Oxysulfonylation of Alkenes with Sulfonyl Hydrazides under Transition-Metal-Free Conditions

Transition-Metal-Free Radical-Triggered Hydrosulfonylation and Disulfonylation Reaction of Substituted Maleimides with Sulfonyl Hydrazides

A convenient and practical hydrosulfonylation and disulfonylation of substituted maleimides was realized using sulfonyl hydrazides as the sulfur reagent and tert-butyl hydroperoxide as the oxidant. The advantages of the reactions include mild and transition-metal-free reaction conditions, good functional group tolerance, and readily available starting materials. The radical species-induced pathway is also demonstrated by mechanistic studies.

Recent advances in the synthesis and applications of β-keto sulfones: new prospects for the synthesis of β-keto thiosulfones

This review mainly focuses on recent developments in the preparation of β-keto sulfones and their extensive synthetic applications. New prospects for the synthesis of β-keto thiosulfones have also been highlighted. Over the last decade, there has been exponential growth in the direct construction of β-keto sulfones using a wide variety of keto and sulfonyl precursors. Of note, the most promising photoredox transformations and electrochemical synthesis methods of β-keto sulfones are also presented. Moreover, β-keto sulfones are versatile building blocks in organic synthesis due to their three essential functional groups: sulfonyl, carbonyl, and active methylene moieties. The convenient preparation of β-keto sulfones allows the synthesis of many valuable carbocyclic and heterocyclic compounds, and the effortless removal of the sulfonyl moiety via transformations is supported. The chemistry of β-keto sulfones (2013 to present) can be divided into several sections based on the sulfonyl surrogates, and ubiquitous synthetic strategies were systematically outlined.

Sulfated tungstate/dioxygen: a new catalytic system for oxysulfonylation of styrenes to form β-keto sulfones

A new green cat./O₂ oxidation system is mild, safe, heterogeneous, simple to make, stable, noncorrosive, produces N₂ as by product, and has an easy to recover–reuse catalyst and wide substrate scope.

Visible-light promoted aerobic difunctionalization of alkenes with sulfonyl hydrazides for the synthesis of β-keto/hydroxyl sulfones

A practical method has been developed for the conversion of alkenes to β-keto/hydroxyl sulfones by their reaction with sulfonyl hydrazides under metal-free conditions. This reaction proceeds through the oxidative addition of alkenes by sulfonyl radicals that are generated by visible-light induced oxidation of sulfonyl hydrazides. Notaly the reaction uses O2 as the terminal oxidant, instead of metal catalysts or oxidants like TBHP, leading to H2O and N2 as the clean by-products. The key features of this reaction include readily available reagents, mild reaction conditions and broad substrate scope.

Visible-Light-Mediated Synthesis of Ketones by the Oxidative Alkylation of Styrenes

The oxidative coupling of photogenerated alkyl radicals with readily available styrenes is disclosed. This visible-light-mediated method allows rapid access to a wide range of α-alkyl-acetophenones in good yields and with high functional group tolerance. In addition, the developed protocol features room temperature conditions, low photocatalyst loadings, and the use of dimethyl sulfoxide as nontoxic and mild terminal oxidant.

MnO2 -Promoted Oxidative Radical Sulfonylation of Haloalkynes with Sulfonyl Hydrazides: C(sp)-S Bond Formation towards Alkynyl Sulfones

A catalyst-free oxidative radical sulfonylation of haloalkynes with sulfonyl hydrazides is reported. It represents an example of C(sp)-S bond formation using sulfonyl hydrazides as sulfonyl radical sources. Various alkynyl sulfones were synthesized in moderate to good yields. Having MnO₂ as the oxidant is very critical for this transformation. Remarkably, the self-coupling reaction of haloalkynes through C(sp)-C(sp) bond formation is significantly inhibited under the standard reaction conditions.