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Magnetic Cobalt Oxide (CoO/Co₂O₃/Co₃${\text{O}}_4)$ and Nickel Oxide (NiO) Nanoparticles have been widely reported as heterogeneous catalysts for the preparation of derivatives of heterocycles. These are abundant, eco-friendly, relatively nontoxic and inexpensive catalysts. This review consists of the previous 10-year publications on the catalytic applications of Cobalt Oxide and Nickel Oxide Nanoparticles for the synthesis of heterocycles and their derivatives. Among the various metal oxide nanomaterials reported in the literature as catalyst materials for the synthesis of varied heterocycles and their derivatives, we have kept our focus on the key materials viz. Cobalt Oxide and Nickel Oxide Nanoparticles. In the conclusion part, we have also commented on the better options for the catalyst selection among the reports covered in this paper. This paper will definitely be useful for new researchers in the metal oxide nanomaterials-based catalytic applications for synthetic heterocyclic compounds.

This article reports the first perbromination of β-pyrrole and meso-phenyl groups of the 5,10,15,20-tetrakis(3',5'-dimethoxyphenyl)porphinato copper(II) to generate highly brominated porphyrin, 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(2',6'-dibromo-3',5'-dimethoxyphenyl)-porphinato copper(II), CuT(3',5'-DMP)PBr₁₆ complex. Its crystal structure exhibited unusual five-coordination geometry with saddle shaped conformation of the porphyrin core. H₂T(3',5'-DMP)PBr₁₆ and its metal complexes exhibited large anodic shift of oxidation potentials with marginal changes in reduction potentials relative to their corresponding octabromotetraphenylporphyrin, MTPPBr₈ derivatives. The enhanced electron deficiency of the ZnT(3',5'-DMP)PBr₁₆ complex was probed by axial ligation of various Lewis bases with differing pK_a values. The ZnT(3',5'-DMP)PBr₁₆ complex exhibited decrease in equilibrium constants for the ligation of bases relative to sterically unhindered ZnTPPBr₈. This has been ascribed to the sterics induced by the bulky ortho-bromo phenyl substituents that prevents the facile binding of Lewis bases to the Zn(II)-center.

In recent years, the field of porphyrin chemistry has expanded to include several new analogs of the original four pyrrole, carbon-bridged systems. This review traces the development of one such class of new macrocycles, namely Schiff-base porphyrin analogs. The review's focus is on the synthesis and properties of these new Schiff-base macrocycles that for ease of division have been divided into four classes: systems with two pyrrole rings, systems with three pyrrole or heterocyclic rings, systems with four pyrrole or heterocyclic rings, and systems with five or more pyrrole or heterocyclic rings. In addition to the role of metal ions as templating agents in the synthesis of these complexes, the rich coordination chemistry of several of the macrocycles is also discussed. X-ray crystallography has played an important role in determining the structures of many of these Schiff-base porphyrin analogs and many of the available structures have been incorporated into this review. Aromaticity of the macrocycles is discussed and has been evaluated from available electronic and NMR spectra. Finally, several potential applications of these molecules are discussed, briefly.

Two series of amphiphilic meso-tetrasubstituted porphyrin conjugates based on 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin ($m$-THPP) covalently linked to L-amino acids and heterocycles were synthesized efficiently in the context of a program targeting new photosensitizers for PDT. 5,10,15-Tris(3-hydroxyphenyl)-20-(3-oxyacetic acid)phenyl]porphyrin and the respective trihexyl ether derivatives were conjugated with polar and non-polar natural L-amino acids such as glycine, L-proline, and L-tyrosine via an amide bond linker using $N,N,N^{\prime },N^{\prime }$-tetramethyl-$O$-(1H-benzotriazol-1-yl)uroniumhexafluorophosphate in diisopropylethylamine (HBTU/DIPEA). $m$-THPP was also conjugated with heterocyclic systems such as indole 3-acetic acid, 4-methylthiazole-5-carboxylic acid, and thiophene-2-carboxylic acid via ester linker using $N$-(3-dimethylaminopropyl)-$N^{\prime }$-ethylcarbodiimide hydrochloride in $N$-hydroxysuccinamide or 1-hydroxybenzotriazole (EDCI, NHS or HOBt). The members of the two series were obtained in good yields and characterized by UV-vis, HRMS MALDI-TOF, ¹H NMR and ¹³C NMR spectroscopy.

In the search for photosensitizers based on 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (m-THPP, 1), a novel series of asymmetric A₃B porphyrin molecules with oxyacetamide linkers have been synthesized. A facile synthetic route was followed through the reaction of m-THPP derived porphyrin monoacid with amino-heterocyclic molecules in the presence of HBTU/DIPEA coupling reagent to obtain the respective porphyrin conjugates 7-10, 16, 18 in satisfactory yields 30–76%. The structures of all compounds were confirmed by the means of ¹H, ${}^{13}$C NMR and by mass spectrometry (MALDI-TOF). The absorption and emission spectra of the synthesized porphyrin conjugates were displayed in methanol and showed high extension coefficient values. These preliminary studies could qualify these new candidates in being added to the porphyrin library for photomedicine applications.

In recent years, antimicrobial agents have been crucial in improving public health worldwide. However, due to improper usage, bacteria have developed resistance to these agents. This has led researchers to explore the use of heterocyclic compounds as alternative antimicrobial agents to combat resistance. Considering the success of heterocyclic derivatives in developing effective antimicrobial drugs, we conducted a 2D-QSAR (QSAR models using 2D-descriptors) study on novel pyrimidine derivatives and performed in silico simulations to evaluate their potential antibacterial activity against quinolone-resistant Escherichia coli. We used QSARINS V.2.2 (Insubria) software for the 2D-QSAR analysis and performed in silico absorption, distribution, metabolism, and excretion (ADME) and docking studies on 16 newly designed compounds. The best QSAR model had a high correlation coefficient ($R^2=0.9633$, $Q_{\mathrm{\text{LOO}}}^2=0.9538$, $Q_{\mathrm{\text{LMO}}}^2=0.9513$) and showed no outliers. Based on these favorable results, we designed 16 new compounds and predicted their antibacterial activity using the best equation. Amongst the top six designed compounds, which had the best docking scores were subjected to practical synthesis. Compound 3cd was found to be good candidature from in-vitro anti-E. Coli activity. This compound may be targeting the DNA gyrases and thus, have inhibitory activity against E. Coli. This observation was also supported by 100ns molecular dynamics and normal mode analysis results. The most promising compounds identified through these computational studies may be synthesized and tested as potential new drug candidates for treating bacterial infections.

Malaria is a serious illness transmitted through the bite of an infected mosquito, which is caused by a type of parasite called plasmodium and can be fatal if left untreated. Thus, newer antimalarials with unique mode of actions are encouraged. Fused pyridines have been vastly reported for numerous pharmacological activities including but not limited to analgesics, antitubercular, antifungal, antibacterial and antiapoptotic agents. In a current study, a series of substituted Imidazo[1,2-a]pyridine-3-carboxamides (IMPCs) (SM-IMP-01-13) along with some hydrazides (DA-01-DA-02) were synthesized and characterized by Fourier-transform infrared spectroscopy (FTIR), ¹H-/${}^{13}$C-NMR (proton/carbon nuclear magnetic resonance), elemental analyses and mass spectra. These synthesized analogies were subjected for in vitro biological activities such as Brine Shrimp lethality (BSL), and assay of $\beta$-hematin formation inhibitions. The BSL assay results suggested that compounds, SM-IMP-09, SM-IMP-05 were found to be less toxic and they also had comparable toxicity as of 5-Flurouracil (control) ((e.g., at 10 $\mu$g/ml: 20% deaths of nauplii). Derivatives SM-IMP-02, and DA-05 inhibited $\beta$-hematin formation: IC${}_{50}$: 1.849 and 0.042 $\mu$M, respectively). Our molecular docking analysis on plasmodial cysteine protease falcipain-2 indicated that compound DA-05 (–9.993 kcal/mol) had highest docking score and it was comparable to standard Chloroquine (–7.673 kcal/mol). The most active molecule, DA-05 was also retained with lower HOMO–LUMO energy gap as 3.36 eV. Further, we have also analyzed MEP, and other global reactivity indexes for all IMPCs using DFT. Finally, our in-silico pharmacokinetic analysis suggested that all compounds were having good% human oral absorption values ($\approx$100%), good Caco-2 cell permeabilities (>1600 nm/s), and non- carcinogenic profiles.

Heterocyclic and fused heterocyclic compounds are ubiquitously found in natural products and biologically interesting molecules, and many currently marketed drugs hold heterocycles as their core structure. In this chapter, recent advances on Pd-catalyzed synthesis of heterocycles in ionic liquids (ILs) are reviewed. In palladium catalysis, ILs with different cations and anions are investigated as an alternative recyclable and environmentally benign reaction medium, and a variety of heterocyclic compounds including cyclic ketals, quinolones, quinolinones, isoindolinones, and lactones are conveniently constructed. Compared to the traditional methods, these new approaches have many advantages, such as environmentally friendly synthetic procedure, easy product and catalyst separation, recyclable medium, which make them have the potential applications in industry.

Benzoic acids with suitable substituents bearing phenyl ring in the ortho position undergo cyclization by intramolecular Friedel-Crafts acylation in the presence of Nafion-H, a perfluorinated resinsulfonic acid catalyst. Synthesis of anthraquinone, anthrone, fluorenone, α-tetralone, 1-benzosuberone and heterocycles such as acridone, xanthone etc. is easily achieved in good to excellent yields (82-95%) by this method.