Improved synthesis of functionalized mesogenic 2,6-bisbenzimidazolylpyridine ligands

A versatile one-pot synthetic platform for the preparation of a range of functionalized 2,6-bisbenzimidazolylpyridine (Bip) derivatives is presented. This protocol significantly reduces the cost and time of previous synthetic routes, while facilitating scale up to multi-gram quantities in good yields (63-90%). The previous synthetic methodology was improved through judicious choice of the reducing agent and solvent in the reduction/ring-closing step. Via this platform, we also successfully accessed a mesogenic Bip ligand and herein report initial liquid crystalline properties of this derivative.     

One-dimensional Hydrogen-bonded Polymer Based on Tetra-iso-butyl-resorcin[4]arene and 2,6-Diacetylpyridine

1INTRODUCTIONResorcin[4]arenesarecavity-shapedmacro-cycleswhichcanbeeasilysynthesizedfromresor-cinolandaldehydesinthepresenceofacidiccataly-sis[1].Theyareattachedmuchinterestinthefieldofsupramolecularchemistryasartificialreceptorsandstartingmaterialsforthepreparationofmoresophis-ticatedmolecules[2].Duetotheirstructuralfeaturestheyplayanimportantroleashostmoleculesforavarietyofneutralandchargedguestcompounds[3].Theresorcin[4]arenesusuallyadoptfourdifferentcon-formers,crown(rccc,C4),boat(rc…     

Synthesis, NMR spectroscopic characterisation and reactions of 2,6-difluorophenylxenon fluoride, 2,6-F2C6H3XeF

[2,6-F₂C₆H₃Xe][BF₄] is quantitatively transferred into 2,6-F₂C₆H₃XeF in reactions with [NMe₄]F. The latter has been isolated as a colourless solid which is stable in dichloromethane solution at room temperature for approximately 1 h. 2,6-F₂C₆H₃XeF readily reacts with Me₃SiX (X = Cl, Br, CN, NCO, OCOCF₃, OSO₂CF₃, C₆F₅, 2,6-F₂C₆H₃) to give compounds of general compositions 2,6-F₂C₆H₃XeX which were identified by multinuclear NMR experiments. Evidence was found for C₆H₅Xe(2,6-F₂C₆H₃) as a product of the reaction with C₆H₅SiF₃.     

Depolymerization of poly(2,6-dimethyl-1,4-phenylene oxide) under oxidative conditions

Depolymerization of an engineering plastic, poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), was accomplished by using 2,6-dimethylphenol (DMP) under oxidative conditions. The addition of an excess amount of DMP to a solution of PPO in the presence of a CuCl/pyridine catalyst yielded oligomeric products. When PPO (M(n)=1.0x10(4), M(w)/M(n)=1.2) was allowed to react with a sufficient amount of DMP, the molecular weight of the product decreased to M(n)=4.9x10(2) (M(w)/M(n)=1.5). By a prolonged reaction with the oxidant, the oligomeric product was repolymerized to produce PPO essentially identical to the starting material, making the oligomer useful as a reusable resource. During the depolymerization reaction, an intermediate phenoxyl radical was observed by ESR spectroscopy. Kinetic analysis showed that the rate of the oxidation of PPO was about 10 times higher than that of DMP. These results show that a monomeric phenoxyl radical attacks the polymeric phenoxyl to induce the redistribution via a quinone ketal intermediate, leading to the substantial decrease in the molecular weight of PPO, which is much faster than the chain growth.     

Synthesis and Thermoreversible Gelation Properties of Main‐Chain Poly(pyridine‐2,6‐dicarboxamide‐triazole)s

A series of main‐chain poly(amide‐triazole)s were prepared by copper(I)‐catalyzed alkyne–azide AABB‐type copolymerizatons between five structurally similar diacetylenes 1 – 5 with the same diazide 6 . The acetylene units in monomers 1 – 5 possessed different degrees of conformational flexibility due to the different number of intramolecular hydrogen bonds built inside the monomer architecture. Our study showed that the conformational freedom of the monomer had a profound effect on the polymerization efficiency and the thermoreversible gelation properties of the resulting copolymers. Among all five diacetylene monomers, only the one, that is, 1 ‐Py(NH)₂ which possesses the pyridine‐2,6‐dicarboxamide unit with two built‐in intramolecular H bonds could produce the corresponding poly(amide‐triazole) Poly‐(PyNH)₂ with a significantly higher degree of polymerization (DP) than other monomers with a lesser number of intramolecular H bonds. In addition, it was found that only this polymer exhibited excellent thermoreversible gelation ability in aromatic solvents. A self‐assembling model of the organogelating polymer Poly‐(PyNH)₂ was proposed based on FTIR spectroscopy, XRD, and SEM analyses, in which H bonding, π–π aromatic stacking, hydrophobic interactions, and the structural rigidity of the polymer backbone were identified as the main driving forces for the polymer self‐assembly process.     

One-Electron Reduction of 2-Mono(2,6-diisopropylphenylimino)acenaphthene-1-one (dpp-mian)

The electrochemical characteristics of 2-mono(2,6-diisopropylphenylimino)acenaphthene-1-one (dpp-mian) have been investigated. One-electron reduction of dpp-mian involves the iminoketone fragment, which is revealed by the EPR spectrum obtained after the electrolysis of the dpp-mian solution in tetrahydrofuran (THF). The reduction of dpp-mian with one equivalent of metallic potassium leads to a similar EPR spectrum. The sodium complex [(dpp-mian)Na(dme)]₂ ( 1 ) produces an EPR signal with hyperfine coupling on the nitrogen atom of the iminoketone fragment of the dpp-mian ligand. Dpp-mian can also be reduced in a one-electron process by SnCl₂×(dioxane). In this case, complex (dpp-mian)₂SnCl₂ ( 2 ) is formed, with the tin atom displaying an oxidation state of +4. Tin(II) chloride dihydrate, SnCl₂×2(H₂O), also reduces dpp-mian, but the two ligands bound to tin in the product form a new carbon–carbon bond between the ketone moieties of the dpp-mian monoanions to form complex (bis-dpp-mian)HSnCl₃ ( 3 ). Metallic tin reduces dpp-mian to form the (bis-dpp-mian)₂Sn ( 4 ) species. Compounds 1 – 4 were characterized by X-ray diffraction.     

Rigid Scaffolds: Synthesis of 2,6-Bridged Piperazines with Functional Groups in all three Bridges

The activity of pharmacologically active compounds can be increased by presenting a drug in a defined conformation, which fits exactly into the binding pocket of its target. Herein, the piperazine scaffold was conformationally restricted by substituted C₂- or C₃-bridges across the 2- and 6-position. At first, a three-step, one-pot procedure was developed to obtain reproducibly piperazine-2,6-diones with various substituents at the N-atoms in high yields. Three strategies for bridging of piperazine-2,6-diones were pursued: 1. The bicyclic mixed ketals 8-benzyl-6-ethoxy-3-(4-methoxybenzyl)-6-(trimethylsilyloxy)-3,8-diazabicyclo[3.2.1]octane-2,4-diones were prepared by Dieckmann analogous cyclization of 2-(3,5-dioxopiperazin-2-yl)acetates. 2. Stepwise allylation, hydroboration and oxidation of piperazine-2,6-diones led to 3-(3,5-dioxopiperazin-2-yl)propionaldehydes. Whereas reaction of such an aldehyde with base provided the bicyclic alcohol 9-benzyl-6-hydroxy-3-(4-methoxybenzyl)-3,9-diazabicyclo[3.3.1]nonane-2,4-dione in only 10 % yield, the corresponding sulfinylimines reacted with base to give N-(2,4-dioxo-3,9-diazabicyclo[3.3.1]nonan-6-yl)-2-methylpropane-2-sulfinamides in >66 % yield. 3. Transformation of a piperazine-2,6-dione with 1,4-dibromobut-2-ene and 3-halo-2-halomethylprop-1-enes provided 3,8-diazabicyclo[3.2.1]octane-2,4-dione and 3,9-diazabicyclo[3.3.1]nonane-2,4-dione with a vinyl group at the C₂- or a methylene group at the C₃-bridge, respectively. Since bridging via sulfinylimines and the one-pot bridging with 3-bromo-2-bromomethylprop-1-ene gave promising yields, these strategies will be exploited for the synthesis of novel receptor ligands bearing various substituents in a defined orientation at the carbon bridge     

水介质中2,6-二甲基苯酚的氧化偶合聚合

聚2,6-二甲基苯醚(PPO)是重要的工程塑料,一般采用在有机溶剂中使2,6-二甲基苯酚(DMP)氧化聚合的方法合成,这就需要溶剂回收装置和防爆反应器,且污染环境.从绿色化学观点出发,以水作为反应介质,不仅对环境友好,而且PPO不溶于水,容易分离.近年来,一些学者研究了在油/水两相或全水介质中使DMP氧化聚合合成PPO的新方法.本文主要综述了该方法的研究进展,包括DMP氧化聚合的机理,油/水两相或水介质中对聚合速率、氧化偶合选择性及PPO分子量等的影响因素.     

New chemical insights using weakly supported voltammetry: ion pairing in the EC2 reduction of 2,6-diphenylpyrylium in acetonitrile

Pairing effect: Varying the concentration of support electrolyte in the electrochemical EC(2) reduction of 2,6-diphenylpyrylium reveals the presence of ion pairing between the electroactive species and BF(4)(-). Experiment and theory are shown to be in good agreement only if ion pairing is included in the simulations. This previously unanticipated effect is only observable if voltammetry is performed under conditions of weak support.     

Synthesis and photophysical properties of self-assembled metallogels of platinum(II) acetylide complexes with elaborate long-chain pyridine-2,6-dicarboxamides

A series of platinum(II) acetylide complexes with elaborate long-chain pyridine-2,6-dicarboxamides was synthesized. These metal complexes are capable of immobilizing organic solvents to form luminescent metallogels through a combination of intermolecular hydrogen bonding, aromatic π-π, and van der Waals interactions. Fibrillar morphologies were identified by TEM for these metallogels. Unique photophysical properties associated with the sol-to-gel transition have been disclosed with luminescence enhancement at elevated temperatures, which is in sharp contrast to typical thermotropic organogels or metallogels reported in the literature. Such unusual luminescence enhancement is attributed to the increased degree of freedom at higher temperatures that results in the formation of favorable molecular aggregates in the excited state through enhanced aromatic π-π and metallophilic Pt(II)···Pt(II) interactions. Structurally similar Pt-bp3 is not able to gel any common organic solvents. The inability of Pt-bp3 to form gels illustrates the importance of gelation to the macroscopic photophysical properties; Pt-bp3 does not show emission enhancement at elevated temperatures due to its low tendency to form strong aggregates in the ground state.     

Anthraquinone‐2,6‐disulfonate as Versatile Ligand for the Synthesis of Hydrogen‐Bonded Supramolecules

The reactions of anthraquinone‐2,6‐disulfonic acid disodium salt (Na₂a‐2,6‐dad) with Cu^II, Mn^II, and Zn^II with 1,10‐phenanthroline (phen) or 2,2′‐dipyridyl (bipy) under hydrothermal conditions formed two or three‐dimensional supramolecules of stoichiometries [Cu(a‐2,6‐dad)(phen)(H₂O)₃](H₂O)₄ ( 1 ), [Mn(a‐2,6‐dad)(bipy)₂(H₂O)](H₂O)₂ ( 2 ), and [Zn(a‐2,6‐dad)(bipy)₂(H₂O)](H₂O)₂ ( 3 ), which were synthesized and characterized. The arrangement around each metal atom is distorted octahedral. The ligands in all the compounds are engaged in intermolecular hydrogen bonding leading to the formation of hydrogen‐bonded networks, the compounds show novel π–π stacking interactions. Photoluminescence measurements indicate that the compound [Zn(a‐2,6‐dad)(bipy)₂(H₂O)](H₂O)₂ ( 3 ) shows strong blue luminescence in the solid state at room temperature.     

2,6-Diaminopyridin

Ohne Zusammenfassung     

2,6-二氯甲苯氨氧化制备2,6-二氯苯腈实验

本实验属于化工基础实验 ,采用对环境友好的氨氧化催化法 ,在连续流动固定床反应器上 ,以 2 ,6 二氯甲苯为原料制备重要的有机合成中间体 2 ,6 二氯苯腈。采用正交设计法筛选到合适的反应条件。本实验可以培养学生处理较复杂问题和初步从事多相催化研究的能力     

Synthesis of 3,4,7,8-bis(3-R-benzo)-2,6-dithia-1,5-diaza-2,6-dihydroanthracene 2,6-dioxides

Derivatives of a new heterocyclic quinoid system, viz., 3,4,7,8-bis (3-R-benzo)-2,6-dithia-1,5-diaza-2,6-dihydroanthracene 2,6-dioxide, were synthesized by the oxidation of 3,4,7, 8-bis (3-R-benzo)-2,6-dithia-1,5-diaza-1,2,5,6-tetrahydroanthracene 2, 6-dioxides with lead tetraacetate in acetic acid or with phenyliodoso diacetate in benzene.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 343–345, March, 1985.