Metalloporphyrin Cr(TPP)Cl-catalyzed Claisen rearrangement of simple aliphatic allyl vinyl ethers and its unique stereoselectivity

The catalytic Z-selective Claisen rearrangement of simple aliphatic allyl vinyl ethers can be achieved using a chromium(III) porphyrin complex, Cr(TPP)Cl, as a catalyst: Cr(TPP)Cl significantly enhances reversal of E-Z selectivity in the thermal Claisen rearrangement of allyl vinyl ethers, especially, 4,5- and 4,6-disubstituted derivatives, at low catalyst loading.     

Synthesis of cyclic allyl vinyl ethers using Pt(II)-catalyzed isomerization of oxo-alkynes

Several alkynyl epoxides and one alkynyl allyl alcohol were isomerized to cyclic allyl vinyl ethers (3,4-dihydro-2H-1,4-oxazines) using PtCl₂ as the catalyst. Three of these allyl vinyl ethers were converted to 2-hydroxymorpholine derivatives by hydrolysis and two were converted to piperidine derivatives by thermal Claisen rearrangement.     

Vibrational spectra and molecular structure of methyl vinyl ether

The IR and Raman spectra of methyl-d₃ vinyl and methyl-d₃ vinyl-d₃ ethers are reported (along with earlier published spectra of the undeuterated molecule). The normal coordinate analysis, based upon CNDO/2 force constant calculations, confirms the absence of significant changes in CH₃ group dynamical properties in methyl vinyl ether compared to saturated ethers. Normal coordinate calculations of possible rotamers (cis structure force field with certain assumptions has been used) favours the planar trans (or close to it) structure of the second isomer.     

Acid catalyzed rearrangement of vinyl and ketene acetals

Substituted vinyl and ketene acetals undergo smooth oxygen-to-carbon rearrangement with a catalytic amount of TMSOTf to afford chain-extended ketones or esters, respectively. The developed procedure has been applied to the stereoselective synthesis of C-glycosides from the corresponding anomeric vinyl ethers.     

Non-catalyzed addition of heterocyclic thiols and 5-substituted-1H-tetrazoles to vinyl ethers

The alkylation of 1-substituted 1H-tetrazole-5-thiols and 4-substituted 4 H-1,2,4-triazole-3-thiols with alkyl halides or sulfonates lead to the formation of S-alkylated products regardless of the substituent on the heterocycle. In this work, we found that substituted 1H-tetrazole-5-thiols and 4 H-1,2,4-triazole-3-thiols readily reacted with vinyl ethers in the absence of a catalyst to exclusively form N-substituted 1H-tetrazole-5(4H)-thiones and 1H-1,2,4-triazole-5(4H)-thiones, respectively. Furthermore, the reactions of 5-substituted-1H-tetrazoles with vinyl ethers under the same conditions selectively yielded 2,5-disubstitued tetrazoles.     

Cationic polymerization of α,β-disubstituted olefins. V. Reactivity of propenyl alkyl ethers in cationic polymerization

To elucidate the effect of the introduction of a methyl group in the β-position of a vinyl monomer, propenyl alkyl ethers were copolymerized with vinyl ethers having the same alkoxy group. Propenyl alkyl ethers with an unbranched alkoxy group (ethyl or n-butyl propenyl ether) were more reactive than the corresponding vinyl ethers. This behavior is quite different from that of β-methylstyrene derivatives. However, propenyl alkyl ethers with branched alkoxy groups at the α carbon atom (isopropyl or tert-butyl propenyl ether) were less reactive than the corresponding vinyl ethers. Also, cis- isomers were more reactive than the trans isomers, regardless of the kind of alkoxy group and the polarity of the solvent.     

Thermodynamics of vinyl ethers—XXI: Evaluation of some cis interaction energies

Thermodynamics of isomerization reactions on some substituted vinyl methyl ethers have been studied for evaluating the magnitudes of the interaction energies S[R¹... R²] between the substituents R¹ and R², juxtaposed in a cis position across the CC bond of vinyl ethers. The results obtained are (values given in kJ mol^-1): S[Me... t-Bu]=18.2±1.0, S[Ph...i-Pr]=11±2, S[i-Pr...Et] =6.1±0.6, S[i-Pr... i-Pr] = 6.0 ± 0.6, S[0...t-Bu]=2.9±0.5, S[O...i-Pr]= -0.7±0.5, S[O...Et] = ?1.5±0.5, S[O...Ph]= ?2.1+-0.6, and S[O... Me] =?2.9 ±0.2 (the symbol O stands for the ethereal oxygen atom of vinyl ethers). The negative interaction energy values reveal that the cis interaction between the ethereal oxygen and the alkyl (aryl) group concerned is stabilizing.     

Pd(II)-catalyzed aliphatic Claisen rearrangements of acyclic allyl vinyl ethers

Palladium (II)-catalyzed [3,3] sigmatropic rearrangement of acyclic allyl vinyl ethers delivers 2,3-anti disubstituted pentenal Claisen adducts with high diastereoselectivity. Reaction conditions for circumventing allyl vinyl ether cleavage that had previously plagued catalyzed rearrangement of α-unsubstituted vinyl ether substrates are described. Merging Pd(II) catalysis with the facile access to the Claisen substrates afforded by Ir(I)-catalyzed olefin isomerization provides an expedient procedure for realizing asymmetric anti-selective Claisen rearrangements.     

Fluorine-containing β,β-disubstituted trimethylsilyl vinyl ethers: synthesis and reactions with N-(1,1,2,2-tetrafluoroethyl)dimethylamine

Fluorine-containing β,β-disubstituted trimethylsilyl vinyl ethers prepared by hydrosilyla-tion of appropriate substituted trifluoromethylketenes react with N-(1,1,2,2-tetrafluoro-ethyl)dimethylamine to give β,β,β’,β’-tetrasubstituted divinyl ethers. Conditions for selective hydrofluorination of tert-butyl perfluoro-2-methylpent-2-enoate into the corresponding saturated ester were developed. Pyrolysis of the latter with P₂O₅ afforded perfluoromethyl-(propyl)ketene.     

Decomposition of vinyl ethers by alkalide K, K(15-crown-5)2 via organopotassium intermediates

The structure of vinyl ethers determines the direction of the C-O bond cleavage by alkalide K⁻, K⁺(15-crown-5)₂1. Highly reactive organopotassium compounds are intermediate products formed in the system containing phenyl vinyl ether, butyl vinyl ether, ethylene glycol butyl vinyl ether or triethylene glycol methyl vinyl ether. Vinylpotassium and butylpotassium react with 15-crown-5. The oxacyclic ring of the latter is opened in this case. Organopotassium ethers possessing CH₂CH₂O units eliminate ethylene. It results in various potassium alkoxides. The reaction of 1 with butyl vinyl ether occurs very slow as compared to other vinyl ethers and most of other reagents used till now.     

Controlled random and alternating copolymerization of (meth)acrylates,acrylonitrile, and (meth)acrylamides with vinyl ethers by organotellurium‐, organostibine‐, and organobismuthine‐mediated living radical polymerization reactions

Random and alternating copolymerizations of acrylates, methacrylates, acrylonitorile, and acrylamides with vinyl ethers under organotellurium‐, organostibine‐, and organobismuthine‐mediated living radical polymerization (TERP, SBRP, and BIRP, respectively) have been studied. Structurally well‐controlled random and alternating copolymers with controlled molecular weights and polydispersities were synthesized. The highly alternating copolymerization occurred in a combination of acrylates and vinyl ethers and acrylonitorile and vinyl ethers by using excess amount of vinyl ethers over acrylates and acrylonitorile. On the contrary, alternating copolymerization did not occur in a combination of acrylamides and vinyl ethers even excess amount of vinyl ethers were used. The reactivity of polymer‐end radicals to a vinyl ether was estimated by the theoretical calculations, and it was suggested that the energy level of singly occupied molecular orbital (SOMO) of polymer‐end radical species determined the reactivity. By combining living random and alternating copolymerization with living radical or living cationic polymerization, new block copolymers, such as (PBA‐alt‐PIBVE)‐block‐(PtBA‐co‐PIBVE), PBA‐block‐(PBA‐alt‐PIBVE), and (PTFEA‐alt‐PIBVE)‐block‐PIBVE, with controlled macromolecular structures were successfully synthesized. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

The Use of tert-Butyl Vinyl Ether in Stepwise Electrophilic Addition Reactions

tert-Butyl vinyl ether (1) reacts with p-TolSCl to give 2-tert-butoxy-2-chloroethyl p-tolyl sulfide (2). In the presence of SnCl₄, 2 reacts with silyl enol ethers, allyltrimethylsilane, and vinyl ethers to form a C-C bond. In the case of vinyl ethers, the reaction proceeds through the formation of the 5-membered sulfonium salt intermediate which in turn can react with H₂O, TMSCN, allyltrimethylsilane, and Grignard reagents.     

Quantum-chemical study of organic reaction mechanisms: I. Addition of selenium dihalides to the double bond of vinyl ethers

The mechanism of addition of selenium dihalides to vinyl ethers was studied at the B3LYP/6-311+G(d,p) level of theory. The reaction goes in two steps through seleniranium intermediate. High selectivity of the addition is ensured by consistent effects of the charge and orbital factors.     

Efficient syntheses of C20-carotene and crocetin (descrocetin) esters promoted by an acidic ionic liquid

Efficient syntheses of C₂₀-carotene and crocetin or descrocetin esters from fumaraldehyde bis-dimethylacetal are described. The key steps of these syntheses are the reactions of fumaraldehyde and (2E,4E,6E)-octa-2,4,6-trienedial bis-dimethylacetals with alkyl vinyl or alkyl propenyl ethers promoted by the acidic ionic liquid, [emim][HSO₄].     

Furfuryl vinyl ethers in [4+2]-cycloaddition reactions

For the first time [4+2]-cycloaddition reactions were carried out between furfuryl vinyl ethers and typical dienophiles and heterodienes proceeding in uncatalyzed conditions and resulting in previously unknown heterocyclic systems containing either free vinyloxy groups or furfuryl substituents. With maleic anhydride and maleimide furfuryl vinyl ethers afforded 1-(vinyloxyalkyl)tricyclodec-8-ene-3,5-diones in up to 72% yields, and with N-benzylideneaniline or acrolein the corresponding functionally substituted tetrahydroquinolines (yield up to 65%) or 3,4-dihydropyrans (yield 23–50%) were obtained.     

Reactivities and NMR spectra of vinyl ethers

Copolymerizations of n-butyl vinyl ether (M₁) with other vinyl ethers were carried out in toluene at ?78°C with EtAlCl₂ catalyst and the monomer reactivity ratios were determined. It was found that the relative reactivity of alkyl vinyl ether log 1/r₁ is higher when the alkyl group is more electron-donating and the reactivity correlates linearly with the Taft σ^* of alkyl group in the monomer. The NMR spectra of vinyl ethers and of vinyl ether–trialkylaluminum complexes were investigated. Close correlations were found between the spectral characteristics and the relative reactivity of vinyl ether in the copolymerization. The degree of resonance contribution in alkyl vinyl ether was also discussed on the basis of NMR data.     

One-pot synthesis of N-protected α-amino aldehyde acetals from three-component reaction of fluoroalkanesulfonyl azide, vinyl ether and alcohol

A facile one-step method has been developed for the synthesis of N-protected α-amino aldehyde acetals in moderate to good yields by three-component reaction of fluoroalkanesulfonyl azides, vinyl ethers and alcohol at 0 °C within 10 min. This practical synthetic method provides a convenient and expeditious access to N-per(poly)fluoroalkanesulfonyl α-amino aldehyde acetals.     

F and C spectra of fluorinated and partially fluorinated vinyl alkyl ethers

Fluorine, hydrogen, and ¹³C NMR spectral data have been obtained for vinyl alkyl ethers containing fluorines. Some of the molecules are perfluorinated and others include hydrogen, bromine, and chlorine substituents. New generalizations regarding FF spin-spin coupling are developed and used, along with previously recognized correlations, in the confirmation of structures and the assignments of resonances. ¹³C spectroscopy, especially the analysis of ¹³C¹⁹F coupling, is critical in several of the structure determinations. Chlorine isotope effects on fluorine chemical shifts are observed when the chlorine and fluorine are attached to the same carbon, and are also used in the structure analyses. Long-range couplings between fluorines in the vinyl group and fluorines in the alkyl group are interpreted in terms of molecular geometry which allows certain of the alkyl fluorines to “touch” the fluorines cis and gem to the ether oxygen but not the fluorine trans to the oxygen. Two bond ¹³C¹⁹F coupling across the vinyl double bond is found to vary dramatically with the electronegativity of the vinyl substituents in the ethers, in accordance with previous observations for olefins.     

ESR studies on radical polymerization of vinyl ethers

ESR studies on the radical polymerization of vinyl ethers were performed from ?50°C to room temperature using di-tert-butylperoxide as a photoinitiator. Well resolved ESR spectra were assigned to propagating radicals of vinyl ethers. Their hyperfine splitting constants due to α-proton were about 16 G, being smaller than those of ethyl acrylate and vinyl acetate. The smaller constants is ascribed to a deviation of the propagating radicals from sp² hybrid structure. The reason why high polymers are not obtained from vinyl ethers by radical polymerization is discussed on the basis of information from the ESR studies.     

Reaction of trifluoromethanesulfonamide with heterodienes under oxidation conditions

Reactions of trifluoromethanesulfonamide with divinyl sulfone, divinyl sulfoxide, divinyl sulfide, diphenyl sulfide, vinyl allyl and diallyl ethers was investigated in the presence of oxidation system t-BuOCl + NaI. The reaction with divinyl sulfone afforded a product of 1,5-heterocyclization, 2,6-diiodo-4-[(trifluoromethyl) sulfonyl]thiomorpholine 1,1-dioxide. The same product was obtained in the reaction with divinyl sulfoxide apparently due to its preliminary oxidation to sulfone. In reactions with divinyl sulfide and unsaturated ethers only the oxidation of substrates was observed accompanied with strong tarring; the products of a reaction with trifluoromethanesulfonamide were absent. With diphenyl sulfide a product was formed resulting from the oxidation at the sulfur atom [S(II) → S(IV)], N-(diphenyl-λ⁴-sulfanylidene)trifluoromethanesulfonamide.