Beilstein Journal of Organic Chemistry最新文献

A pair of an axially chiral platinum(II) complex was synthesized via Sonogashira coupling and subsequent coordination of a pincer ligand to a precursor. The complex exhibited a broad absorption band ranging from 250 to 550 nm in the UV-vis spectrum, with TD-DFT calculations indicating mixed ligand-to-ligand charge transfer (LL'CT) and metal-to-ligand charge transfer (MLCT) character. Photoluminescence measurements in CH₂Cl₂ solution revealed dual emission peaks at 427 nm and 596 nm, with a quantum yield of 3%. In PMMA matrix, the emission peaks were blue-shifted to 408 nm and 558 nm, and the quantum yield slightly increased to 4%. CD spectra showed distinct Cotton effects in the MLCT region, and CPL signals were observed only in the PMMA matrices, with a dissymmetry factor |g _lum| = 0.4 × 10^-3. These results demonstrate that axial chirality of the binaphthyl moiety governs the three-dimensional chiral arrangement of two platinum(II) chromophore units, leading to the chiroptical properties in the MLCT region through exciton coupling under restricted molecular motion.

Three indan-2-one-based donor-π-acceptor-π-donor type dyes with symmetric donor groups were synthesized and characterized to study their nonlinear optical (NLO) properties and their potential use in the rapid and selective determination of cyanide. The designed structures feature symmetrical alkylaminophenyl donor groups and a strong electron-withdrawing dicyanovinylene as an acceptor connected through vinyl groups as a π-bridge. These strongly π-conjugated organic dyes can absorb in the NIR region, and they showed sensitivity towards the polarity of solvents with colorimetric and optical changes. Because of the strong donor-acceptor structure, second-order NLO properties were studied by measuring electric field-induced second harmonic (EFISH) values, which showed significant second-order NLO responses. The experimental results were explained using density functional theory (DFT) methods. The dyes also exhibit chemosensor properties, showing selectivity for cyanide via a Michael addition mechanism that causes the disappearance of the ICT band, and a significant color change was observed in both organic and aqueous media. In addition, the interaction mechanism between cyanide and the chemosensor is determined by a ¹H NMR study and explained by DFT calculations.

New highly electrophilic gem- and spiro-activated trichloromethylnitrocyclopropanes were obtained by the Michael-initiated ring closure (MIRC) reaction of 1-bromo-1-nitro-3,3,3-trichloropropene with linear and cyclic CH-acids catalyzed by bases. Conditions for obtaining the target cyclopropanes were optimized. The process is characterized by high diastereoselectivity and allows obtaining cyclopropanes with trans-configuration of -NO₂ and -CCl₃ groups. Monocyclic (based on malonic acid dinitrile, methyl cyanoacetate, ethyl cyanoacetate, benzoylacetonitrile), spirocarbo- (based on 1,3-indanedione) and spiroheterocyclic (based on Meldrum's acid, dimethylbarbituric acid, 3-methyl-1-phenyl-5-pyrazolone) cyclopropane structures were isolated and characterized.

Arenes and heteroarenes are easily available building blocks in organic chemistry, and saturation the aromatic ring facilitates synthetic chemists to efficiently synthesize natural products with complex three-dimensional structures. Recent advances in catalyst and ligand design have enabled unprecedented progress in the catalytic hydrogenation of (hetero)aromatic systems. Quinoline, isoquinoline, pyridine, and related substrates can now be reduced with high efficiency and stereoselectivity, providing efficient access to saturated and partially saturated architectures vital to synthetic chemistry. Furthermore, catalytic asymmetric aromatic hydrogenation has facilitated the asymmetric total synthesis of complex natural products and pharmaceutical agents. This review highlights recent advances in catalytic (hetero)arene hydrogenation, with a focus on its application in natural product synthesis.

A reactivity umpolung approach for the derivatization of cycloheptatrienes was extended to hexa(methoxycarbonyl)cycloheptatriene, which forms the corresponding anion reactive towards electrophiles. Despite the presence of four potential reactive sites, the reactions mainly involve the initial electrophilic attack onto the α-position relative to the hydrogen atom. The selectivity is either due to the high stability of the α-nucleophilic conformer or due to the promotion by the adjacent ester group. Cascade reactions upon the target connection, if installed, include the formation of norcaradienes, dihydroindazoles, a tetracyclodecene and a hydrazonocycloheptatriene derivative.

Radical reactions, which have been reported in large numbers in recent years, have exerted major influence across fields where organic synthesis plays a central role, including pharmaceuticals, agrochemicals, materials chemistry, organic semiconductors, and organic thin-film solar cells. These areas are intimately linked to human life; thus, advances in organic synthesis are essential for improving human well-being. Nearly two centuries after the seminal 1828 synthesis of urea from inorganic precursors - often regarded as the birth of organic synthesis - the field continues to evolve rapidly and to exert profound impact on society. A retrospective of almost 200 years of organic synthesis shows that the development and discovery of two-electron ionic transformations dominated the early stages. Over time, pericyclic reactions exemplified by the Woodward-Hoffmann rules and one-electron radical processes became prominent research topics. Today, many of these classical transformations have been further refined to afford reactions that are cheaper, safer, and less toxic. In this context, we focus on mild radical reactions mediated by zirconium (Zr), which has recently attracted attention because of its low toxicity and ease of handling. We discuss the utility of Zr in such radical processes and consider prospects for future development.

Alkenyl chlorides constitute a synthetically valuable yet historically underexplored class of organohalides. First prepared in 1868 by Charles Friedel - best known for the Friedel-Crafts reaction - via the reaction of ketones with phosphorus pentachloride, these compounds have steadily gained attention over the decades. In recent years, their distinct reactivity and potential in organic synthesis have been increasingly recognized. This review provides a comprehensive overview of the synthesis and application of alkenyl chlorides, with a focus on developments over the past four decades. By organizing this growing body of work, I aim to highlight key advances and help guide the design of new transformations involving this important and versatile functional group.

An atom- and step-economical electrochemical method for the synthesis of aliphatic nitro-NNO-azoxy compounds from the corresponding nitroso compounds was developed employing ammonium dinitramide, a prospective green oxidant for aerospace propulsion applications, as both electrolyte and source of a =NNO₂ group. The developed method is green, practical, and scalable due to constant current electrolysis in an undivided cell at high current densities. Synthesized products demonstrated pronounced NO-donor activity and fungicidal activity against phytopathogenic fungi.

A novel route to the flavor enhancer ethylmaltol, a synthetic 4-pyrone, from naturally abundant maltol is disclosed. Two strategies were explored for the required C1 homologation. The most direct approach, C-C bond formation via methylation of a dianionic intermediate, proved unsuitable due to competing overalkylation and the necessity of sub-zero temperatures. In contrast, a transient protecting group approach enabled selective methylation under mild conditions. This culminated in a scalable, operationally simple one-pot synthesis of ethylmaltol from a renewable precursor.

The total synthesis of new members of prenylated indole alkaloids exhibiting α-glucosidase activity is described. Asperdinones B, C, D, and E are characterized by the presence of a (3R)-3-indolylmethylbenzodiazepine-2,5-dione unit at C-3 of C4-C7 prenylated indoles. Methods of direct and indirect prenylation of indole and tryptophan were explored. Different approaches were adopted for the functionalization of C4-C7 prenylindoles at C-3 using Negishi cross-coupling methods. The asperdinones are among the rare tryptophan-derived indole alkaloids which appear to have undergone epimerization due to genetic alteration of specific gene clusters that code for a (3R) configuration.