Heterocyclic Quinones in ihe Nenitzescu Reaction. Synthesis of Furo- And Pyrroloquinolines from 2-Methoxycarbonyl-4-oxo-5,8-quinolinequinone

Derivatives of furo[2,3-f]quinoline were synthesized by the reaction of the enamines of acetylacetone and benzoylacetone with 2-methoxycarbonyl-4-oxo-5,8-quinolinequinone. A derivative of pyrrolo[2,3-h]quinoline was obtained from N-benzyl--aminocrotonic ester.     

Synthesis and Crystal Structure of 3,7,7-Trimethyl- 1-phenyl-4-（3-nitrophenyl）- 4,5,6,7,8,9-hexahydro-1H-pyrazolo [3,4-b]quinoline-5（6H）-one

The title compound (C25H24N4O3) has been prepared by the cyclocondensation of 5-amino-3-methyl-l-phenypyrazol, m-nitrobenaldehyde and dimedone in glycol under microwave irradiation without catalyst. The crystal structure was determined by single-crystal X-ray diffraction to be orthorhombic, space group Pbca with a=16.3331(10), b=13.8329(9), c=19.4163(12) A, V= 4386.8(5)A3, Z=8, Dc=1.298g/cm^3,μ=0.087 mm^-1, F(000)=1808, Mr=428.48, the final R=0.0519 and wR=0.1019. X-ray analysis revealed that the pyridine ring is of boat conformation and the six-membered ring fused with it adopts twist boat conformation.     

tert-Amino effect in heterocyclic chemistry. Synthesis of hydrogenated spiro derivatives of quinolines

A new method was developed for the one-step synthesis of spiro derivatives of fused quinolines by the reactions of ortho-amino derivatives of benzaldehyde with Meldrum"s acid, cyclohexane-1,3-dione, or N,N"-disubstituted barbituric acids.     

Separation and determination of carnosine-related peptides using capillary electrophoresis with laser-induced fluorescence detection

A capillary electrophoresis (CE) method with laser-induced fluorescence (LIF) detection was developed for the separation and detection of carnosine-related peptides (carnosine, anserine, and homocarnosine). A sensitive and fluorogenic regent, 3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde (CBQCA) was selected as a precapillary labeling reagent for imidazole dipeptides to form isoindole derivatives. The optimized molar ratio between CBQCA and peptide was found to be 75:1, and 50 mmol/L borate buffer (pH 9.2) was used for the derivatization in order to achieve good efficiency. Three imidazole dipeptides were baseline-separated within 20 min by using 112 mmol/L sodium borate (pH 10.4-10.8) as running buffer. Concentration detection limits (signal-to-noise ratios) for carnosine, anserine, and homocarnosine were 4.73, 4.37, and 3.94 nmol/L, respectively. This method has been applied to the analysis of human cerebrospinal fluid (CSF) and meat dry powder of pig and sheep. Recoveries were in the range of 82.9-104.8% for homocarnosine in CSF. For carnosine and anserine, the recoveries are 98.3% and 80.2% in meat dry powder of pig and 111.2% and 112.8% in meat dry powder of sheep, respectively.     

Synthesis of 3-substituted-4-hydroxyquinoline N-oxides from the Baylis-Hillman adducts of o-nitrobenzaldehydes

The reaction of the Baylis-Hillman adducts 1b-f derived from o-nitrobenzaldehydes in trifluoroacetic acid in the presence of triflic acid (0.2 equiv.) afforded 3-substituted-4-hydroxyquinoline N-oxides 2b-e and 2a in good to moderate yields. The reaction mechanism was evidenced by the experiment with 1f, the Baylis-Hillman adduct of 2-nitrobenzaldehyde N-tosylimine, as the one involving N-hydroxyisoxazoline as the key intermediate.     

The efficient in‐situ reduction and cyclization reaction of aromatic aldehyde, 1,3‐cyclopentanedione (tetronic acid), and nitro‐compound under SnCl2·2H2O‐THF medium

An efficient in‐situ reduction and cyclization reaction for the synthesis of pyrazolo[4,3‐f]quinoline, pyrazolo[3,4‐f]quinoline, and pyrazolo[3,2‐f]quinoline derivatives directly form 5‐nitroindazole, 6‐nitroindazole and 5‐nitroindole in the presence of SnCl₂·2H₂O was reported. Compared to traditional synthetic methods, this approach has the advantages of stable reagents, easy obtaining raw material, and high yields. In this research, SnCl₂·2H₂O is the efficient reducing agent for the in‐situ reduction and cyclization reaction of nitro‐compound. In addition, this process provided an alternative approach for the synthesis of target compounds.     

Cyanine Dyes Containing Quinoline Moieties: History,Synthesis, Optical Properties,and Applications

Cyanine dyes carrying quinoline moieties are an important class of organic molecules that are of great interest for applications in many fields like medicine, pharmacology, and engineering. Despite their exceptional properties, such as stability, high molar extinction coefficients, and high pH-sensitivity, this class of dyes has been less analyzed and reviewed in the last few decades. Therefore, this review article focuses on discussing the history of quinoline compounds, various synthetic routes to prepare quinolinium salts and symmetrical and asymmetrical mono-, di-, tri-, penta- and heptamethine cyanine dyes, containing quinoline moieties, together with their optical properties and applications as photosensitizers in photodynamic therapy, probes in biomolecules for labeling of nucleic acids, as well as imaging agents.     

Synthesis and Structures of Arene Ruthenium (II)–NHC Complexes: Efficient Catalytic α‐alkylation of ketones via Hydrogen Auto Transfer Reaction

A panel of six new arene Ru (II)‐NHC complexes 2a‐f , (NHC = 1,3‐diethyl‐(5,6‐dimethyl)benzimidazolin‐2‐ylidene 1a , 1,3‐dicyclohexylmethyl‐(5,6‐dimethyl)benzimidazolin‐2‐ylidene 1b and 1,3‐dibenzyl‐(5,6‐dimethyl)benzimidazolin‐2‐ylidene 1c ) were synthesized from the transmetallation reaction of Ag‐NHC with [(η⁶‐arene)RuCl₂]₂ and characterized. The ruthenium (II)‐NHC complexes 2a‐f were developed as effective catalysts for α‐alkylation of ketones and synthesis of bioactive quinoline using primary/amino alcohols as coupling partners respectively. The reactions were performed with 0.5 mol% catalyst load in 8 h under aerobic condition and the maximum yield was up to 96%. Besides, the different alkyl wingtips on NHC and arene moieties were studied to differentiate the catalytic robustness of the complexes in the transformations.     

Nicotinic acid-supported cobalt ferrite-catalyzed one-pot synthesis of substituted chromeno[3,4-b]quinolines

One-pot synthesis of substituted chromeno[3,4-b]quinoline derivatives was developed by three-component reaction of aldehydes, dimedone or 1,3-cyclohexadione, and 4-aminocoumarin in the presence of nicotinic acid-supported cobalt ferrite [CoFe₂O₄@SiO₂@Si(CH₂)₃Cl@NA] as a novel magnetic catalyst in chloroform at reflux conditions. Nicotinic acid-supported cobalt ferrite was characterized via Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry. Moreover, the catalyst could be easily recovered by magnetic separation and recycled up to five times without significant loss of its catalytic activity. The products formed in excellent yields over appropriate reaction times under environmentally friendly conditions. High efficiency and easy isolation of the catalyst from products by simple magnetic attraction are some of the considerable advantages of this procedure.