Regiocontrolled Synthesis of α-Sulfonylmethyl o-Nitrostyrenes via ZnI2-Mediated Sulfonylation and AgNO2/Pd(PPh3)4-Promoted o-Nitration

Electrochemical Radical Retro-Allylation of Homoallylic Alcohols with Sulfonyl Hydrazides

We report herein the first examples of electrochemical radical retro-allylation of homoallylic alcohols via the cleavage of the C(sp3)-C(sp3) bond. In this reaction, a variety of sulfonyl hydrazides were employed as the environmentally friendly radical sources via an electrochemical dehydrazination with the release of N2 and H2 as the byproducts, leading to sulfonyl allylic compounds in moderate to good yields. The reaction features metal- and base-free reaction conditions, broad functional group tolerance, and a broad substrate scope.

Nickel-Catalyzed Suzuki-Miyaura Coupling in Water for the Synthesis of 2-Aryl Allyl Phosphonates and Sulfones

An operationally simple and green protocol using a NiSO4·6H2O/cationic 2,2'-bipyridyl ligand system as a water-soluble catalyst for the coupling of arylboronic acids with (2-haloallyl)phosphonates and (2-haloallyl)sulfones in water under air was developed. The reaction was performed at 120 °C with arylboronic acids (2 mmol) and (2-haloallyl)phosphonates or sulfones (1 mmol) in the presence of 5 mol % of the Ni catalytic system in a basic aqueous solution for 1 h, giving the corresponding 2-aryl allyl phosphonates or sulfones in good to excellent yields. This reaction features the use of an abundant transition metal as a catalyst in water and exhibits high functional group tolerance, rendering it an eco-friendly procedure.

KI-Catalyzed Allylic Sulfonation of α-Methylstyrene Derivatives with Sulfonylhydrazides via Electrochemistry

A direct allylic C-H bond activation of α-methylstyrene derivatives with sulfonylhydrazines for the synthesis of allylic sulfones has been developed under exogenous oxidant- and metal-catalyst-free electrochemical conditions. Using the transfer of electrons in the current instead of a stoichiometric chemical oxidant, a series of valuable allylic sulfones were accessed with a wide substrate scope and excellent regioselectivity via radical coupling.

Synthesis and applications of sodium sulfinates (RSO2Na): a powerful building block for the synthesis of organosulfur compounds

This review highlights the preparation of sodium sulfinates (RSO2Na) and their multifaceted synthetic applications. Substantial progress has been made over the last decade in the utilization of sodium sulfinates emerging as sulfonylating, sulfenylating or sulfinylating reagents, depending on reaction conditions. Sodium sulfinates act as versatile building blocks for preparing many valuable organosulfur compounds through S-S, N-S, and C-S bond-forming reactions. Remarkable advancement has been made in synthesizing thiosulfonates, sulfonamides, sulfides, and sulfones, including vinyl sulfones, allyl sulfones, and β-keto sulfones. The significant achievement of developing sulfonyl radical-triggered ring-closing sulfonylation and multicomponent reactions is also thoroughly discussed. Of note, the most promising site-selective C-H sulfonylation, photoredox catalytic transformations and electrochemical synthesis of sodium sulfinates are also demonstrated. Holistically, this review provides a unique and comprehensive overview of sodium sulfinates, which summarizes 355 core references up to March 2020. The chemistry of sodium sulfinate salts is divided into several sections based on the classes of sulfur-containing compounds with some critical mechanistic insights that are also disclosed.

Regio- and Enantioselective Preparation of Chiral Allylic Sulfones Featuring Elusive Quaternary Stereocenters

We describe here the first general asymmetric synthesis of sterically encumbered α,α-disubstituted allylic sulfones via Pd-catalyzed allylic substitution. The design and application of a new and highly efficient phosphoramidite ligand (L10) proved to be crucial, and a wide variety of challenging allylic sulfones featuring quaternary stereocenters could be obtained in good yields and with good to excellent levels of regio- and enantioselectivities under attractive process conditions. The developed methodology employs easily accessible chemical feedstock including racemic allylic precursors and sodium sulfinates. The utility of the method is further demonstrated by the synthesis of the sesquiterpene (-)-Agelasidine A.

Photoinduced synthesis of allylic sulfones using potassium metabisulfite as the source of sulfur dioxide

Synthesis of allylic sulfones through a photoinduced three-component reaction of aryl/alkyl halides, potassium metabisulfite, and allylic bromides under ultraviolet irradiation at room temperature is developed. Diverse allylic sulfones are generated in moderate to good yields.

Copper-catalysed regioselective sulfenylation of indoles with sodium sulfinates

A copper-catalysed sulfenylation of indoles with sodium sulfinates that affords 3-sulfenylindoles in good-to-excellent yields in N,N-dimethyl formamide (DMF) is described. In the process, DMF serves not only as a solvent but also as a reductant. This transformation is easy to carry out and has mild reaction conditions and good functional group tolerance.

Allylic C-S Bond Construction through Metal-Free Direct Nitroalkene Sulfonation

A metal-free, open-flask protocol was developed for the preparation of allylic sulfones through direct condensation of sodium arylsulfinates and β,β-disubstituted nitroalkenes. The key step of this process was the Lewis base-promoted equilibrium between nitroalkenes and allylic nitro compounds. Through this process, the readily available conjugated nitroalkenes can be easily converted into allylic nitro compounds, which contain more reactive C═C bonds toward the sulfonyl radical addition. As a result, allylic sulfones were prepared in excellent yields with a broad substrate scope under mild conditions.

DDQ-mediated regioselective C–S bond formation: efficient access to allylic sulfides

A novel metal-free dehydrocoupling approach for constructing allylic sulfides via oxidative allylic C–H functionalization with high atom- and step-economy has been developed.