Incorporation of main group elements into the π-conjugated frameworks is a sophisticated strategy to alter the fundamental nature of the parent conjugated π-systems, giving rise to attractive ...electronic and photophysical properties that are otherwise inaccessible with classic carbon- or metal-based materials. Out of all π-conjugated heterocycles, those that are structurally constrained by tethered aryl substituents surrounding the main group center deserve a great deal of attention because not only do they commonly possess the maximum efficiency of π-conjugation and intermolecular interaction, but they also enjoy remarkable thermal and morphological stabilities that are especially crucial for solid-state performances. In certain cases, elucidation of the behavior of such compounds may additionally provide sufficient perspective toward graphene materials doped with main group elements, which are widely considered as potential next-generation optoelectronic materials. In this review, we will specifically focus on historical developments of structurally constrained polycyclic π-electron systems particularly of those with boron, nitrogen, silicon, or phosphorus atoms annulated directly into the center of π-conjugated systems.
The 3,4‐ethylenedioxy thiophene (EDOT)‐based conjugated microporous polymers (CMPs) were readily constructed via facile one‐step direct arylation polymerication of CH from simple EDOT as a linker ...and commercially available aryl bromides of different geometries as the knots, without preactivation of CH bonds of aromatic building blocks using organometallic reagents. In contrast to conventional coupling reactions, this synthesis strategy not only has atomic efficiency but also can use simple thiophene derivatives as building blocks for synthesizing thiophene‐based CMPs of different structures, which avoids the synthesis of complex thiophene derivatives and are important for applications, for example, fluorescent sensors. The resulting EDOT‐based CMPs were used to fluorescent sensing to 2,4‐dinitrophenol (DNP), I2, and p‐nitrophenol (p‐NP), with high optimal Stern‐Volmer quenching constants.
Nocardioides, a genus belonging to Actinomycetes, can endure various low-nutrient conditions. It can degrade pollutants using multiple organic materials such as carbon and nitrogen sources. The ...characteristics and applications of Nocardioides are described in detail in this review, with emphasis on the degradation of several hard-to-degrade pollutants by using Nocardioides, including aromatic compounds, hydrocarbons, haloalkanes, nitrogen heterocycles, and polymeric polyesters. Nocardioides has unique advantages when it comes to hard-to-degrade pollutants. Compared to other strains, Nocardioides has a significantly higher degradation rate and requires less time to break down substances. This review can be a theoretical basis for developing Nocardioides as a microbial agent with significant commercial and application potential.
The aryl C-glycoside structure is, among the plenty of biologically active natural products, one of the distinct motifs embedded. Because of the potential bioactivity as well as the synthetic ...challenges, these structures have attracted considerable interest, and extensive research toward the total synthesis has been performed. This Review focuses on the synthetic strategies and tactics employed in the total synthesis of this class of natural products. The Introduction describes the historical background, structural features, and synthetic problems associated with aryl C-glycoside natural products. Next the Review summarizes the methods for constructing the aryl C-glycoside bonds. Completed total synthesesand, in some cases, selected examples of incomplete synthesesof natural aryl C-glycosides are also summarized. Finally described are the strategies for constructing polycyclic structures, which were utilized in the total syntheses.
Methods to functionalize arenes and heteroarenes in a site-selective manner are highly sought after for rapidly constructing value-added molecules of medicinal, agrochemical, and materials interest. ...One effective approach is the site-selective cross-coupling of polyhalogenated arenes bearing multiple, but identical, halogen groups. Such cross-coupling reactions have proven to be incredibly effective for site-selective functionalization. However, they also present formidable challenges due to the inherent similarities in the reactivities of the halogen substituents. In this Review, we discuss strategies for site-selective cross-couplings of polyhalogenated arenes and heteroarenes bearing identical halogens, beginning first with an overview of the reaction types that are more traditional in nature, such as electronically, sterically, and directing-group-controlled processes. Following these examples is a description of emerging strategies, which includes ligand- and additive/solvent-controlled reactions as well as photochemically initiated processes.
One‐pot synthesis of various indolo2,3‐bindoles has been accomplished from a copper‐catalyzed transformation of easily accessible 2‐(substituted‐amino)aryl)(mesityl)iodonium salts and indole ...derivatives. Reaction offers great functional group toleration, providing a series of indolo2,3‐bindole derivatives in good yields. Additionally, intramolecular cyclization of 2‐(substituted‐amino)aryl)(mesityl)iodonium salts in the presence of copper‐catalyst provided direct access to benzoxazole derivatives.Chung Whan Lee was nominated to be part of this collection by EurJOC Board Member Sanghee Kim.
Phenolic compounds are known structural moieties of natural organic matter (NOM), and their reactivity is a key parameter for understanding the reactivity of NOM and the disinfection by-product ...formation during oxidative water treatment. In this study, species-specific and/or apparent second order rate constants and mechanisms for the reactions of bromine and chlorine have been determined for various phenolic compounds (phenol, resorcinol, catechol, hydroquinone, phloroglucinol, bisphenol A, p-hydroxybenzoic acid, gallic acid, hesperetin and tannic acid) and flavone. The reactivity of bromine with phenolic compounds is very high, with apparent second order rate constants at pH 7 in the range of 104 to 107 M−1 s−1. The highest value was recorded for the reaction between HOBr and the fully deprotonated resorcinol (k = 2.1 × 109 M−1 s−1). The reactivity of phenolic compounds is enhanced by the activating character of the phenolic substituents, e.g. further hydroxyl groups. With the data set from this study, the ratio between the species-specific rate constants for the reactions of chlorine versus bromine with phenolic compounds was confirmed to be about 3000.
Phenolic compounds react with bromine or chlorine either by oxidation (electron transfer, ET) or electrophilic aromatic substitution (EAS) processes. The dominant process mainly depends on the relative position of the hydroxyl substituents and the possibility of quinone formation. While phenol, p-hydroxybenzoic acid and bisphenol A undergo EAS, hydroquinone, catechol, gallic acid and tannic acid, with hydroxyl substituents in ortho or para positions, react with bromine by ET leading to quantitative formation of the corresponding quinones. Some compounds (e.g. phloroglucinol) show both partial oxidation and partial electrophilic aromatic substitution and the ratio observed for the pathways depends on the pH. For the reaction of six NOM extracts with bromine, electrophilic aromatic substitution accounted for only 20% of the reaction, and for one NOM extract (Pony Lake fulvic acid) it accounted for <10%. This shows that for natural organic matter samples, oxidation (ET) is far more important than bromine incorporation (EAS).
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•Bromine reacts fast with hydroxy aromatic compounds (k ≥ 104 M−1 s−1, pH 7).•Bromine/chlorine react by electrophilic aromatic substitution or electron transfer.•Electron transfer (ET) reactions of bromine/chlorine may lead to quinones.•The formation of quinones was experimentally demonstrated.•The reaction of bromine with NOM isolates occurs mainly by electron transfer.
Herein, we disclose the synthesis of selenopyrano2,3‐bindol‐4(9H)‐ones and their aryl derivatives using seleno‐pyran ring formation via an in situ‐generated selenide reacting directly with ...α‐halo‐β‐ynones of substituted indoles providing selenopyrano2,3‐bindol‐4(9H)‐ones. Subsequent direct CH arylation of the these compounds by palladium‐catalyzed Heck reaction enables the incorporation of aryl substituents on the selenopyrano2,3‐bindol‐4(9H)‐ones scaffolds with moderate yields. This new chemo‐type incorporating an indole ring may be useful for the biological screenings.
