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A novel nanomagnetic catalyst has been synthesized by immobilization of triethanolamine lactate cellulose with Fe3O4 NPs. The prepared catalyst has been used as an efficient and recoverable catalyst for the regioselective synthesis of pyrazolo quinolones by the three-component reaction of dimedone, 5-amino pyrazolone and aromatic aldehydes in ultrasound condition. This economical catalyst provides high yields of products, short experimental time and easy workup for green synthesis of pyrazolo[3,4-b]quinolone compounds. Theoretical studies have been employed to investigate the reaction mechanism by using the B3LYP/6-311G method. Electronic parameters of all components have been determined in order to reorganize the role of components in the reaction mechanism. [ABSTRACT FROM AUTHOR]

In this article, a synthesis of N’-(benzylidene)-2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazides and their structural interpretation by NMR experiments is described in an attempt to explain the duplication of some peaks in their 1H- and 13C-NMR spectra. Twenty new 6-methyl-1H-pyrazolo[3,4-b]quinoline substituted N-acylhydrazones 6(a–t) were synthesized from 2-chloro-6-methylquinoline-3-carbaldehyde (1) in four steps. 2-Chloro-6-methylquinoline-3-carbaldehyde (1) afforded 6-methyl-1H-pyrazolo[3,4-b]quinoline (2), which upon N-alkylation yielded 2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetate (3). The hydrazinolysis of 3 followed by the condensation of resulting 2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazide (4) with aromatic aldehydes gave N-acylhydrazones 6(a–t). Structures of the synthesized compounds were established by readily available techniques such as FT-IR, NMR and mass spectral studies. The stereochemical behavior of 6(a–t) was studied in dimethyl sulfoxide-d6 solvent by means of 1H NMR and 13C NMR techniques at room temperature. NMR spectra revealed the presence of N’-(benzylidene)-2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazides as a mixture of two conformers, i.e., E(C=N)(N-N) synperiplanar and E(C=N)(N-N)antiperiplanar at room temperature in DMSO-d6. The ratio of both conformers was also calculated and E(C=N) (N-N) syn-periplanar conformer was established to be in higher percentage in equilibrium with the E(C=N) (N-N)anti-periplanar form.

Abstract The application of natural eutectic solvent (NDDES) in organic synthesis has received more and more attention. In this work, a green protocol for one-pot synthesis of spiro[indoline-3,4′-pyrazolo[3,4- b ]pyridines] via three-component reactions of 1 H -pyrazol-5-amin, isatin and enolizable C H activated compound is achieved by the combination of microwave irradiation with choline chloride and lactic acid based NDDES. This novel method is clean, cheap, simple, high yield, chromatography-free and scalable. The use of choline chloride and lactic acid as a biodegradable, recycled and reusable media meets most of the criteria to be considered as a sustainable and environmentally benign process. Graphical abstract Unlabelled Image Highlights • The synthetic procedure of choline chloride and lactic acid based on the natural eutectic solvents is very simple. • The NDDES plays dual role as medium and catalyst for synthesis of spirooxindole derivatives. • This new method is clean, inexpensive, high yield, chromatography-free and scalable. • NDDES is easy to recycle and reuse. [ABSTRACT FROM AUTHOR]

The stereoselective syntheses of a library of novel spiro-tethered pyrazolo[3,4-b]quinoline-pyrrolidine/pyrrolothiazole/indolizine-oxindole/acenaphthene hybrid heterocycles have been achieved through the 1,3-dipolar cycloaddition of azomethine ylides generated in situ from α-amino acids and 1,2-diketones to dipolarophiles derived from pyrazolo[3,4-b]quinoline derivatives. [ABSTRACT FROM AUTHOR]

A novel and green approach for efficient and rapid synthesis of 4-aryl-3-methyl-1-phenyl-1H-benzo[h]pyrazolo[3,4-b]quinoline-5,10-diones has been accomplished by the one-pot condensation reaction of aromatic aldehydes, 3-methyl-1-phenyl-1H-pyrazol-5-amine and 2-hydroxynaphthalene-1,4-dione using PEG1000-based dicationic acidic ionic liquid (PEG1000-DAIL) as a catalyst was reported. Recycling studies have shown that the PEG1000-DAIL can be readily recovered and reused several times without significant loss of activity. The key advantages are the short reaction time, high yields, simple workup, and recovered catalyst. [ABSTRACT FROM AUTHOR]

Fluorescent dye 2-[(2-Hydroxyethyl)-(1,3-diphenyl-1 H-pyrazolo[3,4- b]quinolin-6-ylmethyl)-amino]ethanol (LL1) was examined for its efficiency in the detection of small inorganic cations (lithium, sodium, barium, calcium, magnesium, cadmium, lead and zinc). The dye was synthesized in the laboratory and investigated by means of both, steady-state and time-resolved fluorescence techniques. This compound acts as a fluorescent sensor suitable for detection of small inorganic cations (lithium, sodium, barium, calcium, magnesium, cadmium, lead and zinc) in strongly polar solvent (acetonitrile). An electron transfer from the electro-donative part (receptor) of the molecule to the acceptor part (fluorophore) is thought to be the main mechanism that underlies functionality of the compound as a sensor. This process can be retarded upon complexation of the receptor moiety by inorganic cations. Relatively high sensitivity but poor selectivity of the aminoalcohol thatcontains indicator towards the two-valued cations was observed. However, upon addition of some amounts of water the selectivity of this sensor has been enhanced (especially towards lead cation). The preliminary results in analytical application of the sensor are discussed. [ABSTRACT FROM AUTHOR]

Abstract: A simple, efficient, and eco-friendly synthetic protocol has been developed via one pot three-component reaction between aldehyde, amino pyrazole, and 1,3-cyclohexanedione by using recyclable polyethylene glycol (PEG)-400 as a reaction medium. Utilizing this protocol a variety of pyrazolo[3,4-b]quinoline derivatives were synthesized in excellent yields. [Copyright &y& Elsevier]

An efficient synthesis of 4-aryl-3-methyl-1-phenyl-1 H-benzo[ g]pyrazolo[3,4- b]quinoline-5,10-diones from the three-component condensation reaction of 3-methyl-1-phenyl-1 H-pyrazol-5-amine, aromatic aldehydes, and 2-hydroxy-1,4-naphthoquinone under solvent-free conditions in good to excellent yields and short reaction times using sulfamic acid as heterogeneous acid catalyst has been investigated. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: We have studied the variation of principal spectroscopic parameters (absorption edge, spectral positions of the first three principal bands, oscillator strengths) for three oxadiazoles (pyrazoloquinoline derivatives) with different state dipole moments incorporated into the polymethyl methacrylate (PMMA) polymer matrices in the 3% in weighting units. For investigations we have chosen three derivatives with different values of the state dipole moments. We have found that during illumination by 10ns Nd-YAG laser beam with pulse duration about 10ns, frequency repetition about 10Hz and power density about 0.8–1.3MWcm−2 the observed photoinduced changes red shifted for the three principal spectral bands situated at 330–350nm; 450–500nm and 525–550nm. It was established that under influence of the pulsed Nd-YAG laser we observe substantial spectral shifts of the observed spectral maxima. The value of the shift is increased with decreased state dipole moment values. [Copyright &y& Elsevier]

Ethyl a-cyano-ß-(1-chloro-3,4-dihydronaphthalene-2-yl) acrylate (2) was prepared by the Knoevenagel condensation of 1 with ethyl cyanoacetate. Compound 2 was used as the key intermediate to prepare Schiff bases (3a, b), benzo[ c ]acridine (4), naphthyl thiopyrimidine (5), and pyrazolo[2,3- a ]-benzo[ h ]quinazoline (6) derivatives through its reaction with hydrazines, p-ansidine, thiourea, and 3,5-diamino-4-phenylazopyrazole, respectively. Base-catalyzed cyclocondensation of 1 with hippuric acid gives oxazolone derivative (7). Reaction of compound 7 with aniline gave imidazolone derivative (9). Treatment of compound 1 with different types of diaminopyrazoles gave 6,7-dihydro-pyrazolo[2,3- a ]-benzo[ h ]quinazoline (10–13) derivatives. The multicomponent reaction of compound 1 with pyrazolone and malononitrile in the presence of ammonium acetate furnished pyrazolo[3,4- b ]-benzo[ h ]quinoline (14) while in the presence of piperidine afforded benzo[ h ]chromeno[2,3- c ]pyrazole derivative 15. [ABSTRACT FROM AUTHOR]

Pyrazoloquinoline is the basic structural unit whose derivatives are used in producing light-emitting diodes. The presented computations of ground state energies and equilibrium geometry in these states for three probable pyrazolo[3,4-b] quinolines (PQ) structures and PQ anion have been carried out using density functional theory. The changes in the geometry and energy of the ground states in computations both taking and not taking into account non-polar (cyclohexane) and polar (methanol, DMSO) solvents have been compared. It has been proved that tautomerism phenomenon is most likely between 1H-PQ and 2H-PQ. [Copyright &y& Elsevier]