Regio- and Stereoselective Synthesis of Enol Carboxylate, Phosphate, and Sulfonate Esters via Iodo(III)functionalization of Alkynes

Glyoxylic acid monohydrate promoted reductive addition of sodium sulfinates to pillar[4]arene[1]quinone

An efficient synthesis of sulfonate esters through reductive addition of sodium sulfinates to pillar[4]arene[1]quinone has been established (15 examples). Compared to the arylsulfonylation of p-quinone with sodium arylsulfinates under other acidic conditions, this work affords the hydroquinone-type 4-O-sulfonyl derivatives by using glyoxylic acid monohydrate as a promoter. The protocol features mild reaction conditions and high selectivity and is an alternative protocol for the O-sulfonylation of pillar[4]arene[1]hydroquinone.

Substrate-Controlled Electrochemical Reaction of 2-Alkynylbenzamides, Inorganic Sulfites, and Alcohols

Isoindolones constitute a dominant structural class in synthetic and medicinal chemistry. In this research, an electrochemical reaction involving 2-alkynylbenzamides, inorganic sulfites, and alcohols was first established to provide sulfonyl ester-substituted 3-hydroxyisoindolinone derivatives in moderate to good yields with excellent functional group tolerance. When bulky aryl-substituted 2-alkynylbenzamides are utilized as substrates, sulfonyl ester-substituted 3-alkylideneisoindolinones can be selectively generated with good chemoselectivity. Alkoxysulfonyl radicals derived from the anodic oxidation of inorganic sulfite with alcohols are involved in this transformation.

Silver-Mediated Acetoxyselenylation of Alkynes: Mild Stereoselective Access to Bifunctional Alkenes

Herein, we report a AgF-mediated regio- and stereoselective acetoxyselenylation of terminal/internal alkynes from iodobenzene dicarboxylate [PhI(OCOR)2] and diorganyl diselenides via multiple-site functionalization to afford β-selenyl enol esters in good yields. Alkynes derived from bioactive molecules, such as l(-)-borneol, l-menthol, and acyne oxalate, are also suitable for this transformation and afford the expected compounds.

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

Hypervalent iodine(III) compounds have found wide application in modern organic chemistry as environmentally friendly reagents and catalysts. Hypervalent iodine reagents are commonly used in synthetically important halogenations, oxidations, aminations, heterocyclizations, and various oxidative functionalizations of organic substrates. Iodonium salts are important arylating reagents, while iodonium ylides and imides are excellent carbene and nitrene precursors. Various derivatives of benziodoxoles, such as azidobenziodoxoles, trifluoromethylbenziodoxoles, alkynylbenziodoxoles, and alkenylbenziodoxoles have found wide application as group transfer reagents in the presence of transition metal catalysts, under metal-free conditions, or using photocatalysts under photoirradiation conditions. Development of hypervalent iodine catalytic systems and discovery of highly enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important recent achievement in the field of hypervalent iodine chemistry. Chemical transformations promoted by hypervalent iodine in many cases are unique and cannot be performed by using any other common, non-iodine-based reagent. This review covers literature published mainly in the last 7-8 years, between 2016 and 2024.

Organohypervalent heterocycles

This review summarizes the structural and synthetic aspects of heterocyclic molecules incorporating an atom of a hypervalent main-group element. The term "hypervalent" has been suggested for derivatives of main-group elements with more than eight valence electrons, and the concept of hypervalency is commonly used despite some criticism from theoretical chemists. The significantly higher thermal stability of hypervalent heterocycles compared to their acyclic analogs adds special features to their chemistry, particularly for bromine and iodine. Heterocyclic compounds of elements with double bonds are not categorized as hypervalent molecules owing to the zwitterionic nature of these bonds, resulting in the conventional 8-electron species. This review is focused on hypervalent heterocyclic derivatives of nonmetal main-group elements, such as boron, silicon, nitrogen, carbon, phosphorus, sulfur, selenium, bromine, chlorine, iodine(III) and iodine(V).

Three-component N-alkenylation of azoles with alkynes and iodine(III) electrophile: synthesis of multisubstituted N-vinylazoles

A stereoselective N-alkenylation of azoles with alkynes and iodine(III) electrophile is reported. The reaction between various azoles and internal alkynes is mediated by benziodoxole triflate as the electrophile in a trans-fashion, affording azole-bearing vinylbenziodoxoles in moderate to good yields. The tolerable azole nuclei include pyrazole, indazole, 1,2,3-triazole, benzotriazole, and tetrazole. The iodanyl group in the product can be leveraged as a versatile synthetic handle, allowing for the preparation of hitherto inaccessible types of densely functionalized N-vinylazoles.

Organophosphates as Versatile Substrates in Organic Synthesis

This review summarizes the applications of organophosphates in organic synthesis. After a brief introduction, it discusses cross-coupling reactions, including both transition-metal-catalyzed and transition-metal-free substitution reactions. Subsequently, oxidation and reduction reactions are described. In addition, this review highlights the applications of organophosphates in the synthesis of natural compounds, demonstrating their versatility and importance in modern synthetic chemistry.

Structure-reactivity analysis of novel hypervalent iodine reagents in S-vinylation of thiols

The transition-metal free S-vinylation of thiophenols by vinylbenziodoxolones (VBX) constituted an important step forward in hypervalent iodine-mediated vinylations, highlighting the difference to vinyliodonium salts and that the reaction outcome was influenced by the substitution pattern of the benziodoxolone core. In this study, we report several new classes of hypervalent iodine vinylation reagents; vinylbenziodazolones, vinylbenziodoxolonimine and vinyliodoxathiole dioxides. Their synthesis, structural and electronic properties are described and correlated to the S-vinylation outcome, shedding light on some interesting facets of these reagents.

Stereoselective Approach to Multisubstituted Enolates from Unactivated Alkynes: Oxyalkylidenation of Alkynyl Ketone Enolates with Aldehydes

The preparation of multisubstituted enolates with precise regio- and stereocontrol is a nontrivial task when conventional deprotonation methods are used on the corresponding carbonyl compounds. We describe herein an approach to preparing stereodefined enolates by leveraging the stereoselective oxyfunctionalization of unactivated alkynes, particularly in the context of the alkynylogous aldol reaction. trans-Iodo(III)acetoxylation of alkynes and subsequent Sonogashira coupling allow for the facile preparation of multisubstituted enynyl acetates, which can be deacetylated by MeLi into the corresponding enolates. The alkynyl enolates react with aldehydes to afford γ,δ-unsaturated β-diketones through a cascade of alkynylogous aldol addition, intramolecular Michael addition, and ring opening of the oxetene intermediate.

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

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.