CO/O2 assisted oxidative carbon-carbon and carbon-heteroatom bond cleavage for the synthesis of oxosulfonates from DMSO and olefins

KF-catalyzed direct thiomethylation of carboxylic acids with DMSO to access methyl thioesters

With dimethyl sulfoxide (DMSO) as the methylthio source, a KF-catalyzed strategy was employed for the direct thiomethylation of carboxylic acids with DMSO for the preparation of methyl thioesters. In this process, a wide range of methyl thioesters were obtained in moderate to excellent yields. This novel strategy features the first use of DMSO as a methylthiolating agent for the construction of methyl thioesters, transition metal-free conditions, inexpensive reagents, easy workup, broad substrate scope and sustainability. Additionally, this procedure can be readily scaled up to a gram scale.

Water-Promoted Carbon-Carbon Bond Cleavage Employing a Reusable Fe Single-Atom Catalyst

The development of methods for selective cleavage reactions of thermodynamically stable C-C/C=C bonds in a green manner is a challenging research field which is largely unexplored. Herein, we present a heterogeneous Fe-N-C catalyst with highly dispersed iron centers that allows for the oxidative C-C/C=C bond cleavage of amines, secondary alcohols, ketones, and olefins in the presence of air (O2 ) and water (H2 O). Mechanistic studies reveal the presence of water to be essential for the performance of the Fe-N-C system, boosting the product yield from <1 % to >90 %. Combined spectroscopic characterizations and control experiments suggest the singlet 1 O2 and hydroxide species generated from O2 and H2 O, respectively, take selectively part in the C-C bond cleavage. The broad applicability (>40 examples) even for complex drugs as well as high activity, selectivity, and durability under comparably mild conditions highlight this unique catalytic system.

Selectfluor-Promoted Reactions of Aryl Methyl Ketones with Dimethyl Sulfoxide to Give 2,5-Diacylthiophenes and β-Acyl Allylic Methylsulfones

In this paper, a convenient synthesis of 2,5-diacylthiophenes and β-acyl allylic methylsulfones from aryl methyl ketones with dimethyl sulfoxide (DMSO) through Selectfluor-promoted cascade cyclization and cross-coupling reactions by simple solvent modification is described. This method enables the formation of new C-C and C-S bonds via the selection of different solvent ratios, in which DMSO molecules as synthons can be selectively introduced into methyl ketones. The features of this transformation include readily available starting materials, excellent chemoselectivity, and good functional group tolerance.

Synthesis of 2,4,5-Trisubstituted Oxazoles from Copper-Mediated Benzylic sp3 C-H Aerobic Oxidative Annulation of Ketones and Amines via a Cascade Reaction

The functionalization of sp³ carbons is deemed challenging in synthetic organic chemistry yet has tremendous potential in producing potent organic compounds. A facile synthesis of 2,4,5-trisubstituted oxazoles through an oxidative, copper-catalyzed, and solvent-free annulation is described. Various arylated oxazoles were efficaciously synthesized at a mild temperature from readily available substrates under a molecular oxygen atmosphere. Preliminary mechanistic studies suggested that the reaction proceeds via an anionic-type mechanism and indicated the formation of a keto-imine intermediate. The reaction is notable for the abstraction of six hydrogen atoms, the functionalization of one sp² carbon and two sp³ carbons, and the formation of C-O and C-N bonds.

Lewis Acid-Promoted Typical Friedel-Crafts Reactions Using DMSO as a Carbon Source

This study reports a mild and efficient synthetic protocol for the synthesis of symmetrical and unsymmetrical diarylmethanes (DAMs). Using DMSO as the C₁ source and TMSOTf as the Lewis acid promoter, a series of functionalized symmetrical and unsymmetrical DAMs were synthesized in high yields. Gratifyingly, DMSO plays a dual role as a solvent and a C₁ source and can also be replaced with its deuterated counterpart, DMSO-d₆, enabling the incorporation of the -CD₂ moiety into the diarylmethane skeleton. The developed approach has been applied to a wide range of substrates having various functional groups, and this protocol has also been extended to the synthesis of an anti-breast cancer agent and an anticoagulant agent using common feedstock compounds. In addition, the postulated mechanism has been explicitly demonstrated via control experiments.

Regioselective Synthetic Approach to Higher Alkenes from Lower Alkenes with Sulfoxides in the Fe3+/H2O2 System via Direct Alkylation or Arylation of the Csp2-H Bond on the C═C Bond of Alkenes

The regioselective synthetic approach to higher alkenes from lower alkenes by using sulfoxides as alkyl or aryl reagents in the Fe³⁺/H₂O₂ system has been developed. This reaction realized direct alkylation or arylation of alkenes. In this reaction, sulfoxides afforded one Csp³ or Csp² atom to the C═C bond of alkenes; one new Csp²-Csp³ bond or Csp²-Csp² bond was formed. Nearly 40 products including di-, tri-, and tetra-substituted products were regioselectively synthesized. Both aliphatic and aromatic alkenes could participate in this reaction. Moreover, not only dimethyl sulfoxide but also three other sulfoxides can be applied to this reaction, including diethyl, dibenzyl, and diphenyl sulfoxide. The mechanism studies showed that this reaction may experience a coupling process via radical addition-elimination and the Fe³⁺/H₂O₂ system made the sulfoxides offered one alkyl or aryl radical to the C═C bond of alkenes.

Dioxygen-Triggered Oxosulfonylation/Sulfonylation of Terminal Olefins toward β-Keto Sulfones/Sulfones

A dioxygen-triggered oxosulfonylation/sulfonylation of unactivated olefins to achieve β-keto sulfones/sulfones has been developed. Interestingly, pluralistic mechanisms were found when different types of compounds were applied as substrates, and different products were achieved. The reaction is carried out with a high atomic efficiency in the absence of a metal and a catalyst at room temperature under an air atmosphere. Importantly, as a proof-of-concept, a bioactive molecule was synthesized on a gram-scale level using this method.

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.

Catalytic AgF-Initiated Intramolecular 1,3-Sulfonyl Migration of gem-Difluorovinyl Sulfonates to α,α-Difluoro-β-ketosulfones

A 1,3-sulfonyl migration of difluorovinyl sulfonates initiated by a catalytic amount of silver fluoride is presented. α,α-Difluoro-β-ketosulfones were successfully prepared in excellent yields. This method features high chemoselectivity, good functional group tolerance, high atom economy, and mild, environmentally benign reaction conditions. Furthermore, mechanistic experiments indicate that this migration proceeds in an intermolecular pathway and the corresponding sulfinates are possible intermediates.

Transition-metal mediated carbon-sulfur bond activation and transformations: an update

Carbon-sulfur bond cross-coupling has become more and more attractive as an alternative protocol to establish carbon-carbon and carbon-heteroatom bonds. Diverse transformations through transition-metal-catalyzed C-S bond activation and cleavage have recently been developed. This review summarizes the advances in transition-metal-catalyzed cross-coupling via carbon-sulfur bond activation and cleavage since late 2012 as an update of the critical review on the same topic published in early 2013 (Chem. Soc. Rev., 2013, 42, 599-621), which is presented by the categories of organosulfur compounds, that is, thioesters, thioethers including heteroaryl, aryl, vinyl, alkyl, and alkynyl sulfides, ketene dithioacetals, sulfoxides including DMSO, sulfones, sulfonyl chlorides, sulfinates, thiocyanates, sulfonium salts, sulfonyl hydrazides, sulfonates, thiophene-based compounds, and C[double bond, length as m-dash]S functionality-bearing compounds such as thioureas, thioamides, and carbon disulfide, as well as the mechanistic insights. An overview of C-S bond cleavage reactions with stoichiometric transition-metal reagents is briefly given. Theoretical studies on the reactivity of carbon-sulfur bonds by DFT calculations are also discussed.

Methanesulfinylation of Benzyl Halides with Dimethyl Sulfoxide

A phenyltrimethylammonium tribromide-mediated nucleophilic substitution/oxygen transformation reaction of benzyl halides with DMSO has been developed. In this transition-metal-free reaction, DMSO acts as not only a solvent but also a "S(O)Me" source, thus providing a convenient method for the efficient and direct synthesis of various benzyl methyl sulfoxides.

Acid-Controlled Access to β-Sulfenyl Ketones and α,β-Disulfonyl Ketones by Pummerer Reaction of β-Keto Sulfones and Sulfoxides

A convenient acid-mediated reaction of β-keto sulfones with sulfoxides under metal-free conditions has been developed, thereby delivering the acid-controlled synthesis of β-sulfenyl ketones and α,β-disulfonyl ketones in good to excellent yields. The mechanism of the transformations has been studied carefully, which suggested the involvement of a radical process in the formation of α,β-disulfonyl ketones.

NBS-activated cross-dehydrogenative esterification of carboxylic acids with DMSO

A convenient and versatile cross-dehydrogenative esterification of carboxylic acids with DMSO for preparing (methylsulfinyl)methyl esters has been developed in the presence of N-bromosuccinimide.

I2-DMSO-H2O: A Metal-Free Combination System for the Oxidative Addition of Alkynes to Access (E)-α-Iodo-β-methylsulfonylalkenes

A simple and green reaction was discovered for iodization-methylsulfoxidation of alkynes to access (E)-α-iodo-β-methylsulfonylalkenes. This is the first report for the synthesis of iodovinyl methylsulfones by employing alkynes to react with molecular iodine (I₂), dimethyl sulfoxide (DMSO), and H₂O. Additionally, this protocol represents a new avenue for utilizing DMSO as the source of the -SO₂Me group and H₂O as the "O" source for the construction of the -SO₂Me group from DMSO, which is a valuable finding.

Dioxygen-triggered oxidative cleavage of the C-S bond towards C-N bond formation

Research on the cleavage of C-C bonds has been well developed. By comparison with this, the activation of C-S bonds remains challenging. Herein, dioxygen-triggered oxidative cleavage of C-S bonds has been achieved, delivering a series of N-containing heterocyclic compounds that are frequently found in pesticides and pharmaceuticals. Additionally, the potential utility of this protocol was further demonstrated by a gram-scale experiment. Mechanistically, dioxygen plays a key role in the cleavage of C-S bonds towards C-N bond formation.

Transition metal-free α-Csp3-H oxidative sulfuration of benzyl thiosulfates with anilines to form N-aryl thioamides

A metal-free approach to N-aryl thioamides from Bunte salts and anilines in DMSO has been developed. This method tolerated a wide range of functional groups on the aromatic ring, providing an ideal way to N-aryl thioamides in good to excellent yields from cheap and easily available starting materials. A plausible mechanism was also proposed based on the X-ray single crystal diffraction, NMR and MS analyses of DMSO-concerning intermediates.

ATRA-like alkylation–peroxidation of alkenes with trichloromethyl derivatives by the combination of tBuOOH and NEt3

This protocol provides a unique and innovative approach to the construction of α-tert-butylperoxy-β-dichloromethyl alkanes, employing CHCl₃ as an alkylating reagent to provide a –CHCl₂ group, and TBHP as an oxidant to provide an α-^tBuOO group.

Molecular iodine-mediated formal [2+1+1+1] cycloaddition access to pyrrolo[2,1-a]isoquinolines with DMSO as the methylene source

A molecular iodine-mediated formal [2+1+1+1] cycloaddition for the efficient synthesis of pyrrolo[2,1-a]isoquinolines from acetophenones, 1,2,3,4-tetrahydroisoquinoline (THIQ) and DMSO has been developed.

Acid-promoted oxidative methylenation of 1,3-dicarbonyl compounds with DMSO: application to the three-component synthesis of Hantzsch-type pyridines

A series of polysubstituted pyridines and methylene-bridged bis-1,3-dicarbonyl compounds were prepared in high yields from 1,3-dicarbonyl compounds and DMSO, wherein DMSO serves as solvent, carbon source, and oxidant.