Electrochemical Synthesis of Polysubstituted Oxazoles from Ketones and Acetonitrile

Electrochemical Annulation of p-Alkoxy or p-Hydroxy Anilines with Enaminones for Selective Indole and Benzofuran Synthesis

The green and sustainable electrochemical oxidative cyclization of enaminones with p-methoxy/p-hydroxy anilines has been developed, enabling the regioselective synthesis of indoles and benzofurans. The methods are of significant advantage not only due to the mild and metal-free sustainable electrochemical conditions, but also because of the employment of easily available and stable aniline substrates to replace the unstable quinoneimide for a similar annulation in previous work.

Regioselective 1,4-Addition of P(O)-H Species to In Situ-Formed 1-Benzopyrylium Ion from C3-Substituted 2H-Chromene Hemiketals to Construct C3-Functionalized C4-Phosphorylated 4H-Chromenes

Herein, we report the first example that P(O)-H species including H-phosphonates and H-phosphine oxides could participate in a highly regioselective 1,4-addition to in situ generated 1-benzopyrylium ion from C3-substituted 2H-chromene hemiketals, which provides a brand-new and effective approach for the synthesis of C4-phosphorylated 4H-chromenes with diverse C3-functionality (ketone, ester, sulfonyl, aryl, and alkyl groups). In total, the reaction features the use of inexpensive Zn(ClO4)2·6H2O as a catalyst, low catalyst loading (only 5 mol %), mild reaction conditions (60 °C, 10 min to 24 h), and broad substrate scope (46 examples) as well as good to high yields (>90% yield on average). More importantly, mechanistic experiments demonstrated the essential role of the C3-substituent on 2H-chromene hemiketals in stabilizing the in situ generated 1-benzopyrylium ion and the regioselective 1,4-addition control.

Hydrophilic-lipophilic balance copolymer composite nanofiber as an adsorbent for online solid phase extraction of three estrogens from water samples with column-switching prior to high-performance liquid chromatography

BACKGROUND

In recent years, the increasing accumulation of estrogen pollutants in the environment has raised concerns about their impact on human health, necessitating the development of highly sensitive detection methods for trace pollutant enrichment and analysis in environmental samples. Online pretreatment detection technology offers significant advantages over conventional offline techniques, including high automation, minimal human intervention, and improved efficiency. However, the key to successful implementation lies in the advancement of novel adsorbent materials.

RESULTS

Herein, we present a novel adsorbent material called polyacrylonitrile-hydrophilic-lipophilic balanced copolymer (PAN-HLB) composite nanofiber prepared via electrospinning for efficient online packed fiber solid phase extraction (PFSPE) of three estrogens from water samples. A rapid and highly sensitive online PFSPE-HPLC-FLD method was developed for the quantification of 17 β-Estradiol (E2), Estriol (E3), and 17-ethinylestradiol (EE2). The curves of the target analytes were prepared with good correlation coefficient values (r2 > 0.9900) in the range of 0.1-2 ng/mL. The limit of detection (S/N = 3) was 0.05 ng/mL, the limit of quantitation (S/N = 10) is 0.1 ng/mL. The recoveries of three estrogens were 94.0 %∼110.3 %, and the precisions (RSD) were less than 5 %. The online PFSPE column, packed with the PAN-HLB composite nanofiber, exhibits exceptional stability and can be effectively reused for a minimum of 100 cycles.

SIGNIFICANCE

This study presents the successful preparation of PAN-HLB composite nanofiber for the first time, demonstrating their efficacy as an innovative online pretreatment adsorbent. The proposed online pretreatment and detection approach offers remarkable benefits in terms of sensitivity, labor-saving, and cost-effectiveness that make it highly suitable for practical water sample analysis.

Electrochemical Synthesis of Quinazolines: N-H/C(sp3)-H Coupling of o-Carbonyl Anilines with Amino Acids and Amines

A mild and efficient electrochemical protocol for the synthesis of quinazolines through N-H/C(sp3)-H coupling of o-carbonyl anilines with natural amino acids/amines has been developed. The products quinazolines can easily be isolated in moderate to excellent yields under external chemical oxidant-free conditions. Moreover, this reaction can be safely conducted on gram scale.

The developments of C-N bond formation via electrochemical Ritter-type reactions

With the development of organic electrochemical synthesis, a series of notable achievements have been made in electrochemical Ritter amination reactions, which have enriched the methods available for constructing C-N bonds. In this review, electrochemical Ritter amination reactions are introduced based on the classification of reaction substrates, including olefins, aromatics, alkylbenzenes, and the less reported carboxylic acids, ketones, sulfides, and alkanes. The application of electrochemical technology to Ritter reactions has improved the harsh conditions of the traditional reactions, and extended the substrate scope and the structural diversity of the products. The application value of Ritter reactions in organic synthesis has also been further expanded.

DMSO promoted catalyst-free oxidative C-N/C-O couplings towards synthesis of imidazoles and oxazoles

Dimethyl sulfoxide (DMSO)-promoted catalyst-free oxidative C-N coupling and C-O coupling under oxidant-free conditions are outlined. This protocol is operationally simple and leads to various functionalized substituted imidazoles or oxazoles in good yields. To date, a very limited number of oxidation protocols have been established, where DMSO acts solely as a catalyst or an oxidant or both. In this report, DMSO is not only used as a C-N/C-O coupling agent but is also used as the oxidant required for these oxidative transformations. Hence, our demonstrated DMSO-promoted catalyst-free coupling transformation has the ability to lead to a new dimension in the field of oxidative coupling.

Phytosterol organic acid esters: Characterization, anti-inflammatory properties and a delivery strategy to improve mitochondrial function

Phytosterol organic acid esters are important food resources and the components of biomembrane structure. Due to the lack of extraction and synthesis techniques, more research has been focused on phytosterols, and the research on phytosterol acid esters have encountered a bottleneck, but phytosterol acid esters confer substantial benefits to human health. In this study, stigmasteryl vanillate (VAN), stigmasteryl protocatechuate (PRO) and stigmasteryl sinapate (SIN) were prepared through the Steglich reaction. The processes are promotable and the products reach up to 95% purity. In addition, their stability was evaluated by differential scanning calorimetry and thermogravimetric analysis. HPLC analysis revealed an enhancement in water solubility after esterification with phenolic acid. In an in vitro digestion model, the bioaccessibility of stigmasteryl phenolates was significantly higher than that of stigmasterols (STIs). Regarding the anti-inflammatory properties, VAN, PRO, and SIN exhibit superior effects against TNF-α induced pro-inflammatory responses compared to STI. All stigmasteryl phenolates supplementation increased the ATP production, the basal, and maximal oxygen consumption rate in mitochondrial stress test. Overall, we present a synthesis method for stigmasteryl phenolates. It will contribute to the development and research of phytosterol acid ester analysis, functions and utilization in food. Moreover, the nutrient-stigmasterol hybrids tactic we have constructed is practical and can become a targeted mitochondrial delivery strategy with enhanced anti-inflammatory effects.

Photocatalytic Benzylic C-H Oxidation/Cyclization of Enaminones to the Synthesis of Polysubstituted Oxazoles

Photocatalytic benzylic C-H oxidation/cyclization of enaminones was efficiently achieved to afford oxazole derivatives under mild conditions. The oxygen in the oxazole ring originated from green oxidant molecular oxygen. The synthetic protocol features broad substrate scopes and good functional group tolerance. The combined experimental and theoretical studies reveal that in suit benzylic C-H oxidation/cyclization is involved in the reaction transformations.

Electricity-Promoted Friedel-Crafts Acylation of Biarylcarboxylic Acids

An electricity-promoted method for Friedel-Crafts acylation of biarylcarboxylic acids is described in this research. Various fluorenones can be accessed in up to 99% yields. During the acylation, electricity plays an essential role, which might motivate the chemical equilibrium by consuming the generated TFA. This study is predicted to provide an avenue to realize Friedel-Crafts acylation in a more environmentally friendly process.