有机合成中的高价碘应用

高价碘化物作为一种性能温和、选择性强及环境友好的氧化试剂在有机合成中得到了广泛的应用。近年来,各种不同结构的高价碘试剂和各种新的反应及应用大量涌现出来,使它们的应用领域从传统的醇类氧化扩展到一些结构复杂化合物的合成领域当中。本文以最常用和研究较多的几个高价碘化合物为例,对它们用于有机合成反应,如氧化、加成、取代和重排的最新进展进行了概述,对本研究小组重点研究的五价碘化合物邻羟基苯碘酰与酮类化合物的取代反应和烯烃化合物的加成反应也作了介绍。     

Synthetic application of water-soluble hypervalent iodine reagents in aqueous media

Along with the vigorous development of hypervalent iodine chemistry, water-soluble hypervalent iodine reagents have received considerable attentions in recent years. In order to obtain water-soluble hypervalent iodine reagents, two strategies have been employed including introduction of hydrophilic functional groups onto the phenyl ring and formation of complex of iodosylbenzene with crown ether. And, it is observed that four kinds of hypervalent iodine reagents exhibit more or less solubility in water including hypervalent iodine reagents containing hydrophilic ligands, diaryliodonium salts, oligomeric iodosylbenzene sulfate, and iodylbenzene and its derivatives. In this review, we summarize these water-soluble hypervalent iodine reagents and their broad synthetic applications in aqueous media.     

有机高价碘化学简介及其应用

近几十年来,有机高价碘化学蓬勃发展,有机高价碘试剂也受到化学合成工作者的广泛关注,关于有机高价碘试剂的反应性研究也获得了迅猛发展。有机高价碘试剂作为绿色、高效、多功能化的氧化剂,通常容易制备且操作简单,与已有的合成方法相比,该类试剂参与的反应表现出了许多独特的优点,并且具有与汞、铬、铅、铊等重金属试剂类似的反应性,但却没有这些试剂所带来的毒性和环境污染问题。本文介绍了有机高价碘化学的起源与发展,高价碘试剂的结构特点与分类,高价碘试剂在有机合成、材料化学及工业合成中的应用。     

Chiral Hypervalent Iodine Reagents: Synthesis and Reactivity

Chiral hypervalent iodine chemistry has been steadily increasing in importance in recent years. This review catalogues enantioselective transformations triggered by chiral hypervalent iodine(III/V) reagents, in stoichiometric or catalytic quantities, highlighting the different reactivities in terms of yield and enantioselectivity. Moreover, the synthesis of the most remarkable and successful catalysts has been illustrated in detail.     

Reactions between Diazo Compounds and Hypervalent Iodine(III) Reagents

Site‐selective “cut and sew” transformations employing diazo compounds and hypervalent iodine(III) compounds involve the departure of leaving groups, a “cut” process, followed by a reorganization of the fragments by bond formation, a “sew” process. Bearing controllable cleavage sites, diazo compounds and hypervalent iodine(III) compounds play a critical role as versatile reagents in a wide range of organic transformations because their excellent nucleofugality allows for a large number of unusual reactions to occur. In recent years, the combination of diazo compounds and hypervalent iodine(III) reagents has emerged as a promising tool for developing new and valuable approaches, and has met considerable success. In this Minireview, this combination is systematically illustrated with recent advances in the field, with the aim of elaborating the synthetic utility and potential of this concept as a powerful strategy in organic synthesis.     

Organoiodine(V) reagents in organic synthesis

Organohypervalent iodine reagents have attracted significant recent interest as versatile and environmentally benign oxidants with numerous applications in organic synthesis. This Perspective summarizes synthetic applications of hypervalent iodine(V) reagents: 2-iodoxybenzoic acid (IBX), Dess-Martin periodinane (DMP), pseudocyclic iodylarenes, and their recyclable polymer-supported analogues. Recent advances in the development of new catalytic systems based on the generation of hypervalent iodine species in situ are also overviewed.     

Palladium-Catalyzed Organic Reactions Involving Hypervalent Iodine Reagents

The chemistry of polyvalent iodine compounds has piqued the interest of researchers due to their role as important and flexible reagents in synthetic organic chemistry, resulting in a broad variety of useful organic molecules. These chemicals have potential uses in various functionalization procedures due to their non-toxic and environmentally friendly properties. As they are also strong electrophiles and potent oxidizing agents, the use of hypervalent iodine reagents in palladium-catalyzed transformations has received a lot of attention in recent years. Extensive research has been conducted on the subject of C—H bond functionalization by Pd catalysis with hypervalent iodine reagents as oxidants. Furthermore, the iodine(III) reagent is now often used as an arylating agent in Pd-catalyzed C—H arylation or Heck-type cross-coupling processes. In this article, the recent advances in palladium-catalyzed oxidative cross-coupling reactions employing hypervalent iodine reagents are reviewed in detail.     

Synthesis,characterization, and initial reaction study of two new bicyclic hypervalent iodine(III) reagents

The synthesis of two new bicyclic hypervalent iodine(III) reagents 5 and 6 is described along with their corresponding X-ray crystal structures for the first time. A detailed comparison in the bond lengths and bond angles of reported bicyclic hypervalent iodine(III) reagents is also presented. Furthermore, an initial study shows that these two hypervalent iodine(III) reagents could promote the dipeptide coupling reaction.     

Alternative Strategies with Iodine: Fast Access to Previously Inaccessible Iodine(III) Compounds

Non‐iodinated arenes can be easily and selectively converted into (diacetoxyiodo)arenes in a single step under mild conditions by using iodine triacetates as reagents. The oxidative step is decoupled from the synthesis of hypervalent iodine(III) reagents, which can now be prepared conveniently in a one‐pot synthesis for subsequent reactions without prior purification. The chemistry of iodine triacetates was also expanded to heteroatom ligand exchanges to form novel inorganic hypervalent iodine compounds.     

原位生成的高价碘试剂在有机合成中的应用进展

原位生成的高价碘试剂具有原子经济性、性能温和和绿色环保等优点,在诸多合成和不对称催化等反应中表现活跃.详细介绍了原位生成高价碘的概念以及反应机理,根据不同的反应类型分别对原位生成的三价碘、五价碘以及手性高价碘试剂在有机合成反应中的应用进行了归纳总结,分析了原位生成的高价碘试剂目前面临的问题,并对今后的发展趋势作了展望.     

Iodine(III) mediators in electrochemical batch and flow reactions

The anodic oxidation of aryl iodides is a powerful method for synthesis of hypervalent iodine compounds, which have matured to frequently used reagents in organic synthesis. The electrochemical route eliminates the use of expensive or hazardous oxidants for their synthesis. Hypervalent iodine reagents generated at the anode are successfully used as either in-cell or ex-cell mediators for many valuable chemical transformations including fluorinations and oxidative cyclisations. The recent advances in the area of flow electrochemistry are providing additional benefits and allow new synthetic applications. Mechanistic insights and novel technologies enable the development of new concepts for sustainable chemistry.     

Structure and Reactivity of N-Heterocyclic Alkynyl Hypervalent Iodine Reagents

Ethynylbenziodoxol(on)e (EBX) cyclic hypervalent iodine reagents have become popular reagents for the alkynylation of radicals and nucleophiles, but only offer limited possibilities for further structure and reactivity fine-tuning. Herein, the synthesis of new N-heterocyclic hypervalent iodine reagents with increased structural flexibility based on amide, amidine and sulfoximine scaffolds is reported. Solid-state structures of the reagents are reported and the analysis of the I−C_alkyne bond lengths allowed assessing the trans-effect of the different substituents. Molecular electrostatic potential (MEP) maps of the reagents, derived from DFT computations, revealed less pronounced σ-hole regions for sulfonamide-based compounds. Most reagents reacted well in the alkynylation of β-ketoesters. The alkynylation of thiols afforded more variable yields, with compounds with a stronger σ-hole reacting better. In metal-mediated transformations, the N-heterocyclic hypervalent iodine reagents gave inferior results when compared to the O-based EBX reagents.     

Hypervalent Iodine‐Catalyzed Oxidative Functionalizations Including Stereoselective Reactions

Hypervalent iodine chemistry is now a well‐established area of organic chemistry. Novel hypervalent iodine reagents have been introduced in many different transformations owing to their mild reaction conditions and environmentally friendly nature. Recently, these reagents have received particular attention because of their applications in catalysis. Numerous hypervalent iodine‐catalyzed oxidative functionalizations such as oxidations of various alcohols and phenols, α‐functionalizations of carbonyl compounds, cyclizations, and rearrangements have been developed successfully. In these catalytic reactions stoichiometric oxidants such as mCPBA or oxone play a crucial role to generate the iodine(III) or iodine(V) species in situ. In this Focus Review, recent developments of hypervalent iodine‐catalyzed reactions are described including some asymmetric variants. Catalytic reactions using recyclable hypervalent iodine catalysts are also covered.     

Strategies to Control Hypervalent Iodine – Primary Amine Reactions

The field of hypervalent iodine chemistry has been prevalent since 1886. Its journey from obscurity to coming into the limelight has witnessed many effective transformations which have benefited the synthetic community at large. The reactivity of primary amines with hypervalent iodine reagents causes difficulty in synthetic outcome or not feasible due to high exothermicity of amine iodine which is an acid base reaction. This minireview highlights the worthwhile reactivity of hypervalent iodine reagents with aromatic and aliphatic primary amines. Some recent literature has been discussed to make a clear understanding on how such high reactivity of primary amine is controlled by introducing modulation in either substrate or reaction conditions, most of which are carried out under ambient reaction conditions.     

Continuous‐Flow Electrochemical Generator of Hypervalent Iodine Reagents: Synthetic Applications

An efficient and reliable electrochemical generator of hypervalent iodine reagents has been developed. In the anodic oxidation of iodoarenes to hypervalent iodine reagents under flow conditions, the use of electricity replaces hazardous and costly chemical oxidants. Unstable hypervalent iodine reagents can be prepared easily and coupled with different substrates to achieve oxidative transformations in high yields. The unstable, electrochemically generated reagents can also easily be transformed into classic bench‐stable hypervalent iodine reagents through ligand exchange. The combination of electrochemical and flow‐chemistry advantages largely improves the ecological footprint of the overall process compared to conventional approaches.     

Hypervalent‐Iodine(III)‐Mediated Oxidative Methodology for the Synthesis of Fused Triazoles

The organic chemistry of hypervalent organoiodine compounds has been an area of unprecedented development. This surge in interest in the use of hypervalent iodine compounds has mainly been owing to their highly selective oxidizing properties, environmentally benign character and commercial availability. Hypervalent iodine reagents have also been used as an alternative to toxic heavy metals, owing to their low toxicity and ease of handling. Hypervalent organoiodine(III) reagents are versatile oxidants that have been successfully employed to extend the scope of selective oxidative transformations of complex organic molecules in synthetic chemistry. This Focus Review concerns the tandem in situ generation and 1,5‐electrocyclization of N‐heteroaryl nitrilimines into fused triazoles. We describe the importance of recently developed hypervalent‐organoiodine(III)‐catalyzed oxidative cyclization reactions, building towards the conclusion that hypervalent iodine chemistry is a promising frontier for oxidative cyclization, in particular of hydrazones, for the synthesis of fused triazoles.     

Synthesis of Diverse Aryliodine(Ⅲ) Reagents by Anodic Oxidation

An anodic oxidation enabled synthesis of hypervalent iodine(Ⅲ) reagents from aryl iodides is demonstrated.Under mild electrochemical conditions,a range of aryli...     

Solvent-free reactions with hypervalent iodine reagents

[reaction: see text] We describe solvent-free reactions for the synthesis of hypervalent iodine reagents and their use in solid-state reactions. Improved yields and higher purities of the products are observed.     

Diastereoselective Radical Hydroacylation of Alkylidenemalonates with Aliphatic Aldehydes Initiated by Photolysis of Hypervalent Iodine(III) Reagents

Diastereoselective radical hydroacylation of chiral alkylidenemalonates with aliphatic aldehydes is realized by the combination of a hypervalent iodine(III) reagent and UV‐light irradiation. The reaction is initiated by the photolysis of hypervalent iodine(III) reagents under mild, metal‐free conditions, and is the first example of diastereoselective addition of acyl radicals to olefins to afford chiral ketones in a highly stereoselective fashion. The obtained optically active ketones are useful chiral synthons, as exemplified by the short formal synthesis of (?)‐methyleneolactocin.     

Highly stereoselective metal-free oxyaminations using chiral hypervalent iodine reagents

The ring and I: Hypervalent iodine compounds avoid the issues of toxicity or complicated ligands of many transition-metal-based systems. A highly enantioselective oxyamination of alkenes with N-sulfonyl ureas employing chiral, lactic acid-based hypervalent iodine reagents gives a facile synthesis of enantiomerically pure 2-arylproline derivatives for the first time.