N -Iodosuccinimide as Bifunctional Reagent in (E )-Selective C(sp2 )−H Sulfonylation of Styrenes

Photoinduced Single Electron Transfer via EDA Complexation Enables Decarbonylative C(sp2)-S Bond Formation

We have developed a photoinduced transition-metal-free decarbonylative strategy at ambient temperature through non-covalent interactions to achieve vinyl sulfones. Traditionally, decarbonylative functionalization is accomplished using transition metal catalysts at elevated temperatures. The π-π interaction facilitates the elimination of CO to generate vinyl radical, thereby promoting the creation of C-S bonds with the sulfonyl radical. These interactions and the overall process were illuminated by spectroscopic investigations and mechanistic studies.

Divergent Reaction of Alkynes and TsCN: Synthesis of β-Sulfinyl Alkenylsulfones and (E)-Vinyl Sulfones

An efficient and high-selectivity approach for the divergent synthesis of β-sulfinyl alkenylsulfones and (E)-vinyl sulfones from alkynes and TsCN is described. A series of disulfurized products were constructed under mild conditions in the absence of transition metals. This transformation featured excellent regio- and stereoselectivity, good functional group compatibility, and broad substrate scope. The copper(I)-catalyzed sulfonation of alkynes with TsCN that affords (E)-vinyl sulfones in good to excellent yields was also developed.

Unraveling the photophysical characteristics and biological applications of vinyl sulfones as viscosity sensors

For the first time, a series of vinyl sulfone-NH2-based push-pull fluorophores (4a-4d) were introduced for their potential use in biological applications. The fluorophores 4a-4d were readily synthesized upon reduction of the corresponding vinyl sulfones-NO2 (3a-3d), which were prepared by sulfonylation of nitrostyrene. Both types of probes can be prepared in high yields through a few steps with minimal cost. In diverse solvents, probes 4a-4d exhibited fluorescence with strong emission peaking around 403-490 nm. Additionally, the fluorescence intensity of probe 4d rose approximately 85-fold with increasing viscosity. The probes 4a-4d demonstrated good stability and photostability in a broad pH range. Moreover, probes 4a-4d showed significantly improved biocompatibility compared to those derived from 3a-3d. For cell imaging applications, the developed probes 4a-4d exhibited much stronger blue fluorescence in cancer cells (HepG2) compared to 3a-3d. In addition, probes 4a-4d exhibited low cytotoxicity within 24 h toward both cancer and normal cells (HEK-293). Interestingly, probe 4d showed great sensitivity to viscosity in cancer cells. As a result, readily prepared vinyl sulfone-NH2-based push-pull fluorophores (4a-4d) offer a promising strategy for further development as cancer cell staining agents.

Copper-catalyzed C-3 benzylation of quinoxalin-2(1H)-ones with benzylsulfonyl hydrazides

An unprecedented use of benzylsulfonyl hydrazides as benzylating agents has been demonstrated in the direct C-3 benzylation of quinoxalin-2(1H)-ones. A range of benzylsulfonyl hydrazides participated in the C-3 benzylation of quinoxalin-2(1H)-ones with CuCN as the catalyst and DTBP as the oxidant, delivering structurally diverse 3-benzylquinoxalin-2(1H)-ones in moderate to good yields.

3-Arylsulfonylquinolines from N-Propargylamines via Cascaded Oxidative Sulfonylation Using DABSO

We report a cascaded oxidative sulfonylation of N-propargylamine via a three-component coupling reaction using DABCO·(SO₂)₂ (DABSO). 3-Arylsulfonylquinolines were obtained by mixing diazonium tetrafluoroborate, N-propargylamine, and DABSO under argon atmosphere in dichloroethane (DCE) for 1 h. In a radical pathway, DABSO was utilized as the sulfone source and an oxidant in this radical-mediated cascaded reaction.

Recent Progress and Emerging Technologies towards a Sustainable Synthesis of Sulfones

Sulfones play a pivotal role in modern organic chemistry. They are highly versatile building blocks and find various applications as drugs, agrochemicals, or functional materials. Therefore, sustainable access to this class of molecules is of great interest. Herein, the goal was to provide a summary on recent developments in the field of sustainable sulfone synthesis. Advances and existing limitations in traditional approaches towards sulfones were reviewed on selected examples. Furthermore, novel emerging technologies for a more sustainable sulfone synthesis and future directions were discussed.

Mechanochemical-Cascaded C-N Cross-Coupling and Halogenation Using N-Bromo- and N-Chlorosuccinimide as Bifunctional Reagents

Exploration of alternative energy sources for chemical transformations has gained significant interest from chemists, and mechanochemistry is one of those sources. Herein, we report the use of N-bromosuccinimides (NBS) and N-chlorosuccinimides (NCS) as bifunctional reagents for a cascaded C-N bond formation and subsequent halogenation reactions. Under the solvent-free mechanochemical (ball-milling) conditions, the synthesis of a wide range of phenanthridinone derivatives from N-methoxy-[1,1'-biphenyl]-2-carboxamides is accomplished. During the reactions, NBS and NCS first assisted the oxidative C-N coupling reaction and subsequently promoted a halogenation reaction. Thus, the role of NBS and NCS was established to be bifunctional. Overall, a mild, solvent-free, convenient, one-pot, and direct synthesis of various bromo- and chloro-substituted phenanthridinone derivatives was achieved.

Disulfide metathesis via sulfur⋯iodine interaction and photoswitchability

The idea of constitutional dynamic chemistry (CDC) and dynamic combinatorial chemistry (DCC) is widespread in the literature using the chemistry of disulfides. The synthesis of unsymmetrical diaryl disulfides is challenging due to the presence of a weak S-S bond. We report herein the synthesis of unsymmetrical diaryl disulfides from two symmetrical disulfides via a cross-metathesis reaction which was controlled by a weak sulfur⋯iodine (S⋯I) interaction. The unsymmetrical disulfides were stable in acetonitrile solution in the presence of N-iodosuccinimide (NIS), and found to be reversibly photoswitchable to the symmetrical disulfides under visible light irradiation.

Unconventional approaches for the introduction of sulfur-based functional groups

Organosulfur compounds have a pivotal role in the functionalities of many natural products, pharmaceuticals and organic materials. For these reasons, the search for new methodologies for the formation of carbon-sulfur bonds has been the object of intensive work for organic chemists. However, the proposed strategies suffer from various drawbacks, such as volatility, toxicity, and instability of the sulfur sources or the use of VOC solvents. In this review, we summarise the recent protocols which have the goal of obtaining sulfones, thioethers, thiazines, thiazepines and sulfonamides in an unconventional and/or sustainable way. The use of starting materials less invasive and toxic with respect to the traditional reagents, alternative solvents such as water, ionic liquids or deep eutectic solvents, the exploitation of ultrasound and electrochemistry, increasing the efficiency of the process, are reported. Moreover, representative reaction mechanisms are also discussed.

An iodine-mediated new avenue to sulfonylation employing N-hydroxy aryl sulfonamide as a sulfonylating agent

A novel and highly efficient I2/K2CO3 mediated regioselective sulfonylation of thiophenols, aryl acetylenic acid and aromatic alkynes with N-hydroxy sulfonamide has been developed. N-hydroxy sulfonamide has been used for the first time for the synthesis of these sulfones. The scope and versatility of the reaction has been demonstrated by the regio- and stereoselective synthesis of different analogs of sulfones with various structural features.

I2/DMSO-Catalyzed Transformation of N-tosylhydrazones to 1,2,3-thiadiazoles

An iodine/DMSO catalyzed selective cyclization of N-tosylhydrazones with sulfur without adding external oxidant was developed for the synthesis of 4-aryl-1,2,3-thiadiazoles. In this reaction, oxidation of HI by using DMSO as dual oxidant and solvent is the key, which allowed the regeneration of I₂, ensuring thus the success of the synthesis. This protocol features by simple operation, high step-economy (one-pot fashion), broad substrate scope as well as scale-up ability.

Silver-promoted synthesis of vinyl sulfones from vinyl bromides and sulfonyl hydrazides in water

The synthesis of vinyl sulfones via silver-promoted cross-coupling of vinyl bromides with sulfonyl hydrazides was realized. Water was used as the sole solvent. Multisubstituted vinyl sulfones were easily prepared with excellent alkyl group tolerance. A mechanism involving nucleophilic attack of a sulfinate anion was proposed.

Metal-free C–S coupling of thiols and disulfides

A literature overview on C–S coupling reactions using thiols or disulfides as sulfur surrogates under metal-free conditions is presented. Reagents for the transformations include polyvalent iodines, peroxides, tert-butyl nitrite (TBN), DDQ, and aerial oxygen, among others.

Electrochemical sulfonylation of alkenes with sulfonyl hydrazides: a metal- and oxidant-free protocol for the synthesis of (E)-vinyl sulfones in water

An electrochemical sulfonylation of alkenes with sulfonyl hydrazides for the synthesis of (E)-vinyl sulfones in water is reported.