Site-Selective Synthesis and Concurrent Immobilization of Imine-Based Covalent Organic Frameworks on Electrodes Using an Electrogenerated Acid

Imine-based covalent organic frameworks (COFs) are crystalline porous materials with prospective uses in various devices. However, general bulk synthetic methods usually produce COFs as powders that are insoluble in most of the common organic solvents, arising challenges for the subsequent molding and fixing of these materials on substrates. Here, we report a novel synthetic methodology that utilizes an electrogenerated acid (EGA), which is produced at an electrode surface by electrochemical oxidation of a suitable precursor, acting as an effective Brønsted acid catalyst for imine bond formation from the corresponding amine and aldehyde monomers. Simultaneously, it provides the corresponding COF film deposited on the electrode surface. The COF structures obtained with this method exhibited high crystallinities and porosities, and the film thickness could be controlled. Furthermore, such process was applied for the synthesis of various imine-based COFs, including a three-dimensional (3D) COF structure.     

Theoretical studies on the imine germylenoid HNGeNaF and its insertion reaction with R-H (R = F, OH, NH2, CH3)

The geometries and isomerization of the imine germylenoid HNGeNaF as well as its insertion reactions with R-H (R = F, OH, NH₂, CH₃) have been systematically investigated at the B3LYP/6-311+G^∗ level of theory. The potential barriers of the four insertion reactions are 117.2, 172.6, 219.7, and 322.3 kJ/mol, respectively. Here, all the mechanisms of the four reactions are identical to each other, i.e., an intermediate has been formed first during the insertion reaction. Then, the intermediate could dissociate into the substituted germylene (HNGeHR) and NaF with a barrier corresponding to their respective dissociation energies. Correspondingly, the reaction energies for the four reactions are 185.0, 208.1, 224.4, and 266.9 kJ/mol, respectively, which are linearly correlated with the calculated barrier heights. Compared with the insertion reaction of HNGe: and R-H, the introduction of NaF makes the insertion reaction occur easily though it is more difficult to proceed than that of insertion reaction between H₂GeNaF and R-H. Furthermore, the effects of halogen (F, Cl, Br) substitution and inorganic salts employed on the reaction activity have also been discussed. As a result, the relative reactivity among the four insertion reactions should be as follows: H-F > H-OH > H-NH₂ > H-CH₃.     

Enantioselective Rhodium‐Catalyzed Coupling of Arylboronic Acids, 1,3‐Enynes,and Imines by Alkenyl‐to‐Allyl 1,4‐Rhodium(I) Migration

A chiral rhodium complex catalyzes the highly enantioselective coupling of arylboronic acids, 1,3‐enynes, and imines to give homoallylic sulfamates. The key step is the generation of allylrhodium(I) species by alkenyl‐to‐allyl 1,4‐rhodium(I) migration.     

Cyclic [2]Catenane Dimers,Trimers, and Tetramers

Dimeric, trimeric, and tetrameric cyclic [2]catenanes have been prepared directly through one‐pot sodium‐ion‐templated dynamic imine formation from a diamine and a tetraaldehyde. NaBH₄ mediated reduction of the labile imino bonds of these cyclic [2]catenane oligomers, followed by methylation of the resulting secondary amino groups enabled the isolation and characterization of oligomeric cyclic [2]catenanes as stable, covalently linked compounds.     

温度/pH响应性MPEG-b-PCL/PNVCL-b-PCL共聚物复合胶束的制备及载药性质

以基于亚胺键的嵌段共聚物为构筑单元的温度/pH响应性共聚物复合胶束(CMs), 由于具有亚胺键和核-壳-冠结构, 表现出较高的灵敏度和稳定性. 以聚乙二醇单甲醚(MPEG)、 N-乙烯基己内酰胺(NVCL)和ε-己内酯(ε-CL)为原料, 分别制备了端醛基聚乙二醇单甲醚(MPEG-CHO)、 端醛基聚N-乙烯基己内酰胺(PNVCL-CHO)和端氨基聚己内酯(H₂N-PCL), 利用希夫碱反应, 进一步制备了基于亚胺键的聚乙二醇单甲醚-b-聚己内酯(MPEG-b-PCL)和聚N-乙烯基己内酰胺-b-聚己内酯(PNVCL-b-PCL)嵌段共聚物, 对共聚物结构进行了确认. 以MPEG-b-PCL和PNVCL-b-PCL为构筑单元, 制备了共聚物复合胶束, 研究了复合胶束对阿霉素的包载、 释放性质和细胞毒性等. 研究结果表明, 室温下MPEG-b-PCL和PNVCL-b-PCL能够在水中自组装形成以PCL为核、 MPEG和PNVCL为混合壳的共聚物复合胶束, 在生理温度下, 温敏性PNVCL链段发生相变塌缩在PCL核表面, 能够防止药物扩散释放, 亲水性MPEG链段形成可控通道. 药物体外释放结果表明, 在弱酸性环境中, 亚胺键能够断裂, 胶束被破坏, 促进药物的释放, 噻唑蓝(MTT)实验表明, 复合胶束的细胞毒性较低.     

环化及亚胺/酰胺部分氢化一锅法串联反应合成1,2,3,4⁃四氢喹喔啉

报道了一种利用价廉易得的邻苯二胺衍生物与α-酮酸酯经环化/钌催化的亚胺和酰胺氢化串联反应一锅法制备1,2,3,4-四氢喹喔啉的方法. 该方法使用原位生成的Ru(acac)₃/Triphos配合物和HBF₄共催化剂组成的催化体系, 高效制备了一系列2-取代的1,2,3,4-四氢喹喔啉, 官能团耐受性良好. 在较低的氢气压力和不使用助催化剂的条件下, 反应可停留在只生成3,4-二氢喹喔啉酮产物阶段. 反应机理研究表明, 钌催化剂仅用于还原亚胺和酰胺部分, 而布朗斯台德酸助催化剂的选择对于酰胺部分去氧氢化至关重要. 研究表明, 布朗斯台德酸助催化剂通过活化酰胺部分参与催化过程.     

Selective fluorescence turn-on of a prefluorescent azomethine with Zn

A prefluorescent conjugated azomethine (4) was prepared by condensing 8-hydroxyquinoline-5-carbaldehyde with 2-amine thiophene. The fluorescence of the azomethine was quenched in organic solvents including dichloromethane, methanol, DMSO, and DMF. However, the fluorescence of 4 was selectively revived in the presence of zinc and an absolute quantum yield Φ_fl = 0.15 was measured.     

SYNTHESIS AND CHARACTERIZATION OF DIAQUA(3-pTOLYLIMINO-2-BUTANONE OXIMATO)(3-p-TOLYLIMINO-2-BUTANONE OXIME)NICKEL(II) PERCHLORATE

Abstract

[Ni(L^?1)(HL)(H₂O)₂].ClO₄ with a Schiff base ligand L (HL = 3-p-tolylimino-2-butanone oxime) was prepared and structurally characterized by IR, cyclic voltammetry and X-ray diffraction methods. The nickel atom has distorted octahedral coordination consisting of four nitrogen atoms and two oxygen atoms. The equatorial plane is formed by two oxime nitrogen atoms and two imine nitrogen atoms of two Schiff base ligand (L^?1 and HL) with Ni‐ N bond distances between 2.01(1) and 2.11(1)Å. Water oxygen atoms occupy axial positions with Ni‐ O bond distances of 2.06(1) and 2.15(1) Å. The oxime groups in the Schiff base ligands are coordinated to Ni atom through their nitrogen atoms. One asymmetric intramolecular hydrogen bridge between the two oxime groups is found in the title complex.     

Nucleophilic addition of regioselectively lithiated indoline with aldimines for the syntheses of 2- and 7-indolinyl methanamine derivatives

Indolines bearing different N-protecting groups (N-Tbf and N-Boc) were deprotonated regioselectively at C-2 (sp³ hybridized ortho-H) and C-7 (sp² hybridized para-H) of the indoline ring, respectively. The generated organolithium intermediates reacted with aldimines to give the desired products in good yields with excellent anti-diastereoselectivities (>99:1). The produced N-Ts-(1-Tbf-indolin-2-yl)methanamine was facilely transformed to a fused heterocyclic compound.