Monofluoromethyl‐Substituted Sulfonium Ylides: Electrophilic Monofluoromethylating Reagents with Broad Substrate Scopes

Two electrophilic monofluoromethylating reagents, monofluoromethyl(phenyl)sulfonium bis(carbomethoxy)methylide ( 3 a ) and monofluoromethyl(4‐nitrophenyl)sulfonium bis(carbomethoxy)methylide ( 3 b ), and their reactions under mild conditions with a variety of nucleophiles, such as alcohols and malonate derivatives, sulfonic and carboxylic acids, phenols, amides, and N heteroarenes, are described. Mechanistic studies with deuterated reagents [D₂] 3 a /[D₂] 3 b suggest that these monofluoromethylation reactions proceed through an electrophilic substitution pathway.     

The Pummerer rearrangement of phenyl methyl sulphonium bis(methoxycarbonyl)-methylide

The reaction between phenyl methyl sulphonium bis(methoxycarbonyl)methylide and either acetic anhydride or benzoyl peroxide proceeds via “Pummerer” type rearrangement to afford phenyl α-acyloxymethyl sulphide. The kinetic data suggest that the rate-determining step involves SC bond cleavage after initial acylation or acyloxylation and subsequent proton removal by acyloxy anion unlike the corresponding reaction of the analogous sulphoxide with acetic anhydride in which the rate determining step is proton removal.     

Structure and bonding in 9-hydroxy-1,4-dimethylthioxanthenium bis(carbomethoxy)methylide and related ylides

The single-crystal X-ray structures of 9-hydroxy-1,4-dimethylthioxanthenium bis(carbomethoxy)methylide and 1,4-oxathianium bis(carbomethoxy)methylide are reported. The methylide carbon of the former is pseudo-axial while that of the latter is equatorial. The former exhibits a strong intramolecular hydrogen bond to a carbonyl oxygen atom.     

The proton and carbon-13 NMR spectra of thioxanthone sulfoxide,thioxanthone sulfone and related ylides - chemical shift assignments

The proton and carbon-13 nmr spectra of thioxanthone sulfoxide, thioxanthone sulfone, thioxanthonium bis(carbomethoxyl)methylide and thioxanthonium bis(carbomethoxyl)methylide S-oxide are assigned using 2-D nmr techniques and compared to those of thioxanthone. The pseudo-equatorial methylide fragment shields C4a/5a by ? 11 ppm relative to the corresponding sulfoxide and by ? 4 ppm relative to thioxanthone. The pseudo-axial methylide fragment in the oxysulfonium ylide has the same effect upon C4a/5a as does the pseudo-axial oxygen of the corresponding sulfone. The sulfoxide and the sulfonium ylide have similar chemical shifts for C2/7 (? 131 ppm) as do the sulfone and oxysulfonium ylide (? 133 ppm).     

Electrophilic Reaction of Phenyl Bis(Phenylthio) Sulfonium Cation as an Active Species for the Oxidative Polymerization of Diphenyl Disulfide

Computer modeling predicts that the methyl bis(methylthio) sulfonium cation can act as an efficient electrophile for sulfide bond formation in which the sulfur atoms at the side position of the cation react with the phenyl ring of an aromatic molecule. The electrophilic reaction mechanism of phenyl bis-(phenylthio) sulfonium cation with anisole was examined using computer simulation. The reaction between phenyl bis- (phenylthio) sulfonium cation, which is a homogeneous structure of thecation, and anisole shows the efficient formation of 4-phenylthioanisole with diphenyl disulfide as a by-product. In the oxidative polymerization of diphenyl disulfide, the formation process of polyp-phenylene sulfide) includes an elementary reaction between the phenylthio group at each side position of the phenyl bis(phenylthio) sulfonium cation and the carbon at the para position of the phenyl ring.     

Incorporation of stable organic radicals of the tris(2,4, 6-trichlorophenyl)methyl radical series to pyrrole units as models for semiconducting polymers with high spin multiplicity. 1

The condensation reactions between (4-amino-2,6-dichlorophenyl)bis(2, 4,6-trichlorophenyl)methyl radical and acetylacetone or 1, 4-bis(5-methyl-2-thienyl)-1,4-butanedione yield [2,6-dichloro-4-(2, 5-dimethyl-1-pyrrolyl)phenyl]bis(2,4,6-trichlorophenyl)methyl radical (3(*)()) and [2,6-dichloro-4-[2, 5-bis(5-methyl-2-thienyl)-1-pyrrolyl]phenyl]bis(2,4, 6-trichlorophenyl)methyl radical (4(*)()), respectively. EPR studies of both radicals 3(*)() and 4(*)() in CH(2)Cl(2) solution suggest a weak electron delocalization with coupling constant values of 1.25 and 1.30 G, respectively, with the six aromatic hydrogens. Their electrochemical behavior was analyzed by cyclic voltammetry. Both radicals show reversible reduction processes at E degrees = -0.69 V and -0.61 V versus SSCE, respectively, and anodic peak potentials at E(p)(a) = 1.10 and 0.72 V, respectively, versus SSCE at a scan rate (nu) of 200 mV s(-)(1), being reversible for radical 4(*)(). X-ray analysis of radical 3(*)() shows a high value (65 degrees ) of the dihedral angle between the 2,5-dimethylpyrrolidyl moiety and the phenyl ring. Smooth oxidation of radical 4(*)() in CH(2)Cl(2) containing trifluoroacetic acid gives an ionic diradical species with a weak electron interaction (|D/hc| = 0.0047 cm(-)(1)). A Curie plot of the Deltam(s)() = +/-2 signal intensity versus the inverse of the absolute temperature in the range between 4 and 70 K suggests a triplet or a nearly degenerate singlet-triplet ground state.     

Generation, isolation, and reactivity of a kinetically stabilized diphosphene anion radical

The stable lithium diphosphene anion radical, [Li(dme)₃]⁺[TbtPPTbt]⁻ (dme: 1,2-dimethoxyethane, Tbt: 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl), was readily synthesized by the one-electron reduction of the corresponding neutral diphosphene (TbtPPTbt). The molecular structure of the diphosphene anion radical was discussed in detail on the basis of its ESR, UV-Vis and Raman spectra, and theoretical calculations. The diphosphene anion radical was found to undergo ready chalcogenation reactions using elemental sulfur and selenium to afford the corresponding thiadiphosphirane and selenadiphosphirane, respectively.     

Über den mechanismus der licht-induzierten eliminierung des biphenyl-systems aus cis-bis(phenyl)platin(II)-verbindungen

We report the light-induced reductive elimination of the biphenyl system from compounds of the types bis(phenyl)[η²-1,2-bis(diphenylphosphano)ethan]platinum(II), bis(phenyl)[η²-cis-1,2-bis(diphenylphosphano)ethene]platinum(II) and bis(phenyl)[η²-1,2-bis(diphenylphosphano)benzene]platinum(II) with substituents in the platinum-bound phenyl rings. The elimination proceeds via a concerted reaction mechanism without any observable free radical involvement.     

含噻吩基的三硅烷在辐照下的反应

通过类似的格氏反应合成了2-苯基-2-呋喃基六甲基三硅烷和2-苯基-2-噻吩基六甲基三硅烷.前者在2,3-二甲基-1,3-丁二烯存在时的光解导致正常的硅烯-烯烃加成和硅烯C-H插入反应.而噻吩基三硅烷在甲醇一环乙烷体系中被光解,产生自由基反应,我们怀疑噻吩中的硫原子对硅烷自由基有强烈的稳定作用.通过对典型的自由基反应产品的鉴定以及它的用自由基猝灭剂的猝灭产品的电子自旋共振谱也支持了这一结果.     

Synthesis and structure of a distorted octahedral palladium(II) complex coordinated with a tetrathioether ligand tethered with bulky substituents

A new type of an o-phenylene-bridged tetrathioether ligand tethered with extremely bulky substituents, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt) groups, at its terminal sulfur atoms, TbtS[(o-phenylene)S]3Tbt (1), was synthesized by taking advantage of the coupling reaction of thiols with iodobenzenes using Cu2O in 2,4,6-trimethylpyridine. Complexation of 1 with Na2PdCl4 gave the corresponding dichloropalladium(II) complex, [PdCl2(1)] (7). The X-ray structural analysis of 7 indicated that the central palladium metal is in a distorted octahedral environment, where the two inner sulfur atoms of 1 and the two chlorine atoms form a square planar arrangement around the palladium metal and the two terminal sulfur atoms of 1 weakly coordinate to the palladium center at the axial positions. In addition, a phenyl analogue of 1, PhS[(o-phenylene)S]3Ph (2), was synthesized by a method similar to that for 1. Reaction of 2 with Na2PdCl4 gave the corresponding dichloropalladium(II) complex, [PdCl2(2)] (8). X-ray crystallography of 8 showed a type of the structure different from the distorted octahedral structure in 7, i.e., a square planar arrangement around the central palladium atom with the one terminal sulfur atom of 2, its neighboring sulfur atom, and the two chlorine atoms. The results of the NMR studies on 8 in a CDCl3 solution were not consistent with the results of the X-ray crystallography and suggested the coordination of the two inner sulfur atoms of 2 to the palladium metal, although a possibility of the existence of the rapid interconversion among isomers could not be excluded.     

Studies on ketene and its derivatives. LXXXIII. Reaction of diketene with isoquinolinium and pyridinium methylide derivatives

Reaction of isoquinolinium bis(ethoxycarbonyl)methylide (I) with diketene gave diethyl 1-acetyl-2,3-dihydro-2-oxopyrrolo[2,1-α]isoquinoline-3,3-dicarboxylate (VI), which on hydrolysis with dilute hydrochloric acid afforded ethyl 1-acetyl-2-hydroxypyrrolo[2,1-α]isoquinoline-3-carboxylate (IX) and ethyl 3-methylpyrrolo[2,1-α]isoquinoline-3-carboxylate (X). On the other hand, isoquinolinium cyanoethoxycarbonylmethylide (IIa) reacted with diketene to give isoquinolinium cyano(3-ethoxycarbonyloxy-3-butenoyl)methylide (XIIIa) which was isomerized to isoquinolinium cyano(3-ethoxycarbonyloxy-2-butenoyl)methylide (XIII). Similarly, reactions of isoquinolinium cyanomethoxycarbonylmethylide (IIb) and pyridinium cyanoalkoxycarbonyl-methylide (IIIa,b) with diketene gave rise to the corresponding cyano(3-alkoxycarbonyloxy-3-butenoyl)methylides (XIIb, XVIa,b).     

Synthesis and equilibrium of stereoisomers of 5-phenyl-2-ethoxy-1,3,5-dioxaphosphorinane

Conclusions The reaction of bis(hydroxymethyl)phenylphosphine with orthoformic ester gave 5-phenyl-2-ethoxy-1, 3, 5-dioxaphosphorinane, representing a mixture of two stereoisomers. The preferred conformations of these differ in the orientation of the phenyl residue on the phosphorus atom. The stereoisomer with the equatorial orientation of the phenyl radical predominantes in the equilibrium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 418–422, February, 1986.     

Rhodium(II)-catalyzed transylidation of aryliodonium ylides: electronic effects of aryl groups determine their thermodynamic stabilities

Intermolecular transylidations between aryliodonium ylides under catalytic conditions were developed. Heating a solution of phenyliodonium bis(trifluoromethylsulfonyl)methylide in a large amount (80 equiv) of a substituted iodobenzene in the presence of 5 mol % of rhodium(II) acetate as a catalyst transfers the bis(trifluoromethylsulfonyl)-methylidene group to the iodine(I) atom and affords a substituted aryliodonium ylide in a good yield. Reversible nature of the catalytic intermolecular transylidation makes it possible to evaluate the thermodynamic stability of aryliodonium ylides.     

The structure of sulfonium ylides stabilized by the malonylide moiety

The crystal structures of four thioxanthenium bis(carbomethoxy)methylides and methylides of di-(p-nitro-phenyl)sulfonium and dimethylsulfonium have been determined. The carbanion moiety in all cases is planar and the pi-system is rotated 90° with respect to the sulfur lone pair. All compounds exhibit a pseudo-equatorial orientation of the carbanion system except for the 2,4-dimethylthioxanthenium ylide. The compounds are described in terms of the geometries around the sulfur atom, the interplanar angles and sulfur-oxygen and oxygen-oxygen interactions. Surprisingly, the sulfur atom is not symmetrically placed with respect to the two phenyl rings in the thioxanthenium compounds. The sulfur is coplanar with one phenyl ring but is significantly out of the plane of the other. The ¹³C and ¹H spectra of the ylides are discussed along with the temperature dependence which indicates restricted rotation about the ⁺S? C^? bond in several cases. The factors contributing to the stability of the ylides are analyzed.     

Alkenyl C-H insertion of a β-disulfone iodonium ylide into flavones

The reaction of phenyliodonium bis(phenylsulfonyl)methylide with flavones affords insertion products into the alkenyl carbon-hydrogen bond of the flavone, presumably by an electrophilic attack of the iodonium ylide on the double bond of the flavone.     

A pyrolysis/gas chromatography—mass spectrometry and thermogravimetry/differential thermal analysis study of bis(diethyldithiocarbamato)diphenyl tin (IV)

The P/GC—MS and TG/DTA analysis, in an inert atmosphere, of bis(diethyldithiocarbamato)diphenyl tin (IV) indicates that the thermal decomposition proceeds in two consecutive stages. Loss of the dithiocarbamate ligands and the phenyl groups occurs within the temperature range of 210–380°C leaving tin (II) sulphide as residue. The stability of the phenyl radical as a reactive intermediate, together with the unidentate bonding of the dithiocarbamate ligand, dramatically influence the major mode of thermal decomposition.     

The use of ylide (4-picolinium 4-chloro phenacyl methylide) as an initiator for the polymerization of methyl methacrylate

The thermal polymerization of methyl methacrylate [MMA] was carried out using ylide (4-picolinium 4-chloro phenacyl methylide) as an initiator. The rate of polymerization (R_p) increases with increasing monomer and initiator concentrations; The exponent value has been computed to be 1 ± 0.02 and 0.5, respectively. The reaction was carried out at four different temperatures and the overall activation energy has been computed to be 16.01 kcal/mol. The polymerization was inhibited in the presence of hydroquinone as a radical scavanger. Kinetic studies indicates that the overall polymerization takes place by a radical mechanism.     

Structural Studies of a Copper(II) Complex with Inequivalent 2‐Acetylpyridine 3‐Piperidylthiosemicarbazonato Ligands and a Nickel(II) Complex with Different Modes of Coordination by the Two Thiosemicarbazonato Moieties of 1‐Phenylglyoxal Bis{N(4)‐diethylthiosemicarbazone}

The crystal structure of a copper(II) complex of 2‐acetylpyridine 3‐piperidylthiosemicarbazone, [Cu(Acpip)₂], indicates a tridentate, monoanionic ligand (i. e., pyridine nitrogen, imine nitrogen and thiolato sulfur atoms) and a bidentate, monanionic ligand (i. e., imine nitrogen and thiolato sulfur atoms). The stereochemistry approaches square pyramidal with the bidentate ligand occupying an apical (imine nitrogen atom) and basal (thiolato sulfur atom) position. The structure of a nickel(II) complex of 1‐phenylglyoxal N(4)‐diethylthiosemicarbazone, [Ni(Pg4DE)], has a 4‐6‐5 trichelate system rather than the 5‐5‐5 system common to bis(thiosemicarbazones). Coordination of the hydrazinic nitrogen atom of the “phenyl arm” along with the thiolato sulfur atom provides the 4‐membered chelate ring.     

Direct Difluoromethylation of Alcohols with an Electrophilic Difluoromethylated Sulfonium Ylide

A general method for the formation of alkyl difluoromethylethers under mild reaction conditions and with good functional‐group tolerance was developed. The development of the method was based on the invention of a stable, electrophilic, difluoromethylating reagent, difluoromethyl‐(4‐nitrophenyl)‐bis(carbomethoxy) methylide sulfonium ylide, which was synthesized by reaction of the easily available 4‐nitrophenyl (difluoromethyl)thioether and dimethyl diazomalonate in the presence of a rhodium catalyst.     

Heteroaromatic annulation studies on 10,11-dihydro-11-[bis(methylthio)methylene]dibenzoxepin-10-one: a facile access to novel dibenzoxepino[4,5]-fused heterocycles

10,11-Dihydro-11-[bis(methylthio)methylene]dibenzoxepin-10-one has been shown to be a useful three carbon synthon for the efficient regiospecific annulation of a variety of five- (pyrazoles, isoxazoles, thiophene, and γ-lactone) and six-membered (pyrimidines, pyridone and pyridines) heterocycles by cyclocondensation with heterobinucleophiles such as hydrazine, hydroxylamine, dimethylsulfonium methylide, guanidine, thiourea, cyanoacetamide, and substituted β-lithioaminoacrylonitrile.