A Facile Approach for One-Pot Synthesis of 1H-pyrazolo [1,2-b]phthalazine-5,10-dione Derivatives Catalyzed by ZrCl4 as an Efficient Catalyst Under Solvent-Free Conditions

Synthesis, characterization and in vitro, in vivo, in silico biological evaluations of substituted benzimidazole derivatives

A series of substituted benzimidazole derivatives were synthesized by reacting O-phenylenediamine with various aromatic aldehydes or glycolic acid using various inexpensive reagents in aqueous media. Synthesized compounds were characterized and elucidated by IR, ¹H NMR, ESI-MS spectra. Resultant compounds were screened for in vitro antimicrobial, cytotoxic, antioxidant, lipid peroxidation and cholinesterase inhibitory activities, in vivo analgesic and anti-inflammatory, and in silico anti-acetylcholinesterase and anti-butyrylcholinesterase activities. Among the synthesized compounds, compound 3b showed most promising central analgesic effect (46.15%) compared to morphine (48.08%), whereas compounds 6, 3c and 3a showed significant peripheral analgesic activity at two different dose levels (25 mg/kg and 50 mg/kg). Compounds 3b and 3a at the dose of 100 mg/kg showed significant anti-inflammatory effects from the first hour and onward, whereas compounds 6 and 3b showed moderate cytotoxic activities. In addition, compound 3a showed significant antioxidant activity having IC₅₀ value of 16.73 µg/ml compared to 14.44 µg/ml for the standard BHT. Compound 6, 3a and 3b exhibited mild to moderate cholinesterase inhibitory activity. In silico studies revealed that compound 3a and 3b might be suitable for cholinesterase inhibitory activity. A comprehensive computational and experimental data suggested compounds 3b and 3a as the best possible candidates for pharmacological activity. All the experimental data were statistically significant (p < 0.01 level).

Superparamagnetic Polyaniline-co-m-phenylenediamine@Fe3O4 Nanocomposite as an Efficient Heterogeneous Catalyst for the Synthesis of 1H-pyrazolo [1,2- a]pyridazine-5,8-diones & 1H-pyrazolo[1,2-b]phthalazine-5, 10-diones" Instead of 1H-pyrazolo[1,2-b] Phthalazinedione Derivatives

BACKGROUND

The use of polymer-based catalysts has increased because of their high potential application as an effective catalyst in organic reactions. They have benefits such as high efficiency and reactivity, simple separation, and safety compared to other heterogeneous catalysts.

AIM AND OBJECTIVE

The objective of the current research is to prepare solid polymer-based catalysts, poly(aniline-co- m-phenylenediamine) (PAmPDA), and its superparamagnetic nanocomposite. Then, the catalytic activity of the resulting superparamagnetic nanocomposite was investigated in the synthesis of 1H-pyrazolo[1,2-b]phetalazine-5,10-diones and 1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives. A series of some 1H-pyrazolo[1,2-b]phetalazine-5,10-diones and 1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives was tested for its antibacterial properties against the Staphylococcus aureus and E.coli bacteria.

MATERIALS AND METHODS

PAmPDA copolymer was synthesized in a 1:2 molar ratio of Ani to mPDA via radical oxidative polymerization at room temperature. Superparamagnetic PAmPDA@Fe3O4 nanocomposite was synthesized from a mixture of Fe(II), Fe(III) solution, and PAmPDA copolymer via the in-situ co-precipitation technique. 1H-pyrazolo[1,2-b]phetalazine-5,10-diones were synthesized via one-pot three-component condensation reaction of Phthalhydrazide, aromatic aldehyde derivatives, and malononitrile in the presence of PAmPDA under solvent-free conditions at 80 °C. The synthesis of 1Hpyrazolo[1,2-a]pyridazine-5,8-dione derivatives was carried out via a one-pot three-component condensation reaction of maleic hydrazide, aromatic aldehyde derivatives, and malononitrile in the presence of PAmPDA under reflux conditions at EtOH/H2O 1:1. The antibacterial activity of some derivatives was tested against Gram-positive and Gram-negative bacteria.

RESULTS

First, superparamagnetic PAmPDA@Fe3O4 nanocomposite was synthesized and characterized successfully, and then the resulting nanocatalyst was used for the synthesis of pyrazolo[1,2-b]phthalazine and pyrazolo[1,2-a]pyridazine. We obtained the maximum yield of the desired 1H-pyrazolo[1,2- b]phthalazine-5,10 dione derivatives with 0.05 g of catalyst at 80°C, under solvent free conditions, whereby the reaction was complete within 30 min. A wide range of 1H-pyrazolo[1,2-b]phthalazine-5,10 dione derivatives were synthesized in good to excellent yield. On the other hand, pyrazolo[1,2- a]pyridazine derivative was synthesized successfully in high yield using PAmPDA as a nanocatalyst. The antibacterial activity of some derivatives, according to the data (inhibition zone%), showed good activity against Staphylococcus aureus and E.coli.

CONCLUSION

In this research, PAmPDA was used for mild preparation of 1H-pyrazolo [1,2-a]pyridazine5,8-diones & 1H-pyrazolo[1,2-b]phetalazine-5,10-diones derivatives with excellent yields and short reaction times. The attractive features of this protocol are simple procedure, cleaner reaction, and the use of recyclable nanocatalyst. Satisfactory yields of products and easy workup make this a useful protocol for the green synthesis of this class of compounds. The antibacterial activity of some derivatives, according to the data (inhibition zone%), showed good activity against Staphylococcus aureus and E.coli.

Experimental and DFT mechanistic insights into one-pot synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones under catalysis of DBU-based ionic liquids

Kinetic impacts of two DBU-based ionic liquids in the three-component synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones and the mechanism of the reaction were investigated by DFT calculations.