst,they gave higher selectivities for BTX and cyclohexane as a result of suppression of benzene ring hydrogenation and C–C bond hydrogenolysis.They also showed lower methanation activity.These results will be useful for enhancing carbon yields and reducing H2consumption.In addition,the lower the Ni/In ratio was,the greater was the effect of In on the catalytic performance.The selectivity for BTX was primarily determined by the Ni/In ratio and was little affected by the Ni content.We suggest that the performance of the Ni‐In bimetallic catalyst can be ascribed to the geometric and electronic effects of In.

Calculation on model of weakening hydrogen bond of thick oil of petroleum

The process of use catalyst or functional material that contains iron ion to weaken -O-H-O- hydrogen bond of the thick oil to reduce viscidity or crack, in aspects of the ion charge. covalent bond order, total energy and the average distance of Fe-O. is studied with density function theory and discrete variational method （DFT-DVM）, one of the first principle methods. With the decrease of the distance of Fe-O. the charge of Fe ion increases, the charge of hydrogen ion decreases, and hydrogen bond is weakened. There are obvious and more stable effects to use the catalyst that contains multiple metal ions or increase the catalyst amount in weakening hydrogen bond of the thick oil. This theoretic work is helpful to exploit and process the thick oil of petroleum and maybe overcome the crisis of petroleum energy is approaching to us.

1,1'-Methylenediimidazolium-Based Multiple Hydrogen-Bond Donor Catalysts Facilitate the Cycloaddition of CO_(2) with Epoxides under Atmospheric Pressure

The quest for innovative hydrogen-bond donor(HBD)catalysts has led to a significant advancement in the field of organic synthesis.Considering the electron-withdrawing strength of imidazolium cations and the spatial requirements of hydrogen bond donors,a novel HBD catalyst based on the 1,1'-methylenediimidazolium scaffold by bridging two imidazolium cations with methylene was developed.The 1,1'-methylenediimidazolium-based catalysts exhibit excellent performance in the cycloaddition reaction of CO_(2) and epoxides,achieving up to 99% yield and 99%selectivity under mild conditions(atmospheric pressure,80℃ for 12 h,with 1 mol%catalyst).The geometric structure,atomic charge distribution,and synergistic effect of HBD catalysts were studied in detail through 1H NMR spectroscopy and density functional theory(DFT)calculations.The research results indicate that the protons at positions C2-H,C2'-H,C5-H,and C5'-H on the imidazolium rings,as well as the protons on the bridged methylene,contribute to the formation of multiple hydrogen bonds with appropriate distance and synergistic effects,which are crucial for activating CO_(2) and epoxides.This research highlights the distinctive attributes of 1,1'-methylenediimidazolium-based catalysts and offers valuable insights into the development of highly efficient multiple HBD catalysts.

离子液体调控化学反应研究进展

离子液体是由有机阳离子和无机/有机阴离子组成的一类低温熔融盐,兼具分子溶剂和融盐的特性,在化学反应中既可用作反应介质,又可起到催化和助催化作用.本文总结了近年来本课题组在离子液体介导二氧化碳和纤维素及其平台分子转化、离子液体无金属催化炔醇水合反应和离子液体氢键催化化学反应中的研究进展,并针对该领域存在的问题提出观点,对发展前景进行了展望.