Beilstein Journal of Organic Chemistry最新文献

The C-H arylation of 2-quinolinecarboxyamide bearing a C-Br bond at the N-aryl moiety is carried out with a palladium catalyst. The reaction proceeds at the C-H bond on the pyridine ring adjacent to the amide group in the presence of 10 mol % Pd(OAc)₂ at 110 °C to afford the cyclized product in 42% yield. The yield is improved to 94% when the reaction is performed with PPh₃ as a ligand of palladium. The reaction is examined with amides derived from unsubstituted picoline, 6-methylpicoline, and 2,6-pyridinedicarboxylic acid in a similar manner to afford the cyclized products in 70%, 77%, and 87% yield, respectively. The related reaction is also carried out with amides of non-pyridine derivatives terephthal- and benzamides to afford multiply fused heterocyclic compounds in 81% and 89% yields, respectively.

Asymmetric cycloaddition is a straightforward strategy which enables the synthesis of structurally distinct cyclic derivatives which are difficult to access by other methodologies, using an efficient and atom-economical path from simple precursors. In recent years several asymmetric catalytic cyclization strategies have been accomplished for the construction of N-heterocycles using various catalytic systems such as chiral metal catalysts, chiral Lewis acids or chiral organocatalysts. This review presents an overview of the recent advances in enantioselective cyclization reactions of 1-azadienes catalyzed by non-covalent organocatalysts.

The marine sponge Suberea ianthelliformis was investigated for new chemistry after the recent discovery that polyamines ianthelliformisamines A-C (1-3) - originally sourced from this Australian sponge - act as Pseudomonas aeruginosa biofilm inhibitors and antibiotic enhancers. Large-scale extraction and isolation studies resulted in the discovery of four new and minor natural products, ianthelliformisamines D-G (4-7) and the known steroid, aplysterol (8). Compounds 4-7 were fully characterised following 1D/2D NMR, MS and UV data analyses. All compounds were assessed for their inhibition on planktonic growth of P. aeruginosa PAO1 in addition to their ability to inhibit the formation of biofilms. None of the tested natural products inhibited planktonic growth or biofilm formation of PAO1 when screened at 50 µM. Ianthelliformisamine D (4) contains a rare N-(3-aminopropyl)-2-pyrrolidone moiety only found in <30 natural products. Owing to the novelty of compound 4, we undertook the first total synthesis of this natural product, which was achieved in three steps.

A new psammaplysin derivative, ceratinadin G (1), was obtained from the Okinawan marine sponge Pseudoceratina sp., and the gross structure was clarified through spectroscopic and spectrometric analyses. The absolute configuration of compound 1 was established by comparing its NMR and ECD data with those of the known psammaplysin derivative, psammaplysin F (2). Ceratinadin G (1) is a rare nitrile containing a cyano group as aminoacetonitrile, and is the first psammaplysin derivative possessing a cyano group. In vitro assays indicated that compound 1 displayed moderate cytotoxicity against L1210 murine leukemia cells and KB epidermoid carcinoma cells.

Methods for the preparation of 3-aryl-2H-azirine-2,2-dicarboxylic acids and their amides, esters, and azides by FeCl₂-catalyzed isomerization of 3-aryl-5-chloroisoxazole-4-carbonyl chlorides into 3-aryl-2H-azirine-2,2-dicarbonyl dichlorides followed by their reaction with nucleophiles are reported. Two approaches to the preparation of 3-aryl-5-chloroisoxazole-4-carbonyl chlorides have been developed.

We report the synthesis of germanyl triazoles formed via a copper-catalysed azide-alkyne cycloaddition (CuAAC) of germanyl alkynes. The reaction is often high yielding, functional group tolerant, and compatible with complex molecules. The installation of the Ge moiety enables further diversification of the triazole products, including chemoselective transition metal-catalysed cross-coupling reactions using bifunctional boryl/germyl species.

The synthesis of tripeptides incorporating new fluorinated heterocyclic hydrazino acids, based on the tetrahydropyridazine scaffold is described. Starting from simple fluorinated hydrazones, these non-proteinogenic cyclic β-amino acids were easily prepared by a zinc-catalyzed aza-Barbier reaction followed by an intramolecular Michael addition. Preliminary conformational studies on tripeptides including this scaffold in the central position show an extended conformation in solution (NMR) and in the solid state (X-ray).

A novel study on the hypervalent iodine-mediated polyfluoroalkylation of sulfoxonium ylides was developed. Sulfoxonium ylides, known for their versatility and stability, are promising substrates for numerous transformations in synthetic chemistry. This report demonstrates the successful derivatization of sulfoxonium ylides with trifluoroethyl or tetrafluoropropyl groups, and provides valuable insights into the scope and limitations of this approach. Nineteen examples have been prepared (45-92% yields), with structural diversity modified at two key sites on the sulfoxonium ylide reactants. Finally, DFT calculations provided insights about the mechanism of this transformation, which strongly suggest that an S_N2 reaction is operative.

The ongoing quest to discover effective treatments for diseases remains a significant challenge for the scientific community. Multicomponent reactions (MCRs) have emerged as powerful tools in accelerating drug discovery, enabling the rapid generation of chemical libraries with high diversity in a time-efficient and environmentally sustainable manner. In this review, we focus on central nervous system (CNS) disorders, particularly Alzheimer's disease, Parkinson's disease, schizophrenia, depression, and epilepsy, where MCRs have contributed to the development of promising ligands in recent years. Rather than providing an exhaustive overview, this review aims to highlight key studies that address major CNS pathologies, relevant drug targets, and various MCR approaches. We have carefully selected representative articles and apologize to the authors whose important contributions may not be included. By concentrating on these pivotal studies, we strive to offer a clear and concise perspective on current research trends and breakthroughs in this field.

Quantitative assessment of the first acidity constant (pK _a) for BFC (27.6 in CH₃CN) and FIC (27.8 in CH₃CN) shows the methylene protons to be significantly more acidic than those in related cyclopentadiene (32 in CH₃CN), indene (34 in CH₃CN), or fluorene (37 in CH₃CN) and comparable to the methine of 9-perfluorophenylfluorene (28.14 in CH₃CN). This work reports quantitative pK _a values of BFC and FIC, places those values in a broadened context of CpH-cognate hydrocarbon acidity and presents a Clar-Loschmidt graph perspective to help understand the "surprises".