Beilstein Journal of Organic Chemistry最新文献

Carbazoles are ubiquitous and privileged heterocyclic scaffolds in various functional organic materials and naturally occurring products. Although extensive efforts have focused on developing synthetic strategies toward carbazole derivatives, direct regioselective functionalization of the carbazole core remains challenging due to the inherently higher reactivity at the C3/C6 positions. In this study, we report a palladium-catalyzed, directing group-assisted, regioselective C1-H nitration of carbazoles. The protocol features a removable directing group and is amenable to gram-scale synthesis. This strategy provides a valuable platform for the selective functionalization of carbazoles, offering potential applications in optoelectronics, functional organic materials, and related areas while contributing to the advancement of C-H activation methodologies.

Furanoside derivatives are broadly present in the antigenic structures of pathogenic microorganisms and play a key role in their recognition by the host immune system. Despite the high demand for vaccine and diagnostic development, their chemical synthesis remains challenging. During the development of a new methodology for the synthesis of galactofuranoside building blocks, we encountered an unexpected predominance of the furanoside form in the equilibrium mixture of benzoylated β-galactosides. Since the furanoside form is typically less stable and is usually present only in minor amounts, we turned to computational studies to elucidate the driving force of this pyranoside-into-furanoside isomerisation. The DFT B3LYP-D3 approach was employed for this task with additional validation of its results at DLPNO-CCSD(T) level for the lowest energy conformers. The results demonstrate that the van-der-Waals interactions between phenyl rings of the benzoate substituents are crucial for the stabilization of the furanoside isomer. This outcome could not be rationalized within the framework of conventional carbohydrate chemistry, as the key intramolecular interactions determining the equilibrium lie outside the carbohydrate ring system. Consideration of such effects is essential to rationalize the reactivity of structurally complex and densely protected carbohydrate compounds.

The synthesis of fluorinated haloacetimidates relies on the access to the corresponding fluoroacetonitriles, which are toxic gaseous molecules difficult to store and handle. In this work we develop a safe two-chamber method for the ex-situ generation of these reagents in one chamber and their subsequent reaction with O-nucleophiles in the second chamber. The method is easy to setup, control and gives access to new haloacetimidates under mild conditions, similar to the ones used for the synthesis of the more commonly used trichloroacetimidates.

Atropisomers are not only prevalent in biologically active natural products and pharmaceuticals, but they have also garnered increasing attention for their effectiveness as ligands and catalysts in the field of catalytic asymmetric synthesis. Asymmetric catalysis serves as a key strategy for the enantioselective synthesis of atropisomers, and significant progress has been made in recent years. However, selenium-containing atropisomers have long remained underexplored as synthetic targets, and only in recent years have they begun to attract increasing attention from the community. Recently, several synthetic approaches for constructing selenium-containing atropisomers have been reported, such as C-H selenylation of arenes, selenosulfonylation of vinylidene o-quinone methides (VQM), and hydroselenation of alkynes. Nevertheless, a comprehensive review that systematically summarizes these advances is currently lacking. This review aims to provide an overview of recent developments in the catalytic enantioselective synthesis of selenium-containing atropisomers via C-Se bond formation. We hope this review will serve as a valuable reference for researchers interested in further exploring this area.

The review is devoted to strategies for contraction of six-membered cycles in the synthesis of functionalized cyclopentane/enones, which are biologically active compounds. The main synthetic methods of ring contraction (ozonolysis-aldol condensation, ozonolysis-Dieckmann reaction, Baeyer-Villiger cleavage-Dieckmann reaction) and rearrangements (benzil, semipinacol, with the participation of thallium- and iodine-based oxidants, photochemical, Wolff, Meinwald, Wagner-Meerwein and Favorskii) are presented. The review summarizes literature data covering the last 12 years, with some exceptions of earlier works due to the importance of the published information.

In the present study, 21 fused isoxazolidines were synthesized in yields ranging from good to excellent. Methyl laurate was identified as the easily accessible optimal solvent medium for the reaction, and the related compounds were obtained through straightforward isolation techniques in a relatively short time frame (5-80 minutes). A comprehensive investigation was conducted utilizing various web platforms, encompassing ecological and environmental risk assessments, toxicity, pesticide similarity, and biodegradability of methyl laurate in comparison with a series of conventional organic solvents, water, some fatty acids and their derivatives. The findings of this investigation revealed that methyl laurate exhibited better green solvent properties when evaluated against other solvents.

A synthetic strategy for the preparation of spiro[indoline-3,2'-pyrrolidine] derivatives has been developed, featuring a two-step sequence consisting of the reaction of 2-arylindoles with α,β-unsaturated ketones, followed by Fe(II)-catalyzed spirocyclization of readily accessible oxime acetates. The method exhibits a broad substrate scope and good functional group tolerance. The synthesized spirocyclic compounds showed no significant antimicrobial activity.

A synthetic study toward vibralactone, a potent inhibitor of pancreatic lipase, is reported. The synthesis of the challenging all-carbon quaternary center within the cyclopentene ring was achieved through intramolecular alkylidene carbene C-H insertion.

To our knowledge, this work represents one of the earliest comparative studies on the anion-binding behaviors of carbazole-based structural analogs, demonstrating that a flexible macrocycle markedly improves iodide binding affinity via an induced-fit mechanism. The flexible analog PBG exhibits a 22.78-fold higher fluorescence quenching efficiency upon iodide binding compared to the rigid WDG (K _PBG /K _WDG = 22.78), demonstrating its potential as a highly sensitive optical probe and offering a novel strategy for engineering dynamic supramolecular receptors. Two carbazole-based macrocyclic probes, PBG (flexible benzene ring) and WDG (rigid fluorene backbone), were synthesized via Friedel-Crafts reactions. Their iodide (I^-) recognition properties were systematically explored using ¹H NMR, UV-vis absorption, and fluorescence spectroscopy. Quantitative analysis via the Benesi-Hildebrand equation and nonlinear fitting demonstrated that flexible PBG achieves superior I^- binding (K _PBG = 1.387 × 10⁵ M^-1) through induced-fit conformational adjustments, whereas rigid WDG (K _WDG = 6.089 × 10³ M^-1) is constrained by preorganized cavity geometry, adhering to a conformational selection mechanism. This work elucidates the synergistic interplay between conformational dynamics and localized structural adaptations governing anion recognition. The findings advance the rational design of tunable, high-affinity anion receptors and deepen the understanding of conformational regulation in supramolecular systems.