Pd-Cu–Mediated Synthesis of 2-Substituted Imidazo[1,2-α]pyridines in Water

The reaction of 2-amino-1-(2-propynyl)pyridinium bromide with various iodobenzenes, catalyzed by Pd-Cu, in the presence of sodium lauryl sulfate as the surfactant and cesium carbonate as the base, in water, leads to the formation of 2-substituted imidazo[1,2-α]pyridines.     

XRD studies,vibrational spectra,and molecular structure of 1H‐imidazo [4,5‐b]pyridine based on DFT quantum chemical calculations

The molecular structures and vibrational properties of 1H‐imidazo[4,5‐b]pyridine in its monomeric and dimeric forms are analyzed and compared to the experimental results derived from the X‐ray diffraction (XRD), infrared (IR), and Raman studies. The theoretical data are discussed on the basis of density functional theory (DFT) quantum chemical calculations using Lee–Yang–Parr correlation functional (B3LYP) and 6‐31G(d,p) basis. This compound crystallizes in orthorhombic structure, space group Pna2₁(C_2v⁹) and Z = 4. The planar conformation of the skeleton and presence of the N H···N hydrogen bond was found to be characteristic for the studied system. The temperature dependence of IR and Raman modes was studied in the range 4–294 K and 8–295 K, respectively. The normal modes, which are unique for the imidazopyridine derivatives are identified. Copyright © 2009 John Wiley & Sons, Ltd.     

Vibrational spectra,X‐ray and molecular structure of 1H‐ and 3H‐imidazo[4,5‐b]pyridine and their methyl derivatives: DFT quantum chemical calculations

Molecular structure, vibrational energy levels and potential energy distribution of 1H‐imidazo[4,5‐b]pyridine, 3H‐imidazo[4,5‐b]pyridine, 5‐methyl‐1H‐imidazo[4,5‐b]pyridine, 6‐methyl‐1H‐imidazo[4,5‐b]pyridine and 7‐methyl‐3H‐imidazo[4,5‐b]pyridine were determined using density functional theory (DFT) at the B3LYP/6‐31G(d,p) level. The optimised bond lengths and bond angles are in good agreement with the X‐ray data of 5‐methyl‐1H‐imidazo[4,5‐b]pyridine obtained in the present work (Pbca space group; a = 8.660(2), b = 11.078(2), c = 11.078(3) Å, Z = 8). The N⁺H group plays the role of a proton donor in a medium strong hydrogen bond of the type N H…N, linking the N‐atom of the pyridine with the adjacent molecule related by the symmetry operation: 1/2 − x, y − 1/2, z(N…N = 2.869(25) Å). The presence of hydrogen bond is confirmed by appearance in the IR spectra of a very broad and strong contour in the 2000–3100 cm⁻¹ range. The place of substitution of the methyl group at the pyridine ring influences the proton position of the NH group at the imidazole unit. Copyright © 2007 John Wiley & Sons, Ltd.     

CN-Modified Imidazopyridine as a New Electron Accepting Unit of Thermally Activated Delayed Fluorescent Emitters

Two efficient thermally activated delayed fluorescent (TADF) emitters were developed by utilizing CN-modified imidazopyridine as an acceptor unit. The CN-modified imidazopyridine acceptor was combined with either an acridine donor or a phenoxazine donor through a phenyl linker to produce two TADF emitters, Ac-CNImPy and PXZ-CNImPy. The acridine-based Ac-CNImPy emitter exhibited sky-blue emission with a CIE coordinate of (0.18, 0.38), whereas the phenoxazine-donor-based PXZ-CNImPy showed greenish-yellow emission with a CIE coordinate of (0.32, 0.58). A high photoluminescence quantum yield of 80 % was observed for the PXZ-CNImPy emitter compared with 40 % for the Ac-CNImPy emitter. Organic light-emitting diodes based on the PXZ-CNImPy emitter demonstrated high external quantum efficiency of 17.0 %. Hence, the CN-modified imidazopyridine unit can be considered as a useful electron acceptor for the future design of highly efficient TADF emitters.     

咪唑并吡啶类化合物的合成及其应用*

咪唑并吡啶类化合物具有与吲哚、氮杂吲哚等类似的特殊结构和良好的生物活性,在医药和农药工业有着广泛的应用,成为有机化学家和药物化学家的研究热点。咪唑并吡啶类化合物主要有咪唑并[4,5-b]吡啶、咪唑并[4,5-c]吡啶、咪唑并[1,2-a]吡啶和咪唑并[1,5-a]吡啶等4个类型。本文阐述了近年来咪唑并吡啶类化合物的合成研究进展和应用情况,主要介绍了咪唑并[4,5-b]吡啶和咪唑并[4,5-c]吡啶这两类化合物的合成方法和在医药及农药领域的应用。     

Gluconic acid promoted cascade reactions of 2-phenylimidazo[1,2-a] pyridine-3-carbaldehyde with cyclohexane-1,3-dione to create novel fused bisheterocycles

Here in, we described the synthesis of novel bisheterocycles imidazopyridine bearing xanthenedione by reacting various substituted 2-phenylimidazo [1,2-a] pyridine-3-carbaldehyde with cyclohexane-1,3-dione in gluconic acid aqueous solution (GAAS) via a tandem Knoevenagel followed by Michael, cyclization & tautomerization sequence. The use of GAAS in organic synthesis offers significant benefits like cost-effective, simple operation, reusable catalyst and green method. The reaction completed in 2–12?h to afford white stable solid compounds with very good yield. The structures of the compounds are confirmed by analyzing MS, IR, ¹H NMR and ¹³C NMR spectra. Further, the structure of compound 3?h was confirmed by XRD analysis.     

Simple synthesis of imidazo[1,2-A]pyridine derivatives bearing 2-aminonicotinonitrile or 2-aminochromene moiety

A simple and general method for the synthesis of new imidazopyridines bearing an aminopyridinyl, chromenyl, or quinolinyl moiety in the C2 position was developed. The Knoevenagel reaction between imidazo[1,2-a]pyridine-2-carbaldehyde 1 and malononitrile resulted in the formation of starting material 2. Subsequently, intramolecular cyclization between the cyano group of 2 and acetophenones, naphtols, hydroxyquinolines, or phenols, gave 3, 4, 5, and 6 compounds, respectively. This is a simple, reproducible, and environmentally friendly method of synthesizing substituted imidazopyridines using water as a solvent or under solvent-free conditions.     

基于咪唑并吡啶类配体新型磷光材料的合成与表征

设计开发了系列新型咪唑并吡啶类铱(Ⅲ)配合物(BIPy)₂Ir(acac)、(PIPy)₂Ir(acac)、 (4'-MPIPy)₂-Ir(acac)。在化合物Ⅲ中,当R=Ph时得到(BIPy)₂Ir(acac)材料,其中BIPy和acac分别表示2-(4-联苯基)咪唑并吡啶和乙酰丙酮。将(BIPy)₂Ir(acac)掺杂在N,N'-二咔唑-(1,1'-联苯)-4,4'-二胺(CBP)中制备了高效OLEDs器件,器件的最大电流效率为26.7 cd/A,最大亮度为18 000 cd/cm²,色坐标为(0.32,0.60),是首次报道的新型苯基咪唑并吡啶类铱(Ⅲ)配合物绿色磷光材料。     

咪唑并吡啶化合物的合成研究进展

咪唑并吡啶类化合物是一类非常重要的含氮稠杂环化合物, 在医药、农药和染料工业有着广泛的应用. 该类化合物由于其特定的生理活性以及和吲哚、氮杂吲哚等在结构上的类似性, 引起了人们广泛的兴趣. 常见的咪唑并吡啶类化合物有咪唑并[1,2-a]吡啶、咪唑并[1,5-a]吡啶、咪唑并[4,5-b]吡啶和咪唑并[4,5-c]吡啶等类型. 以咪唑并[1,2-a]吡啶和咪唑并[1,5-a]吡啶化合物为例, 阐述该类化合物近十年来的合成研究进展.     

异噁唑啉基咪唑[1,2-a]吡啶C-核苷类化合物的合成

以异恶唑啉基环取代呋喃核糖环（ribose ring）为基本单元,成功地合成了一系列咪唑[1,2-a]吡啶衍生物的C－核苷化合物3和4（其中碱基和异恶唑啉基环之间以C－C化学键方式连接）。这两种异构体中N和O原子处于相互交换的位置,分别可以利用相应的烯烃和腈氧化物中间体进行偶极环合加成反应制得。