Review on the Role of the Metal Catalysts in the Synthesis of Pharmacologically Important Quinoline Substrate

Trifluoromethylated Quinolone-Hydantoin Hybrids: Synthesis and Antibacterial Evaluation

A series of new trifluoromethyl-substituted quinolones and hydantoin hybrids has been synthesized and evaluated against Gram-positive bacterium (Staphylococcus aureus MTCC 96) and Gram-negative bacteria (Pseudomonas aeruginosa MTCC 441, Klebsiella pneumonia MTCC 109, and Escherichia coli MTCC 442). Compound  19c, having the 6-propene group on the quinolone ring, showed similar activity to a standard drug (chloramphenicol) by exhibiting MIC values of 50 µg/mL against S. aureus and P. aeruginosa. Physicochemical properties of compound 19c were also determined, which were in line with Lipinski’s rule of five, suggesting the suitability of compound 19c in biological systems. Various types of binding interactions of 19c within the active site of DNA gyrase of S. aureus were also streamlined by molecular docking studies, suggesting its capability to block the catalytic process of the DNA gyrase, which could be the possible reason for its antibacterial potential.

Catalytic Approaches to Multicomponent Reactions: A Critical Review and Perspectives on the Roles of Catalysis

In this review, we comprehensively describe catalyzed multicomponent reactions (MCRs) and the multiple roles of catalysis combined with key parameters to perform these transformations. Besides improving yields and shortening reaction times, catalysis is vital to achieving greener protocols and to furthering the MCR field of research. Considering that MCRs typically have two or more possible reaction pathways to explain the transformation, catalysis is essential for selecting a reaction route and avoiding byproduct formation. Key parameters, such as temperature, catalyst amounts and reagent quantities, were analyzed. Solvent effects, which are likely the most neglected topic in MCRs, as well as their combined roles with catalysis, are critically discussed. Stereocontrolled MCRs, rarely observed without the presence of a catalytic system, are also presented and discussed in this review. Perspectives on the use of catalytic systems for improved and greener MCRs are finally presented.

Synthesis of quinolines via sequential addition and I2-mediated desulfurative cyclization

An efficient one-pot approach for the synthesis of quinolines from o-aminothiophenol and 1,3-ynone under mild conditions is disclosed. With the aid of ESI-MS analysis and parallel experiments, a three-step mechanism is proposed-a two-step Michael addition-cyclization condensation step leading to intermediate 1,5-benzothiazepine catalyzed by zirconocene amino acid complex Cp2Zr(η1-C9H10NO2)2, followed by I2-mediated desulfurative step.

Microwave-assisted One-pot Synthesis of 2-Substituted Quinolines by Using Palladium Nanoparticles as a Catalyst developed from Green Alga Botryococcus braunii

Background:

Quinoline is a type of N-based organic heterocyclic biologically active compound. Quinolines have grasped the interest of scientists because of their wide scope of applications. Several methods have been developed for the synthesis of quinoline and its derivatives. In this study, a new, efficient, simple, one-pot synthesis of the substituted quinolines was developed by using palladium nanoparticles as a catalyst.

Methods:

Catalyst synthesized by algal extract of green alga Botryococcus braunii and palladium acetate solution, and characterized by different instrumental techniques like FTIR, SEM, and XRD. The synthesized palladium nanoparticles explored for the catalytic activity in the synthesis of quinoline derivatives by the use of 2-aminobenzyl alcohol in toluene with acetyl derivatives followed by the addition of potassium hydroxide. The formation of the product was confirmed by 1HNMR, 13C NMR, and electron ionization mass spectra.

Results:

The formation of palladium nanoparticles characterized by visual observation means the color change from light pale yellow to dark brown indicates the reduction of palladium ions into palladium nanoparticles. Synthesized palladium nanoparticles characterized by FTIR spectrum of the algal extract of green algae B. braunii for the presence of proteins, lipids, carbohydrates, carotenoids, vitamins and other secondary metabolites in algal extract, which function as active components for bioreduction. The morphology of the catalyst was confirmed by SEM and X-ray diffraction measurements for shape, crystalline nature and size. The synthesized palladium nanoparticles explored for the catalytic activity in the synthesis of quinoline derivatives by use of 2-aminobenzyl alcohol in toluene and added acetyl derivatives followed by the addition of potassium hydroxide. In order to establish the optimum heating method, a comparative study between conventional and microwave heating method was carried out in the presence of palladium nanoparticles as a catalyst.

Conclusion:

This protocol provides a convenient and practical procedure for the preparation of quinoline derivatives from 2-aminobenzyl alcohol, acetyl derivatives, potassium hydroxide and palladium nanoparticles as a catalyst. This protocol will be helpful in synthesizing other quinoline derivatives and several organic heterocycles which are used in different fields such as biological, industrial, pharmaceutical, chemical, medical, etc.