Synthesis of chromeno[3,4- $${\varvec{b}}$$ b ]quinoline derivatives by heterogeneous [Cu(II)BHPPDAH] catalyst without being immobilized on any support under mild conditions using PEG 300 as green solvent

Fifty Shades of Phenanthroline: Synthesis Strategies to Functionalize 1,10-Phenanthroline in All Positions

1,10-Phenanthroline (phen) is one of the most popular ligands ever used in coordination chemistry due to its strong affinity for a wide range of metals with various oxidation states. Its polyaromatic structure provides robustness and rigidity, leading to intriguing features in numerous fields (luminescent coordination scaffolds, catalysis, supramolecular chemistry, sensors, theranostics, etc.). Importantly, phen offers eight distinct positions for functional groups to be attached, showcasing remarkable versatility for such a simple ligand. As a result, phen has become a landmark molecule for coordination chemists, serving as a must-use ligand and a versatile platform for designing polyfunctional arrays. The extensive use of substituted phenanthroline ligands with different metal ions has resulted in a diverse array of complexes tailored for numerous applications. For instance, these complexes have been utilized as sensitizers in dye-sensitized solar cells, as luminescent probes modified with antibodies for biomaterials, and in the creation of elegant supramolecular architectures like rotaxanes and catenanes, exemplified by Sauvage's Nobel Prize-winning work in 2016. In summary, phen has found applications in almost every facet of chemistry. An intriguing aspect of phen is the specific reactivity of each pair of carbon atoms ([2,9], [3,8], [4,7], and [5,6]), enabling the functionalization of each pair with different groups and leading to polyfunctional arrays. Furthermore, it is possible to differentiate each position in these pairs, resulting in non-symmetrical systems with tremendous versatility. In this Review, the authors aim to compile and categorize existing synthetic strategies for the stepwise polyfunctionalization of phen in various positions. This comprehensive toolbox will aid coordination chemists in designing virtually any polyfunctional ligand. The survey will encompass seminal work from the 1950s to the present day. The scope of the Review will be limited to 1,10-phenanthroline, excluding ligands with more intracyclic heteroatoms or fused aromatic cycles. Overall, the primary goal of this Review is to highlight both old and recent synthetic strategies that find applicability in the mentioned applications. By doing so, the authors hope to establish a first reference for phenanthroline synthesis, covering all possible positions on the backbone, and hope to inspire all concerned chemists to devise new strategies that have not yet been explored.

Synthetic Methods for Various Chromeno-fused Heterocycles and their Potential as Antimicrobial Agents

Chromenes are a significant family of heterocyclic chemicals that have a wide range of biological applications, a simple chemical structure, and only mildly undesirable side effects. The synthesis of a wide range of chromene analogs that displayed unexpected behaviors via numerous mechanisms was investigated by a number of different research teams, which led to the discovery of multiple pathways for their synthesis. In addition, different chromene-fused heterocycles exhibit a wide variety of fascinating biological actions, including those that are anticancer, anticonvulsant, antibacterial, anticholinesterase, antituberculosis, and anti-diabetic. In light of this, the purpose of this study is to highlight the many synthesis techniques and antibacterial activity associated with chromene-fused heterocyclic compounds. Moreover, such research can open avenues for exploring other therapeutic applications of these compounds in various disease areas, as their biological activities extend beyond antibacterial effects.

Copper nanoparticles supported on charcoal mediated one-pot three-component synthesis of N-substituted-2H-indazoles via consecutive condensation C–N and N–N bond formation

An efficient and straightforward protocol for direct synthesis of 2H-indazoles is achieved from consecutive condensation of 2-halobenzaldehydes, primary amines, and sodium azide catalyzed by heterogeneous copper nanoparticles on charcoal (Cu/C) is achieved. The recoverable heterogeneous copper nanoparticles on charcoal (Cu/C) catalyst exhibited an impressive activity for the title reaction without any additives (expensive ligands, etc.). A series of structurally diverse 2H-indazoles were prepared in good to excellent yields from easily accessible starting materials by employing this protocol.

Recent advances in research of natural and synthetic bioactive quinolines

Many natural products that consist of quinoline core are found to be bioactive and the versatility of quinoline and its derivatives have attracted great attention in the field of drug development. As a result, in recent years, many green and sustainable synthetic approaches for the synthesis of structurally diverse quinolines have been developed. This review covers four main aspects, namely bioactive quinoline alkaloids, the biological activity and mechanism of action of quinoline-based compounds as well as various quinoline syntheses.

Application of a new phosphorus-free palladium heterogeneous nanocatalyst supported on modified MWCNT the highly selective and efficient cleavage of propargyl, allyl, and benzyl phenol ethers under mild conditions

A stable and efficient phosphorus-free, low Pd-loading heterogeneous nanocatalyst comprising palladium and a multi-walled carbon nanotube was prepared and characterized by various techniques such as SEM, TEM, AFM, FT-IR, and Raman spectrometry, N2 adsorption isotherm and thermogravimetric analysis. This catalyst was used for the deprotection of phenol ethers. The catalyst selectivity for deprotection of between propargyl, allyl, and benzyl, as a protecting group, was studied. Also, the presence of different functional groups was studied to establish the scope and limitations of this method. The catalytic activity of recycled catalyst was evaluated. The results indicated that the catalyst is heterogeneous, stable, and very active under the established conditions, and it could be reused up to five times without any significant leaching. In addition, according to ICP analysis, low leaves of leaching of palladium from the catalyst was observed, which indicates that anthraquinone has an excellent ability to coordinate with palladium.