Direct Nitration of Vinylcycles with Copper Nitrate

A direct nitration of vinylcyclopropanes is disclosed with Cu(NO₃)₂ and KI in a regio- and stereoselective manner to afford nitroalkenes efficiently, where the cyclopropane skeleton was retained. The given method could be extended to other vinylcycles as well as biomolecule derivatives with wide substrate scope, good functionality tolerance, and efficient synthesis modularity. Further transformations illustrated the obtained products as versatile building blocks in organic synthesis. The proposed ionic pathway could account for the untouched small ring and the effect of KI during the reaction.

From α-keto acids to nitrile oxides enabled by copper nitrate: a facile access to fused isoxazolines

An unprecedented generation of nitrile oxides was developed from α-keto acids and copper nitrate through a novel carbon–carbon bond cleavage mode, affording pharmacologically interesting fused isoxazolines via 1,3-dipolar cycloadditions.

Synthesis of Poly-Substituted Pyridines via Noble-Metal-Free Cycloaddition of Ketones and Imines

An eco-friendly and noble-metal-free formal [4+2] cycloaddition reaction was developed for the efficient synthesis of biologically interesting poly-substituted pyridines from easily available ketones and imines, whereby two sequential C-C bonds are formed. The given approach features a unique synthetic strategy of imines and ketones with wide substrate scope, good functional group tolerance, mild conditions and operational simplicity, which represents a more direct pathway to synthesize poly-substituted pyridines than traditional methods.

2-Isoxazolines: A Synthetic and Medicinal Overview

Isoxazolines are nitrogen- and oxygen-containing five-membered heterocyclic scaffolds with extensive biological activities. This framework can be readily obtained in good to excellent yields through 1,3-dipolar cycloaddition between nitrones with alkynes or allenes, aryl/alkyl halides, alkynes, and oxaziridines under mild conditions. This scaffold has been an emerging area of interest for many researchers given their wide range of bioactivities. Herein we review synthetic strategies toward isoxazolines and the role these efforts have had in enhancing the biological activity of natural products and synthetic compounds such as antitubercular agents, COX-1 inhibitors, COX-2 inhibitors (e. g., valdecoxib), nicotinic receptor modulators, and MIF inhibitors. With a focus on efforts from 2010 onward, this review provides in-depth coverage of the design and biological evaluation of isoxazoline systems and their impact on various pathologies.

5-(4H)-Oxazolones and Their Benzamides as Potential Bioactive Small Molecules

The five membered heterocyclic oxazole group plays an important role in drug discovery. Oxazolones present a wide range of biological activities. In this article the synthesis of 4-substituted-2-phenyloxazol-5(4H)-ones from the appropriate substituted aldehydes via an Erlenmeyer–Plochl reaction is reported. Subsequently, the corresponding benzamides were produced via a nucleophilic attack of a secondary amine on the oxazolone ring applying microwave irradiation. The compounds are obtained in good yields up to 94% and their structures were confirmed using IR, ¹H-NMR, ¹³C-NMR and LC/MS data. The in vitro anti-lipid peroxidation activity and inhibitory activity against lipoxygenase and trypsin induced proteolysis of the novel derivatives were studied. Inhibition of carrageenin-induced paw edema (CPE) and nociception was also determined for compounds 4a and 4c. Oxazolones 2a and 2c strongly inhibit lipid peroxidation, followed by oxazolones 2b and 2d with an average inhibition of 86.5%. The most potent lipoxygenase inhibitor was the bisbenzamide derivative 4c, with IC₅₀ 41 μM. The benzamides 3c, 4a–4e and 5c were strong inhibitors of proteolysis. The replacement of the thienyl moiety by a phenyl group does not favor the protection. Compound 4c inhibited nociception higher than 4a. The replacement of thienyl groups by phenyl ring led to reduced biological activity. Docking studies of the most potent LOX inhibitor highlight interactions through allosteric mechanism. All the potent derivatives present good oral bioavailability.

[2 + 2 + 1] Heteroannulation of Alkenes with Enynyl Benziodoxolones and Silver Nitrite Involving C≡C bond Oxidative Cleavage: Entry to 3-Aryl-Δ2-isoxazolines

A copper-catalyzed [2 + 2 + 1] heteroannulation of alkenes with enynyl benziodoxolones and AgNO₂ involving oxidative cleavage of the C≡C bond promoted by cooperative Zn(OTf)₂, KOAc, and 4 Å MS for producing 3-aryl Δ²-isoxazolines is reported. Mechanistic studies indicate that AgNO₂ serves as the N/O two-atom unit source, enabling the formation of three bonds through NO₂ addition across the C≡C bond, NO-transfer, C≡C bond cleavage, and annulation cascades.

From Alkenes to Isoxazolines via Copper-Mediated Alkene Cleavage and Dipolar Cycloaddition

An unprecedented copper-mediated anion transformation is reported, along with selective C═C double bond cleavage and dipolar cycloaddition reaction from simple alkenes and inexpensive copper nitrate. Various transformations demonstrate the generality of this method. Further mechanistic investigation indicates a novel ionic pathway for alkene cleavage and highlights the coeffect of iodide and boric acid as additives on the inhibition of well-documented competitive nitration byproducts.

An Isoxazole Derivative SHU00238 Suppresses Colorectal Cancer Growth through miRNAs Regulation

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. Isoxazoline and isoxazole derivatives represent an important class of five-membered heterocycles, which play a pivotal role in drug discovery. In our previous study, we developed a series of isoxazole derivatives with an efficient method. In this study, we evaluated their effects on tumor cell growth. HCT116 cells were treated with isoxazole derivatives; an cholecystokinin octapeptide (CCK-8) assay was used to calculate the IC₅₀ (half maximal inhibitory concentration) of each derivative. Compound SHU00238, which was obtained by the copper nitrate-mediated [2+2+1] cycloaddition reaction of olefinic azlactone with naphthalene-1,4-dione, has a lower IC₅₀; we analyzed its inhibitory activity in further assays. Cell apoptosis was estimated by flow cytometry analysis in vitro. SHU00238 injection was used to treat tumor-bearing mice. We found that SHU00238 suppressed cell viability and promoted cell apoptosis in vitro. SHU00238 treatment significantly inhibited colonic tumor growth in vivo. Furthermore, we compared the miRNAs expression changes in HCT116 cells before and after SHU00238 treatment. MiRNA profiling revealed that SHU00238 treatment affected cell fate by regulating a set of miRNAs. In conclusion, SHU00238 impedes CRC tumor cell proliferation and promotes cell apoptosis by miRNAs regulation.