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1. Recyclable Hypervalent Iodine Reagents in Modern Organic Synthesis

   https://doi.org/10.1055/s-0041-1737909  

   Rimi, Rimi; Soni, Sakshi; Uttam, Bhawna; China, Hideyasu; Dohi, Toshifumi; Zhdankin, Viktor V; Kumar, Ravi (March 2022, Synthesis)

   Abstract Hypervalent iodine (HVI) reagents have gained much attention as versatile oxidants because of their low toxicity, mild reactivity, easy handling, and availability. Despite their unique reactivity and other advantageous properties, stoichiometric HVI reagents are associated with the disadvantage of generating non-recyclable iodoarenes as waste/co-products. To overcome these drawbacks, the syntheses and utilization of various recyclable hypervalent iodine reagents have been established in recent years. This review summarizes the development of various recyclable non-polymeric, polymer-supported, ionic-liquid-supported, and metal–organic framework (MOF)-hybridized HVI reagents. 1 Introduction 2 Polymer-Supported Hypervalent Iodine Reagents 2.1 Polymer-Supported Hypervalent Iodine(III) Reagents 2.2 Polymer-Supported Hypervalent Iodine(V) Reagents 3 Non-Polymeric Recyclable Hypervalent Iodine Reagents 3.1 Non-Polymeric Recyclable Hypervalent Iodine(III) Reagents 3.2 Recyclable Non-Polymeric Hypervalent Iodine(V) Reagents 3.3 Fluorous Hypervalent Iodine Reagents 4 Ionic-Liquid/Ion-Supported Hypervalent Iodine Reagents 5 Metal–Organic Framework (MOF)-Hybridized Hypervalent Iodine Reagents 6 Conclusion 

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2. Recent Progress in Synthetic Applications of Cyclic Hypervalent Iodine(III) Reagents

   https://doi.org/10.1002/adsc.202300275  

   Yoshimura, Akira; Saito, Akio; Zhdankin, Viktor_V (May 2023, Advanced Synthesis & Catalysis)

   Abstract Hypervalent iodine compounds have found broad application in modern organic chemistry as reagents and catalysts. Cyclic hypervalent iodine reagents based on the benziodoxole heterocyclic system have higher stability compared to their acyclic analogues, which makes possible the preparation and safe handling of the reagents with special ligands such as azido, cyano, and trifluoromethyl groups. Numerous iodine‐substituted benziodoxole derivatives have been prepared and utilized as reagents for transfer of the substituent on hypervalent iodine to organic substrate. Reactions of these reagents with organic substrates can be performed under metal‐free conditions, in the presence of transition metal catalysts, or using photocatalysts under photoirradiation conditions. In this review, we focus on the most recent synthetic applications of cyclic hypervalent iodine(III) reagents with the following ligands: N₃, NHR, CN, CF₃, SCF₃, OR, OAc, ONO₂, and C(=N₂)CO₂R. The review covers literature published mainly in the last 5 years. 

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3. Sustainable Methods in Hypervalent Iodine Chemistry

   Frey, B.; Maity, A.; Tan, H.; Roychowdhury, P.; Powers, D. C. (January 2022, Organic synthesis)

   Muniz, K.; Ishihara, K. (Ed.)

   Hypervalent iodine compounds are a widely used class of metal-free oxidants that find application in organic synthesis. Due to the homology between the reactivity of hypervalent iodine and many transition metals ¾ oxidative addition, ligand exchange, and reductive elimination can be facile for both ¾ hypervalent iodine species find application in a variety of synthetically important organic transformations. Major limitations of these reagents include the frequent need for (super)stoichiometric loading and the intrinsically poor atom economy that results from the generation of stoichiometric quantities of iodoarene byproducts. In addition, hypervalent iodine reagents are often synthesized using metal-based terminal oxidants, which compound the resulting waste stream. Recently, substantial progress has been made to address these limitations. Here, we discuss progress towards sustainable synthetic methods for the preparation of hypervalent iodine compounds and application of those methods in the context of hypervalent iodine catalysis. The discussion is organized according to the active oxygen content, and thus atom economy, of the terminal oxidant employed. Hypervalent iodine electrochemistry and the development of recyclable iodoarenes are also discussed. 

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4. Cyclic Diaryl λ ³ ‐Bromanes as a Precursor for Regiodivergent Alkynylation Reactions

   https://doi.org/10.1002/anie.202319960  

   De_Abreu, Maxime; Rogge, Torben; Lanzi, Matteo; Saiegh, Tomas_J; Houk, Kendall_N; Wencel‐Delord, Joanna (March 2024, Angewandte Chemie International Edition)

   Abstract Regiodivergent reactions are a fascinating tool to rapidly access molecular diversity while using identical coupling partners. We have developed a new approach for regiodivergent synthesis using the dual character of hypervalent bromines. In addition to the recently reported reactivity of hypervalent bromines as aryne precursors, the first transition metal‐catalyzed reaction is reported. Accordingly, the development of these two complementary transformations allows for the alteration of regioselectivity to furnish bothortho‐ andmeta‐substituted alkynylation products. Mechanistic and computational studies show how these selectivities are controlled. 

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5. Aryl-, Akynyl-, and Alkenylbenziodoxoles: Synthesis and Synthetic Applications

   https://doi.org/10.3390/molecules28052136  

   Mironova, Irina A.; Noskov, Dmitrii M.; Yoshimura, Akira; Yusubov, Mekhman S.; Zhdankin, Viktor V. (March 2023, Molecules)

   Hypervalent iodine reagents are in high current demand due to their exceptional reactivity in oxidative transformations, as well as in diverse umpolung functionalization reactions. Cyclic hypervalent iodine compounds, known under the general name of benziodoxoles, possess improved thermal stability and synthetic versatility in comparison with their acyclic analogs. Aryl-, alkenyl-, and alkynylbenziodoxoles have recently received wide synthetic applications as efficient reagents for direct arylation, alkenylation, and alkynylation under mild reaction conditions, including transition metal-free conditions as well as photoredox and transition metal catalysis. Using these reagents, a plethora of valuable, hard-to-reach, and structurally diverse complex products can be synthesized by convenient procedures. The review covers the main aspects of the chemistry of benziodoxole-based aryl-, alkynyl-, and alkenyl- transfer reagents, including preparation and synthetic applications. 

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