Synthesis of novel dipyrazolo[3,4-b:3,4-d]pyridines and study of their fluorescence behavior

A convenient route was successfully developed for the synthesis of novel heterocycles such as pyrazolo[3,4-h][1,6]naphthyridine and dipyrazolo[3,4-b:3,4-d]pyridine (DPP) from pyrazolo[3,4-b]pyridine in good yield. The DPP derivatives synthesized were further studied for their fluorescence properties.     

Synthesis of Novel Pyrrolo[1′,5′‐a]‐1,8‐naphthyridine Derivatives through a Facile One‐Pot Process

Novel pyrrolo[1′,5′‐a]‐1,8‐naphthyridine compounds have been synthesized through a facile one‐pot process by the reaction of the corresponding 1,8‐naphthyridines with aliphatic anhydride. The structures were established by spectroscopic data. Further X‐ray crystal analysis of 4′‐acetyl‐7‐methyl‐pyrrolo[1′,5′‐a]‐1,8‐naphthyridine (1) identifies its intriguing molecular structure and reveals the strong π‐π stacking.     

A Chiral Naphthyridine Diimine Ligand Enables Nickel‐Catalyzed Asymmetric Alkylidenecyclopropanations

A novel class of chiral naphthyridine diimine ligands (NDI*) readily accessible from C₂‐symmetric 2,6‐di‐(1‐arylethyl)anilines is described. The utility of these ligands, particularly one with fluorinated aryl side arms, is demonstrated by a reductive Ni‐catalyzed enantioselective alkylidene transfer reaction from 1,1‐dichloroalkenes to olefins. This transformation provides direct access to a broad range of synthetically valuable alkylidenecyclopropanes in high yields and enantioselectivities.     

氢化喹啉及其芳(杂)环稠合衍生物的合成

通过环己二酮与β-二腈基苯乙烯的Michael加成得到2-氨基-3-氰基-4-芳基-5-氧代-1,4,5,6,7,8-六氢喹啉(1); 4-苯基六氢喹啉(1a)与环己二酮发生胺的加成缩合反应生成2-N-(3-氧代-1-环己烯基)氨基-3-氰基-4-苯基-5-氧代-1,4,5,6,7,8-六氢喹啉(2), 在碱性和氯化亚铜催化下进一步环合成4-苯基-5-氨基-二-(2-氧代环己烷)并[b,g]-1,3-二氢萘啶(3). 芳醛、α-萘胺和环己二酮在乙醇中共回流, 则一锅法完成9-芳基-5,6,7,8,9,10-六氢苯并[c]吖啶酮(4)的合成. 对合成中所涉及的化学反应机理进行了尝试性的讨论. 新化合物1a～4c均经IR, ¹H NMR 及元素分析证明其结构.     

Synthesis and characterization of new complexes of the type [Ru(CO)2Cl2 (2‐phenyl‐1,8‐naphthyridine‐kN) (2‐phenyl‐1,8‐naphthyridine‐kN′)]. Preliminary applications in homogeneous catalysis

Novel ruthenium (II) complexes were prepared containing 2‐phenyl‐1,8‐naphthyridine derivatives. The coordination modes of these ligands were modified by addition of coordinating solvents such as water into the ethanolic reaction media. Under these conditions 1,8‐naphthyridine (napy) moieties act as monodentade ligands forming unusual [Ru(CO)₂Cl₂(η¹‐2‐phenyl‐1,8‐naphthyridine‐ kN )(η¹‐2‐phenyl‐1,8‐naphthyridine‐kN′)] complexes. The reaction was reproducible when different 2‐phenyl‐1,8‐naphthyridine derivatives were used. On the other hand, when dry ethanol was used as the solvent we obtained complexes with napy moieties acting as a chelating ligand. The structures proposed for these complexes were supported by NMR spectra, and the presence of two ligands in the [Ru(CO)₂Cl₂(η¹‐2‐phenyl‐1,8‐naphthyridine‐ kN )(η¹‐2‐phenyl‐1,8‐naphthyridine‐kN′)] type complexes was confirmed using elemental analysis. All complexes were tested as catalysts in the hydroformylation of styrene showing moderate activity in N,N′‐dimethylformamide. Copyright © 2008 John Wiley & Sons, Ltd.     

A Polypyridyl‐Based Layered Complex as Dual‐Functional Co‐catalyst for Photo‐Driven Organic Dyes Degradation and Water Splitting

With the ever‐increasing concerns on environmental pollution and energy crisis, it is of great urgency to develop high‐performance photocatalyst to eliminate organic pollutants from wastewater and produce hydrogen via water splitting. Herein, a polypyridyl‐based mixed covalent Cu^I/II complex with triangular {Cu₃} and rhombic {Cu₂Cl₄} subunits alternately extended by mixed SCN^– and Cl^– heterobridges [Cu₄(DNP)(SCN)Cl₄]_n ( 1 ) [DNP = 2,6‐bis(1,8‐naphthyridine‐2‐yl)pyridine] was solvothermally synthesized and employed as a dual‐functional co‐photocatalyst. Resulting from a narrowed band‐gap of 1.07 eV with suitable redox potential and unsaturated Cu^I/II sites, the complex together with H₂O₂ can effectively degrade Rhodamine B and methyl orange up to 87.4 and 88.2 %, respectively. Meanwhile, the complex mixed with H₂PtCl₆ can also accelerate the photocatalytic water splitting in the absence of a photosensitizer with the hydrogen production rate of 27.5 μmol · g^–1 · h^–1. These interesting findings may provide informative hints for the design of the multiple responsive photocatalysts.     

Crystal structure analysis of 5‐amino‐7‐(pyrrolidin‐1‐yl)‐2,4,4‐trimethyl‐1,4‐dihydro‐1,6‐naphthyridine‐8‐carbonitrile

The title compound [CCDC 199359], C₁₆H₂₀N₅ crystallized in Monoclinic system with the space group C2/c. The unit cell parameters are: a = 16.554(6), b = 12.145(4), c = 16.221(5)Å and β = 102.67(1)°. The molecular structure is stabilized by an intramolecular C‐H…N type hydrogen bond and the molecular packing by the intermolecular C‐H…N and N‐H…N type hydrogen bonds. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Enhancement of Antibiotic Activity by 1,8-Naphthyridine Derivatives against Multi-Resistant Bacterial Strains

The search for new antibacterial agents has become urgent due to the exponential growth of bacterial resistance to antibiotics. Nitrogen-containing heterocycles such as 1,8-naphthyridine derivatives have been shown to have excellent antimicrobial properties. Therefore, the purpose of this study was to evaluate the antibacterial and antibiotic-modulating activities of 1,8-naphthyridine derivatives against multi-resistant bacterial strains. The broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of the following compounds: 7-acetamido-1,8-naphthyridin-4(1H)-one and 3-trifluoromethyl-N-(5-chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide. The antibiotic-modulating activity was analyzed using subinhibitory concentrations (MIC/8) of these compounds in combination with norfloxacin, ofloxacin, and lomefloxacin. Multi-resistant strains of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were used in both tests. Although the compounds had no direct antibacterial activity (MIC ≥ 1.024 µg/mL), they could decrease the MIC of these fluoroquinolones, indicating synergism was obtained from the association of the compounds. These results suggest the existence of a structure–activity relationship in this group of compounds with regard to the modulation of antibiotic activity. Therefore, we conclude that 1,8-naphthyridine derivatives potentiate the activity of fluoroquinolone antibiotics against multi-resistant bacterial strains, and thereby interesting candidates for the development of drugs against bacterial infections caused by multidrug resistant strains.     

A valuable heterocyclic ring transformation: from isoxazolin-5(2H)-ones to quinolines

A new synthesis of quinoline derivatives was achieved by catalytic hydrogenation of 3,4-disubstituted 2-(2-formylphenyl)-isoxazolin-5(2H)-ones. In the same way, 2,3-disubstituted [1,8]naphthyridine was obtained.