Search Results (167)

The in situ-generated thiocarbonyl S-methanides derived from cycloaliphatic thioketones undergo (3+2) cycloaddition onto the C=C bond of levoglucosenone yielding anticipated, polycyclic tetrahydrothiophene derivatives in a regio- and stereoselective manner. The cycloaddition process occurred stereoselectively via the less hindered exo-face approach; exo-diastereoisomers were formed in all studied reactions. Some of the obtained crystalline (3+2) cycloadducts were studied by the monocrystal X-ray diffraction analysis, which unambiguously confirmed the postulated structure. Stable (3+2) cycloadducts were isolated in good yields (50–80%). Full article

This work explores a novel and efficient synthetic approach to a new class of boron cluster derivatives via the nucleophilic addition of stabilized phosphorus ylides, Ph₃P=CHR² (R² = COOEt, CN), to a series of nitrilium salts of the closo-decaborate anion, [2-B₁₀H₉NCR¹]⁻ (R¹ = Me, Et, ⁿPr, ⁱPr, Ph). The reaction proceeds regio- and stereospecifically, affording a diverse range of iminoacyl phosphorane derivatives, [2-B₁₀H₉NH=C(R¹)C(PPh₃)R²]⁻, in high isolated yields (up to 95%). The obtained compounds (10 examples) were isolated as tetrabutylammonium or tetraphenylphosphonium salts and thoroughly characterized by multinuclear NMR (¹¹B, ¹H, ¹³C, ³¹P), high-resolution mass spectrometry, and single-crystal X-ray diffraction. The reaction feasibility was found to be strongly influenced by the steric hindrance of the R¹ group. Furthermore, the practical utility of these novel hybrids was demonstrated by employing the [2-B₁₀H₉NH=C(CH₃)C(COOC₂H₅)=PPh₃]⁻ anion as a highly effective membrane-active component in ion-selective electrodes. The developed tetraphenylphosphonium (TPP⁺) sensor exhibited a near-Nernstian response, a low detection limit of 3 × 10⁻⁸ M, and excellent selectivity over a range of common inorganic and organic cations, showcasing the potential of closo-borate-based ionophores in analytical chemistry. Full article

Pyridinium ylides, along with related azaheterocyclic ylides, are widely used in synthetic organic chemistry. However, reactions that yield stable zwitterionic adducts from these ylides remain underexplored. In this work, we demonstrate that the reaction of pyrrole-2,3-diones with in situ-generated pyridine-based azomethine ylides affords stable zwitterionic adducts, which are typically transient species in analogous processes. These betaines are used as key intermediates for the synthesis of cyclopropane-fused pyrroles or pyridine-2,3-diones via thermolysis in chlorobenzene. Full article

Background/Objectives: Natural metabolites, due to their abundance, structural diversity, and availability in enantiomerically pure form, are broadly utilized in the synthesis of reagents, catalysts, building blocks, and potential therapeutics. To date, various organoselenium compounds, including selenides, diselenides, selenols, selenonium salts, and ylides, have been created based on the scaffold of primary and secondary metabolites like amino acids, sugars, nucleic bases, terpenes, and steroids. Their synthesis and application routes as reagents and catalysts in organic synthesis and biological systems are summarized in the presented review. Methods: The gathered material has been divided into two sections—naturally derived organoselenium compounds, such as antioxidants and GPx-mimetics, and reagents utilized in modern organic transformations. Results: The review summarizes the utility of natural scaffolds in the construction of organoselenium compounds with promising applications as antioxidant-type catalysts in biological systems (GPx-mimetics) and potent reagents for organic transformations, including asymmetric reactions. Conclusions: This review provides a comprehensive overview of known organoselenium reagents derived from natural compounds, discusses the advantages of their use in medicinal chemistry and modern organic synthesis, and outlines prospective directions for future development in this area. Full article

We report the first green and diastereoselective synthesis of novel thiophene bioisosteres designed to mimic the privileged pyrrolo[3,2-c]quinoline core of martinelline alkaloids. The key step features an intramolecular 1,3-dipolar cycloaddition of in situ generated non-stabilized azomethine ylides from sarcosine, which proceeds with excellent yield and diastereoselectivity. This sustainable protocol, leveraging ultrasonic irradiation, recyclable hydrotalcite catalysts, and the green solvent cyclopentyl methyl ether (CPME), efficiently constructs the complex tricyclic framework. The structure and stereochemistry of the novel bioisostere were unambiguously confirmed by X-ray crystallography. This method offers a valuable, eco-friendly approach for diversifying natural product-inspired libraries in medicinal chemistry. Full article

Azomethine ylides (AMYs) have a nitrogen–carbon double bond and an electron lone pair on the nitrogen atom. They are essential 1,3-dipoles for [3+2] cycloadditions in the synthesis of pyrrolidine-containing heterocycles. Significant progress in 1,3-diplolar cycloadditions has been made in the construction of novel heterocyclic scaffolds, with efforts to broaden substrate scope, enhance stereoselectivity, and integrate green chemistry principles. This article summarizes double cycloadditions of AMYs derived from amino esters and amino acids for the synthesis of novel polyheterocycles. The design of double cycloadditions through the pot, atom, and step economic (PASE) method to increase the reaction efficiency is discussed. The examples presented in this paper may be applied to the synthesis of biologically active molecules. Full article

Three new series of indolizines (5a–f, 6a–f and 7a–g), functionalized with bromine or ethyl ester substituents on the pyridine ring, were designed and synthesized as promising anticancer agents. The synthesis of indolizine derivatives was carried out using the 1,3-dipolar cycloaddition of pyridinium N-ylides to ethyl propiolate as a key step. Spectral characterization (using NMR, FT-IR, HRMS and X-ray diffraction) showed that two types of cycloadducts 5a–f and 6a–f were obtained when the ylides generated by the 3-bromopyridinium salts were used as 1,3-dipoles in Huisgen cycloaddition reactions to ethyl propiolate. The anticancer effect of selected compounds was in vitro assessed against the National Cancer Institute (NCI) panel of 60 human tumor cells, at 10 μM concentration, with three compounds (5c, 6c and 7g) showing promising inhibitory activity on the growth of several cell lines including lung, brain, renal cancer and melanoma, as well as a cytotoxic effect against HOP-62 non-small cell lung cells (34% for compound 5c and 15% for compound 7g) and SNB-75 glioblastoma cells (15% for compound 5c and 14% for derivative 7c). Molecular docking revealed favorable binding affinities for 5c, 6c and 7g (–9.22 to –9.88 kcal/mol) at the colchicine-binding site of tubulin with key interactions involving βASN-258, βALA-317, and βLYS-352 residues for 5c, βASN-258 in case of 6c, and αVAL-181 and βLYS-254 for derivative 7g. According to the in silico ADMET analysis, the active compounds are predicted to exhibit good oral bioavailability, promising drug-like qualities and low toxicity risks. Full article

An efficient protocol was developed for the microwave-mediated metallation of 5-(4-methoxycarbonylphenyl)-10,15,20-tris(pentafluorophenyl)porphyrin (P1) with bis(benzonitrile)platinum dichloride salt and subsequent 1,3-dipolar cycloaddition of the resulting PtP1 with an azomethine ylide to give two isomeric metallochlorins: PtC1 (main isomer) and PtC3. The methyl ester group of metalloporphyrin PtP1 and metallochlorin PtC1 was successfully hydrolysed in an alkaline medium to yield the corresponding derivatives PtP2 and PtC2 in moderate-to-good yields. As a proof of concept of the reactivity of the carboxy group in PtP2 and PtC2, these compounds were conjugated with a hydroxylated derivative of indomethacin, a known potent non-steroidal anti-inflammatory, obtaining the conjugates PtP2-Ind and PtC2-Ind. The obtained platinum(II) porphyrins and chlorins were characterized by UV-Vis, NMR spectroscopy and mass spectrometry. The structure of PtP1 was also confirmed by X-ray crystallography. Singlet oxygen generation studies were carried out, as well as theoretical calculations, which demonstrated that the prepared Pt(II) complexes can be considered potential photosensitizers for PDT. Full article

Density functional theory calculations have been performed to explore the detailed mechanism of a ruthenium-catalyzed dehydrogenative annulation between α-carbonyl phosphonium ylide (A) and sulfoxonium ylide (B). The proposed catalytic cycles consist of several elementary steps in succession, namely the C–H activation of ylide A, the insertion of ylide B, reductive elimination, protodemetallation, and an intramolecular Wittig reaction, in which C–H activation is rate-limiting, with a free energy barrier of 31.7 kcal/mol. As A and B are both capable of being a C–H activation substrate and a carbene precursor, there are potentially four competing pathways including homo-coupling reactions. Further calculations demonstrate that A is more reactive in the C–H activation step than B, while the opposite conclusion is true for the ylide insertion step, which can successfully explain the fact that the solely observed product originated from the use of A as the C–H activation substrate and B as the carbene precursor. Molecular electrostatic potential, charge decomposition, and electron density difference analyses were performed to understand the distinct behaviors of the two ylides and the nature of the key ruthenium–carbene intermediate. Full article

A series of 3-azabicyclo[3.1.0]hexanes and cyclopropa[a]pyrrolizidines spiro-fused to acenaphthylene-1(2H)-one and aceanthrylene-1(2H)-one frameworks have been studied for their in vitro antiproliferative activity against human erythroleukemia (K562), cervical carcinoma (HeLa), melanoma (Sk-mel-2), osteosarcoma (U2OS), as well as murine melanoma (B16) cell lines. Using confocal microscopy, it was found that cultivation with the tested spiro-fused compounds led to the disappearance of stress fibers (granular actin was distributed diffusely in the cytoplasm in up to 56% of treated cells) and decrease in filopodia-like deformations (up to 69% after cultivation), which indirectly suggests a decrease in cell motility. The human melanoma cell line scratch test showed that these cells lose their ability to move after cultivation with the tested spiro-fused compounds and do not fill the scratched strip. This was also supported by docking simulations with actin-related targets (PDB ID: 8DNH, 2Q1N). Using flow cytometry, the impact on the mitochondrial membrane potential showed that the tested compounds led to a significant increase in the number of cells with decreased mitochondrial membrane potential from 10% for the control up to 55–80% for the cyclopropa[a]pyrrolizidine adducts. The obtained results support the antitumor effect of the tested spiro-compounds and encourage the extension of the study in order to improve their anticancer activity as well as reduce their toxicological risks. Full article

A concerted five-component reaction strategy has been developed, featuring double [3+2] cycloadditions utilizing aspartic acid. This approach provides valuable insights into mechanistic pathways, allowing for the distinction between concerted and stepwise processes based on reaction efficiency and diastereoselectivity. Both aspartic and glutamic acids have been employed for a thorough evaluation and exploration of decarboxylation-driven double annulations. This method effectively constructs pyrrolizidine frameworks through a concerted double 1,3-dipolar cycloaddition with aspartic acid, as well as tetrahydropyrrolizinones via three-component double annulations, which include decarboxylative 1,3-dipolar cycloaddition and lactamization with glutamic acid. These highly convergent, decarboxylation-driven multicomponent reactions (MCRs) efficiently produce fused polyheterocyclic systems while being environmentally friendly, generating only CO₂ and water as byproducts. Full article

The controlled functionalization of graphene is critical for tuning and enhancing its properties, thereby expanding its potential applications. Covalent functionalization offers a deeper tuning of the geometric and electronic structure of graphene compared to non-covalent methods; however, the existing techniques involve side reactions and spatially uncontrolled functionalization, pushing research toward more selective and controlled methods. A promising approach is 1,3-dipolar cycloaddition, successfully utilized with carbon nanotubes. In the present work, this method has been extended to graphene flakes with low defect concentration. A key innovation is the use of a custom-synthesized ylide with a protected amine group (Boc), facilitating subsequent attachment of functional molecules. Indeed, after Boc cleavage, fluorescent dyes (Atto 425, 465, and 633) were covalently linked via NHS ester derivatization. This approach represents a highly selective method of minimizing structural damage. Successful functionalization was demonstrated by Raman spectroscopy, photoluminescence spectroscopy, and confocal microscopy, confirming the effectiveness of the method. This novel approach offers a versatile platform, enabling its use in biological imaging, sensing, and advanced nanodevices. The method paves the way for the development of sensors and devices capable of anchoring a wide range of molecules, including quantum dots and nanoparticles. Therefore, it represents a significant advancement in graphene-based technologies. Full article

This review probes the recent developments in stereoselective reactions within the area of sulfoxonium ylide chemistry since the early 2000s. An abundance of research has been applied to sulfoxonium ylide chemistry since its emergence in the early 1960s. There has been a continued effort since then with work in traditional areas, such as epoxidation, aziridination and cyclopropanation. Efforts have also been applied in novel areas, such as olefination and insertion reactions, to develop stereoselective methodologies using organocatalysis and transition metal catalysis. The growing research area of interrupted Johnson–Corey–Chaykovsky reactions is also described, whereby unexpected stereoselective cyclopropanation and epoxidation methodologies have been developed. In general, the most observed mechanistic pathway of sulfoxonium ylides is the formal cycloaddition: (2 + 1) (e.g., epoxides, cyclopropanes, aziridines), (3 + 1) (e.g., oxetanes, azetidines), (4 + 1) (e.g., indanones, indolines). This pathway involves the formation of a zwitterionic intermediate through nucleophilic addition of the carbanion to an electrophilic site. An intramolecular cyclization occurs, constructing the cyclic product. Insertion reactions of sulfoxonium ylides to X–H bonds (e.g., X = S, N or P) are also observed, whereby protonation of the carbanion is followed by a nucleophilic addition of X, to form the inserted product. Full article

A novel class of chiral sulfonium salts, derived from L- and D-methionine, was designed and successfully employed for the diastereoselective synthesis of epoxy amides. This new methodology of asymmetric epoxidation was exploited for the stereoselective construction of fused polycyclic ethers, which are structural motifs present in a great variety of natural products of marine origin. This methodology proved to be useful for the synthesis of the tricyclic A–C system contained in yessotoxin and adriatoxin, and also in many other related natural products of marine origin belonging to the fused polycyclic ether toxins. Full article