Beilstein Journal of Organic Chemistry最新文献

Over the past decade, dioxazolones have been widely used as N-acylamide sources in amidation processes of challenging substrates, typically employing precious transition metals. However, these catalytic systems often present several challenges associated with cost, toxicity, stability, and recyclability. Among the 3d transition metals, copper catalysts have been gaining increasing attention owing to their abundance, cost-effectiveness, and sustainability. Recently, these catalytic systems have been applied to the chemical transformation of dioxazolones, conferring a convenient protocol towards amidated products. This review highlights recent advancements in the synthetic transformations of dioxazolones, with particular examples of copper salts.

The CF₂H group can act as a hydrogen bond donor, serving as a potential surrogate for OH or SH groups but with a weaker hydrogen bond donation ability. Here, we describe a series of CF₂H group-containing moieties that facilitate hydrogen bond interactions. We survey hydrogen bond donation ability using several established methods, including ¹H NMR-based hydrogen bond acidity determination, UV-vis spectroscopy titration with Reichardt's dye, and ¹H NMR titration using tri-n-butylphosphine oxide as a hydrogen bond acceptor. Our experiments reveal that the direct attachment of the CF₂H group to cationic aromatic systems significantly enhances its hydrogen bond donation ability, a result consistent with theoretical calculations. We anticipate that this chemistry will be valuable for designing functional molecules for chemical biology and medicinal chemistry applications.

Orthogonal self-assembly represents a useful methodology to construct supramolecular polymers with AA- and AB-type monomers, as commonly used for covalently linked polymers. So far, the design of such monomers has relied heavily on three-dimensional macrocycles, and the use of two-dimensional shape-persistent macrocycles for this purpose remains rather rare. Here, we demonstrate a dimerization motif based on a hydrogen-bonded macrocycle that can be effectively applied to form orthogonal supramolecular polymers. The macrocycle-mediated connectivity was confirmed by single-crystal X-ray diffraction, which revealed a unique 2:2 binding motif between host and guest, bridged by two cationic pyridinium end groups through π-stacking interactions and other cooperative intermolecular forces. Zinc ion-induced coordination with the macrocycle and a terpyridinium derivative enabled orthogonal polymerization, as revealed by ¹H NMR, DLS, and TEM techniques. In addition, viscosity measurements showed a transition from oligomers to polymers at the critical polymerization concentration of 17 μM. These polymers were highly concentration-dependent. Establishing this new dimerization motif with shape-persistent H-bonded macrocycles widens the scope of noncovalent building blocks for supramolecular polymers and augurs well for the future development of functional materials.

In recent decades, organic electrosynthesis has emerged as a practical, sustainable, and efficient approach that facilitates valuable transformations in synthetic chemistry. Combining electrochemistry with transition-metal catalysis is a promising and rapidly growing methodology for effectively forming challenging C-C and C-heteroatom bonds in complex molecules in a sustainable manner. In this review, we summarize the recent advances in the combination of electrochemistry and copper catalysis for various organic transformations.

2-Fluorobenzofurans underwent efficient nickel-catalyzed coupling with arylboronic acids through the activation of aromatic C-F bonds. This method allowed us to successfully synthesize a range of 2-arylbenzofurans with various substituents. The reaction, which proceeded under mild conditions, involved β-fluorine elimination from nickelacyclopropanes formed by the interaction of 2-fluorobenzofurans with zero-valent nickel species. This protocol facilitates orthogonal coupling reactions of aromatic C-F and C-Br bonds with arylboronic acids.

This review reports the achievements in copper(II) triflate-catalyzed processes concerning the multicomponent reactions, applied to the synthesis of acyclic and cyclic compounds. In particular, for the heteropolycyclic systems mechanistic insights were outlined as well as cycloaddition and aza-Diels-Alder reactions were included. These strategies have gained attention due to their highly atom- and step-economy, one-step multi-bond forming, mild reaction conditions, low cost and easy handling.

Axial chirality is present in a variety of naturally occurring compounds, and is becoming increasingly relevant also in medicine. Many axially chiral compounds are important as catalysts in asymmetric catalysis or have chiroptical properties. This review overviews recent progress in the synthesis of axially chiral compounds via asymmetric organocatalysis. Atroposelective organocatalytic reactions are discussed according to the dominant catalyst activation mode. For covalent organocatalysis, the typical enamine and iminium modes are presented, followed by N-heterocyclic carbene-catalyzed reactions. The bulk of the review is devoted to non-covalent activation, where chiral Brønsted acids feature as the most prolific catalytic structure. The last part of the article discusses hydrogen-bond-donating catalysts and other catalyst motifs such as phase-transfer catalysts.

Polysarcosine emerges as a promising alternative to polyethylene glycol (PEG) in biomedical applications, boasting advantages in biocompatibility and degradability. While the self-assembly behavior of block copolymers containing polysarcosine-containing polymers has been reported, their potential for shape transformation remains largely untapped, limiting their versatility across various applications. In this study, we present a comprehensive methodology for synthesizing, self-assembling, and transforming polysarcosine-poly(benzyl glutamate) block copolymers, resulting in the formation of bowl-shaped vesicles, disks, and stomatocytes. Under ambient conditions, the shape transformation is restricted to bowl-shaped vesicles due to the membrane's flexibility and permeability. However, dehydration of the polysarcosine broadens the possibilities for shape transformation. These novel structures exhibit asymmetry and possess the capability to encapsulate smaller structures, thereby broadening their potential applications in drug delivery and nanotechnology. Our findings shed light on the unique capabilities of polysarcosine-based polymers, paving the way for further exploration and harnessing of their distinctive properties in biomedical research.

Phenethylamines and phenylisopropylamines of scientific relevance can be prepared with a NaBH₄/CuCl₂ system in 10 to 30 minutes via reduction of substituted β-nitrostyrenes. This one-pot procedure allows the quick isolation of substituted β-nitrostyrene scaffolds with 62-83% yield under mild conditions, without the need for special precautions, inert atmosphere, and time-consuming purification techniques.

The discovery of the optimal conditions for chemical reactions is a labor-intensive, time-consuming task that requires exploring a high-dimensional parametric space. Historically, the optimization of chemical reactions has been performed by manual experimentation guided by human intuition and through the design of experiments where reaction variables are modified one at a time to find the optimal conditions for a specific reaction outcome. Recently, a paradigm change in chemical reaction optimization has been enabled by advances in lab automation and the introduction of machine learning algorithms. Therein, multiple reaction variables can be synchronously optimized to obtain the optimal reaction conditions, requiring a shorter experimentation time and minimal human intervention. Herein, we review the currently used state-of-the-art high-throughput automated chemical reaction platforms and machine learning algorithms that drive the optimization of chemical reactions, highlighting the limitations and future opportunities of this new field of research.