Search Results (67)

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 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

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

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

Unsymmetrical urea derivatives are essential structural motifs in a wide array of biologically significant compounds. Despite the well-established methods for synthesizing symmetrical ureas, efficient strategies for the synthesis of unsymmetrical urea derivatives remain limited. In this study, we present a novel approach for the synthesis of unsymmetrical urea derivatives through the coupling of amides and amines. Utilizing hypervalent iodine reagent PhI(OAc)₂ as a coupling mediator, this method circumvents the need for metal catalysts, high temperatures, and inert atmosphere. The reaction proceeds under mild conditions and demonstrates broad substrate scope, including various primary and secondary amines and primary benzamides. This protocol not only offers a practical and versatile route for synthesizing unsymmetrical ureas but also shows significant potential for the late-stage functionalization of complex molecules in drug development. Full article

Magnetic nanoparticles (MNPs) based on magnetite (Fe₃O₄) are attractive catalyst supports due to their high surface area, easy preparation, and facile separation, but they lack stability in acidic reaction media. The search for MNPs stable in oxidative acidic reaction media is a necessity if one wants to combine the advantages of MNPs as catalyst supports with those of iodine(III) reagents being environmentally benign oxidizers. In this work, immobilized iodophenyl organocatalysts on magnetite support (IMNPs) were obtained by crossed-linking polymerization of 4-iodostyrene with 1,4-divinylbenzene in the presence of MNPs. The obtained IMNPs were characterized by TGA, IR, SEM, STEM, and HAADF to gain information on catalyst morphology, average particle size (80–100 nm), and their core–shell structure. IMNP-catalysts tested in (i) the α-tosyloxylation of propiophenone 1 with meta-chloroperbenzoic acid (m-CPBA) and (ii) in the oxidation of 9,10-dimethoxyanthracene 3 with Oxone^® as the side-oxidant showed a similar performance as reactions using stoichiometric amounts of iodophenyl. The developed IMNPs withstand strong acidic conditions and serve as reusable organocatalysts. They are recyclable up to four times for repeated organocatalytic oxidations with rates of recovery of 80–92%. This is the first example of a—(4-iodophenyl)polystyrene shell—magnetite core-structured organocatalyst withstanding strong acidic reaction conditions. Full article

An electron donor–acceptor complex was utilized to generate alkoxy radicals from alcohols under mild conditions using visible light. This approach was combined with a hydroxybromination process to achieve the deconstructive functionalization of alkenes, leading to the production of geminal dibromides. Mechanistic investigations indicated the intermediacy of hypervalent iodine (III) compounds. Full article

Studies have shown that the incorporation of fluorine into materials can improve their properties, but C–F bonds are not readily formed in nature. Although some researchers have studied the reaction of fluorinating alkenes catalyzed by hypervalent iodine, far too little attention has been paid to its reaction mechanism. This study aimed to explore the mechanism of the hypervalent iodine-catalyzed 1,4-difluorination of dienes. We found that the catalyst is favorable for the activation of C1=C2 double bonds through halogen bonds, and then two HFs interact with one F atom in the catalyst via hydrogen bonds, resulting in the cleavage of I–F bonds and the formation of [F–H∙∙∙F]⁻. Subsequently, the catalyst interacts with C1, and the roaming [F–H···F]⁻ attacks C4 from the opposite side of the catalyst. After the fluorination step is completed, the nucleophile F⁻ substitutes the catalyst via the S_N2 mechanism. Our calculations demonstrated that the interaction between HF and F⁻ is favorable for the stabilization of the transition state within the fluorination process for which the presence of two HFs in the reaction is the best. We also observed that [F–H∙∙∙F]⁻ attacking C4 from the opposite side of the catalyst is more advantageous than attacking from the same side. This study therefore offers a novel perspective on the mechanism of the hypervalent iodine-catalyzed fluoridation of dienes. Full article

Dibenzoxazepinones exhibit unique biological activities and serve as building blocks for synthesizing pharmaceutical compounds. Despite remarkable advancements in organic chemistry and recent developments in synthetic approaches to dibenzoxazepinone motifs, there is a strong demand for more streamlined synthesis methods. The application of the catalytic C–H amination strategy, which enables the direct transformation of inert aromatic C–H bonds into C–N bonds, offers a rapid route to access dibenzoxazepinone frameworks. Hypervalent-iodine-catalyzed oxidative C–H amination has the potential to become an effective approach for synthesizing dibenzoxazepinones. In this study, we present our method of employing μ-oxo hypervalent iodine catalysis for intramolecular oxidative C–H amination of O-aryl salicylamides, facilitating the synthesis of target dibenzoxazepinone derivatives bearing various functional groups in a highly efficient manner. Full article

The functionalization of unactivated substrates through the combination of copper catalysts and hypervalent iodine reagents represents a versatile tool in organic synthesis to access various classes of compounds. The hypervalent iodine derivatives can be used simply as oxidizing agents to regenerate the catalytic species or they can associate the functionalization of the starting material. In this review, special attention will be paid to methodologies which provide the introduction of nucleophiles into the reagent by use of suitable benziodoxol(on)es or iodonium salts. Many reactions concern C- and N-arylations, but may also involve formation of different carbon–carbon and carbon–nitrogen bonds, carbon–oxygen as well as carbon–halogen and carbon–phosphorus bonds. Full article