Plausible PEPPSI catalysts for direct C-H functionalization of five-membered heterocyclic bioactive motifs: synthesis, spectral, X-ray crystallographic characterizations and catalytic activity.

In this study, a series of benzimidazolium salts were synthesized as asymmetric N-heterocyclic carbene (NHC) precursors. Nine novel palladium complexes with the general formula [PdX2(NHC)(pyridine)] were synthesized using benzimidazolium salts in the PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) theme. All synthesized Pd(ii) complexes are stable. The synthesized compounds were thoroughly characterized by respective spectroscopic techniques, such as 1HNMR, 13C NMR, FTIR spectroscopy, X-ray crystallography and elemental analysis. The geometric structure of the palladium N-heterocyclic carbene has been optimized in the framework of density functional theory (DFT) using the B3LYP-D3 dispersion functional with LANL2DZ as a basis set. The on/off mechanism of pyridine assisted Pd-NHC complexes made them the best C-H functionalized catalysts for regioselective C-5 arylated products. Five membered heterocyclic compounds such as 2-acetyl furan, furfuryl acetate 2-acetylthiophene and N-methylpyrrole-2-carboxaldehyde were treated with numerous aryl bromides and arylchlorides under optimal catalytic reaction conditions. Interestingly, all the prepared catalysts possessed essential structural features that facilitated the formation of desired coupling products in quantitative yield with excellent selectivity. The arylation reaction of bromoacetophenone was highly catalytically active with only 1 mol% catalyst loading at 150 °C for 2 hours. To check the efficiency of the synthesized complexes, three different five member heterocyclic substrates (2-acetylfuran, 2-acetylthiophen, 2-propylthaizole) were tested with a number of aryl bromides bearing both electron-donating and electron-withdrawing groups on para position. The data in Tables 2-4. Indicated that electron-donating groups on the para position of aryl halide decreased the catalytic conversion while electron-withdrawing groups increased the catalytic conversion this was due to the high nucleophilicity of the electron-donating substituents.

Synthesis, Characterization, Antimicrobial Properties, and Antioxidant Activities of Silver-N-Heterocyclic Carbene Complexes.

The emergence of antimicrobial resistance has become a major handicap in the fight against bacterial infections, prompting researchers to develop new, more effective, and multimodal alternatives. Silver and its complexes have long been used as antimicrobial agents in medicine because of their lack of resistance to silver, their low potency at low concentrations, and their low toxicity compared to most commonly used antibiotics. N-Heterocyclic carbenes (NHCs) are widely used for coordination of transition metals, mainly in catalytic chemistry. In this study, several N-alkylated benzimidazolium salts 2a-j were synthesized. Then, the N-heterocyclic carbene (NHC) precursor was treated with Ag2O to give silver (I) NHC complexes (3a-j) at room temperature in dichloromethane for 48 h. Ten new silver-NHC complexes were fully characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and LC-MSMS (for complexes) techniques. The antibacterial and antioxidant activities of salt 2 and its silver complex 3 were evaluated. All of these complexes were more effective against bacterial strains than comparable ligands. With MIC values ranging from 6.25 to 100 g/ml, the Ag-NHC complex effectively showed strong antibacterial activity. Antioxidant activity was also tested using conventional techniques, such as 2, 2-diphenyl-1-picrylhydrazine (DPPH) and hydrogen peroxide scavenging assays. In DPPH and ABTS experiments, compounds 3a, 3b, 3c, 3e, 3g, and 3i showed significant clearance.

Effective Synthesis and Biological Evaluation of Dicoumarols: Preparation, Characterization, and Docking Studies.

A series of 3,3-arylidene bis (4-hydroxycoumarins) 2 were synthesized by the reaction of aromatic aldehydes with 4-hydroxycoumarin using dodecylbenzenesulfonic acid as Brønsted acid-surfactant catalyst in aqueous media and under microwave irradiation. The present method is operationally simple and the use of water as the reaction medium makes the process environmentally benign. The epoxydicoumarins 5 were then obtained with a good yield by heating 3,3'-arylidenebis-4-hydroxycoumarins 2 in acetic anhydride. Techniques such as elemental analysis, 1H, 13C-1H NMR, and infrared spectroscopy were employed to characterize these compounds. The synthesized compounds displayed good antibacterial potential against Escherichia coli (ATCC 25988), Pseudomonas aeruginosa (ATCC 27853), Klebsilla pneumonia (ATCC 700603), Staphylococcus aureus (ATCC 29213), methicillin-resistant Staphylococcus aureus (ATCC 43300) and Candida albicans (ATCC 14053). The MIC values of 23 mg/mL for compound 5e against Escherichia coli (ATCC 25988) and 17 mg/mL for 2a were observed. Furthemore, a molecular docking simulation has been performed to evaluate the antibacterial activities and the probable binding modes of the studied compounds 2a-f and 5a-g toward the active sites of a series of well known antibacterial targets. Among the investigated compounds, the binding modes and docking scores demonstrate that 2a has the most antibacterial and antifungal activities. Additionally, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS has been tested for their ability to scavenge hydrogen peroxide and free radicals. According to our results, these compounds exhibit excellent radical scavenging properties. Furthermore, compounds 2-5 were evaluated for anti-inflammatory activity by indirect haemolytic and lipoxygenase inhibition assays and revealed good activity.

A Short Route to the Ester (±) HomoSarkomycin via Johnson-Claisen Rearrangement.

BACKGROUND: α-Methylene cycloalkanones are considered of interest because of their biological activity. Herein, in this paper the synthesis of (±) HomoSarkomycine Esters was described and characterized. METHODS: Using Bylis-Hillman adducts, triethlorthoacetate and propanoic acid, (±) HomoSarkomycine Esters could be synthesized by smoothly Johnson-Claisen rearrangement. RESULTS: A small library of target compounds was prepared under optimized reaction conditions in moderate yields. The reaction mechanism and the DFT study have been investigated. CONCLUSION: This methodology provides ready access to 2-hydroxymethyl-2-cyclopentenone 1a which can be served as the raw materials of the synthesis of (±) HomoSarkomycine Ester.