Ir(I)-Catalyzed Synthesis of Furanones from Vinyl Sulfoxonium Ylides

Computational exploration of vinyl sulfoxonium ylide chemistry

This review comprehensively examines the computational techniques employed to elucidate the reactivity, selectivity, and mechanistic pathways of vinyl sulfoxonium ylides. By delving into a spectrum of reactions ranging from insertion and cycloaddition to annulation, multicomponent reactions, and carbene-mediated transformations, we demonstrate the pivotal role of computational techniques in understanding the mechanism, reactivity and selectivity. The synergy between experimental and computational approaches is emphasized as a driving force for future breakthroughs and the continuous evolution of this dynamic and emerging field.

Ylide-Induced Ring Contraction of Coumarins to Benzofurans: Applications to the Synthesis of Bis-Heterocycles

We report an unusual ring contraction of 4-chlorocoumarin to benzofuranoyl sulfoxonium ylides using a Corey-ylide. These stabilized ylides were subsequently utilized for the synthesis of various valuable bis-heterocycles under both metal and metal-free conditions. The synthetic utility of this method is illustrated through the synthesis of known bioactive compounds. Detailed mechanistic investigations and quantum chemical calculations have provided valuable insights into the mechanism of the ring contraction reaction.

Regioselective Synthesis of N-Aryl Pyrazoles from Alkenyl Sulfoxonium Ylides and Aryl Diazonium Salts

A convenient and practical method has been developed for synthesizing various N-aryl pyrazoles from vinyl sulfoxonium ylides and diazonium salts. When using 1,3-disubstituted vinyl sulfoxonium ylides, the reaction selectively yields 1,3,5-trisubstituted pyrazoles. On the other hand, employing 2,3-disubstituted vinyl sulfoxonium ylides results in the formation of 1,3,4-trisubstituted pyrazoles. The reaction proceeds through the novel aryl diazene-derived vinyl sulfoxonium ylide. Furthermore, this method efficiently produces pyrazoles from aniline derivatives in a one-pot transformation. The reaction takes place under transition metal-free, mild conditions using easily accessible starting materials, making it a practical approach for generating pyrazoles in pharmaceutical chemistry.

Nucleophilic Dearomatization of Activated Pyridines Using Vinyl Sulfoxonium Ylides: Application to the Synthesis of Bis-Heterocycles

A highly efficient method has been developed for synthesizing 4-dienyl dihydropyridines through the nucleophilic dearomatization of activated pyridines using vinyl sulfoxonium ylides. This reaction follows the sequence involving ylide addition to activated pyridine, [2,3]-sigmatropic rearrangement, and subsequent sulfenic acid elimination. The resulting 4-dienyl dihydropyridines are then used in the synthesis of highly substituted bis-heterocyles. Control experiments and quantum chemical calculations were conducted to elucidate the selectivity and the mechanistic pathway.

Direct synthesis of α-functionalized amides via heteroatom-hydrogen insertion reactions using amide-sulfoxonium ylides

α-Functionalized Si-, Ge-, B-, Se-, and S-amide moieties are present in many medicinally active molecules, but their synthesis remains challenging. Here, we demonstrate a high-throughput synthesis using amide-sulfoxonium ylides as carbene precursors in a Si-H, Ge-H, B-H, Se-H, and S-H insertion reactions to target a wide range of α-silyl, α-geryl, α-boryl, α-selenyl, and α-sulfur (hetero)amides. The process is featured as simple operation, mild conditions, broad substrate scope, high functional group compatibility, and excellent chemoselectivity. Both experimental and computational studies are conducted to explore the mechanisms underlying the formation of C-Si/Ge/B/Se/S bond. This research highlights the use of highly selective X-H insertion reactions with amide-sulfoxonium ylide-derived carbenes, paving the way for the preparation of diverse functional organosilane, organogermane, organoboron, organoselenium, and organosulfur compounds from accessible and bench-stable precursors.

LiBr-Promoted Reaction of β-Ketodithioesters and Thioamides with Sulfoxonium Ylides to Synthesize Functionalized Thiophenes

An operationally simple and highly efficient synthesis of functionalized thiophenes has been developed by LiBr promoted heteroannulation of β-ketodithioesters and thioamides with bench-stable sulfoxonium ylides in open air for the first time. This one-pot strategy involves formal Csp3-H bond insertion/intramolecular cyclization cascade, featuring readily accessible starting materials, TM and additive-free condition, broad substrate scope, high functional group compatibility, and scalability. Moreover, the carbonyl, thiomethyl, and amino groups in the resulting thiophene provide a good handle on downstream transformations.

Revisiting the Reaction of Sulfur Ylides with Acetylenic Esters: Synthesis of Trisubstituted 1,3-Dienes, α-Carbonyl Vinyl Sulfoxides and α-Carbonyl Vinyl Sulfoxonium Ylides

We report herein a reexamination of the reactions between sulfoxonium ylides and acetylenic esters. Continuing our previous study of conjugate additions using α-carbonyl sulfoxonium ylides, we came across an interesting transformation when dimethyl acetylenedicarboxylate (DMAD) was employed as a Michael acceptor. Trisubstituted electron-deficient 1,3-dienes and α-carbonyl vinyl sulfoxides were obtained for the first time from these sulfur ylides, in a stereoselective manner (exclusively forming the E-isomer), achieving yields of up to 70 % and 83 %, respectively. Selected dienes were subsequently utilized in the synthesis of novel nitrogen heterocycles. Interestingly, when di-tert-butyl acetylenedicarboxylate (DtBAD) or alkyl propiolates were evaluated, the isolated product arose from the classical Michael addition, yielding α-carbonyl vinyl sulfoxonium ylides in yields of up to 89 %.

Synthesis of N-Aryl-4-trifluoromethylthiazol-2-amines via Insertion/Annulation of Trifluoromethylimidoyl Sulfoxonium Ylides with Sodium Thiocyanate

An efficient p-TsOH-mediated insertion of sodium thiocyanate into trifluoromethylimidoyl sulfoxonium ylides has been reported, affording annulated N-aryl-4-trifluoromethylthiazol-2-amines in 42-84% yields in a one-pot manner. This protocol encompasses a variety of trifluoromethylimidoyl sulfoxonium ylides with thiocyanate serving as the source of the "S-C═N" moiety of the thiazole ring. The versatile transformations of the resulting pharmacologically important N-aryl-4-trifluoromethylthiazol-2-amines were also demonstrated.

Diastereoselective cyclopropanation of α,β-unsaturated carbonyl compounds with vinyl sulfoxonium ylides

Herein, we report a three-component stereoselective cyclopropanation of vinyl sulfoxonium ylides with indane 1,3-dione and aldehydes under mild reaction conditions. In contrast to previous reports, the present work shows that electrophilic addition selectively takes place at the α-position of the vinyl sulfoxonium ylide. The interesting feature of this approach is that the multicomponent reaction selectively proceeds because of the difference in nucleophilic reactivity of vinyl sulfoxonium ylides and indane 1,3-dione with electrophilic partners, such as aldehydes and in situ generated arylidenes. Additionally, density functional theory (DFT) studies were conducted to investigate the difference in the reactivity of these reactants, as well as to unveil the mechanism of this three-component reaction. Furthermore, non-covalent interactions of selectivity-determining transition states explain the origin of the diastereoselectivity of cyclopropanation.

Influence of steric hindrance on the 1,4- versus 1,6-Michael addition: synthesis of furans and pentasubstituted benzenes

We described the influence of steric hindrance on the 1,4- versus 1,6-Michael addition reaction on 2-(3,3-bis(methylthio)-1-arylallylidene)malononitriles. An efficient and direct synthesis of trisubstituted furans was achieved through the reaction of 2-(3,3-bis(methylthio)-1-arylallylidene)malononitriles and acetone under mild conditions in good to moderate yield by the 1,4-Michael addition. Further exploration of the reaction with a sterically hindered aryl group containing 2-(3,3-bis(methylthio)-1-arylallylidene)malononitriles afforded biaryls by an in situ generated nucleophile through the 1,6-Michael addition. The synthetic utility of furan is further explored. These precursors are easily accessible from aryl methyl ketones. Various functional groups like alkyl, aryl, nitrile, amine, aroyl, and thiomethyl can be directly installed in the benzene and furan rings. A one-pot approach for the construction of a benzene nucleus was also developed. The structure of two compounds was confirmed by X-ray crystallography.

Lithium Bromide-Promoted Formal C(sp3)-H Bond Insertion Reactions of β-Carbonyl Esters with Sulfoxonium Ylides to Synthesize 1,4-Dicarbonyl Compounds

A LiBr-promoted formal C(sp3)-H bond insertion reaction between β-carbonyl esters and sulfoxonium ylides is established. This practical reaction has a wide range of substrate scope for both β-carbonyl esters and sulfoxonium ylides to give a variety of 1,4-dicarbonyl compounds with 43-94% yields. The reaction features transition-metal-free reaction conditions and exclusive C-alkylation chemselectivity. The use of bench-stable sulfoxonium ylides overcomes previous methods that require transition metal as catalysts and unstable diazo compounds or toxic haloketones as alkylation reagents.

Carbene-mediated stereoselective olefination of vinyl sulfoxonium ylides with diazo compounds and acetals

The development of stereoselective olefination using sulfur ylide-derived vinyl carbenes with diazo esters and acetals is reported. Both reactions proceed through nucleophilic addition to electrophiles at the γ-position of an in situ-generated 2-alkoxy furan intermediate. The synthetic utility of the developed method is demonstrated by the total synthesis of rubrolide E. Detailed mechanistic investigations and quantum chemical calculations provide insight into the reaction mechanism.

Visible Light-Promoted Regioselective Benzannulation of Vinyl Sulfoxonium Ylides with Ynoates

Herein, we report a highly regioselective [4 + 2]-annulation of vinyl sulfoxonium ylides with ynoates under light-mediated conditions. The reaction proceeds through the new dienyl sulfoxonium ylide, which undergoes photolysis under blue light irradiation to give highly substituted naphthalene scaffolds. The method presented here operates at room temperature and does not require the addition of an external photosensitizer. The in situ-generated dienyl sulfoxonium ylide absorbs light and acts as a photosensitizer for the formation of arenes. The synthetic potential of these benzannulations was further illustrated by various synthetic transformations and a scale-up reaction. Moreover, control experiments and quantum chemical calculations reveal the mechanistic details of the developed reaction.

Catalyst-Controlled Divergent Synthesis of 2H-Chromenes via [3 + 3] Annulation of Vinyl Sulfoxonium Ylides with Quinones

Herein, we report the synthesis of 2H-chromenes via catalyst-controlled highly regioselective [3 + 3] annulation of vinyl sulfoxonium ylides with quinones. Under boron-catalyzed conditions, the reaction between the ylide and quinone resulted in the formation of 2H-chromene-4-carboxylates. In contrast, a different mechanistic pathway was observed when utilizing a Ru(II) catalytic system, which led to the formation of 2H-chromene-2-carboxylates through a furan intermediate.

Divergent Approach to Highly Substituted Arenes via [3 + 3] Annulation of Vinyl Sulfoxonium Ylides with Ynones

Herein, we report the divergent benzannulation for highly substituted arenes using vinyl sulfoxonium ylides and ynones. The addition of ynone at the γ-position of vinyl sulfoxonium ylides leads to dienyl sulfoxonium ylide that can undergo selective annulation under different conditions to give m-terphenyls and parabens. Moreover, control experiments and quantum chemical calculations reveal two distinct reaction mechanisms for both annulations.

High-Throughput Experimentation and Machine Learning-Assisted Optimization of Iridium-Catalyzed Cross-Dimerization of Sulfoxonium Ylides

A novel and convenient approach that combines high-throughput experimentation (HTE) with machine learning (ML) technologies to achieve the first selective cross-dimerization of sulfoxonium ylides via iridium catalysis is presented. A variety of valuable amide-, ketone-, ester-, and N-heterocycle-substituted unsymmetrical E-alkenes are synthesized in good yields with high stereoselectivities. This mild method avoids the use of diazo compounds and is characterized by simple operation, high step-economy, and excellent chemoselectivity and functional group compatibility. The combined experimental and computational studies identify an amide-sulfoxonium ylide as a carbene precursor. Furthermore, a comprehensive exploration of the reaction space is also performed (600 reactions) and a machine learning model for reaction yield prediction has been constructed.

Synthesis and Applications of π-Conjugation-Extended Vinyl Sulfoxonium Ylides

Herein, we report the synthesis of π-conjugation-extended vinyl sulfoxonium ylides from vinyl sulfoxonium ylide and electron-deficient alkynes. The new dienoate ylides are used in various transformations, such as X-H (X = S, O) insertion, halogenation, carbene-mediated transformation, and radical-mediated reductions to obtain a variety of conjugated dienoates.

Insights into the multifaceted applications of vinyl sulfoxonium ylides

Sulfoxonium ylides are important synthetic precursors in various organic transformations. Their synthetic potential was well explored in the synthesis of various bioactive natural products and pharmaceuticals. Vinyl sulfoxonium ylide is a stabilized sulfoxonium ylide containing an electron-deficient alkene at the ylidic carbon. Similar to α-keto sulfoxonium ylides, these reagents can generate vinyl carbenes in the presence of metals under suitable conditions. These vinyl carbenes can be used for various organic transformations such as X-H (X = C, N, O, S) insertions, annulations, and rearrangement reactions. Due to the dipole structure of the vinyl sulfoxonium ylide, it can undergo electrophilic addition with electrophiles at the α-position. These reagents are used as synthons for various aromatic and heteroaromatic compound syntheses. Moreover, their stability and convenient handling make them potential replacements for thermally less stable vinyl diazo compounds. Herein, we provide an overview of early efforts in this area, with particular emphasis on our own recent development of vinyl sulfoxonium ylide-mediated transformations in the presence and absence of metal catalysis, and also give personal perspectives on the challenges and future scope for improving the application of vinyl sulfoxonium ylides.

Divergent Synthesis of Tetrasubstituted Phenols via [3 + 3] Cycloaddition Reaction of Vinyl Sulfoxonnium Ylides with Cyclopropenones

Two categories of tetrasubstituted phenols were prepared via the cycloaddition reaction of vinyl sulfoxonnium ylides with cyclopropenones in a switchable manner. Copper carbenoid was proposed as the active intermediate in the process of 2,3,4,5-tetrasubstituted phenols formation, while 2,3,5,6-tetrasubstituted phenols were generated via the direct [3 + 3] annulation of vinyl sulfoxonnium ylides with cyclopropenones under metal-free conditions. Further synthetic applications were also demonstrated.

Iridium-Catalyzed Diastereo- and Enantioselective [4 + 1] Cycloaddition of Hydroxyallyl Anilines with Sulfoxonium Ylides

We present here an iridium-catalyzed diastereo- and enantioselective [4 + 1] cycloaddition reaction of hydroxyallyl anilines with sulfoxonium ylides under mild reaction conditions, leading to 3-vinyl indolines in moderate to good yields with excellent enantioselectivities. Control experiments disclosed a plausible reaction mechanism.