Synthesis of 2-Aryl/Heteroaryloxazolines from Nitriles under Metal- and Catalyst-Free Conditions and Evaluation of Their Antioxidant Activities

A Review of the Synthesis of Oxazoline Derivatives

Oxazolines are important heterocyclic systems due to their biological activities, such as antibacterial, antimalarial, anticancer, antiviral, anti-inflammatory, antifungal, antipyretic, and antileishmanial. They have been widely applied as chiral auxiliaries, polymers, catalysts, protecting groups, building blocks, and ligands in asymmetric synthesis. Due to their importance, many synthetic routes to prepare oxazoline moieties have been investigated and developed by researchers around the world. In this review, we summarized several synthetic methodologies published in the literature. The main substrates are nitriles, carboxylic acids, and acid derivatives, which react with a variety of reactants under conventional heating, microwave irradiation or ultrasound irradiation conditions. Syntheses via intramolecular cyclisation from amides have also been reported. Many publications have highlighted procedures based on solvent-free conditions using eco-friendly, reusable, and easy-availability catalysts.

Synthesis of 3-heteroaryl-pyrrolo[2,3-b]pyridines as potent inhibitors of AP-2-associated protein kinase 1 (AAK1) with antiviral activity

Inhibition of AP-2-associated protein kinase 1 (AAK1) has been shown to be a promising avenue for the development of broad-spectrum antiviral agents. On a previously described AAK1 inhibitor based on a pyrrolo[2,3-b]pyridine scaffold, the concept of isosterism was applied, by replacing a carboxamide linker by various five-membered heterocycles. It led to the discovery of a novel series of AAK1 inhibitors with IC50 values in the low nM range, that also displayed antiviral activity against the dengue virus and Venezuelan equine encephalitis virus.

Catalytic reduction of nitroarenes by palladium nanoparticles decorated silica@poly(chitosan-N-isopropylacrylamide-methacrylic acid) hybrid microgels

Conversion of toxic nitroarenes into less toxic aryl amines, which are the most suitable precursors for different types of compounds, is done with various materials which are costly or take more time for this conversion. In this regards, a silica@poly(chitosan-N-isopropylacrylamide-methacrylic acid) Si@P(CS-NIPAM-MAA) Si@P(CNM) core-shell microgel system was synthesized through free radical precipitation polymerization (FRPP) and then fabricated with palladium nanoparticles (Pd NPs) by in situ-reduction method to form Si@Pd-P(CNM) and characterized with XRD, TEM, FTIR, SEM, and EDX. The catalytic efficiency of Si@Pd-P(CNM) hybrid microgels was studied for reduction of 4-nitroaniline (4NiA) under diverse conditions. Different nitroarenes were successfully transformed into their corresponding aryl amines with high yields using the Si@Pd-P(CNM) system as catalyst and NaBH4 as reductant. The Si@Pd-P(CNM) catalyst exhibited remarkable catalytic efficiency and recyclability as well as maintaining its catalytic effectiveness over multiple cycles.

CuI-Catalyzed Radical Reaction of Benzimidates to Form Valuable 4,5-Dihydrooxazoles through Regioselective Aerobic Oxidative Cross-Coupling

A straightforward Cu(I)-catalyzed oxidative cross-coupled organic transformation has been developed under mild conditions for the construction of functionalized 4,5-dihydrooxazoles through a four-bond-forming regiocontrolled C-C/C-N/C-O coupling strategy emerging benzimidates, paraformaldehyde, and 1,3-diketo analogues using eco-friendly O2 as the sole oxidant. The fundamental features of these designed approaches involve operational simplicity, selectivity, generality, and a broad substrate scope with high yields under the same reaction conditions.

In-silico investigations on the anticancer activity of selected 2-aryloxazoline derivatives against breast cancer

As the in-silico study has become an important tool to search for new drugs in the concurrent era with towering acceptance and accuracy, it has been employed in our research to unearth effective cancer drugs. Breast cancer has accounted for the most serious diseases for both men and women. Although few research outputs have been obtained on breast cancer, these are not an adequate amount to ascertain new drugs. Due to this gap, virtual screening, in-silico study, and computational techniques have been used to provide the ability to design and select anticancer compounds with desirable drug-like properties of breast cancer protein, which is commonly known as fatty acid synthase. A total of nine derivatives of 2-aryloxazoline compounds were chosen, and In-silico was studied to evaluate as a potential anticancer agent with the comparison of seven Food and Drug Administration(FDA) approved breast cancer drugs. These compounds were subjected to computational studies for quantum calculations, ADME and Lipinski analysis, as well as molecular docking and MD simulations against a variety of therapeutic targets involved in cell proliferation of fatty acid synthase (PDB ID:3TJM, 3ERT, 4OAR, 2J6M). An in-silico docking study reveals that ligands Hit-4, Hit-6, and Hit-8 had the highest docking scores at -10.3 kcal/mol, -10.3 kcal/mol, and -10.2 kcal/mol towards the protein of fatty acid synthase. The ligands had docking scores better than the standard anti-breast cancer drug gefitinib (-5.3 kcal/mole). Our findings demonstrate how crucial it is for pharmaceutical researchers to develop novel drugs for the treatment of breast cancer.Communicated by Ramaswamy H. Sarma.

Electrochemical Trifluoromethylation and Sulfonylation of N-Allylamides: Synthesis of Oxazoline Derivatives

We report a new method for the synthesis of trifluoromethylated and sulfonylated oxazolines by electrochemical radical cascade cyclizations of N-allylamides with sodium trifluoromethanesulfinate or sulfonylhydrazines. This protocol provides a green and useful strategy to synthesize trifluoromethylated and sulfonylated oxazolines with a broad substrate scope under ambient conditions.

The diversity and utility of arylthiazoline and aryloxazoline siderophores: challenges of total synthesis

Siderophores are unique ferric ion chelators produced and secreted by some organisms like bacteria, fungi and plants under iron deficiency conditions. These molecules possess immense affinity and specificity for Fe³⁺ and other metal ions, which attracts great interest due to the numerous possibilities of application, including antibiotics delivery to resistant bacteria strains. Total synthesis of siderophores is a must since the compounds are present in natural sources at extremely small concentrations. These molecules are extremely diverse in terms of molecular structure and physical and chemical properties. This review is focused on achievements and developments in the total synthesis strategies of naturally occurring siderophores bearing arylthiazoline and aryloxazoline units.

A review presents advances in total synthesis of thiazoline and oxazoline-bearing siderophores, unique ferric ion chelators found in some bacteria, fungi and plants.

Photoredox-catalyzed synthesis of sulfonated oxazolines from N-allylamides through the insertion of sulfur dioxide

Photoredox-catalyzed generation of sulfonated oxazolines starting from N-allylamides, DABCO·(SO2)2, and aryldiazonium salts has been developed and a range of sulfonated oxazolines were obtained in moderate to good yields.

Diastereoselective One-Pot Synthesis of Oxazolines Using Sulfur Ylides and Acyl Imines

This work describes an extended version of the Corey-Chaykovsky reaction to access oxazolines using sulfur ylides and stable precursors of acyl imines. The reaction proceeds through a mixture of aziridines and oxazolines, which provides the trans-oxazolines following in situ Heine-type aziridine ring expansion upon treatment with BF₃·OEt₂. Following the same one-pot procedure, amidine imides react with the sulfur ylides to provide imidazolines.

Chiral selenide-catalyzed enantioselective synthesis of trifluoromethylthiolated 2,5-disubstituted oxazolines

Chiral selenide-catalyzed enantioselective trifluoromethylthiolation of 1,1-disubstituted alkenes is disclosed. By this method, a variety of chiral trifluoromethylthiolated 2,5-disubstituted oxazolines were obtained in good yields with high enantioselectivities. This work not only provides a new pathway for the synthesis of chiral oxazolines, but also expands the library of chiral trifluoromethylthiolated molecules.

Metal-free annulation of β-acylamino ketones: facile access to spirooxazolines and oxazolines via oxidative C–O bond formation

A metal-free annulation reaction of β-acylamino ketone derivatives has been reported for the synthesis of a group of functionalized spirooxazolines and oxazolines in good to excellent yields.

Iodoarene-catalyzed cyclizations of N-propargylamides and β-amidoketones: synthesis of 2-oxazolines

Two complementary iodoarene-catalyzed methods for the preparation of 2-oxazolines are presented. The first involves the cyclization of N-propargylamides and the second involves the cyclization of β-amidoketones. These are proposed to proceed through different mechanisms and have different substrate scopes.

Synthesis and Antioxidant Properties of New Oxazole-5(4H)-one Derivatives

Objectives

To synthesize and characterize 4-(substituted benzylidene)-2-(substituted phenyl)oxazol-5(4H)-one derivatives (E1-E10), and evaluate them for antioxidant activity.

Materials and Methods

Required oxazole-5(4H)-one derivatives were synthesized in two steps to obtain novel hippuric acid derivatives (7-13); glycine and acylated appropriate benzoic acid derivatives were used and then, final compounds were obtained with condensation of 7-13 with appropriate benzaldehydes (E1-E10). These products were purified by column chromatography using ethyl acetate/n-hexane as eluent. All the compounds were unequivocally characterized using the combination of ¹H and ¹³C-nuclear magnetic resonance, mass spectrometry (ESI-MS), and elemental analysis. The inhibition of lipid peroxidation and its effects on hepatic cytochrome P450-dependent ethoxyresorufin-O-deethylase (EROD) enzyme were determined in rats in vitro.

Results

The most active analogue on the microsomal EROD activity was E3 which inhibited the microsomal EROD activity (89%) and was similarly better than that of the specific inhibitor caffeine (85%) at 10-3 M concentration.

Conclusion

The findings of this study indicate that the synthesized compounds, such as E3, display significant antioxidant activity.

Direct arylation of benzoazoles with aldehydes utilizing metal–organic framework Fe3O(BDC)3 as a recyclable heterogeneous catalyst

Aryl-substituted azoles were effectively produced via the direct arylation of azoles with benzaldehydes under metal–organic framework catalysis.

Efficient Synthesis and Antibacterial Evaluation of (±)-Yanglingmycin and Its Analogues

An efficient synthetic route was developed for the large-scale preparation of (±)-Yanglingmycin and its analogues. Three series of derivatives of (±)-Yanglingmycin were synthesized and the structures of all compounds were elucidated by analyses of NMR and ESI-MS spectra data. Moreover, their antibacterial activities against seven species of bacteria were systematically evaluated by the micro-broth dilution method, most of which displayed considerable activity. It was worth noting that compounds 5b, 5c, 5d, 6g, and 7 were found to be the most promising leading candidates, with peak MIC values of 0.98 μg·mL⁻¹ for Bacillus subtilis, which is superior to positive controls (MIC = 3.91 μg·mL⁻¹). The above results might lay the firm foundation for the design and synthesis of novel antibacterial drugs based on (±)-Yanglingmycin.

Half-sandwich cycloruthenated complexes from aryloxazolines: synthesis, structures, and catalytic activities

The half-sandwich cycloruthenated complexes [Ru(p-cymene)LCl] show promising catalytic activity in nitroarene reduction.

Copper N-Heterocyclic Carbene Complexes As Active Catalysts for the Synthesis of 2-Substituted Oxazolines from Nitriles and Aminoalcohols

The reaction between nitriles and aminoalcohols to access 2-substituted oxazolines was investigated. Using copper-NHC complexes, various nitriles were successfully converted into the corresponding oxazolines, under milder and less wasteful conditions than those of previously reported methods.

Zincation of 4,4-dimethyloxazoline using TMPZnCl·LiCl. A new preparation of 2-aryloxazolines

4,4-Dimethyloxazoline is directly zincated using TMPZnCl·LiCl and further functionalized by Pd-catalyzed cross-couplings, as well as Cu-mediated acylation and allylation reactions.