Search

Benzolactams have unique biological activity and high utility in the synthesis of valuable compounds with direct applicability to oxindole alkaloids and antibacterial agents. Despite recent advances in organic chemistry and the growing number of reported methods for synthesizing benzolactams, their preparation still requires a multistep process. C-H amination reactions can convert aromatic C(sp

Functionalized nucleobases are utilized in a wide range of fields; therefore, the development of new synthesis methods is essential for their continued application. With respect to the C6-arylation of halopurines, which possess a substituent at the N7-position, only a small number of successful cases have been reported, which is predominately a result of large steric hinderance effects. Herein, we report efficient and metal-free C6-arylations and SNAr reactions of N7-substituted chloropurines in aromatic and heteroatom nucleophiles promoted by triflimide (Tf2NH) in fluoroalcohol.

We have found that the combination of Oxone® with an organoiodine compound, i.e., 2-iodobenzoic acid (2-IB), selectively yields p-quinones from monomethoxyarenes under mild conditions. In this reaction system, an organoiodine compound is immediately oxidized by Oxone® to generate cyclic hypervalent iodine (III) species in situ, which serves as the specific mediator for the selective p-quinone synthesis, preventing o-quinone formation.

Oxidative coupling strategies that can directly convert the C–H group for chemical transformations are, in theory, ideal synthetic methods to reduce the number of synthetic steps and byproduct generation. Hypervalent iodine reagents have now become one of the most promising tools in developing oxidative couplings due to their unique reactivities that are replacing metal oxidants. As part of our continuous development of oxidative coupling reactions, we describe in this report highly efficient μ-oxo hypervalent iodine catalysts for the direct oxidative coupling of N-methoxyamides and related compounds with aromatic hydrocarbons. The excellent TONs, up to over 100 times, with a best catalyst loading of 0.5 mol% were determined for the oxidative C–H/N–H coupling method, which can provide the most straightforward route to obtaining these unique arylamide compounds.

Functionalized nucleobases are utilized in a wide range of fields; therefore, the development of new synthesis methods is essential for their continued application. With respect to the C

We report a convenient and practical method for the preparation of nonexplosive cyclic hypervalent iodine(III) oxidants as efficient organocatalysts and reagents for various reactions using Oxone® in aqueous solution under mild conditions at room temperature. The thus obtained 2-iodosobenzoic acids (IBAs) could be used as precursors of other cyclic organoiodine(III) derivatives by the solvolytic derivatization of the hydroxy group under mild conditions of 80 °C or lower temperature. These sequential procedures are highly reliable to selectively afford cyclic hypervalent iodine compounds in excellent yields without contamination by hazardous pentavalent iodine(III) compound.

Nucleophilic aromatic substitution (SNAr) reactions can provide metal-free access to synthesize monosubstituted aromatic compounds. We developed efficient SNAr conditions for p-selective substitution of polyfluoroarenes with phenothiazine in the presence of a mild base to afford the corresponding 10-phenylphenothiazine (PTH) derivatives. The resulting polyfluoroarene-bearing PTH derivatives were subjected to a second SNAr reaction to generate highly functionalized PTH derivatives with potential applicability as photocatalysts for the reduction of carbon–halogen bonds.

In organic synthesis, due to their high electrophilicity and leaving group properties, halogens play pivotal roles in the activation and structural derivations of organic compounds. Recently, cyclizations induced by halogen groups that allow the production of diverse targets and the structural reorganization of organic molecules have attracted significant attention from synthetic chemists. Electrophilic halogen atoms activate unsaturated and saturated hydrocarbon moieties by generating halonium intermediates, followed by the attack of carbon-containing, nitrogen-containing, oxygen-containing, and sulfur-containing nucleophiles to give highly functionalized carbocycles and heterocycles. New transformations of halogenated organic molecules that can control the formation and stereoselectivity of the products, according to the difference in the size and number of halogen atoms, have recently been discovered. These unique cyclizations may possibly be used as efficient synthetic strategies with future advances. In this review, innovative reactions controlled by halogen groups are discussed as a new concept in the field of organic synthesis.

An oxidation system comprising phenyliodine(III) diacetate (PIDA) and iodosobenzene with inorganic bromide, i.e., sodium bromide, in an organic solvent led to the direct introduction of carboxylic acids into benzylic C–H bonds under mild conditions. The unique radical species, generated by the homolytic cleavage of the labile I(III)–Br bond of the in situ-formed bromo-λ3-iodane, initiated benzylic carboxylation with a high degree of selectivity for the secondary benzylic position.

A new type of binaphthyl-based chiral iodide functionalized at positions 8 and 8' of the naphthalene rings has been found as a promising structural motif for the asymmetric hypervalent iodine(III) oxidations, specifically, for the dearomatizing spirocyclization of naphthol carboxylic acids showing expectedly better enantioselectivities versus other atropisomeric biaryls, i.e., a conventionally used binaphthalene having the diiodides in the minor groove.

The C2-symmetric tetralin-fused 1,4-diiodo-1,3-butadiene derivatives, (Z,Z)-2,3-di(1-iodoalkylidene)tetralin 1a-c, are atropisomeric and can be resolved into the two persistent axially chiral enantiomers by HPLC on a chiral stationary phase. The enantiomerically pure compounds can serve as chiral organocatalysts for dearomatizing spirolactonization to show good performances in up to 73 % ee.

This Special Issue covers the hot topics on recent synthetic interest in halogen and related chemistry as well as the unique characteristics of halogen compounds. The excellent reviews by the experts and eminent researchers engaged in the recent advances, i.e., preparations, reactions, and mechanistic studies of unique organohalogen compounds, halogen bond interaction as the catalysis, and halogen-controlled unique reactions for synthesizing useful organic molecules, such as pharmaceutical compounds and organic materials, are provided in this Special Issue.

Iodonium(III) salts bearing uracil moieties have recently appeared in the literature, but their structural scope and utilization are limited because of their hygroscopic characteristics. In this study, we describe our detailed investigations for synthesizing a series of uracil iodonium(III) salts derived with various structural motifs and counterions. These new compounds have been utilized as attractive synthetic modules in constructing functionalized nucleobase and nucleosides.

The data in this article are related to research article ‘‘Efficient N-arylation of azole compounds utilizing selective aryl-transfer TMP-iodonium (III) reagents (Koseki et al., 2019). For the title compound, phenyl(2,4,6-trimethoxyphenyl)iodonium(III) acetate (Ph(TMP)IOAc), the single-crystal X-ray diffraction measurement together with NMR analysis, like also the method of synthesis and crystallization are presented. The X-ray structure analysis has revealed that the two types of geometries regarding the acetate anion attached to phenyl (TMP)iodonium (III) cation are found in the crystal states. Keywords: Hypervalent iodine compound, Iodonium(III) salt, Acetate ligand, Two geometrical states

Thioglycosides are available donors in glycosylation due to the stability of the anomeric C-S bond under general reaction conditions of protection and deprotection, and offer orthogonality in their activation. We report now that the hypervalent iodine effectively induced glycosylation reaction of thioglycosides with various alcohols. This method features a high efficiency, completion in a short time, and proceeding under very mild conditions.

The facile and clean oxidative coupling reaction of pyrroles with azoles has been achieved using the recyclable hypervalent iodine(III) reagents having adamantane structures. These iodine(III) reagents could be recovered from the reaction mixtures by a simple solid-liquid separation, i.e., filtration, for reuse.

Various aryl-substituted purine derivatives were synthesized through the direct arylation of halopurines with aromatic compounds, facilitated by the combination of triflic acid and fluoroalcohol. This metal-free method is complementary to conventional coupling reactions using metal catalysts and reagents for the syntheses of aryl-substituted purine analogues.

We have developed the iodoarene-catalyzed nucleophilic fluorination of β-dicarbonyl compounds and intramolecular aminofluorination of ω-amino-alkenes using the same reaction conditions. The key for this reaction is the in situ generation of a hypervalent iodine compound ArIF2 by hydrogen fluoride, mCPBA and a catalytic amount of iodoarene. Preliminary trials of catalytic asymmetric nucleophilic fluorination were conducted.

Thioglycosides are available donors in glycosylation due to the stability of the anomeric C-S bond under general reaction conditions of protection and deprotection, and offer orthogonality in their activation. We report now that the hypervalent iodine effectively induced glycosylation reaction of thioglycosides with various alcohols. This method features a high efficiency, completion in a short time, and proceeding under very mild conditions.

By utilizing a specific solvent and highly active 2-azaadamantane-N-oxyl (AZADO) as an organocatalyst, we have improved the recycling protocol of the adamatane reagent 1 to be faster and more operationally simple for the hypervalent iodine/nitroxyl radical mediated alcohol oxidation. This very mild system can efficiently mediate the oxidation of a range of alcohols to carbonyl compounds with a broad substrate scope, and after the reactions, the reduced adamantane tetraiodide 1', which automatically precipitated from the reaction mixtures as the reactions progresses, could be directly recovered by filtration.

Hypervalent iodine reagents, such as phenyliodine diacetate (PIDA) and phenyliodine bis(trifluoroacetate) (PIFA), are promising alternatives to metal-based oxidants for developing environmentally benign oxidation reactions, due to their low toxicities, mild reactivities, ready availability, high stabilities, and easy handling. During the study on the hypervalent iodine chemistry, we first determined in the 1990’s the single-electron-transfer (SET) oxidation ability of the hypervalent iodine(III) reagent toward electron-rich aromatic rings, such as the phenyl ether compounds, affording the corresponding aromatic cation radicals. This discovery led us to develop a series of metal-free carbon-hydrogen (C-H) bond functionalizations of aromatic compounds using the hypervalent iodine oxidants. We have extended the strategy to the carbon-carbon bond formation of biaryls based on the double aromatic C-H bond couplings, which can now provide a novel technology to the synthetic area of metal-free cross couplings for producing mixed biaryls from two molecules of unfunctionalized aromatic compounds. These achievements found by us during the development of hypervalent iodine-induced metal-free C-H cross couplings are now summarized in detail.

Oxidation is synthetically important as functional group transformation as well as bond-forming method. Hypervalent iodine reagents such as phenyliodine (III) diacetate (PIDA) and phenyliodine (III) bis (trifluoroacetate) (PIFA) are one of the promising reagents for development of environmentally benign oxidations, due to their mild reactivity, low toxicity, safety, ready availability, and easy handling. Our recent challenge to this chemistry is to enhance the synthetic value of the reagents as useful alternative to highly toxic heavy metal oxidants and even rare transition metals, by pioneering a new method for enabling their efficient utilization and development of unique and new reactivities. During this course, we have succeeded in the development of new recyclable reagent 1 and its catalytic utilization, and design of a new chiral reagent 2 and its application to asymmetric oxidations. The summary of these important achievements in hypervalent iodine (III) chemistry is described herein.

The facile and clean oxidative biaryl coupling reaction of thiophenes and pyrroles has been achieved using the recyclable hypervalent iodine(III) reagents having adamantane or methane structures. These iodine(III) reagents could be recovered from the reaction mixtures by a simple solid-liquid separation, i.e., filtration.

We have found that unreactive and insoluble polymeric iodosobenzene [PhIO] n induced aqueous benzylic C-H oxidation to effectively give arylketones, in the presence of KBr and montmorillonite-K10 (M-K10) clay. Water-soluble and reactive species 1 having the unique I(III)-Br bond, in situ generated from [PhIO]n and KBr, was considered to be the key radical initiator during the reactions.

We have developed a new and reliable method for the direct construction of biologically important aryl lactones and phthalides from carboxylic and benzoic acids, using a combination of hypervalent iodine(III) reagents with KBr.

The facile and clean oxidative coupling reaction of pyrroles with azoles has been achieved using the recyclable hypervalent iodine(III) reagents having adamantane structures. These iodine(III) reagents could be recovered from the reaction mixtures by a simple solid-liquid separation, i.e., filtration, for reuse.

We have synthesized a novel, nonpolymer-supported recyclable hypervalent iodine (III) reagent, 1,3,5,7-tetrakis[4-(diacetoxyiodo)phenyl]adamantane 3a and its derivatives 3b, c and utilized them in environmentally benign oxidations. The new reagents 3a-c mediate a wide range of oxidative transformations with efficiencies similar to those of conventional reagents, phenyliodine (III) diacetate (PIDA), pheyliodine (III) bis (trifluoroacetate) (PIFA), and (hydroxyl(tosyloxy)iodo). benzene (HTIB), and have higher reactivity compared with polymer-supported recyclable reagents such as poly(diacetoxyiodo)styrene (PDAIS) and poly{bis(trifluoroacetoxy)iodo}styrene (PBTIS). In all cases, tetraiodide 4 was recovered nearly quantitatively in a pure form after simple workup, i.e., filtration. Reoxidation of 4 to 3a with m-chloroperbenzoic acid also proceeded quantitatively, without loss of oxidative activity. Recyclable 3a-c are used in various organic solvents as well as water, and thus mild and clean oxidation of alcohols in water has been achieved using 3a. A facile synthesis of aldehydes from primary alcohols has also been demonstrated using a dual recycling strategy, with 3a and recyclable 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO).