Synthesis of α‐phosphonylated phosphonium and sulfonium ylides: Study of their thermal behavior

The additions of two equivalents of trialkylphosphites onto phosphonodithioformates produce stabilized α‐sulfanyl‐α‐phosphonyl phosphonium ylides. Their subsequent reaction with alkyl or benzyl halides gives stabilized sulfonium ylides. Thermal treatment of these phosphonium and sulfonium ylides leads to α‐sulfanyl methylene bis‐phosphonates through protonation–dealkylation intramolecular reactions. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:164–171, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20530     

Trisubstituted thiazoles by a 6π-electrocyclization of iminothiocarbonyl ylides

Iminothiocarbonyl ylides are generated by a sulfur ligand exchange reaction of sulfonium salts and undergo a 6π-electrocyclic closure and aromatization to trisubstituted thiazoles. Related carbonyl ylides preferred a 4π-electrocyclization.     

Electrochemical reductions of substituted pyridinium 2-pyridylcarbonylmethylides,their Pt(II) complexes,and substituted n-(2-pyridylcarbonyl)methylpyridinium perchlorates

The title pyridinium salts and pyridinium ylide-platinum(II) complexes have been reduced through a one-electron process at more positive potentials by 0.3 $\text{\$}\text{?}$0.6 V than the corresponding ylides. Both the reduced pyridinium salts and Pt(II)-ylide complexes reacted with dioxygen, followed by elimination of the N-methylene and ylide protons to form pyridinium ylides and Pt(II)-pyridinium ylide complexes containing the three-coordinate ylide carbon atom, respectively.     

Reactions of sulfur ylides with α,β-unsaturated thioamides: Synthesis of dihydrothiophenes and cyclopropanes

The reactions of stabilized sulfonium ylides with arylmethylenecyanothioacetamides proceed stereoselectively to yield 2-amino-4,5-dihydrothiophenes and cyclopropane-thiocarboxamides. The structures of the latter compounds were confirmed by X-ray diffraction analysis.     

Regioselectivity in the reaction of azinium salts and ylides with tetracyanoethylene

The reactions of pyridinium, picolinium, and quinolinium salts and ylides with tetracyanoethylene have been found to be regioselective. Reaction of azinium salts with tetracyanoethylene in aqueous methanol affords azinium tricyanoethylenolates, but pyridinium ylides react differently, with the highly stereo-selective formation of the Z-isomers of 3-aroyl-3-(R-1-pyridinio)-1,1,2-tricyano-2-propen-1-ides, which are 1,4-ylides with maximum charge separation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1431–1439, June, 1991.     

Enantioselective synthesis of vinylcyclopropanes and vinylepoxides mediated by camphor-derived sulfur ylides: rationale of enantioselectivity, scope, and limitation

By a sidearm approach, camphor-derived sulfur ylides 1 were designed and synthesized for the cyclopropanation of electron-deficient alkenes and epoxidation of aldehydes. Under the optimal conditions, the exo-type sulfonium salts 4a and 4b reacted with beta-aryl-alpha,beta-unsaturated esters, amides, ketones, and nitriles to give 1,3-disubstituted-2-vinylcyclopropanes with high diastereoselectivities and enantioselectivities. When the endo-type sulfonium salts 5a and 5b were used, the diastereoselectivities were not changed, whereas the absolute configurations of the products became the opposite to those of the reactions of 4a and 4b. An ylide cyclopropanation of chalcone derivatives with phenylvinyl bromide in the presence of catalytic amount of chiral sulfonium salts 4b and 5b has been developed. The sidearmed hydroxyl group was found to play a key role in the control of enantioselectivity and diastereoselectivity. The origins of the high diastereoselectivity and enantioselectivity were also studied by density functional theory calculations, which reveal the importance of the hydrogen-bonding between the sidearmed hydroxyl group and the substrate in determining the diastereoselectivity and enantioselectivity. The ylides 1 were also successfully applied for the epoxidation of aromatic aldehydes.     

Etude des reactions des diazoderives avec les cycloimmonium ylures-I : Action des sels de diazonium sur quelques pyridinium - ylures

The synthesis of cycloimmonium salts of the type $\text{7}$, $\text{8}$ and the corresponding cycloimmonium ylides $\text{9}$, $\text{10}$ are reported. In the reaction with diazonium salts $\text{11}$, $\text{12}$ the pyridinium monosubstituted carbanion ylides $\text{9}$, $\text{10}$ give the pyridinium disubstituted carbanion ylides $\text{17}$ – $\text{20}$. These are new types of isolable stable ylides. The synthesis involves the formation “in situ” of ylides $\text{9}$, $\text{10}$ which are bonded by their nucleophile ylide carbon atom to the nitrogen atom in diazonium salts. The intermediat formation of cycloimmonium salts $\text{13}$ – $\text{16}$ must be accepted. The structures of all compounds presented in this paper have been established by using elementary analysis, IR and ¹H-RMN spectra.     

Gold-catalyzed synthesis of furans and furanones from sulfur ylides

A golden switch: Doubly stabilized sulfonium ylides can be coupled with alkynes in a gold-catalyzed synthesis of heterocycles. This method hinges on a switch in the reactivity of the sulfur ylide resulting from the simple modification of the electron-withdrawing moieties and leads to either furans or furanones bearing a quaternary center.     

Two-Step Synthesis of trans-2-Arylcyclopropane Carboxylates with 98–100 % ee by the Use of a Phosphazene Base

Only the axial diastereomer of sulfonium salts 2 are formed upon alkylation of 1 . Deprotonation of 2 results in ylides, which allow the highly enantioselective cyclopropanation of Michael systems. The chiral auxiliary 1 is recovered and can be reused.     

Sulfonium nitroylides

Conclusions The nitro derivatives of sulfonium ylides were obtained by the reaction of nitro compounds or their salts with the complexes of dialkyl sulfoxides and sulfur trioxide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 240–244, January, 1977.     

Etude par ESCA de la repartition des charges dans les ylures de pyridinium

The charge density distribution in pyridinium type A and B ylides has been studied by ESCA. From the binding energies of the 1s electrons of their nitrogen atoms it can be concluded that the negative charge remains on the nitrogen atom of type A compounds, but that the negative charge usually assigned to the carbon atom on type B ylides is delocalised in electronegative substituents. From this fact, we propose a new mechanism to explain the reactivity of type B ylides, which react either by a 1,2-cycloaddition mechanism or as 1,5-dipoles. The reactions of the type B ylides can be interpreted better on this basis.     

A Highly Stereoselective Synthesis of Glycidic Amides Based on a New Class of Chiral Sulfonium Salts: Applications in Asymmetric Synthesis

A new type of chiral sulfonium salts that are characterized by a bicyclic system has been designed and synthesized from α‐amino acids. Their corresponding ylides, which were prepared by basic treatment of the sulfonium salts, reacted smoothly with a broad array of simple and chiral aldehydes to provide trans‐epoxy amides in reasonable to very good yields and excellent stereoselectivities (>98 %). The obtained epoxy amides were found to be useful as synthetic building blocks. Thus, they were reduced into their corresponding epoxy alcohols and subjected to oxirane‐ring‐opening reactions with different types of nucleophiles.     

Generation of sulfur ylides by the desilylation of α-trimethylsilylbenzyl sulfonium salts

The [2,3]-sigmatropic rearrangement of sulfur ylides derived via the desilylation of several α-trimethylsilylbenzyl sulfonium salts has been studied. The initially formed ylide was found to rapidly equilibrate with the thermodynamically more stable ylide. In the absence of trapping reagents, a Sommelet-Hauser type rearrangement occurs.     

Phenacyl onium salt photoinitiators: synthesis, photolysis, and applications

Onium salts, namely sulfonium, phosphonium, ammonium, and pyridinium salts containing phenacyl group are photoinitiators appropriate for the polymerization of monomers such as oxiranes and vinyl ethers, which are not polymerizable by a free-radical mechanism. The initiation is accomplished by direct or indirect (sensitized) photolysis of the salts. Depending on the type of the salt, the direct photoinitiation of cationic polymerization involves reversible or irreversible processes. The photolysis of phenacylsulfonium compounds proceeds by a reversible process, while the other types undergo irreversible photolysis leading to complete fragmentation of the photoinitiator. An additionally useful tool, namely photosensitized generation of initiating species enlarges the versatility of these salts as photoinitiators. Photoinitiated free-radical and zwitterionic polymerizations by using phenacyl-type salts are also addressed. Keto-enol tautomerization of phenacyl pyridinium salts is discussed. Moreover, an interesting application concerning in situ synthesis of clay-poly(methyl methacrylate) nanocomposites with the aid of the phenacyl anilinium salt-based photopolymerization technique is noted.     

Sulfonium ylides

The thermal transformations of phthalimido-substituted keto-stabilized sulfonium ylides, including optically active ylides, were studied. The thermolysis of sulfonium ylides obtained from α- and β-amino acids leads to methylthio-substituted pyrrolizidine- and indolizidinediones. Racemization of optically active ylides does not occur. Sulfonium ylides with longer carbon chains do not undergo intramolecular cyclization.     

Addition nucleophile des anions d'esters α-cyanoacetiques sur les cations succinimidosulfonium: Fragmentation ionique ou radicalaire des′ σ-sulfuranes intermediaires

Reactions of substituted cyanoacetate anions 4 with S,S-dialayklsuccinimidosulfonium salts resulted generally in the formation of N-alkylthiomethylketenimines and α-alkylthiomethylesters. Coupling products were also obtained with anion 4d and only observed in the case of methyl phenylcyanoacetate anion 4b. The results were interpreted by the formation of instable σ-sulfurane intermediates. Homolytic cleavage of these intermediates gave radical pairs, then the coupling products. Heterocyclic clevage gave new sulfonium salts which rearranged via sulfonium ylides.     

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.     

Design of latent catalysts and their application to polymer synthesis

Design of latent catalysts such as benzyl sulfonium, benzyl ammonium, benzyl pyridinium, benzyl phosphonium, and hydrazinium salts, and their application to polymer synthesis have been described. They have been demonstrated as excellent thermal or photolatent catalysts for polymerizations of cyclic monomers such as epoxides, bicyclo orthoesters, spiro orthocarbonates, and vinyl monomers such as styrene and vinyl ethers.     

A Direct Route to C-Vinylaziridines: Reaction of N-Sufonylimines with Allylic Ylides under Phase-Transfer Conditions or with Preformed Ylides at Low Temperature

Allylic sulfonium salts 3, 5, 7, 11, 12, 13, and arsonium salt 14 react with aromatic, heteroaromatic, and alpha,beta-unsaturated N-sulfonylimines under solid-liquid phase-transfer conditions in the presence of KOH at room temperature to produce, respectively, vinyl-, (beta-phenylvinyl)-, and [beta-(trimethylsilyl)vinyl]aziridines in excellent yields within several minutes. In some cases, pyrroline compound 9 is obtained as a minor product. This aziridination reaction has also been carried out with preformed ylides, generated from sulfonium salts 3, 7, arsonium salt 14, and telluronium salts 15, 16 with a base in THF at -78 degrees C. In most examples, quantitative yields were achieved. However, the trans/cis selectivity of the reaction was not high in either case. A semistable allylic sulfonium ylide, i.e., dimethylsulfonium 3-(trimethylsilyl)allylide, was found to not undergo an expected [2,3]-sigma-rearrangement and so can also be used in this reaction.     

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.