Paired Electrocatalysis-Enabled Cross Coupling of Sulfinamides with Olefins toward the Synthesis of Vinyl Sulfoximines

We present here a novel paired electrocatalysis-enabled convenient synthesis of the (E)-vinyl sulfoximines through the cross-coupling reaction of sulfinamides and olefins. This protocol showed a broad substrate scope and excellent E selectivity of products under metal- and oxidant-free conditions. A preliminary mechanistic study suggested that fluorinated sulfoximine generated from anodic oxidation of sulfinamide was the key intermediate that was then converted into the sulfonimidoyl radical at the cathode with the help of DBU in this reaction.

Strategies for oxidative synthesis of N-triflyl sulfoximines

The oxidation of various structurally different N-trifluoromethylthio sulfoximines was investigated using different oxidizing agents and conditions. Mono- and disubstituted phenyl methyl and phenyl cyclopropyl N-trifluoromethylthio sulfoximines were oxidized with NaOCl·5H2O in water, while sterically hindered substrates bearing bulkier alkyl chains or two phenyl rings required the addition of MeCN to the reaction mixture. Chloro-, bromo-, and cyano-substituted substrates, as well as substrates bearing the benzyl groups, required a completely different approach using m-CPBA in DCM. Each method was tested on a gram-scale, with almost no difference in yield or reaction profile. The methods were also tested on N-p-tolylthio sulfoximine where successful oxidation to the corresponding sulfone derivative was observed. Finally, the N-triflyl sulfoximines acquired in the oxidations were examined in terms of stability and reactivity in Suzuki-Miyaura and Sonogashira coupling reactions, as well as many others. The selective mono- and dinitration of 4-methoxyphenyl N-triflyl sulfoximine was demonstrated by using nitric and sulfuric acid. N-triflyl sulfoximines were found to be stable in concentrated aqueous NaOH and HCl solutions and at elevated temperatures.

Ultrasmall CsPbBr3 Nanocrystals as a Recyclable Heterogeneous Photocatalyst in 100% E- and Anti-Markovnikov Sulfinylsulfonation of Terminal Alkynes

The precise synthesis of ultrasmall, monodisperse CsPbBr3 nanocrystals is crucial due to their enhanced photophysical properties resulting from strong quantum confinement effects. Traditional methods struggle with size control, complicating synthesis. Although CsPbBr3 nanocrystals find applications in LEDs and photovoltaics, their use in photocatalysis for organic reactions remains limited. Our study introduces ultrasmall TBIA-CsPbBr3 nanocrystals (∼5.6 nm), synthesized via a three-precursor hot injection method using tribromoisocyanuric acid (TBIA) as a bromine precursor for the first time. These nanocrystals exhibit a near-unity photoluminescence quantum yield (PLQY) of 0.99 and an elevated oxidation potential of +1.80 V. We demonstrate their efficacy as recyclable heterogeneous photocatalysts in a one-pot, 100% E-selective, anti-Markovnikov sulfinylsulfonation of terminal alkynes under visible light, achieving a high product conversion rate (PCR) of 62,500 μmol g-1 h-1 and recyclability for up to five cycles. Density functional theory (DFT) calculations support the exclusive formation of the E-isomer. TBIA-CsPbBr3 outperforms other CsPbBr3 perovskites in photocatalysis, with superior efficiency attributed to their extended excited-state lifetime and higher surface area, which accelerates the organic transformation process.

Turning sulfonyl and sulfonimidoyl fluoride electrophiles into sulfur(VI) radicals for alkene ligation

Sulfonyl and sulfonimidoyl fluorides are versatile substrates in organic synthesis and medicinal chemistry. However, they have been exclusively used as S(VI)+ electrophiles for defluorinative ligations. Converting sulfonyl and sulfonimidoyl fluorides to S(VI) radicals is challenging and underexplored due to the strong bond dissociation energy of SVI-F and high reduction potentials, but once achieved would enable dramatically expanded synthetic utility and downstream applications. In this report, we disclose a general platform to address this issue through cooperative organosuperbase activation and photoredox catalysis. Vinyl sulfones and sulfoximines are obtained with excellent E selectivity under mild conditions by coupling reactions with alkenes. The synthetic utility of this method in the preparation of functional polymers and dyes is also demonstrated.

Syn-Selective Chlorosulfonylation of Alkynes via a Copper-Powder-Initiated Atom Transfer Radical Addition Reaction and Mechanistic Studies

Copper-powder-catalyzed syn-selective chlorosulfonylation of readily available alkynes by an atom transfer radical addition (ATAR) process has been developed, providing straightforward access to a broad range of (Z)-β-chlorovinylsulfones in good yields under mild conditions. In addition, this method is ligand-free and features excellent stereoselectivity and high atom economy. Moreover, the product was obtained without an apparent loss of yield when the reaction was performed on the gram scale at a low catalyst loading. In this reaction, the copper powder not only acts as a sulfone radical initiator but also produces the catalytically active CuCl species. Mechanistic investigations and DFT calculation studies revealed that the stereoselectivity is controlled by the thermodynamic stabilities of the in situ-generated cyclic alkenyl Cu^II complex intermediate, which can serve as a chlorine atom transfer agent.

Electro-mechanochemical approach towards the chloro sulfoximidations of allenes under solvent-free conditions in a ball mill

An electro-mechanochemical protocol for the synthesis of vinylic sulfoximines has been developed. Utilising mechanochemically strained BaTiO₃ nanoparticles, the catalytic active system is generated in situ by the reduction of copper(II) chloride. Various combinations of electron-donating and -withdrawing groups are tolerated, and the approach leads to products with difunctionalised double bonds in good to excellent yields. Attempts to add a sulfoximidoyl chloride to an alkyne proved difficult. Additions of a sulfonyl iodide to allenes and alkynes proceeded smoothly in the presence of silica gel without the need for activation by a piezoelectric material.

Photoactive Copper Complexes: Properties and Applications

Photocatalyzed and photosensitized chemical processes have seen growing interest recently and have become among the most active areas of chemical research, notably due to their applications in fields such as medicine, chemical synthesis, material science or environmental chemistry. Among all homogeneous catalytic systems reported to date, photoactive copper(I) complexes have been shown to be especially attractive, not only as alternative to noble metal complexes, and have been extensively studied and utilized recently. They are at the core of this review article which is divided into two main sections. The first one focuses on an exhaustive and comprehensive overview of the structural, photophysical and electrochemical properties of mononuclear copper(I) complexes, typical examples highlighting the most critical structural parameters and their impact on the properties being presented to enlighten future design of photoactive copper(I) complexes. The second section is devoted to their main areas of application (photoredox catalysis of organic reactions and polymerization, hydrogen production, photoreduction of carbon dioxide and dye-sensitized solar cells), illustrating their progression from early systems to the current state-of-the-art and showcasing how some limitations of photoactive copper(I) complexes can be overcome with their high versatility.

Copper-Catalyzed anti-Selective Radical 1,2-Alkylarylation of Terminal Alkynes

A copper-catalyzed highly anti-selective radical 1,2-alkylarylation of terminal alkynes with aryl boronic acids and alkyl bromides has been established. The reaction exhibits high compatibility with a wide range of terminal alkynes and diverse aryl boronic acids, thus providing facile access to various stereodefined trisubstituted alkenes in high yield under mild reaction conditions. Preliminary mechanistic investigations support the formation of alkyl radicals and their subsequent addition to alkynes in the reaction.

Visible Light-Promoted Synthesis of β-Keto Sulfoximines from N-Tosyl-Protected Sulfoximidoyl Chlorides

Under visible light, N-tosyl-protected sulfoximidoyl chlorides react with aryl alkynes to give β-keto sulfoximines. The reaction is characterized by a high functional group tolerance and good yields. It can be improved by the presence of a ruthenium photocatalyst. Air is the source of the ketonic oxygen in the products.

Recent advances in visible-light mediated functionalization of olefins and alkynes using copper catalysts

Over the past decade, visible-light photoredox catalysis has blossomed as a powerful strategy and offers a discrete activation mode complementary to thermal controlled reactions. Visible-light-mediated photoredox catalysis also offers exciting...

Visible-light-promoted iron catalyzed C‒H functionalization of 1,4-naphthoquinones via oxidative coupling with sulfoximines

A catalytic oxidative addition of sulfoximines to naphthoquinones via its C-H functionalization has been achieved using iron catalytic system, which exhibits good reactivity and high regioselectivity in presence of visible...