Search Results (95)

A metal-free, efficient, iodine(III)-promoted oxidative transformation of allylic sulfones/allylic triflones with water participation for accessing sulfonyl ketones and triflyl allylic alcohols is reported. This strategy enables the selective construction of two SO₂-containing compounds with chemical and biological significance, and its success mainly relies on the substitution effect of the starting materials. Water serves as an eco-friendly oxygen atom source. This transformation has excellent selectivity, broad substrate scope, mild reaction conditions, and ease of scale-up. Full article

In this study, a metal-free approach was developed for the synthesis of isocoumarin frameworks by exploiting the reactivity between ortho-carboxylate-ester-substituted diaryliodonium salts and acetoacetates. This transformation involved the sequential C-arylation of an activated methylene substrate, followed by in situ enolization and intramolecular lactonization to construct an isocoumarin core. Under operationally simple conditions, a range of diaryliodonium salts and acetoacetate esters were employed to afford structurally diverse isocoumarins. The resulting products contained synthetically valuable functional groups, including halogen, nitro, carboxylate ester, and azide substituents, which facilitated further derivatization and extension toward complex architectures and potential applications. Subsequent transformation of the selected isocoumarin products enabled the synthesis of furo[3,4-c]isochromene-1,5-dione motifs, which are observed in several natural products. Full article

The preparation of the novel optically active sulfoxides (-)-(S)-1,1,1,3,3,3-hexafluoro-2-[o-(p-tolylsulfinyl)phenyl]propan-2-ol 1, (-)-(S)-1,1,1,3,3,3-hexafluoro-2-[o-(methylsulfinyl)phenyl]propan-2-ol 2 and (-)-(S)-1,1,1,3,3,3-hexafluoro-2-[o-(t-butyl-sulfinyl)phenyl]propan-2-ol 3 according to the Andersen methodology and their spectroscopic characterization is presented. The NMR and CD spectroscopic evidence of the existence of the equilibrium between sulfoxide and hypervalent sulfurane forms of these compounds in solution and attempts at the isolation of corresponding sulfuranes are shown. For compound 3, the unprecedented subsequent irreversible transformation in solution into corresponding cyclic sulfinate ester–sultine 17 was established on the basis of NMR spectroscopy measurements. The mechanism of this transformation was investigated by means of GC-MS analysis and confirmed on the basis of synthesized long alkyl chain analog 23 transformation in solution. Moreover, the oxidation properties of obtained sulfoxides 2 and 3 for the selected compounds are described. Full article

Classical chemical bonding is typically categorized into primary, strong interactions, such as covalent, ionic, and metallic bonds, and secondary, weak interactions, such as van der Waals forces, the hydrogen bond, and their likes (halogen bond, chalcogen bond, etc.). However, other not-so-known bonding mechanisms also play a crucial role in chemical systems. Particularly important are the charge-shift bond (CSB) and the multicenter bonds, i.e., the electron-rich multicenter bond (ERMB), also known as hypervalent or three-center-four-electron (3c-4e) bond, and the electron-deficient multicenter bond (EDMB), also known as the three-center-two-electron (3c-2e) bond in molecules and, more recently, as the two-center-one-electron (2c-1e) bond in extended solids. We consider that these latter interactions have not yet received the proper attention of the scientific community, even though multicenter interactions were proposed in the early days of Quantum Mechanics. In this work, we aim at providing: (i) a concise historical overview of the two types of multicenter bonds; (ii) a short introduction to the recently proposed unified theory of multicenter bonding (UTMB), which elucidates the origin and mechanisms of formation of both ERMBs and EDMBs; and (iii) an extension of the UTMB to include CSBs, due to the strong relationship between ERMBs and CSBs. We hope that the integrated perspective of chemical bonding, the heartland of chemistry, offered by the UTMB (beyond traditional and historical assumptions) will help researchers to understand materials properties and will provide a framework allowing the development of advanced materials for enhanced technological applications. Full article

The direct chlorination, bromination and azidation of beta keto esters, 2-acetyl-1-tetralone and methyl 1-oxo-2,3-dihydro-1H-indene-2-carboxylate is achieved utilizing anion-coordinated hypervalent iodine benziodazoles derived from hypervalent iodine macrocycles. This reaction, which introduces the halogen, azido or cyano group at the alpha carbon atom of beta keto esters, is accomplished in chloroform at 60 °C and results in the formation of a chiral center. Depending on the structure of the benziodazole reagent, the reaction can have mild enantioselectivity. The reaction between 2-acetyl-1-tetralone and phenylalanine-derived hypervalent iodine benziodazoles results in the chlorinated product with 26% enantiomeric excess. Full article

Piancatelli–Margarita oxidation is a reaction where primary and secondary alcohols are converted to aldehydes and ketones, respectively. It utilizes TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl), a stable aminoxy radical, as the catalyst and BAIB (bis(acetoxy)iodobenzene), a hypervalent iodine compound, as the stoichiometric oxidant. The reaction proceeds at room temperature, without the need for strong acids, bases, or anhydrous conditions. Mild reaction conditions allow for the chemoselective oxidation of complex and sensitive substrates and the selective oxidation of primary alcohols in the presence of secondary alcohols. The reaction conditions can be controlled to favor the oxidation of primary alcohols to aldehydes or promote the overoxidation of aldehydes to carboxylic acids. This review highlights some recent applications (2020–2025), especially in total synthesis, with special emphasis on large-scale reactions. This review aims to honor the memory of Prof. Piancatelli (1936–2025) and Dr. Roberto Margarita (1970–2016), who developed this reaction. Full article

Diaryliodonium salts are an important part of hypervalent iodine chemistry, owing to their highly electrophilic character, non-toxicity, and air and moisture stability, have been identified as an important arylating agent. It has been widely applied in the synthesis of natural products, drugs, and bioactive molecules bearing active α-arylation carbonyl units. Within the domain of α-arylation of carbonyl compounds using diaryliodonium salts, there is a notable absence in the literature of a comprehensive compilation dedicated to exclusive arylation processes involving these compounds. In this review, we focus on the overview of the recent advancements in utilizing diaryliodonium salts for α-arylation reactions, encompassing both racemic and asymmetric approaches to various carbonyl compounds including ketones, esters, enolates, and amides. Furthermore, we discuss the unique advantages and inherent limitations of diaryliodonium salts as arylating agents, as well as the underexplored application potentials that warrant further investigation in this rapidly evolving field. Full article

Fluorinated organic molecules have become indispensable in modern chemistry, owing to the unique properties imparted by fluorine to other compounds, including enhanced metabolic stability, controlled lipophilicity, and improved bioavailability. The site-selective incorporation of fluorine atoms into organic frameworks is essential in pharmaceutical, agrochemical, and material science research. In recent years, catalytic fluorination has become an important methodology for the efficient and selective incorporation of fluorine atoms into complex molecular architectures. This review highlights advances in catalytic fluorination reactions over the past six years and describes the contributions of transition metal catalysts, photocatalysts, organocatalysts, and electrochemical systems that have enabled site-selective fluorination under a variety of conditions. Particular attention is given to the use of well-defined fluorinating agents, including Selectfluor, N-fluorobenzenesulfonimide (NFSI), AlkylFluor, Synfluor, and hypervalent iodine reagents. These reagents have been combined with diverse catalytic systems, such as AgNO₃, Rh(II), Mo-based complexes, Co(II)-salen, and various organocatalysts, including β,β-diaryl serine catalysts, isothiourea catalysts, and chiral phase-transfer catalysts. This review summarizes proposed mechanisms reported in the original studies and discusses examples of electrophilic, nucleophilic, radical, photoredox, and electrochemical fluorination pathways. Recent developments in stereoselective and more sustainable protocols are also examined. By consolidating these strategies, this article provides an up-to-date perspective on catalytic fluorination and its impact on synthetic organic chemistry. Full article

This study employs ab initio metadynamics to simulate the carbonization of Si(001) surfaces with chemical vapor deposition at a temperature of 1423 K. We reveal the complete reaction mechanism, including the beginning of silicon carbide crystal formation. The existence of surficial native oxide is incorporated into the theoretical model. The mechanism determination includes clarification of all intermediate products and transition states. The free-energy surface of the reaction chain has been found. Carbonization initiates with alkylated surface products and continues with consecutive dehydrogenation steps. Carbon is integrated in the volume, near the crystal surface, only if no covalent interactions with hydrogen atoms remain. The native oxide was not found to prohibit the process of carbonization. The oxygen atoms have certain surface mobility at high temperatures. It was revealed that hypervalency of carbon atoms is possible in transition state structures. The theoretical activation free energy of the rate-determining step was found to be only 166 kJ/mol. This work sheds light on the advantage of the practical use of Si(001) substrates for the synthesis of silicon carbide and Si-O-C glasses using direct carbonization via chemical vapor deposition. We also aim to enable more methodical designs of future synthetic routes and better-informed decisions for experimental investigations. Full article

Benzimidazolinones exhibit unique biological activities and serve as building blocks in synthesizing pharmaceutical compounds. Although multiple synthetic approaches involving intermolecular cyclization reactions have been reported, intramolecular cyclization reactions are scarce, and more rational synthetic methods are required. Hypervalent iodine-catalyzed oxidative C–N coupling is a potentially effective approach for synthesizing benzimidazolinones under metal-free conditions. In this study, we present a method utilizing hypervalent iodine catalysis for the oxidative cyclization of N’-aryl urea compounds, resulting in the first metal-free synthesis of various benzimidazolinones. Full article

Spirocalcaridines A and B are among the most challenging members of the marine invertebrate-derived Leucetta alkaloids. Approaches to the construction and elaboration of the highly compact spirocyclic core are described. The synthesis of tricyclic guanidine via tandem oxidative amination dearomatizing spirocyclization (TOADS) using hypervalent iodine set the stage for total synthesis via the migration of the C4/C8 double bond to the C4/C5 position, followed by oxidation. The undesired but not surprising propensity of the spirocyclic cyclohexadienone to undergo rearrangement to the phenol hindered the desired olefin migration. Furthermore, initial efforts to install the oxidation sequentially, first at C5 and then at C4 in the complete carbon skeleton, were fraught with unforeseen challenges and unusual outcomes. In addition, the scope and limitations of hypervalent iodine-mediated tandem oxidative dearomatizing spirocyclization on various substrates were explored. Urethanes and thiourethanes underwent spirocyclization with an excellent yield, whereas the reaction with allylic substrates and species lacking the p-methoxy substituent did not proceed. Attempts to prepare other guanidine precursors are briefly discussed. Full article

A rapid microwave-assisted process minimizing waste was set up to produce bio-based benzoxazine-like monomers produced from vanillylamine and melamine. Without excessive purification, different viscous liquid precursors had a remarkable ability to form four strong and transparent different solid cross-linked thermosets, displaying lower curing temperatures under 130 °C. The long and strong adhesive performance of the cured materials was observed using glass slides or aluminum surfaces and they could become a good alternative to adhesive epoxy resin for metal surfaces. At the higher temperatures, these solids could act as efficient flame-retardants proven by thermogravimetric measurements. The best candidates gave a limiting oxidation index value of 41.9. In order to improve the intrinsic surface hydrophobicity of the phenolic resins, slight amounts of silica and iron oxide nanoparticles were dispersed in the polymer matrix, and finally mechanical resistance was pointed out. The most promising of our melamine-based resin was loaded with aluminum pigment to furnish a silver-colored paste ready for being cured to afford a robust solid, which does not undergo contraction or deformation. Full article

The Group 16 elements of the periodic table have a characteristic valence shell configuration instrumental to their chemical properties and reactivities. The electrostatic potentials of these so-called chalcogens have been exploited in the design of materials that require the efficient passage of electrons including supermagnets, photocatalytic dyes, and solar panels. Likewise, the incorporation of the heavy chalcogen selenium into organic frameworks has been shown to increase the reactivities of double bonds and heterocyclic rings, while its interactions with aromatic side chains in the hydrophobic core of proteins via selenomethionine impart a stabilizing effect. Typically present in the active site, the hypervalence of selenocysteine enables it to further stabilize the folded protein and mediate electron transfer. Selenium’s native occurrence in bacterial tRNA maintains base pair fidelity, most notably during oxidative stress, through its electronic and steric effects. Such native modifications at the positions 2 and 5 of uridine render these sites relevant in the design of RNA-based therapeutics. Innocuous selenium substitution for oxygen in the former and the standard methods of selenium-derivatized oligonucleotide synthesis and detection have led to the establishment of a novel class of therapeutics. In this review, we summarize some progress in this area. Full article

The 2-(4-hydroxyphenoxy)benzamide scaffold is frequently found in a variety of bioactive compounds, displaying a broad spectrum of properties, such as antibacterial and antitumor effects. In this study, we developed a new method for synthesizing 2-(4-hydroxyphenoxy)benzamide derivatives from 2-aryloxybenzamide via a PhIO-mediated oxidation reaction. The optimal reaction conditions were established as follows: TFA was used as the solvent, PhIO served as the oxidant with a substrate-to-oxidant ratio of 1:2, and the reaction was conducted at room temperature. This method, characterized by mild reaction conditions, broad applicability, and a metal-free nature, considerably improves the accessibility of 2-(4-hydroxyphenoxy)benzamide derivatives, which have been challenging to prepare using previously reported methods. Full article

The hypervalent iodine-mediated formation of steroidal 5/5-spiroiminals and 5/5-spiroaminals from steroidal amines is presented. Under the influence of excess PhI(OAc)₂ and iodine in acetonitrile at 0 °C, steroidal amines smoothly underwent cyclization to give a mixture of 5/5-spiroiminals and 5/5-spiroaminals. This reaction represents the first example of a C-H-activation-mediated formation of a spiroiminal. Presumably, the formation of 5/5-spiroiminals occurs through aminyl radical-mediated cyclization followed by amine-to-imine oxidation. Full article