4-Benzylamino-1-chloro-6-substituted phthalazines: synthesis and inhibitory activity toward phosphodiesterase 5

p-Toluenesulfonic acid-promoted organic transformations for the generation of molecular complexity

Since the beginning of this century, p-toluenesulfonic acid (p-TSA) catalysed organic transformations have been an active area of research for developing efficient synthetic methodologies. Often, catalysis using p-TSA is associated with many advantages, such as operational simplicity, high selectivity, excellent yields, and ease of product isolation, which make organic synthesis convenient and versatile. Notably, p-TSA is a non-toxic, commercially available, inexpensive solid organic compound that is soluble in water, alcohols, and other polar organic solvents. p-TSA is a strong acid compared to many protic or mineral acids and its high acidity helps activate different organic functional groups. p-TSA-promoted conversions are fast, have a high atom and pot economy, and feature a multiple bond-forming index. Therefore, the utilization of p-TSA enables the synthesis of many important structural scaffolds without any hazardous metals, making it desirable in numerous applications of sustainable and green chemistry. Recently, this emerging area of research has become one of the pillars of synthetic organic chemistry to synthesise biologically relevant, complex carbocycles and heterocycles. This study provides a comprehensive summary of methods, applications, and mechanistic insights into p-TSA-catalysed organic transformations, covering the literature reports that have appeared since 2012.

Unexpected synthesis of 4-(4,5-dihydro-1H-imidazol-2-ylsulfanyl)butyl-H-sulfite as a catalyst for the synthesis of pyrazolophthalazines

Several attempts for preparation of 4,4'-(2-thioxoimidazolidine-1,3-diyl)bis(butane-1-sulfonic acid) were not successful despite taking 2 mmol of 1,4-butane sultone in reaction with 1 mmol of imidazolidine-2-thione. Instead, 4-(4,5-dihydro-1H-imidazol-2-ylsulfanyl)butyl hydrogen sulfite (DISBHS) was prepared unexpectedly, characterized and used for the synthesis of diverse pyrazolophthalazines from the one-pot three component condensation reaction of phthalhydrazide, malononitrile and aldehydes under mild conditions.

Magnetically recoverable Fe3O4 nanocatalyst for the synthesis of biodynamically significant 1H-pyrazolo[1,2-b]phthalazine-5,10-diones derivatives and its DFT study

An environmentally sustainable and proficient method is reported for the synthesis of medicinally important pyrazolo[1,2-b] phthalazine dione derivatives by aqueous micellar medium catalysed by Fe3O4 NPs. Dialkyl acetylenedicarboxylate with isocyanides in the presence of phthalhydrazide is used as starting material. The main advantages of this protocol are the availability of starting materials, short reaction times, green solvents and practical simplicity.

Ag NPs supported chitosan-agarose modified Fe3O4 nanocomposite catalyzed synthesis of indazolo[2,1-b]phthalazines and anticancer studies against liver and lung cancer cells

In this article we report a novel Ag NPs fabricated chitosan-agarose composite functionalized core-shell type Fe₃O₄ nanoparticle (Ag/CS-Agar@Fe₃O₄). The biogenic material was analyzed over a number of physicochemical methods like, FT-IR, FE-SEM, TEM, EDX, XRD, VSM and ICP-OES. In catalytic exploration we aimed the synthesis of diverse 2H-indazolo0-b]phthalazine-trione derivatives via one-pot three component coupling of phathalalhydrazide, dimedone and different aldehydes. It afforded good to excellent yields under solvent-less conditions. Robustness of the catalyst was justified by catalyst recyclability for consecutive 10 times, hot filtration and leaching tests. Again, biological activity of the material was evaluated by studying the antioxidant and cytotoxicity properties over lung and liver cancer cell lines. Antioxidant potential of Ag/CS-Agar@Fe₃O₄ was assessed by DPPH radical scavenging studies and the corresponding IC50 was found to be 96.57 μg/mL. Liver and lung cancer studies over Ag/CS-Agar@Fe₃O₄ was carried out by MTT assay against HepG2 and A549 cell lines. The corresponding IC50 values were found as 192.35 and 365.28 μg/mL respectively. % Cell viability of the nanomaterial decreased dose dependently over both the cell lines without any cytotoxicity on normal cell line. The results demonstrates Ag/CS-Agar@Fe₃O₄ nanocomposite to be an efficient chemotherapeutic drug against the lung and hepatocellular carcinoma cells.

Lipase-mediated multicomponent synthesis of 1H-Pyrazolo[1,2-b]phthalazine-5,10-dione derivatives in a binary solvent medium

A new method for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives via lipase from the Aspergillus niger-catalyzed multicomponent reaction of aldehydes, malononitrile, and phthalhydrazide is reported herein for the first time. This novel method holds several advantages, including its efficiency, environmental friendliness, simple workup procedure, and good yield (70-86%). The effects of temperature, organic solvents, and water content were investigated. This protocol has the potential to replace traditional chemical synthesis routes for the synthesis of nitrogen-containing heterocyclic compounds.

In vitro and in silico lipoxygenase inhibition studies and antimicrobial activity of pyrazolyl-phthalazine-diones

The series of pyrazolyl-phthalazine-dione derivatives (PPDs) was subjected to evaluation of their in vitro lipoxygenase (LOX) inhibition and antimicrobial activities. Results obtained for LOX inhibition activities of PPDs showed that all compounds exhibit good to excellent activity, whereby compounds with eudesmic, syringic, vanillic or toluic moiety are the most active. Molecular modelling study was performed to investigate the possible mechanism of action and binding mode of compounds within the LOX active site. Docking results revealed that activity of the examined compounds depends on the functional group ability to create hydrogen bond accepting (HBA) and hydrophobic features (Hy) in the LOX-Ib active site. In addition, all substances were tested for their antibacterial and antifungal activities. The investigated compounds showed better antifungal than antibacterial activity. The highest antifungal activity was on Aspergillus fumigatus ATTC 204305 and Trichoderma viridae ATCC 13233.

Synthesis, spectroscopic and molecular docking studies on new schiff bases, nucleosides and α-aminophosphonate derivatives as antibacterial agents

New Nucleosides, analogues derived from 1, 3, 4-oxadiazole, arylidene analogues and α-aminophosphonate were prepared. Infrared (IR), elemental analysis and ¹HNMR elucidated nucleosides; arylidines and phosphonate derivatives. The prepared derivatives were purified and allowed to test against bacteria strains. Phosphonate derivative 12a showed the higher antibacterial against E. coli with inhibition zone 35 mm, P. aeruginosa with inhibition zone 30 and S. aureus with inhibition zone 22 while compounds 4, 6d, 9a, 9c and 12c showed moderate to weak activity against these bacteria species with inhibition zones ranged from 12 mm to 24 mm. The molecular docking studies was applied on compound 12a, which showed the binding at the active DNA Gyrase.

Ag NPs on chitosan-alginate coated magnetite for synthesis of indazolo[2,1-b]phthalazines and human lung protective effects against α-Guttiferin

Biocomposite nanomaterials have been evolved as the new generation catalysts and therapeutic supplement in these days. Magnetically isolation has added new features to this category. This has encouraged us to synthesize a novel Ag NP adorned chitosan-alginate dual bio-polysaccharide (two of the more versatile polysaccharides) modified core-shell magnetic nanocomposite (Fe₃O₄/CS-Alg/Ag NPs). The material was meticulously characterized following different physicochemical techniques, such as, FT-IR, ICP-OES, FESEM, EDX, atomic mapping, TEM, VSM, XRD and XPS studies. The as synthesized material was catalytically explored in the one-pot multicomponent synthesis of biologically potent 2H-indazolo[2,1-b]phthalazine-trione derivatives involving a wide range of substrates. The reactions were ended up with excellent yields under solvent-free heating conditions. The catalyst recyclability, heterogeneity and leaching tests were performed to ensure its high stability and robustness. It could be reused as much as 10 times in succession with almost unchanged catalytic performances. In the lung protective part of the present research, the human lung toxicity was induced by α-Guttiferin. The cell viability of lung MRC-5, CCD19Lu, WI-38, and BEAS-2B cell lines was measured by trypan blue assay. Caspase-3 activity was assessed by the caspase activity colorimetric assay kit and mitochondrial membrane potential of lung cells was studied by Rhodamine123 fluorescence dye. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) test was used to show DNA fragmentation and apoptosis of lung cells. Also, the Rat inflammatory cytokine assay kit was used to measure the concentrations of inflammatory cytokines. The catalyst-treated cell cutlers significantly (p ≤ 0.01) reduced the DNA fragmentation, caspase-3 activity, and inflammatory cytokines concentrations, and raised the mitochondrial membrane potential and cell viability in the high concentration of α-Guttiferin-treated lung MRC-5, CCD19Lu, WI-38, and BEAS-2B cells. The best result of lung protective properties of catalyst against α-Guttiferin was seen in the high dose of catalyst i.e., 4 μg. DPPH test revealed similar antioxidant potentials for catalyst and butylated hydroxytoluene. The catalyst inhibited half of the DPPH molecules in the concentration of 171 μg/mL. According to the above results, catalyst can be administrated as a lung protective drug for the treatment of lung diseases after approving in the clinical trial studies in humans.

Phthalazinone Scaffold: Emerging Tool in the Development of Target Based Novel Anticancer Agents

Phthalazinones are important nitrogen-rich heterocyclic compounds which have been a topic of considerable medicinal interest because of their diversified pharmacological activities. This versatile scaffold forms a common structural feature for many bioactive compounds, which leads to the design and development of novel anticancer drugs with fruitful results. The current review article discusses the progressive development of novel phthalazinone analogues that are targets for various receptors such as PARP, EGFR, VEGFR-2, Aurora kinase, Proteasome, Hedgehog pathway, DNA topoisomerase and P-glycoprotein. It describes mechanistic insights into the anticancer properties of phthalazinone derivatives and also highlights various simple and economical techniques for the synthesis of phthalazinones.

Ultrasound-promoted Green Synthesis of pyrido[2,1-a]isoquinoline Derivatives and Studies on their Antioxidant Activity

Aims & Objective: An efficient procedure for the synthesis of pyrido[2,1-a]isoquinoline derivatives in excellent yields was investigated using catalyst-free multicomponent reaction of phthaladehyde, methylamine, activated acetylenic compounds, alkyl bromides and triphenylphosphine in water under ultrasonic irradiation at room temperature. In addition, Diels- Alder reactions of pyrido[2,1-a]isoquinoline derivatives with activated acetylenic compounds under ultrasonic irradiation are investigated in two procedures. The advantages of this procedure compared to report methods are short time of reaction, high yields of product, easy separation of product, clean mixture of reaction and green media for performing reaction. In addition, because of having isoquinoline core in synthesized compounds, in this research antioxidant activity of some synthesized compounds was studied.

MATERIALS AND METHODS

To a stirred mixture of phthalaldehyde 1 (2 mmol) and methylamine 2 (2 mmol) in water (3 mL) under ultrasonic irradiation was added to activated acetylenic compounds 4 after 20 min. Alkyl bromide 3 and triphenylphosphine 5 react in another pot in water (3 mL) under ultrasonic irradiation for 15 min. After this time, this mixture was added to the first pot. After completion of the reaction, the solid residue was separated by filtration and washed with Et2O to afforded pure title compound 6.

RESULTS

In this work, generation of pyrido[2,1-a]isoquinoline derivatives 6 are performed using phthalaldehyde 1, methylamine 2, α-halo substituted carbonyls 3, activated acetylenic compounds 4 and triphenylphosphine 5 in water under ultrasonic irradiation condition at room temperature in excellent yield at short time.

CONCLUSION

In summary, multicomponent reaction of phthaladehyde, methylamine, activated acetylenic compounds, alkyl bromides and triphenylphosphine in water under ultrasonic irradiation at room temperature produced pyrido[2,1-a]isoquinoline derivatives in excellent yields. Also, Diels-Alder reaction of pyrido[2,1-a]isoquinoline derivatives with activated acetylenic compounds and triphenylphosphine under ultrasonic irradiation is investigated in two procedures. Also, the antioxidant activities of 6a, 6c, 6g and 6i were evaluated by DPPH radical scavenging and ferric reducing power analyzes. The compounds 6a exhibit excellent DPPH radical scavenging activity and FRAP compared to synthetic antioxidants BHT and TBHQ. The chief benefits of our method are high atom economy, green reaction conditions, higher yield, shorter reaction times, and easy work-up, which agree with some principles of green chemistry.

Efficient ZrO(NO3)2.2H2O Catalyzed Synthesis of 1H-Indazolo[1,2-b] phthalazine-1,6,11(13H)-triones and Electronic Properties Analyses, Vibrational Frequencies, NMR Chemical Shift Analysis, MEP: A DFT Study

The synthesis of 1H-indazolo[1,2-b]phthalazine-1,6,11(13H)-trione derivatives, using one-pot three-component condensation reaction of 3-nitrophthalic anhydride, hydrazine monohydrate, dimedone, and aromatic aldehydes in the presence of ZrO(NO3)2.2H2O as the novel catalyst and in reflux conditions in EtOH was reported. Quantum theoretical calculations for three structures of compounds (5a, 5b, and 5c) were performed using the Hartree–Fock (HF) and density functional theory (DFT). From the optimized structure, geometric parameters were obtained and experimental measurements were compared with the calculated data. The structures of the products were confirmed by IR, 1H NMR, 13C NMR, mass spectra, and elemental analyses. The IR spectra data and 1H NMR and 13C NMR chemical shift computations of the 1H-indazolo[1,2-b]phthalazine-1,6,11(13H)-trione derivatives in the ground state were calculated. Frontier molecular orbitals (FMOs), total density of states (DOS), thermodynamic parameters, and molecular electrostatic potential (MEP) of the title compounds were investigated by theoretical calculations. Molecular properties such as the ionization potential (I), electron affinity (A), chemical hardness (η), electronic chemical potential (µ), and electrophilicity (ω) were investigated for the structures. Thus, there was an excellent agreement between experimental and theoretical results.

Preparation, characterization, and use of novel Cu@Fe3O4 MNPs in the synthesis of tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones and 2H-indazolo[2,1-b]phthalazine-triones under solvent-free conditions

Cu@Fe₃O₄ MNPs as novel nanomagnetic reagents were prepared to investigate their catalytic behavior in the preparation of tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones, as important biologically active compounds. Then, characterization of the synthesized nanoparticles was performed using different methods including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM). All reactions were performed with small amounts of the Cu@Fe₃O₄ MNPs under solvent-free conditions. After completion of the reaction, because of the magnetic nature of the nanocatalyst, they could be simply separated with an external magnet and easily reused with no considerable decrease in the catalytic behavior even after seven runs.

Regiocontrolled and Stereoselective Syntheses of Tetrahydrophthalazine Derivatives using Radical Cyclizations

Tetrahydrophthalazine derivatives have found important applications in pharmaceutical research, but existing synthetic methods are unable to access them regio- and stereoselectively. Here, a new approach is presented that addresses these challenges by utilizing a 6-endo-trig radical cyclization in the key step. The desired tetrahydrophthalazines can be accessed in high yields (55-98 %) and high diastereoselectivities for the trans-product (>95:5) starting either from readily accessible hydrazones, or from the corresponding aldehydes and substituted Boc-hydrazides in a one-pot process. The synthetic versatility of the tetrahydrophthalazine core was demonstrated by its straightforward conversion to dihydro-phthalazines, phthalazines, or pyrazolo dione derivatives. Furthermore, the N-N bond was reduced to afford a new route to 1,4-diamines.

Phthalazine-trione as a blue-green light-emitting moiety: crystal structures, photoluminescence and theoretical calculations

Phthalazine-trione was found to be a new robust blue-green light-emitting fluorophore, regardless of the substitution pattern.