Organic & Biomolecular Chemistry最新文献

A mild and regioselective nitration-cyclization of alkynyl aryl ketones has been developed to access 3-nitroflavones promoted by Zn(OTf)₂. Tandem nitration and intramolecular cyclization is achieved using 68% HNO₃ under room-temperature conditions, delivering substituted 3-nitroflavones in generally good to excellent yields.

We report a transition metal-free method for the intermolecular hydroamination of olefins using solvated electrons, generated in situ from granulated lithium under sonication in 2-methyltetrahydrofuran (2-MeTHF). This additive-free protocol enables rapid formation of mixed secondary and tertiary amines under ambient conditions and is broadly applicable to vinylarenes and alkyl amines. Selected allylarenes and conjugated dienes are also competent substrates, exhibiting distinct regioselectivity under the reaction conditions. Mechanistic studies support an SET and HAT pathway, with lithium amide intermediates acting as both reductants and nucleophiles. The method offers excellent atom economy, sustainability, and synthetic utility, exemplified by the selective synthesis of the pharmaceutical benzphetamine in high yield.

An acid-triggered cascade transformation of donor-acceptor cyclopropanes, containing a 2-indolyl fragment as a donor and an acyl group as an acceptor, into carbazole derivatives was developed. The starting cyclopropanes, which were easily synthesized via an aldol condensation/Corey-Chaykovsky reaction sequence on a gram scale, were readily converted into 4-substituted carbazoles by the action of both equimolar hydrochloric acid in methanol and catalytic HCl-dioxane in methylene chloride. The reaction mechanism involves small ring opening and common ring closure via the Friedel-Crafts reaction as key steps; however, the current results do not allow conclusions to be drawn about the order of the proceeding steps in each case.

The regioselective functionalization of the C-H bond at the C2-position of 3-substituted thiophenes is challenging, as both thienyl α-positions may be reactive, generally affording mixtures of C2-, C5- and C2,C5-(di)functionalized thiophenes. We established that using palladium 1,4-migration allows for the regioselective functionalization of only one of the two α-positions of 3-arylthiophenes. The oxidative addition of the 3-(2-bromoaryl)thiophenes to palladium followed by such palladium migration, regioselectively activates the thienyl C2-α-position. Next, C2-heteroarylated 3-arylthiophene derivatives can be obtained through palladium-catalyzed direct coupling with heteroarenes. The new C-C bond that this reaction generates comes from the functionalization of two C-H bonds. This thienyl heteroarylation method tolerates a variety of heteroarenes and several substituents on the 3-arylthiophene. In addition, an easily available air-stable catalyst and an inexpensive base were employed for this reaction.

The synthesis of novel carbohydrate-oligonucleotide conjugates is described. These bioconjugates, which feature glycosyl-nucleoside moieties linked to a thymine base via a 1,2,3-triazole linker, were prepared using a 'click' chemistry route. This synthetic approach enables the generation of oligonucleotide conjugates designed to engage specific sugar receptors, including glucose transporters as well as GalNAc and maltoheptaose-binding receptors.

A versatile route for the preparation of chemically and electronically diverse Mes₂BPh-based boranes (Mes = mesityl, 2,4,6-trimethylphenyl) is presented that allows the conversion of tetrazolyl rings in a common borane precursor (2H) into boranes bearing variously substituted oxadiazolyl groups. A series of eight boranes (4a-4h) was prepared with functional groups on the 5-position of the oxadiazole ranging from electron donating (4a: 4-Me-phenyl, 4b: 4-MeO-phenyl, etc.) to strongly electron withdrawing (4d: 4-O₂N-phenyl, 4e: 3,5-bis(CF₃)-phenyl, 4h: CF₃) and also including a bifunctionalized example bearing two Mes₂B moieties (4g). A full characterization study of the optical, electrochemical and electronic properties, both experimentally and by DFT calculations, was carried out. Our investigation shows that the boranes exhibit dynamic equilibria between closed intramolecularly N→B-coordinated and open non-coordinated conformers, as indicated by variable temperature NMR, ¹¹B NMR and anion binding studies with F^- and CN^-. The anion binding studies reveal substantial differences in the fluorescence response of the compounds ranging from differing degrees of quenching to fluorescence shifts (4g) and enhanced emission (4c) (4-OMe-phenyl). These results show that this synthetic strategy allows easy creation of a series of compounds with incrementally varied optical properties and Lewis acidities.

3H-Phenothiazin-3-one is a small organic molecule with established biological properties, yet its potential as an organic photocatalyst remains largely unexplored. Herein, we report a green and efficient aerobic oxidation of boronic acids employing 3H-phenothiazin-3-one as the photocatalyst. The transformation proceeds under mild conditions, using green LED irradiation and atmospheric oxygen as the terminal oxidant. A broad range of boronic acids were successfully converted to the corresponding hydroxy derivatives, showcasing the excellent functional-group tolerance and synthetic utility of the developed photochemical protocol. Preliminary mechanistic investigations were undertaken to elucidate the reaction pathway and to identify the reactive oxygen species involved.

Thiocarbamates are a class of molecules with important value and significant roles in organic chemistry. Due to their unique chemical properties and heteroatom-rich molecular structure, thiocarbamates have broad application prospects in organic synthesis, analytical chemistry, materials science and biomedicine. In recent years, methodological studies on the synthesis of these compounds have garnered increasing attention in the scientific community. This mini-review summarizes the representative progress in the effective synthesis of thiocarbamates through different synthetic strategies from thermochemistry to photochemistry or electrochemistry in the past decade, emphasizes the diversity and applicability of their products, and expounds their mechanism principles where possible.

The transformation of alkynes into nitrogen-containing compounds has emerged as a crucial strategy in modern synthetic chemistry. This review article highlights diverse catalytic approaches for incorporating nitrogen from amines, hydroxylamines, nitriles, and related functional groups into alkynes, leading to valuable acrylamides. Various transition metals, including copper, nickel, iron, zinc, and palladium, play key roles in facilitating hydroamination, hydroboration, carbonylation, and other transformations. This review explores both recent metal-catalyzed and metal-free methodologies published in the last 15 years, emphasizing the importance of precise control over selectivity and functional-group compatibility.

Nitrogen-containing heterocycles are pivotal in modern drug discovery, constituting a significant proportion of newly approved small-molecule drugs. However, the asymmetric catalytic hydrogenation (ACH) of these substrates remains challenging due to their high aromatic stability and the propensity of basic nitrogen atoms to deactivate catalysts. This review systematically summarizes recent advances in overcoming these hurdles for five key nitrogen heterocycles: pyridine, pyrrole, pyrazole, piperidine, and quinoline. We provide a comparative analysis of the three primary catalytic strategies: transition-metal complexes (e.g., Rh, Pd, and Ir), which offer the broadest substrate scope and high turnover numbers; organocatalytic systems, which provide environmentally benign alternatives for specific substrates; and biocatalytic approaches, which demonstrate exquisite selectivity under mild conditions. A distinguishing feature of this review is the integration of mechanistic rationalizations derived from Density Functional Theory (DFT) calculations. Rather than treating theoretical studies as a separate topic, we highlight how atomic-scale modeling clarifies critical factors governing stereocontrol that are often inaccessible via experiment alone. Specifically, we discuss theoretical insights into (1) the thermodynamic competition between substrate adsorption and hydrogen evolution on metal surfaces, (2) the origins of solvent-induced enantiodivergence via explicit solvent-bridged transition states, and (3) the determination of stereodetermining steps (e.g., enamine protonation vs. hydride transfer) in organocatalysis. By bridging empirical synthetic results with these theoretical insights, this work aims to provide a comprehensive guide for selecting appropriate catalytic systems and facilitating the rational design of next-generation catalysts for high-value chiral heterocycles.