Sulfur Ylides Research Articles

Protecting group-directed annulations of tetra-substituted oxindole olefins and sulfur ylides: regio- and chemoselective synthesis of cyclopropane- and dihydrofuran-fused spirooxindoles.

Protecting group-controlled annulations of tetra-substituted oxindole olefins and sulfur ylides have been achieved for the synthesis of multifunctional cyclopropane- and dihydrofuran-fused spirooxindoles. Under precise annulation regulation, a variety of cyclopropane- and dihydrofuran-fused spirooxindoles containing vicinal quaternary carbon centers were produced in up to 90% yield with up to 20 : 1 dr. This reaction demonstrates high regio-, chemo- and diastereoselectivity, broad functional group tolerance and gram-scale capacity.

Diastereoselective synthesis of cyclopropanes bearing trifluoromethyl-substituted all-carbon quaternary centers from 2-trifluoromethyl-1,3-enynes beyond fluorine elimination.

Herein, a one-pot, two-step procedure for the diastereoselective synthesis of cyclopropanes bearing trifluoromethyl-substituted all-carbon quaternary centers has been described. Trifluoromethyl-activated 1,3-enynes undergo cyclopropanation reactions with sulfur ylides under mild reaction conditions without fluoride elimination, which affords the cis-isomer mainly. Interestingly, a sequential TBAF-mediated deprotection of the triisopropylsilyl group results in a diastereoenriched epimerization which gives rise to the trans-cyclopropanes as the sole isomers.

Metal-free tandem reaction synthesis of spiro-cyclopropyl fused pyrazolin-5-one derivatives

A highly efficient cascade annulation approach was developed for the synthesis of novel spiro-cyclopropyl fused pyrazolin-5-ones from pyrazole-3-ketone substrates and two-component sulfur ylides in an acidic environment.

An efficient synthesis of 2-isoxazolines from α-haloketone oximes and dimethyl sulfonium salts

2-Isoxazolines were synthesized efficiently from a formal [4+1] cycloaddition of nitrosoalkenes and sulfur ylides, which were generated in situ from α-haloketone oximes and dimethyl sulfonium salts. This approach provides a new method to synthesize a range of 2-isoxazolines in high yields and high regioselectivity.

Catalytic Asymmetric Ring-Opening/Cyclopropanation of Cyclic Sulfur Ylides: Construction of Sulfur-Containing Spirocyclopropyloxindoles with Three Vicinal Stereocenters.

A highly efficient asymmetric ring-opening/cyclopropanation reaction of ( E)-3-(oxyethylidene)-2-oxoindolines with 1-alkyl-3-oxotetrahydro-1 H-thiophen-1-ium salts as cyclic sulfur ylides was realized by using a chiral N, N'-dioxide/Mg(OTf)2 complex as catalyst. A range of sulfur-containing syn, anti spirocyclopropyloxindoles with three contiguous stereocenters were obtained in excellent yields with excellent dr and good ee values under mild reaction conditions. The origin of stereoselectivity was discussed.

Substrate‐Controlled Diastereoselectivity Switch in the Formation of Dihydrothieno[3,4‐c]coumarins via [4+1] Annulations

AbstractAn expedient and practical route for realizing a novel, substrate‐controlled diastereoselective switch strategy has been successfully developed. The [4+1] annulation of thioamides with sulfur ylides proceeded smoothly via a Michael addition triggered sequential process, and trans‐dihydrothieno[3,4‐c]coumarins were obtained because of steric hindrance effects between the benzoyl group and the unit of 2H‐chromen‐2‐one as shown in the Newman projection. Nucleophilic substitution was observed as the key step when the sulfur ylides were replaced with acetophenones in the [4+1] annulation, and a double π,π‐stacking donor‐acceptor interaction stabilized the transition state that led to the cis‐dihydrothieno[3,4‐c]coumarins. In addition, a facile chemoselective reaction was also investigated, providing a series of thieno[3,4‐c]coumarins.magnified image

Construction of Azepino[2,3- b]indole Core via Sulfur Ylide Mediated Annulations.

A novel [4 + 3] annulation of indoline-based aza-dienes and crotonate-derived sulfur ylides is described. This method could be further expanded by using more efficient synthetic strategies, including three-component [3 + 1 + 3] cascade and the direct sulfide-catalyzed [4 + 3] cyclization. These protocols enable the rapid construction of azepino[2,3- b]indole cores, and a broad spectrum of the desired products with diverse substituents was facilely accessed in generally high yield.

Recent advance in sulfur ylide and sulfonium salts chemistry

Organosulfur compounds are ubiquitous in natural products and active pharmaceutical ingredients. They are also versatile scaffold that are widely applicable in material and food chemistry. The increasing demand indeed lead to a continuous progress in developing of new methodologies in organosulfur chemistry. Among them, sulfur ylides and sulfonium salts with unique reactivities have been employed to provide simple, effective, and often stereoselective methods to gain access to sulfur containing molecules. The essential goal of this review is to provide a comprehensive account of representative research progress on sulfonium salt and sulfur ylide chemistry in the past three years. Seminal reports on this topic are occasionally covered with the purpose of providing a brief research background. For the sake of convenience, this review is organized in three parts based on the role they played in organic reactions (synthetic intermediates, reagents and catalysts). In the first section, the development of new approaches for generate sulfur ylide or sulfonium salt intermediates were summarized. Electrophilic aryne species could be employed to react with sulfides or sulfoxides to form the desired sulfur intermediates, which could underwent a variety of interesting transformations. Moreover, recent progress in metal carbene-based sulfur ylide approaches have also been introduced. Both the progress in asymmetric catalysis variants and reactions in aqueous solution have been presented. The second section describes the transformations using stabilized sulfonium salts and sulfur ylides as bench-stable reactants. The extra stability of these species is accompanied by a compromise in the reactivity, which usually requires developing activation methods. With transition metal catalysts to activate sulfonium salts, they have been discovered as efficient coupling partners in carbon-carbon bond and carbon-heteroatom bond formation reactions. Stable sulfur ylides could also be utilized to install fluorine-containing groups in a large variety of transformations. The third section covers recent progress in employing sulfonium salts as catalysts in organic reactions. The acidity of the α C−H in sulfonium salt is relatively high than its nitrogen and phosphine analogues. Therefore, it could be easily removed to form the sulfur ylide, which have restricted its application as catalysts. On one hand, scientists took advantage of these properties and developed new cyclic sulfonium salts as hydrogen bonding catalysts. On the other hand, sulfonium salts could be used as stable phase transfer catalysts under base free conditions in order to avoid degradations. Finally, the review discussed the limitations of the known chemistry in this field as well as the future opportunities. Sulfur ylide and sulfonium salts have displayed many unique reactivities as summarized in this review. New reactivity will still be the central theme of research given the importance of organosulfur compounds. In addition, insights into the factors controlling the reactivity via mechanistic studies will be of great importance for further research and development. Moreover, the applications of sulfonium salts as organocatalysts are still limited to a relatively narrow range of transformations. Therefore, it remains to be an elusive task to unlock their full potential, and future research must include the development of scalable and cost-efficient methods, broadening of reaction scopes, and integration with other catalytic manifolds. We hope that this review will pique the interests of readers and deliver inspiration for future development in this interesting and promising field.

Substrate-Controlled Domino Reactions of Crotonate-Derived Sulfur Ylides: Synthesis of Benzothiophene Derivatives.

Substrate-controlled domino reactions between thioaurones or their analogues and crotonate-derived sulfur ylides were developed and produced a broad spectrum of benzothiophene-fused pyran derivatives, substituted chromene derivatives. In these reactions, crotonate-derived sulfur ylides acting as two-carbon synthons (α and β carbons or β and γ carbons) in annulation reactions are reported for the first time. These investigations nicely complement and expand previously studied reactions of crotonate-derived sulfur ylides. In addition, reaction mechanisms for these domino reactions are proposed, one of which is supported by DFT calculations.

Synthesis, X-ray characterization, and in vitro biological approach of dimeric and polymeric mercury(II) complexes with α-keto stabilized sulfur ylide

Reaction of α-keto stabilized sulfur ylide (Me)2SCHC(O)C6H4-p-CN (Y) with HgX2 (X = Cl, Br, and I) led to the formation of new dinuclear products of the type [HgX2(Y)]2 (X = Cl (1), Br (2), and I (3)). Furthermore, the reaction of the corresponding sulfur ylide (Y) with Hg(NO3)2·H2O in equimolar ratio, using methanol as a solvent, was shown to produce the polynuclear complex [(Y)Hg(NO3)2]n (4). The obtained compounds were characterized using elemental analysis, IR, 1H and 13C NMR techniques. The structures of compounds Y and 1 were characterized by single-crystal X-ray diffraction (XRD) analysis. Also, in order to confirm the crystalline nature of complexes 1–3, powder XRD pattern was used. Likewise, the antioxidant property of the complexes was examined by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging which revealed the strong-to-moderate radical scavenging ability (IC50; 0.163 ± 0.004 to 0.936 ± 0.012 mg·mL−1) of the synthesized compounds. Further, results from this study indicated that the compounds possess moderate antibacterial activity.

Divergent Domino Reactions of Sulfur Ylides: Access to Functionalized Six- and Seven-Membered Nitrogen-Heterocycles.

Divergent domino annulation reactions of sulfur ylides and azadienes were developed. A wide range of functionalized benzofuran-fused six- and seven-membered nitrogen-heterocyclic compounds were prepared in moderate to excellent yields under mild conditions. It is worth noting that the crotonate-derived sulfur ylides could be used as a novel C2 synthon or C3 synthon selectively by simply transforming the base.

Recent Applications of α-Carbonyl Sulfoxonium Ylides in Rhodium- and Iridium-Catalyzed C–H Functionalizations

Sulfoxonium ylides are a special type of sulfur ylides that serve as new C1 or C2 synthons recently developed for use in C–H functionalization to access acylmethylated or cyclized compounds through the formation of metal carbene species. Many excellent works have reported the syntheses of various useful skeletons from these versatile synthons. These developments have not previously been completely investigated or reviewed. In this review, we summarize recent advances in the use of α-carbonyl sulfoxonium ylides in C–H functionalizations, including ortho-C–H acylmethylation reactions and ortho-C–H activation/cyclization reactions. Table of Contents 1 Introduction2 Ortho-C–H Acylmethylation Reactions3 Ortho-C–H Activation/Cyclization Reactions3.1 Ortho-C–H Activation/Cyclization of Anilines and Enamines3.2 Ortho-C–H Activation/Cyclization of Azobenzenes3.3 Ortho-C–H Activation/Cyclization of N-Methoxybenzamide3.4 Ortho-C–H Activation/Cyclization of Imines3.5 Ortho-C–H Activation/Cyclization of N-Azoloimines3.6 Ortho-C–H Activation/Cyclization of Benzoylacetonitriles3.7 Ortho-C–H Activation/Cyclization of Benzoyl Sulfoxonium Ylides4 Conclusion

Domino Corey-Chaykovsky Reaction for One-Pot Access to Spirocyclopropyl Oxindoles.

The development of the sequential Corey-Chaykovsky reactions of isatins, spiroepoxy-, or spiroaziridine oxindoles with sulfur ylide has led to the discovery of a unique reaction mode that allows easy and direct one-pot access to a range of spirocyclopropyl oxindoles.

Copper‐Catalyzed Formal [4+2] Cycloaddition of Enoldiazoimides with Sulfur Ylides

AbstractEnoldiazoimides, a new subclass of enoldiazo compounds, generate enol‐substituted carbonyl ylides whose reactions with sulfur ylides enable an unprecedented formal [4+2] cycloaddition. The resulting multifunctionalized indolizidinones, which incorporate sulfur, are formed in good yields under mild reaction conditions. The uniqueness of this transformation stems from the role of the silyl‐protected enol, since the corresponding acetyldiazoimide failed to provide any cross‐products in metal‐catalyzed reactions with sulfur ylides. This copper‐catalyzed cycloaddition is initiated with the generation of enol‐substituted carbonyl ylides and sulfur ylides from enoldiazoimides and sulfonium salts, respectively, and proceeds through stepwise six‐membered ring formation, C−O and C−S bond cleavage, and silyl and acetyl group migration.

Copper-Catalyzed Formal [4+2] Cycloaddition of Enoldiazoimides with Sulfur Ylides.

Enoldiazoimides, a new subclass of enoldiazo compounds, generate enol-substituted carbonyl ylides whose reactions with sulfur ylides enable an unprecedented formal [4+2] cycloaddition. The resulting multifunctionalized indolizidinones, which incorporate sulfur, are formed in good yields under mild reaction conditions. The uniqueness of this transformation stems from the role of the silyl-protected enol, since the corresponding acetyldiazoimide failed to provide any cross-products in metal-catalyzed reactions with sulfur ylides. This copper-catalyzed cycloaddition is initiated with the generation of enol-substituted carbonyl ylides and sulfur ylides from enoldiazoimides and sulfonium salts, respectively, and proceeds through stepwise six-membered ring formation, C-O and C-S bond cleavage, and silyl and acetyl group migration.

Asymmetric Sulfur-Ylide-Mediated Formal [4+1]-Annulation Reaction: Scope and Mechanism.

A formal [4+1]-annulation strategy between sulfur ylides and 1,3-dienes was developed to afford functionalized cyclopentanoids. The process consists of a stereoselective cyclopropanation reaction followed, in situ, by a stereospecific MgI2 -catalyzed vinylcyclopropane-cyclopentene rearrangement. The use of chiral sulfur ylides provided cyclopentanoids with excellent enantiocontrol. A combined experimental and computational mechanistic study showed that the stereospecificity of the rearrangement could be accounted for by a double SN 2 reaction mechanism involving iodide.

(3 + 3) Annulation of Nitroallylic Acetates with Stabilized Sulfur Ylides for the Synthesis of 2-Aryl Terephthalates.

A novel (3 + 3) annulation approach has been developed for the synthesis of 2-aryl terephthalates from nitroallylic acetates and stabilized sulfur ylides. The 2-aryl terephthalates, which are also biaryls bearing a terephthalate moiety, are formed through a cascade of reactions such as a γ-selective SN2' reaction, γ-selective intramolecular Michael addition, and two eliminations in the presence of Cs2CO3 in CH3CN at room temperature. The products are formal precursors of farnesyltransferase inhibitors and are also potential monomers in polymer chemistry.

A Formal [5+1] Annulation Reaction of Sulfur Ylides and 2‐(1H‐indol‐2‐yl)phenols: Access to Indole‐Fused 4H‐benzo[e][1,3]oxazines

AbstractThe first sulfur ylides involved formal [5+1]‐annulation reaction was developed between prop‐2‐ynylsulfonium salts and 2‐(1H‐indol‐2‐yl)phenols. Prop‐2‐ynylsulfonium salt participates in the reaction with its β‐carbon atom and acts as a novel C1 synthon. Various indole‐fused 4H‐benzo[e][1,3]oxazines bearing a thioether moiety were constructed in good to high yields under mild conditions.magnified image

Substrate-Controlled Synthesis of Spirocyclopropylpyrazolones and Bicyclic 4,5-Dihydropyrazoles from 1,2-Diaza-1,3-dienes with Sulfur Ylides.

Substrate-controlled reactions have been developed for the synthesis of spirocyclopropylpyrazolones and bicyclic 4,5-dihydropyrazoles from 1,2-diaza-1,3-dienes and sulfur ylides. These protocols were carried out under mild reaction conditions without any additives in generally moderate to good yields. Plausible mechanisms for the transformations were proposed.

Synthesis of 2-Aroylbenzofurans from Arynes and Sulfur Ylides

Synthesis of 2-Aroylbenzofurans from Arynes and Sulfur Ylides