Synthesis of β-trifluoroacetyl-substituted vinyl sulfones and vinyl sulfides

Oxidation of -(trifluoroacetyl)vinyl sulfides afforded a series of the corresponding sulfones. The reactions of sulfones with various alkyl- and arylthiols were studied. These reactions provide the basis for a new procedure for the synthesis of -(trifluoroacetyl)vinyl sulfides.     

An approach to α-keto vinyl carbinols

Adducts from the radical addition of xanthates to ethyl vinyl sulfide readily undergo elimination of the xanthate group upon thermolysis to give vinylic and/or allylic sulfides, depending on the structure. In the case of α-xanthyl ketones, the adducts are converted into α-keto vinyl carbinols by rearrangement of the sulfoxides derived from the vinylic and allylic sulfides.     

Synthesis and structures of α-lithiated vinyl ethers

The structures of α-lithiated vinyl ethers were explored on the basis of a combined computational and NMR study. Calculations (M06/6-31 + G(d)) on free energies of aggregate formation for a series of α-lithiated vinyl ethers indicated that the tetramer is generated preferentially in both the gas phase and THF solution, except for cyclohexylidene derivatives. (1-(Methoxymethoxy)vinyl)lithium, (2,2-difluoro-1-(methoxymethoxy)vinyl)lithium, and (1-butoxyvinyl)lithium were prepared in NMR tubes by the deprotonation of alkyl/alkoxylalkyl vinyl ethers or by the transmetalation of tin compounds. The NMR spectra of these lithium species in THF solution showed that in each species one aggregate is primarily present at 173 K, which is consistent with the preference of the tetramer.     

Catalytic asymmetric synthesis of γ-substituted vinyl sulfones

A fast new entry for the stereoselective construction of γ-substituted vinyl sulfones is presented. The key for success is the use of a readily available chiral secondary amine catalyst that allows the use of base-sensitive β-nitroethyl sulfones as masked β-sulfonyl vinyl anions in conjugate additions. The method performed in a three-step one-pot operation gives access to a great variety of vinyl sulfones in good yields and with excellent enantioselectivities. The method has also been extended to other relatively base-sensitive β-electron-withdrawing-substituted nitroalkanes to afford products with manifold functionality, providing a quick entry to very attractive synthetic intermediates for organic synthesis.     

Structural defects in poly(vinyl chloride)—IV. Thermal degradation of vinyl chloride/acetylene copolymers

Vinyl chloride/acetylene copolymers have been prepared under subsaturation conditions. Copolymerization rates and molecular weights of the copolymers decrease with increasing concentration of acetylene in the monomer feed, indicating that acetylene is a retarder in vinyl chloride polymerization. The concentration of internal double bonds in the copolymers determined by ozonolysis increases with increasing amount of acetylene in the feed. Thermal degradation has been performed at 110 with solid samples and at 170° in solution under inert atmosphere. The extent of HCl loss as a function of time shows a rapid initial phase followed by a slower steady rate The initial dehydrochlorination rates are higher for copolymer samples containing higher concentrations of internal double bonds. Quantitative analysis of the u.v. and visible spectra of degraded copolymers shows that the sum of the concentration of polyenes with 4–12 conjugated double bonds increases rapidly in the first phase of degradation, but then decreases slowly, due to secondary reactions of polyene sequences.     

Nickel-catalyzed reductive coupling of glucosyl halides with aryl/vinyl halides enabling β-selective preparation of C-aryl/vinyl glucosides

This work describes stereoselective preparation of β-C-aryl/vinyl glucosides via mild Ni-catalyzed reductive arylation and vinylation of C1-glucosyl halides with aryl and vinyl halides. A broad range of aryl halides and vinyl halides were employed to yield C-aryl/vinyl glucosides in 42%–93% yields. Good to excellent β-selectivities were obtained for C-glucosides by using tridentate ligand.     

A convenient synthesis of vinyl sulfoximines from β-hydroxyalkyl sulfoximines

Previously unknown free and N-acylated vinyl sulfoximines were readily prepared via elimination of β-hydroxyalkyl methylphenylsulfoximines.     

Reactions of α-fluorine-containing β-functionalized vinyl sulfides with N-nucleophiles

-Fluorine-containing -functionalized vinyl sulfides readily react with N-nucleophiles to form -fluorine-substituted products. The reactions with phenylhydrazines and amidines of acids are accompanied by cyclization at the functional group. Thermal cyclization of cyanotrifluoromethylketene N,S-acetals proceeds at the trifluoromethyl group to give substituted 3-cyanoquinolin-4-ones.     

Structural defects in poly(vinyl chloride)—V. Thermal and photodegradation of copolymers of vinyl chloride with various acetylene derivatives

Vinyl chloride has been copolymerized with various acetylene derivatives in bulk at 50. It has been shown by ozonolysis that these copolymers contain a significantly increased amount of internal double bonds. A comparison of the thermal and photodegradation behaviours of the copolymers has been made. The built-in double bonds show an effect on the reactivity of the adjacent allylic chlorine depending on the electron-withdrawing or repelling nature of the substituent. Among the comonomers investigated, copolymers containing 3-chloropropine have the least reactive defect sites, because of the electron-withdrawing chloromethyl substituent. On the contrary, the electron-repelling n-butyl group, built-in by using hexine-1 as comonomer, results in enhanced reactivity of the allylic chlorines.     

On the electro-initiated polymerization of β-N-carbazolyl ethyl vinyl ether

β-N-carbazolyl ethyl vinyl ether, a monomer having the carbazolyl substituent at a distance from the vinyl group, was submitted to electro-initiated polymerization. Polymers with η_red = 0.015–0.07 dlg⁻¹ were obtained in the anodic compartment of a two compartment cell. The i.r., NMR and u.v. spectra show structural characteristics similar to those obtained by conventional cationic polymerization of the monomer but also some peculiarities associated with the conditions of electrochemical synthesis.     

Synthesis of γ-ketophosphonates via aerobic hydroacylation of vinyl phosphonates

γ-Ketophosphonates are commonly employed as non-hydrolysable phosphate mimetics and as tools in synthesis. The synthesis of γ-ketophosphonates under mild conditions via interception of acyl radicals generated by aldehyde auto-oxidation is described.     

Selenium catalyzed conversion of vinyl halides into α-alkoxy acetals

The reaction of vinyl halides with phenylselenenyl chloride in alcohols affords α-alkoxy acetals and diphenyl diselenide which can be oxidized to PhSe cations by nitrate or persulfate anions. The reaction can be carried out with catalytic amounts of PhSeCl or PhSeSePh. The reaction proceeds through the formation of the methoxyselenenylation product which then suffers solvolysis. Under controlled conditions, the 1-phenyl-1-methoxy-2-bromo-2-phenylselenenyl ethane was isolated from the reaction of β-bromostyrene and PhSeCl in methanol. Several deselenenylation reactions of this α-halogenoselenide are reported.     

Additions of free dimethylgermylene to vinyl ketones and α-diketones

Derivatives of 1-oxa-2-germacyclopent-4-ene are obtained from germylenes with a number of cyclic or acyclic vinyl ketones, and 1,3-dioxa-2-germacyclopent-4-enes with different non-enolizable α-diketones. Structure-mechanism relationships are discussed.     

A chiral π-stacked vinyl polymer emitting white circularly polarized light

An optically active, π-stacked poly[2,7-bis(4-tert-butylphenyl)dibenzofulvene] having a preferred-handed helical conformation was synthesized by anionic polymerization. A thin film sample of the polymer exhibited broad-band white circularly polarized light (CPL) emission on photo excitation.     

Traceless solid-phase synthesis of 3-substituted isoxazoles from polystyrene-supported vinyl selenide

A novel facile procedure for traceless solid-phase synthesis of 3-substituted isoxazoles in good yields and with excellent purities using polymer-supported vinyl selenide has been developed.